Las células madre musculares embrionarias tienen la clave de la regeneración muscular

Fuente: http://www.abc.es/salud/enfermedades/abci-celulas-madre-musculares-embrionarias-tienen-clave-regeneracion-muscular-201602190211_noticia.html

La capacidad de regeneración es mayor cuando las células madre musculares adultas habitan en el entorno típico del desarrollo embrionario.

Generación de tejido muscular por las células madre musculares

Entre otras muchas consecuencias, el envejecimiento conlleva una pérdida progresiva de masa muscular. Una degeneración asociada de forma natural al paso de los años pero que, sin embargo, puede producirse de manera acelerada en algunas patologías, caso del cáncer o, sobre todo, de las distrofias musculares. Sin embargo, y según muestra un estudio llevado a cabo por investigadores del Instituto de Investigación Médica Sanford Burnham Prebys en La Jolla (EE.UU.), el tejido muscular podría ser regenerado con el uso de células madre musculares. O más concretamente, de células madre musculares embrionarias, mucho más capaces de formar nuevos tejidos que sus homónimas obtenidas de los adultos.

Como explica Matthew Tierney, co-autor de esta investigación publicada en la revista «Cell Reports», «en nuestro estudio hemos observado que las células madre musculares embrionarias reestructuran su microentorno mediante la secreción de proteínas específicas, y luego hemos analizado cuáles son las condiciones idóneas de este microambiente para que las células madre musculares adultas generen nuevo tejido muscular de la forma más eficiente posible. Es decir, las células madre musculares adultas normalmente colaboran en el crecimiento del músculo, pero esta no es una función intrínseca de este tipo de células. Sin embargo, como muestran nuestros resultados, esta situación puede modificarse».

Concretamente, el estudio muestra cómo las células madre musculares embrionarias secretan proteínas que componen la matriz extracelular, esto es, la estructura que mantiene unida a las células para formar un tejido. Sin embargo, y una vez maduran en células madre musculares adultas, adquieren otras funciones y responsabilidades, por lo que secretan otro tipo de proteínas.

El resultado es que las células madre musculares embrionarias tienen como función primordial la generación de nuevo tejido muscular, orientadas a la reparación de las lesiones en el músculo y a dividirse para constituir un ‘bote’ de células madre embrionarias que garanticen la curación de las futuras lesiones.

Como indica Alessandra Sacco, directora del estudio, «nuestros resultados ayudan a explicar la diferente capacidad que tienen las células madre musculares embrionarias y las adultas a la hora de reparar el músculo. Un hallazgo sumamente importante y necesario dado que, aún en la actualidad, no contamos con tratamientos disponibles para las distrofias musculares y los trastornos que cursan con una pérdida de tejido muscular».

Y este hallazgo, ¿tiene alguna aplicación en la práctica clínica? Es decir, ¿podría utilizarse para el tratamiento de aquellas enfermedades en las que, caso de las distrofias musculares, la degeneración progresiva del tejido muscular supera la capacidad regenerativa de las células madre musculares adultas? Pues según destacan los autores, sí, dado que «nuestro estudio demuestra que las células madre musculares adultas que habitan en un microentorno con características embrionarias tienen mayor capacidad de regeneración muscular, lo que ofrece una base para el desarrollo de fármacos que puedan dirigir esta transición».

Como concluye Alessandra Sacco, «el comportamiento de las células está condicionado por su entorno estructural y bioquímico. Así, la modificación de este microambiente se presenta como un enfoque cada vez más aceptado en el tratamiento de numerosas enfermedades, desde el cáncer a las patologías cardiovasculares y neurodegenerativas. Estamos realmente emocionados con las posibles implicaciones de nuestro estudio en el tratamiento de las enfermedades musculares, y seguiremos trabajando para que nuestras conclusiones puedan ser aplicadas en el desarrollo de tratamientos».

New research shows young muscle stem cells can improve adult muscle regeneration

Fuente: http://medicalxpress.com/news/2016-02-young-muscle-stem-cells-adult.html

Muscle stem cells both generate new muscle (shown here in green) and regenerate it after damage.

Scientists at Sanford Burnham Prebys Medical Discovery Institute (SBP) have found a key to enhancing repair of damaged muscle. In work published in Cell Reports, scientists describe why fetal muscle stem cells (MuSCs) are better at regenerating muscle compared to adult MuSCs. The research opens the door for new approaches to treat muscle diseases including muscular dystrophies, which affect approximately 50,000 people in the U.S., and muscle wasting associated with cancer and aging.

"We found that fetal MuSCs remodel their microenvironment by secreting specific proteins, and then examined whether that same microenvironment can encourage adult MuSCs to more efficiently generate new muscle. It does, which means that how adult MuSCs normally support muscle growth is not an intrinsic characteristic, but can be changed," explained Matthew Tierney, a graduate student at SBP and first author of the study.

The proteins that fetal MuSCs secrete are part of the extracellular matrix (ECM), the meshwork of strand-like proteins and starches that make up the structure of MuSCs' microenvironment. As fetal MuSCs mature into adult MuSCs, they take on different responsibilities and help change their microenvironment over time to support their distinct functions. Fetal MuSCs are geared toward creating new muscle, whereas adult MuSCs repair damaged muscle and self-replicate to sustain the pool of stem cells to mend future injuries.

In muscular dystrophies and muscle wasting, progressive degeneration overwhelms the regenerative capacity of adult MuSCs. The new study, showing that adult MuSCs living in a microenvironment with fetal characteristics are better at regenerating muscle, provides rationale for developing drugs that could trigger this transition.

"These results help explain the differences between the capacity of fetal and adult MuSCs to repair muscle. Such an understanding is urgently needed, as no treatments are yet available for muscular dystrophies and muscle-wasting disorders," stated Alessandra Sacco, Ph.D., associate professor in the Development, Aging, and Regeneration Program at SBP and senior author of the study.

