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Biotech companies leading the way with exosome human clinical trials – Born2Invest

Posted: February 9, 2020 at 7:50 pm

Testing a new therapeutic in human subjects for the first time is a major step in the translation of any novel treatment from the laboratory bench to clinical use.

When the therapeutic represents a paradigm shift, reaching this milestone is even more significant.

After years of planning, preparation and hard work to establish a base camp, starting human clinical trials is the first step towards the summit itself: gaining regulatory approval for product sales.

Exosomes tiny packets of proteins and nucleic acids (e.g. mRNA and miRNA) released by cells, that have powerful regenerative properties ranging from promoting wound healing to stimulating brain injury recovery following stroke represent just such a paradigm-shifting potential advance in human medicine.

The first commercial exosome therapeutics conference was held in Boston in September 2019 and over 15 companies participated.

This conference signals the emergence of exosomes as a new class of regenerative medicine products.

So far, just one or two of the companies working in the novel field of exosome-based therapies have reached the pivotal point and transitioned into human clinical trials. In this article we survey the field, starting with the pace-setters.

During the past few years, a handful of universities and research hospitals have carried out small scale, first-in-human Phase I clinical trials using exosomes. In each case where the study results are available, the exosome treatment was found to be safe and well-tolerated.

But the field has hotted up in the past few months, with the first companies reaching the pivotal point of testing exosome-based products in people.

On 28th January 2020, Melbourne-based Exopharm announced the first dosing under its first human clinical trial, becoming the first company to test exosomes potential for healing wounds in people.

The PLEXOVAL Phase I study will test Exopharms Plexaris product, a cell-free formulation of exosomes from platelets, which in preclinical animal studies have shown a regenerative effect, improving wound closure and reducing scarring.

The main readouts of the PLEXOVAL study the results of which are expected to be available sometime after mid-2020 will be safety, wound closure and scarring.

Joining Exopharm at the front of the pack is Maryland-based United Therapeutics.

Founded in 1996, United Therapeutics specialises in lung diseases and has a portfolio of FDA-approved conventional small molecule and biologic drugs on the market for a range of lung conditions.

On 26th June 2019, United Therapeutics announced approval for a Phase I trial (NCT03857841) of an exosome-based therapy against bronchopulmonary dysplasia (BDP), a condition common in preterm infants that receive assisted ventilation and supplemental oxygen.

Recruitment has commenced but dosing has not been announced. The study is due to conclude by December 2021. BDP is characterised by arrested lung growth and development, with health implications that can persist into adulthood.

Human clinical trials of a stem cell therapy for BDP, by Korean stem cell company Medipost, are already underway. However as with many stem cell therapies recent animal studies have shown that is the exosomes released by stem cells that are responsible for the therapeutic effect.

United Therapeutics therapy, UNEX-42, is a preparation of extracellular vesicles that are secreted from human bone marrow-derived mesenchymal stem cells. The company has not released any information about how its exosomes are produced or isolated.

A little behind the two leaders, three other companies have announced their aim to initiate their first clinical trials of exosome therapeutics within the next 12 months.

Launched in 2015, Cambridge, Massachusetts-based Codiak has long been considered among the leaders in developing exosome-based therapies.

Rather than exploiting the innate regenerative potential of select exosome populations, Codiak is developing engineered exosomes that feature a defined therapeutic payload. The companys initial focus has been to target immune cells, leveraging the immune system to combat cancer.

The company plans to initiate clinical trials of its lead candidate, exoSTING, in the first half of 2020. The therapeutic is designed to trigger a potent antitumor response from the patients own immune system, mediated by T cells. A second immuno-oncology candidate, exoIL-12, is due to enter clinical trials in the second half of 2020, the company says.

In nearby New Jersey, Avalon Globocare is also developing engineered exosomes. Its lead product, AVA-201, consists of exosomes enriched in the RNA miR-185, which are produced using engineered mesenchymal stem cells.

In animal tests, miR-185 suppressed cancer cell proliferation, invasion and migration in oral cancer. In July 2019, the company announced plans to start its first exosome clinical trial before the close of 2019. As of February 2020, however, no further announcement regarding this clinical trial has been made.