"Our findings fit with the growing appreciation of the importance of a cell's structural and biochemical surroundings in influencing cellular behavior. Managing the microenvironment is an emerging approach to treat many diseases, from cancer to cardiovascular disease to neurodegeneration. We're excited about the implications of our research for treating muscle diseases, and look forward to applying our conclusions toward development of therapies."

Explore further: Stem cell foundation for muscular dystrophy treatment

Journal reference: Cell Reports

Nueva terapia genética de células madre que podría ser capaz de tratar la distrofia muscular de Duchenne

Fuente: http://noticiasdelaciencia.com/not/18306/nueva-terapia-genetica-de-celulas-madre-que-podria-ser-capaz-de-tratar-la-distrofia-muscular-de-duchenne/es/

Una nueva terapia genética con células madre, todavía en fase experimental, podría aplicarse, si se cumplen las expectativas sobre su validez, al 60 por ciento de las personas que sufren de distrofia muscular de Duchenne, una de las enfermedades genéticas mortales más habituales en la infancia y adolescencia (los afectados no suelen vivir mucho más allá de esa franja de edad).

La técnica ideada por el equipo de las científicas April Pyle, Courtney Young y Melissa Spencer, de la Universidad de California en Los Ángeles, Estados Unidos, utiliza una tecnología de edición genética llamada CRISPR/Cas9 para corregir las mutaciones genéticas que causan la enfermedad, y se ha diseñado teniendo en mente su posible uso médico futuro para tratarla, aunque, tal como advierte Spencer, este método se encuentra probablemente todavía a 10 años de ser probado en personas.

La enfermedad de Duchenne aparece normalmente a través de una mutación en un gen responsable de una proteína esencial. En las personas sin la enfermedad, esa proteína ayuda a fortalecer y conectar fibras musculares y células. Existen cientos de mutaciones en el gen que pueden llevar a la enfermedad, pero en el 60 por ciento de las personas con ella, su mutación sucede en un punto muy específico del gen.

De izquierda a derecha, April Pyle, Courtney Young y Melissa Spencer, coautoras del estudio, en el laboratorio del Centro Broad de Investigación en Células Madre de la UCLA.

Las mutaciones de la enfermedad de Duchenne causan una producción anormalmente baja de la proteína distrofina, lo que a su vez hace que los músculos se degeneren y se hagan progresivamente más débiles. Los síntomas empiezan usualmente a principios de la niñez; los pacientes pierden gradualmente movilidad y suelen fallecer por fallos cardiacos o respiratorios hacia los 20 años de edad. Algunos medicamentos actuales pueden tratar los síntomas de la enfermedad, pero ninguno puede detener su progresión o mejorar de forma significativa la calidad de vida de los pacientes, y no existe actualmente una forma de revertirla o curarla.

Información adicional

Stem cell gene therapy could be key to treating Duchenne muscular dystrophy

Fuente: http://medicalxpress.com/news/2016-02-stem-cell-gene-therapy-key.html

Skeletal muscles without dystrophin (top row) and after dystrophin has been restored (bottom) using the CRISPR/Cas9 platform developed by UCLA scientists.

Scientists at the UCLA Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research and Center for Duchenne Muscular Dystrophy at UCLA have developed a new approach that could eventually be used to treat Duchenne muscular dystrophy. The stem cell gene therapy could be applicable for 60 percent of people with Duchenne, which affects approximately 1 in 5,000 boys in the U.S. and is the most common fatal childhood genetic disease.

The approach uses a technology called CRISPR/Cas9 to correct genetic mutations that cause the disease. The study, which was led by co-senior authors April Pyle and Melissa Spencer and first author Courtney Young, was published in the journal Cell Stem Cell.

The researchers designed the approach to be useful in a clinical setting in the future.

"This method is likely 10 years away from being tested in people," said Spencer, professor of neurology in the UCLA David Geffen School of Medicine, co-director of the Center for Duchenne Muscular Dystrophy at UCLA and member of the Broad Stem Cell Research Center. "It is important that we take all the necessary steps to maximize safety while quickly bringing a therapeutic treatment to patients in clinical trials."

Duchenne typically occurs through one mutation in a gene called dystrophin, which makes a protein with the same name. In people without the disease, the dystrophin protein helps strengthen and connect muscle fibers and cells. There are hundreds of mutations in the dystrophin gene that can lead to the disease, but in 60 percent of people with Duchenne, their mutation will occur within a specific hot spot of the gene.

Duchenne mutations cause abnormally low production of the dystrophin protein, which in turn causes muscles to degenerate and become progressively weaker. Symptoms usually begin in early childhood; patients gradually lose mobility and typically die from heart or respiratory failure around age 20. Some current medications can treat the disease's symptoms but none can stop the progression of the disease or significantly improve patients' quality of life—and there is currently no way to reverse or cure the disease.

The platform developed by the UCLA researchers focuses on the hot spot of the dystrophin gene.

To test the platform, they obtained skin cells from consenting patients at the Center for Duchenne Muscular Dystrophy, all of whom had mutations that fell within the dystrophin gene hot spot. The researchers reprogrammed the cells to create induced pluripotent stem cells in an FDA-compliant facility at the Broad Stem Cell Research Center; the use of this facility is an important step in the process as preclinical research moves toward human clinical trials. Induced pluripotent stem cells, or iPS cells, have the ability to become any type of human cell while also maintaining the genetic code from the person they originated from.

Next, the scientists removed the Duchenne mutations in the iPS cells using a gene editing platform they developed that uses the CRISPR/Cas9 technology. (CRISPR stands for "clustered regularly interspaced short palindromic repeats.") The platform targets and removes specific regions of the hot spot of the dystrophin gene, which harbors 60 percent of Duchenne mutations, which restores the missing protein.

CRISPR/Cas9 is a naturally occurring reaction that bacteria use to fight viruses. In 2012, scientists discovered they could adapt the process to make cuts in specific human DNA sequences. One part of the CRISPR/Cas9 system acts like a navigation system and can be programmed to seek out a specific part of the genetic code—a mutation, for example. The second part of the system can cut mutations out of the genetic code, and in some cases can replace the mutation with a normal genetic sequence.

Once the UCLA researchers had produced iPS cells that were free from Duchenne mutations, they differentiated the iPS cells into cardiac muscle and skeletal muscle cells and then transplanted the skeletal muscle cells into mice that had a genetic mutation in the dystrophin gene.

They found that the transplanted muscle cells successfully produced the human dystrophin protein.

The result was the largest deletion ever observed in the dystrophin gene using CRISPR/Cas9, and the study was the first to create corrected human iPS cells that could directly restore functional muscle tissue affected by Duchenne. (Previously, scientists had used CRISPR/Cas9 to repair mutations that affect smaller numbers of people with Duchenne, and in cell types that weren't necessarily clinically relevant.)

"This work demonstrates the feasibility of using a single gene editing platform, plus the regenerative power of stem cells to correct genetic mutations and restore dystrophin production for 60 percent of Duchenne patients," said Pyle, associate professor of microbiology, immunology and molecular genetics and member of the Broad Stem Cell Research Center.

Young, a UCLA predoctoral fellow and president of a UCLA student group called Bruin Allies for Duchenne, is particularly passionate about Duchenne research because she has a cousin with the disease.

"I already knew I was interested in science, so after my cousin's diagnosis, I decided to dedicate my career to finding a cure for Duchenne," Young said. "It makes everything a lot more meaningful, knowing that I'm doing something to help all the boys who will come after my cousin. I feel like I'm contributing and I'm excited because the field of Duchenne research is advancing in a really positive direction."

Duchenne muscular dystrophy is the most common and severe of the 30 forms of muscular dystrophy.

The UCLA researchers plan to develop strategies to test the Duchenne-specific CRISPR/Cas9 platform to treat the disease in animals as the next step toward perfecting a method that can be used in humans.

The CRISPR/Cas9 platform for Duchenne developed by the UCLA scientists is not yet available in clinical trials and has not been approved by the FDA for use in humans.

Explore further: New hope in fight against muscular dystrophy

More information: Courtney S. Young et al. A Single CRISPR-Cas9 Deletion Strategy that Targets the Majority of DMD Patients Restores Dystrophin Function in hiPSC-Derived Muscle Cells, Cell Stem Cell (2016). DOI: 10.1016/j.stem.2016.01.021

Journal reference: Cell Stem Cell

Revelan que la distrofia muscular de Duchenne afecta directamente a las células madre musculares

Fuente: http://noticias.lainformacion.com/salud/investigacion-medica/investigaciones-desvelan-que-la-distrofia-muscular-de-duchenne-es-una-enfermedad-de-las-celulas-madre_oWLJKAXYVuJTGYwxu07GR3/

• La distrofia muscular de Duchenne afecta directamente a las células madre musculares, este hallazgo desecha la premisa que señalaba únicamente al deterioro celular como responsable de la patología.
• Las investigaciones, aún solo probadas en animales, podrían generar nuevos tratamientos que alivien esta patología que afecta a uno de cada 3.600 niños.

Un nuevo estudio del Hospital de Ottawa y la Universidad de Ottawa, en Canadá, está a punto de cambiar por completo la comprensión sobre la distrofia muscular de Duchenne y allanar el camino para tratamientos más eficaces. El trabajo, publicado en la revista 'Nature Medicine', muestra que la distrofia muscular de Duchenne afecta directamente a las células madre musculares.

"Durante casi 20 años, hemos pensado que la debilidad muscular observada en pacientes con distrofia muscular de Duchenne se debe principalmente a problemas en sus fibras musculares, pero nuestra investigación muestra que también se debe a defectos intrínsecos en la función de sus células madre de los músculos", afirma el autor principal del estudio, el doctor Michael Rudnicki.

"Esto cambia completamente nuestra comprensión de la distrofia muscular de Duchenne y eventualmente podría llevar a tratamientos más eficaces", destaca Rudnicki, director del Programa de Medicina Regenerativa del Hospital de Ottawa y profesor de la Universidad de Ottawa, además de titular de la Cátedra de Investigación de Canadá en Genética Molecular.

La distrofia muscular de Duchenne es la forma más común de distrofia muscular, que afecta a aproximadamente uno de cada 3.600 niños. Es causada por mutaciones genéticas que dan como resultado la pérdida de la proteína distrofina, que lleva a la debilidad muscular progresiva y la muerte durante la segunda o tercera década de la vida.

Las células madre del músculo son responsables de la reparación del músculo después de las lesiones normales y el ejercicio. En respuesta al daño muscular, estas células madre se dividen para generar células precursoras que se convierten en las fibras que forman los músculos.

Durante muchos años, se pensaba que la distrofina era una proteína estructural sencilla que sólo se encuentra en las fibras musculares. En el estudio actual, Rudnicki y su equipo descubrieron que las células madre musculares también expresan la proteína distrofina y sin esta proteína producen diez veces menos células precursoras del músculo, que generan a su vez un menor número de fibras musculares funcionales. También descubrieron que la distrofina es un miembro clave de la maquinaria molecular que permite a las células madre de músculo presentir su orientación hacia tejido circundante.