Avalon has also made no further announcement on a second planned clinical trial, also intended to start during the fourth quarter of 2019, of a second exosome candidate, AVA-202.

These angiogenic regenerative exosomes, derived from endothelial cells, can promote wound healing and blood vessel formation, the company says. The planned Phase I trial was to test AVA-202 for vascular diseases and wound healing.

Meanwhile, Miami-based Aegle Therapeutics plans to begin a Phase I/IIa clinical trial of its exosome therapy, AGLE-102, during 2020. AGLE-102 is based on native regenerative exosomes isolated from bone marrow mesenchymal stem cells.

After initially focussing on burns patients, in January 2020 to company announced had raised the funds to commence an FDA-cleared clinical trial of AGLE-102 to treat dystrophic epidermolysis bullosa, a rare paediatric skin blistering disorder. The company says it plans to commence this clinical trial in the first half of 2020.

A number of companies are in the preclinical phase of exosome therapy research.

Some of these companies have been set up specifically to develop exosome-based products. In the UK, Evox co-founded by University of Oxford researcher Matthew Wood in 2016 is developing engineered exosomes to treat rare diseases.

The company has developed or sourced technology that allows it to attach proteins to exosomes surface, or to load proteins or nucleic acids inside the exosome, to deliver a therapeutic cargo to a target organ.

Its lead candidate targets a lysosomal storage disorder called Niemann-Pick Disease type C, using exosomes that carry a protein therapeutic cargo. Evox says it plans to submit the Investigational New Drug (IND) application to the FDA during 2020, paving the way for the first clinical trial. It currently has five other candidates, for various indications, at the preclinical stage of development.

In Korea, Ilias and ExoCoBio are developing exosome therapeutics. Ilias founded by faculty from the Korean Advance Institute of Science and Technology specialises in loading large protein therapeutics into exosomes.

It is currently carrying out preclinical research toward treating sepsis, preterm labour and Gauchers disease. ExoCoBio is focusing on the native regenerative capacity of exosomes derived from mesenchymal stem cells, including to treat atopic dermatitis.

New companies continue to enter the exosome space. In August 2019, Carmine Therapeutics was launched, with the aim to develop gene therapies that utilize exosomes from red blood cells to deliver large nucleic acid cargoes. The company is targeting the areas of haematology, oncology and immunology.

Meanwhile, a wave of companies originally set up to develop live stem cell therapies are diversifying into stem cell derived exosome production and research.

It is now generally acknowledged that stem cell exosomes are the main therapeutically active component of stem cells, and that medical products based on exosomes will be safer to apply, and easier and cheaper to make and transport, than live cell therapies.

Originally established to produce neural stem cells for other research organisations, Aruna Bio has developed proprietary neural exosomes that can cross the blood brain barrier.

The company is now developing an exosome therapy for stroke. In October 2019, the Athens, Georgia-based company said had raised funding to support the research and development to enable its first IND application to the FDA in 2021.

In the UK, ReNeuron has also focussed on stroke, and has several clinical trials underway assessing its CTX stem cells to promote post stroke rehabilitation. The company is also working with third parties to investigate the drug- and gene therapy delivery potential of exosomes derived from CTX stem cells.

Switzerland-based Anjarium is also developing an exosome platform to selectively deliver therapeutics.20 The company is focussing on engineering exosomes loaded with therapeutic RNA cargo and displaying targeting moieties on its surface.

California-based Capricor has commenced clinical trials of a cardiosphere-derived stem cell therapy for the treatment of Duchenne muscular dystrophy (DMD).

At an earlier phase, its regenerative exosome therapy CAP-2003 is in pre-clinical development for a variety of inflammatory disorders including DMD.

A number of other stem cell companies, including TriArm, Creative Medical, AgeX Therapeutics and BrainStorm Cell Therapeutics, are reported to be investigating exosome-based therapies derived from their stem cell lines.

Exopharms position as a frontrunner in bringing exosomes into humans is no lucky accident. The companys operations are based around its unique, proprietary method for manufacturing and isolating exosomes, known as LEAP technology.