"Las células madre del músculo que carecen de distrofina no puede decir qué dirección está en marcha y qué dirección está reducida --apunta Rudnicki--. Esto es crucial porque las células madre de músculo necesitan percibir su entorno para decidir si producir más células madre o formar nuevas fibras musculares. Sin esta información, las células madre de músculo no se pueden dividir adecuadamente y no pueden reparar el músculo dañado".

Esta investigación se llevó a cabo en células de ratón, pero se espera que los resultados se reproduzcan en los seres humanos, ya que la proteína distrofina es casi idéntica en todos los animales. Los tratamientos actuales para la distrofia muscular de Duchenne se limitan a los esteroides y la terapia física para ralentizar la enfermedad y disminuir los síntomas. También se están investigando enfoques experimentales, como la terapia génica, pero la investigación de Rudnicki sugiere que estas vías tendrán que modificarse para dirigirse a las células madre musculares así como a las fibras musculares.

"Ya estamos viendo enfoques para corregir este problema en las células madre de músculo --relata Rudnicki--. No estoy seguro de si alguna vez curaremos la distrofia muscular de Duchenne, pero estoy muy esperanzado de que algún día en el futuro, tendremos nuevas terapias que corrijan la capacidad de las células madre de músculo para reparar los músculos de los pacientes afectados y convertir esta enfermedad devastadora y mortal en una enfermedad crónica pero manejable".

El descubrimiento ha sido aclamado por los expertos en la materia, entre ellos el doctor Ronald Worton, quien codescubrió el gen de la distrofia muscular de Duchenne en 1987 y trabajó como vicepresidente de Investigación del Hospital de Ottawa durante 11 años.

"Cuando descubrimos el gen de la distrofia muscular de Duchenne, había grandes esperanzas de que seríamos capaces de desarrollar un nuevo tratamiento con bastante rapidez -relata Worton, que ahora está jubilado--. Esto ha sido mucho más difícil de lo que inicialmente pensábamos, pero la investigación del doctor Rudnicki es un gran avance que debe renovar la esperanza de los investigadores, los pacientes y sus familias".

Primer ensayo en fetos con células madre para corregir los «huesos de cristal»

Fuente: http://www.abc.es/salud/noticias/20151013/abci-ensayo-celulas-madre-fetos-201510121259.html

El Instituto Karolinska y el Hospital infantil Ormond Street probarán en 15 mujeres embarazadas la terapia.

El objetivo es que las células madre permitan que los huesos se formen intraútero más fuertes

Por primera vez, un equipo de científicos suecos y británicos intentará corregir antes del nacimiento la osteogénesis imperfecta, también llamada la «enfermedad de los huesos de cristal».

Los niños diagnosticados con esta rara patología genética poseen un esqueleto tan débil, que ante la mínima presión o movimiento sus huesos se rompen. La mayoría nacen ya con múltiples fracturas y los que sobreviven lo hacen con una media de 15 huesos rotos al año, caída de dientes y a veces problemas de crecimiento y audición.

Quince mujeres embarazadas, entre la semana 20 y 34 de gestación a las que se les diagnostique esta malformación, se someterán a una terapia que consistirá en introducir células madre a través de su útero. Las células proceden de tejidos materno-fetales de otras gestaciones. El objetivo es que las células madre sean capaces de regenerar hueso y cartílago para fortalecer el esqueleto de los fetos. Los primeros tratamientos empezarán el próximo mes de enero y el ensayo se prolongará durante dos años para conseguir suficiente número de pacientes.

No es la primera vez que se prueba esta terapia. Este tipo de trasplante celular ya se ha utilizado en dos casos de osteogénesis imperfecta, pero sin un ensayo clínico regulado será imposible demostrar que realmente funciona. En los dos casos tratados se ha visto que alivia los síntomas. ¿Por qué no esperar al nacimiento? La hipótesis del Hospital Infantil Ormond Street de Londres y del Instituto Karolinska de Estocolmo es que intraútero el tratamiento sea más eficaz y las células puedan fortalecer los huesos cuando aún está en pleno desarrollo.

El riesgo de que las células produzcan un rechazo «es bajo», explicó a la BBC Cecilia Gotherstrom, del Instituto Karolinska. El momento elegido para el trasplante, entre las 20 y las 34 semanas de gestación, también es el más seguro. «Si pudiéramos reducir la frecuencia de las fracturas, fortalecer el uso y mejorar su crecimiento, ya habremos dado un gran paso en el tratamiento de la enfermedad».

Gotherstrom cree que si el ensayo tiene éxito «allanará el camino para otros tratamientos prenatales cuando los padres no tienen más opción». Otra enfermedad candidata a un tratamiento similar podría ser la distrofia muscular o enfermedad de Duchenne.

El origen de la osteogénesis es genético con lo que la terapia celular no curará la enfermedad, pero la paliará. Cada uno de los genes que originan la osteogénesis imperfecta están relacionados de alguna manera con la producción de colágeno en el cuerpo. El colágeno es el material que ayuda a mantener los huesos fuertes. Cuando estos genes dejan de funcionar como deben, no se produce suficiente colágeno o el colágeno no funciona adecuadamente. Esto hace que los huesos se debiliten y se rompan con facilidad.

Los tratamientos actuales contra la osteogénesis pasan por utilizar prótesis ortopédicas, realizar ejercicios de fisioterapia para reducir discapacidades motoras y tomar bifosfonatos, los medicamentos que también se indican para fortalecer los huesos en las personas con osteoporosis. La prevención del déficit de vitamina D y de calcio es esencial durante toda la vida. La cirugía también permite corregir las deformaciones óseas y espinales y prevenir las fracturas de huesos largos.

La terapia con células madre podría tratar casos de distrofia muscular

Fuente: http://www.diariomedico.com/2015/08/03/area-cientifica/especialidades/biotecnologia/investigacion/terapia-con-celulas-madre-podria-tratar-casos-de-distrofia-muscular

Un estudio del Birgham and Women´s Hospital (Reino Unido) y el Harvard Stem Cell Institute (Reino Unido) ha conseguido desarrollar células que derivan en fibras musculares con capacidad de contracción y de reproducirse en grandes números. El trabajo ha sido publicado por Nature Biotechnology y puede resultar muy útil en el estudio de la distrofia muscular.

Hasta la aparición de esta investigación ya se había conseguido crear pequeñas cantidades de células musculares, pero este proyecto buscaba una técnica que permitiese desarrollar grandes números para un uso eficiente en materia clínica. Oliver Pourquie, director del estudio, explica que el proceso implicó recrear y analizar todas las fases en el desarrollo de la célula muscular para generar líneas que se pudieran mezclar correctamente para imitar, en cada fase, el proceso de creación celular.

El equipo puso a prueba su trabajo consiguiendo fibras sanas a partir de células madre humanas y de ratones, así como células satélite, que cuando se añaden a ratones  con distrofia muscular de Duchenne, producen nuevas fibras musculares. Este último descubrimiento se estudia como camino para terapias en humanos.

Además de la efectividad demostrada en la distrofia muscular de Duchenne, este protocolo podría analizarse para otras patologías musculares como sarcopenia o cachexia. Pourquie advierte que la habilidad para producir células musculares en laboratorio es la pieza que faltaba para poder aventurarse en la terapia de regeneración muscular.

Japón busca diversos tratamientos para la distrofia muscular con células iPS

Fuente: http://www.abc.es/agencias/noticia.asp?noticia=1820299

Dos equipos de investigación japoneses presentarán en una conferencia en Yokohama (vecina de Tokio) sus avances para hallar, mediante células pluripotentes inducidas (iPS), tratamientos para la distrofia muscular que frenen el desarrollo de la enfermedad.

Uno de los grupos, formado por personal de la Universidad de Kioto y de la compañía química Asahi Kasei, ha creado células madre de músculo esquelético a partir de iPS, un tipo de célula reprogramada que tiene capacidad de convertirse en cualquier tipo de tejido.

Estas células madre se inyectaron en la pata de un ratón con distrofia y se adhirieron a la masa muscular, la cual contribuyeron a regenerar gracias a una proteína específica.

El profesor de la Universidad de Kioto que lidera el proyecto, Hidetoshi Sakurai, dijo que este descubrimiento podría conducir al desarrollo de un terapia para ralentizar el avance de la enfermedad.

El equipo realizará pruebas en perros con la esperanza de certificar la seguridad del tratamiento con la vista puesta en comenzar a realizar pruebas clínicas en el futuro.

Por su parte, otro equipo del Centro Nacional de Neurología y Psiquiatría de Tokio -que también expondrá sus hallazgos en la conferencia que celebra la Sociedad Japonesa de Medicina Regenerativa en Yokohama- está trabajando en un sistema de trasplante celular.

El grupo, liderado por el doctor Shinichi Takeda, creó también células madre musculares a partir de iPS y las modificó a nivel molecular antes de trasplantarlas a un ratón aquejado de distrofia.

Parte del tejido afectado por la enfermedad resultó regenerado y algunos músculos recuperaron la movilidad tres semanas después del trasplante.

Este equipo también espera empezar a probar la terapia en perros el año próximo antes de la fase de ensayo clínico.

La distrofia muscular es un trastorno degenerativo hereditario poco frecuente cuyos síntomas suelen manifestarse en la infancia y que ataca y debilita a los músculos que producen los movimientos voluntarios del cuerpo.

Su forma más usual, la distrofia muscular de Duchenne, puede causar fallos respiratorios y cardíacos, y actualmente no existe ningún tratamiento para curarla.

Stem cells faulty in Duchenne muscular dystrophy, Stanford researchers find

Fuente: http://www.sciencecodex.com/stem_cells_faulty_in_duchenne_muscular_dystrophy_stanford_researchers_find-147754

Like human patients, mice with a form of Duchenne muscular dystrophy undergo progressive muscle degeneration and accumulate connective tissue as they age. Now, researchers at the Stanford University School of Medicine have found that the fault may lie at least partly in the stem cells that surround the muscle fibers.

They've found that during the course of the disease, the stem cells become less able to make new muscle and instead begin to express genes involved in the formation of connective tissue. Excess connective tissue -- a condition called fibrosis -- can accumulate in many organs, including the lungs, liver and heart, in many different disorders. In the skeletal muscles of people with muscular dystrophy, the fibrotic tissue impairs the function of the muscle fibers and leads to increasing weakness and stiffness, which are hallmarks of the disease.

The researchers discovered that this abnormal change in stem cells could be inhibited in laboratory mice by giving the animals a drug that is already approved for use in humans. The drug works by blocking a signaling pathway involved in the development of fibrosis. Although much more research is needed, the scientists are hopeful that a similar approach may one day work in children with muscular dystrophy.

"These cells are losing their ability to produce muscle, and are beginning to look more like fibroblasts, which secrete connective tissue," said Thomas Rando, MD, PhD, professor of neurology and neurological sciences. "It's possible that if we could prevent this transition in the muscle stem cells, we could slow or ameliorate the fibrosis seen in muscular dystrophy in humans."

A paper describing the researchers' findings will be published in Science Translational Medicine. Rando, the paper's senior author, is director of the Glenn Laboratories for the Biology of Aging and founding director of the Muscular Dystrophy Association Clinic at Stanford. Former postdoctoral scholar Stefano Biressi, PhD, is the lead author. Biressi is now at the Centre for Integrative Biology at the University of Trento in Italy.

Duchenne muscular dystrophy is a devastating disease that affects about 1 in every 3,600 boys born in the United States. Patients usually experience severe, progressive muscle weakness that confines them to a wheelchair in early adolescence and eventually leads to paralysis. It's caused by mutations in the dystrophin gene, which encodes the dystrophin protein. The dystrophin protein serves to connect muscle fibers to the surrounding external matrix. This connection stabilizes the fibers, enhancing their strength and preventing injury. Sufferers are nearly always boys because the dystrophin gene is located on the X chromosome. (Girls would need to inherit two faulty copies, which is unlikely because male carriers often die in early adulthood.)

Under normal conditions, muscle stem cells respond to muscle damage by dividing into cells, one of which becomes new muscle, while the other remains a stem cell. However, in the mice missing the dystrophin gene, the muscle stem cells slowly assume a different fate. They begin to resemble fibroblasts instead of muscle-making machines.

To conduct the research, Biressi and Rando used a strain of laboratory mice in which the muscle stem cells were engineered to glow with a fluorescent light when treated with a drug called tamoxifen. They then bred the mice with another strain in which the dystrophin gene is mutated, and followed the fate of the cells over time.

The researchers found that the expression of myogenic genes, which are associated with the regeneration of muscle in response to injury, was nearly completely lacking in many of the muscle stem cells in the mice after just 11 months, while the expression of fibrotic genes had increased compared with that of control animals. The cells from the dystrophic animals were also oddly located: Rather than being nestled next to the muscle fibers, they had begun to move away into the spaces between tissues.

Rando and Biressi knew that a similar, but much less pronounced, accumulation of connective tissue in muscle fibers occurs during normal aging. That process is governed by signaling proteins, which include the Wnt and TGF-beta protein families. Wnt plays a critical role in embryonic development and cancer; TGF-beta controls cell division and specialization. They wondered whether blocking the Wnt/TGF-beta pathway in the dystrophic mice would inhibit fibrosis in the animals' muscles.

The researchers turned to a drug called losartan, which is used to treat high blood pressure. Losartan inhibits the expression of the genes for TGF-beta types 1 and 2. The researchers thought it would probably interrupt the signaling pathway that leads the muscle stem cells astray.

Treating the mice with losartan, they found, did in fact prevent the muscle stem cells from expressing fibrosis-associated genes and partially maintained their ability to form new muscle.

"This scar tissue, or fibrosis, leaves the muscle less elastic and impairs muscle function," Rando said. "So we'd like to understand why it happens, and how to prevent it. It's also important to limit fibrosis to increase the likelihood of success with other possible therapies, such as cell therapy or gene therapy."

Because TGF-beta type 1 plays many roles throughout the body, the researchers are now working to find ways to specifically inhibit TGF-beta type 2, which is involved in the transition of the muscle stem cells. They're also interested in learning how to translate the research to other diseases.

"Fibrosis seems to occur in a vicious cycle," Rando said. "As the muscle stem cells become less able to regenerate new muscle, the tissue is less able to repair itself after damage. This leads to fibrosis, which then further impairs muscle formation. Understanding the biological basis of fibrosis could have a profound effect on many other diseases."

iPS cells used to correct genetic mutations that cause muscular dystrophy

Fuente: http://medicalxpress.com/news/2014-11-ips-cells-genetic-mutations-muscular.html

This image shows immunofluorescence staining of skeletal cells differentiated from DMD-iPS cells. Untreated DMD skeletal cells do not express dystrophin (green) due to the deletion of exon 44. However, after any of the three correction strategies are applied to iPS cells, differentiation into skeletal cells results in normal dystrophin expression. Scale bar, 50 μm. 

Researchers at the Center for iPS Cell Research and Application (CiRA), Kyoto University, show that induced pluripotent stem (iPS) cells can be used to correct genetic mutations that cause Duchenne muscular dystrophy (DMD). The research, published in Stem Cell Reports, demonstrates how engineered nucleases, such as TALEN and CRISPR, can be used to edit the genome of iPS cells generated from the skin cells of a DMD patient. The cells were then differentiated into skeletal muscles, in which the mutation responsible for DMD had disappeared.

DMD is a severe muscular degenerative disease caused by a loss-of-function mutation in the dystrophin gene. It inflicts 1 in 3500 boys and normally leads to death by early adulthood. Currently, very little is available in terms of treatment for patients outside palliative care. One option gaining interest is genomic editing by TALEN and CRISPR, which have quickly become invaluable tools in molecular biology. These enzymes allow scientists to cleave genes at specific locations and then modify the remnants to produce a genomic sequence to their liking. However, programmable nucleases are not pristine and often mistakenly edit similar sequences that vary a few base pairs from the target sequence, making them unreliable for clinical use because of the potential for undesired mutations.

For this reason, induced pluripotent stem cells (iPS cells) are ideal models, because they provide researchers an abundance of patient cells on which to test the programmable nucleases and find optimal conditions that minimize off-target modifications. CiRA scientists took advantage of this feature by generating iPS cells from a DMD patient. They used several different TALEN and CRISPR to modify the genome of the iPS cells, which were then differentiated into skeletal muscle cells. In all cases, dystrophin protein expression was convalesced, and in some cases, the dystrophin gene was fully corrected.

One key to the success was the development of a computational protocol that minimized the risk of off-target editing. The team built a database that all possible permutations of sequences up to 16 base pairs long. Among these, they extracted those that only appear once in the human genome, i.e. unique sequences. DMD can be caused by several different mutations; in the case of the patient used in this study, it was the result of the deletion of exon 44. The researchers therefore built a histogram of unique sequences that appeared in a genomic region that contained this exon. They found a stack of unique sequences in exon 45. According to Akitsu Hotta, who headed the project and holds joint positions at CiRA and the Institute for Integrated Cell-Materials Sciences at Kyoto University, "Nearly half the human genome consists of repeated sequences. So even if we found one unique sequence, a change of one or two base pairs may result in these other repeated sequences, which risks the TALEN or CRISPR editing an incorrect region. To avoid this problem, we sought a region that hit high in the histogram".

With this target, the team considered three strategies to modify the frame-shift mutation of the dystrophin gene: exon skipping by connecting exons 43 and 46 to restore the reading frame, frame shifting by incorporating insertion or deletion (indel) mutations, and exon knock-in by inserting exon 44 before exon 45. All three strategies effectively increased dystrophin synthesis in differentiated skeletal cells, but only the exon knock-in approach recovered the gene to its natural state. Importantly, editing showed very high specificity, suggesting that their computational approach can be used to minimize off-target editing by the programming nucleases.

Moreover, the paper provides a proof-of-principle for using iPS cell technology to treat DMD in combination with TALEN or CRISPR. The group now aims to expand this protocol to other diseases. First author Lisa Li explains, "We show that TALEN and CRISPR can be used to correct the mutation of the DMD gene. I want to apply the nucleases to correct mutations for other genetic-based diseases like point mutations".

More information: Precise correction of the DYSTROPHIN gene in Duchenne Muscular Dystrophy patient-derived iPS cells by TALEN and CRISPR-Cas9, Stem Cell Reports, 2014.

Cardiac stem cell therapy may heal heart damage caused by Duchenne muscular dystrophy

Fuente: http://medicalxpress.com/news/2014-11-cardiac-stem-cell-therapy-heart.html

Researchers at the Cedars-Sinai Heart Institute have found that injections of cardiac stem cells might help reverse heart damage caused by Duchenne muscular dystrophy, potentially resulting in a longer life expectancy for patients with the chronic muscle-wasting disease.

The study results were presented at a Breaking Basic Science presentation during the American Heart Association Scientific Sessions in Chicago. After laboratory mice with Duchenne muscular dystrophy were infused with cardiac stem cells, the mice showed steady, marked improvement in heart function and increased exercise capacity.

Duchenne muscular dystrophy, which affects 1 in 3,600 boys, is a neuromuscular disease caused by a shortage of a protein called dystrophin, leading to progressive muscle weakness. Most Duchenne patients lose their ability to walk by age 12. Average life expectancy is about 25. The cause of death often is heart failure because the dystrophin deficiency leads to cardiomyopathy, a weakness of the heart muscle that makes the heart less able to pump blood and maintain a regular rhythm.

"Most research into treatments for Duchenne muscular dystrophy patients has focused on the skeletal muscle aspects of the disease, but more often than not, the cause of death has been the heart failure that affects Duchenne patients," said Eduardo Marbán, MD, PhD, director of the Cedars-Sinai Heart Institute and study leader. "Currently, there is no treatment to address the loss of functional heart muscle in these patients."

During the past five years, the Cedars-Sinai Heart Institute has become a world leader in studying the use of stem cells to regenerate heart muscle in patients who have had heart attacks. In 2009, Marbán and his team completed the world's first procedure in which a patient's own heart tissue was used to grow specialized heart stem cells. The specialized cells were then injected back into the patient's heart in an effort to repair and regrow healthy muscle in a heart that had been injured by a heart attack. Results, published in The Lancet in 2012, showed that one year after receiving the experimental stem cell treatment, heart attack patients demonstrated a significant reduction in the size of the scar left on the heart muscle.

Earlier this year, Heart Institute researchers began a new study, called ALLSTAR, in which heart attack patients are being infused with allogeneic stem cells, which are derived from donor-quality hearts.

Recently, the Heart Institute opened the nation's first Regenerative Medicine Clinic, designed to match heart and vascular disease patients with appropriate stem cell clinical trials being conducted at Cedars-Sinai and other institutions.

"We are committed to thoroughly investigating whether stem cells could repair heart damage caused by Duchenne muscular dystrophy," Marbán said.

In the study, 78 lab mice were injected with cardiac stem cells. Over the next three months, the lab mice demonstrated improved pumping ability and exercise capacity in addition to a reduction in heart inflammation. The researchers also discovered that the stem cells work indirectly, by secreting tiny fat droplets called exosomes. The exosomes, when purified and administered alone, reproduce the key benefits of the cardiac stem cells.

Marbán said the procedure could be ready for testing in human clinical studies as soon as next year. The process to grow cardiac-derived stem cells was developed by Marbán when he was on the faculty of Johns Hopkins University. Johns Hopkins has filed for a patent on that intellectual property and has licensed it to Capricor, a company in which Cedars-Sinai and Marbán have a financial interest. Capricor is providing funds for the ALLSTAR clinical trial at Cedars-Sinai.

The Cedars-Sinai Heart Institute has been at the forefront of developing investigational stem cell treatments for heart attack patients.

Researchers working to regenerate heart and nerve cells

Fuente: http://medicalxpress.com/news/2014-09-regenerate-heart-nerve-cells.html

Under a microscope inside a lab at UT Southwestern Medical Center, a dish of cells pulsates with the rhythm of a human heart.

Days ago, these building blocks of heart muscle had a different identity altogether: They were scar-forming cells that proliferate in the wake of a heart attack and weaken the organ's ability to pump blood.

Researchers at UT Southwestern and other institutions may have found a way to reverse the damage that patients sustain from heart attacks, traumatic brain injuries and other conditions.

They accomplish this by converting a less desirable type of cell, such as a scar-forming cell, into a highly desirable one, such as a nerve cell, using a process known as direct reprogramming.

Most recent efforts to convert one cell type into another have relied on stem cells - immature versions of adult cells. But stem cells can be difficult to manipulate and have caused controversy because they are sometimes derived from embryos donated by fertility clinics.

Many scientists say direct reprogramming is a promising new approach to regenerative medicine - a field dedicated to curing disease by helping the body repair and regrow its own tissues.

In recent years, scientists have used the method to grow new brain cells, liver cells, pancreatic tissue and parts of the inner ear responsible for hearing loss.

Researchers hope to one day develop drugs that will enable patients' bodies to repair their own damaged organs, much the way a salamander can regrow its own heart and a python can double the size of its liver.

At UT Southwestern's new Hamon Center for Regenerative Science and Medicine, researchers are focused on cultivating heart and nerve cells.

The center, led by biologist Eric Olson, opened in May with a $10 million gift from the Hamon Charitable Foundation. Its areas of research include stem cells as well as direct reprogramming.

Olson hopes the center will help UT Southwestern attract top college graduates from around the U.S.

"Regenerative biology is one of the most popular majors," he says. "The center will give us a new tool to recruit some of the best students to Dallas."

Olson's career-long interest in how a single cell develops into the trillions that make up the human body led to his lab's current work.

"I wanted to understand how specialized cells were formed and how large sets of genes turned on and off during development," he said.

After pondering what cell type to focus on, Olson settled on muscle cells, because muscles make up 40 percent of our body mass and turn on thousands of genes as they develop.

The idea was that a deep understanding of one particular system could be applied more widely. It could also help scientists gain insight into how diseases develop when errors creep into the process.

Over the years, Olson's lab has uncovered several of the major genes that control muscle development.

Recent work from his lab has led to a promising approach to treating Duchenne muscular dystrophy, a congenital disease that causes muscles to progressively weaken and degenerate.

In the center's inaugural publication this month in the journal Science, Olson and his colleagues outlined a way to "edit" the gene abnormalities responsible for the disorder in a mouse and rectify the body's ability to grow healthy muscle.

Olson's lab extended its work into heart muscle cells in the early 1990s. At the time, Deepak Srivastava, then a postdoctoral researcher, was working in the lab.

"I was trained as a pediatric cardiologist and was interested in how the heart forms in the embryo and how that goes awry in human disease," says Srivastava, who now directs cardiac and stem cell research at the Gladstone Institutes and is a professor at the University of California San Francisco. The two went on to discover many of the genes that control heart development.

Using some of that research, Srivastava pioneered cardiac reprogramming several years later.

"We took the years of knowledge that our lab and other labs had developed about how nature normally makes a heart in the embryo and essentially redeployed those same methods in the adult heart," he says.

In a 2010 paper in the journal Cell, Srivastava showed that scar-forming cells known as fibroblasts could be converted into beating heart cells by adding just three ingredients. Those ingredients, proteins known as transcription factors, are master regulators that flip genes on and off. The genes involved are the same ones that direct heart formation in the womb.

In 2012, Srivastava and Olson, writing separate papers in the same issue of the journal Nature, showed that the process could be performed successfully in living mice.

Each group used a different combination of transcription factors to reprogram the cells, but both found that the technique improved heart function in the animals following a heart attack.

For the last two decades, stem cells have been virtually synonymous with regenerative medicine.

Scientists use them in many different ways. In one approach, researchers take a sample of skin, fat or bone marrow from a patient, convert the mature cells into their previous immature states, then reprogram them to form a new type of tissue.

In a second approach, scientists can extract stem cells from embryos and then convert them.

In clinical trials, researchers have also used a third approach: They have taken so-called adult stem cells from bone marrow and injected them into the heart, hoping the stem cells take on the properties of muscle cells.

Adult stem cells have had mixed results. "The reality is this has shown limited benefits after a decade of clinical trials," says Olson.

So far, researchers have tried direct reprogramming in mice and in human cells in a lab dish.

Chun-Li Zhang, a colleague of Olson's at the Hamon Institute, is using direct reprogramming to rebuild nerve cells, or neurons. He starts with glial cells, which reproduce in the brain and spinal cord following an injury and can form scars.

"Basically, these are the fibroblasts of the brain," he says.

In a series of papers published over the last year, Zhang and his colleagues reported generating new neurons from glial cells in mice following a traumatic brain or spinal cord injury. The lab is now investigating how much the new cells can contribute to the animals' recovery.

Most scientists who work on direct reprogramming are continuing their research on stem cells in parallel. "They each have advantages and disadvantages," says Srivastava.

George Daley, director of stem cell transplantation at Children's Hospital Boston and a past president of the International Society of Stem Cell Research, compared the effectiveness of the two methods in a paper published last month in the journal Cell.

Neurons and heart cells created using direct reprogramming "aren't as close to normal tissue as those generated from stem cells," he said.

Another advantage of using stem cells is that the process creates a lot more cells to work with than direct reprogramming.

"Right now, if you take a dish of fibroblasts in a lab and reprogram that dish, you can get maybe 10 percent of those cells to turn into heart muscle cells, and we'd like to improve that efficiency," says Olson.

Yet direct reprogramming, says Zhang, is more akin to true regeneration. "We design a way to help the tissue repair or regenerate itself," he says. Stem cells, by contrast, involve growing cells in a dish and then injecting them into patients.

The ultimate hope with direct reprogramming is that it will lead to a drug that will stimulate patients' bodies to heal themselves.

With both approaches, Food and Drug Administration-approved treatments are still at least several years away.

Srivastava is testing his direct reprogramming technique in pigs, whose hearts are closer in size to those of humans. The goal is to see if he can generate enough muscle to dramatically improve the heart's pumping ability.

If all goes well, he hopes to approach the FDA with a plan for clinical trials within two to three years.

"It's not inconceivable that we could know if this works in humans within the next five years," he says.

Journal reference: Cell Science