As academics and observers of the exosome field have pointed out, reliable and scalable exosome manufacture has threatened to be a major bottleneck that limits the translation of exosome therapeutics into clinical use. The standard laboratory-scale method for collecting the exosomes produced by cultured cells has been to spin the liquid cell culture medium in an ultracentrifuge, or pass it through a fine filter.

The most common technique used so far, the ultracentrifuge, has major scalability limitations. Issues include the high level of skill and manual labour required, the time-intensive nature of the process, and the associated costs of reagents and equipment. It is impossible to imagine collecting enough exosomes for a late stage clinical trial this way.

Another issue is the low purity of the exosomes collected. These techniques sort the contents of cell culture medium by their mass and/or size. Although the exosomes are concentrated, they could be accompanied by other biological components present in the cell culture medium that happen to be a similar size or mass to the exosome.

Importantly, a biotechnology company needs a proprietary step in the process to make a proprietary product over which it has exclusivity. Exopharms LEAP technology is a good example of a proprietary manufacturing step. Ultracentrifuge is not a proprietary process.

So the big players in the emerging exosome field have generally placed a strong emphasis on developing their manufacturing and purification capability.

Exopharm developed a chromatography-based purification method, in which a patent-applied-for inexpensive functionalised polymer a LEAP Ligand is loaded into a chromatography column. The LEAP Ligand sticks to the membrane surface of exosomes passed through the column. Everything else in the cell culture medium mixture is simply washed away. The pure exosome product is then eluted from the column and collected for use. As well as being very scalable, the technique is versatile. LEAP can be used to produce a range of exosome products, by isolating exosomes from different cell sources.

Codiak, similarly, says it has developed scalable, proprietary chromatography-based methods to produced exosomes with comparable identity, purity, and functional properties as exosomes purified using methods such as ultracentrifugation. Chromatography is a flow-based technique for separating mixtures. In an April 2019 SEC filing, the company said it is establishing its own Phase 1/2 clinical manufacturing facility, which it is aiming to have fully-operational by first half 2020.

Avalon GloboCare teamed up with Weill Cornell Medicine to develop a standardised production method for isolating clinical-grade exosomes. Aegle also says it has a proprietary isolation process for producing therapeutic-grade exosomes. And Evox emphasises the GMP compliant, scalable, commercially viable manufacturing platform it has developed.

At Exopharm, the manufacturing technique that has allowed the company to leap ahead of the pack and into human clinical trials is its proprietary LEAP platform. Overcoming the exosome production and isolation bottleneck was exactly the problem the companys scientists set out to solve when Exopharm formed in 2013.

In addition to the Plexaris exosomes, isolated from platelets, currently being tested in human clinical trials, Exopharm is progressing toward human clinical trials of its second product, Cevaris, which are exosomes isolated from stem cells.

Exosomes are now under development by around 20 companies across the world. The leaders in the field are now entering clinical trials with both nave exosome products and engineered exosome products. A number of cell therapy companies are also moving across into the promising exosome product space.

The coming years promise dynamic changes, with partnerships and eventually product commercialization. Exopharm is a clear leader in this emerging field.

(Featured image by Darko Stojanovic from Pixabay)

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Muscular dystrophy collaboration aims to correct muscle stem cells’ DNA – Harvard Office of Technology Development

Posted: January 18, 2020 at 7:50 pm

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January 13, 2020

We expect that a satellite cell with the corrected DMD gene would quite quickly and continuously propagate the edited gene throughout the muscle tissue, said Prof. Amy Wagers, who leads the research. (Photo credit: Jon Chase/Harvard Staff Photographer.)

Cambridge, Mass. January 13, 2020 Harvard University stem cell researchers led by Amy Wagers, PhD, are embarking on a major study of Duchenne muscular dystrophy (DMD). Supported by research funding from Sarepta Therapeutics, under a multi-year collaboration agreement coordinated by Harvards Office of Technology Development (OTD), the project aims to use in-vivo genome editing, in mouse models of DMD, to fully and precisely restore the function of the dystrophin protein, which is crucial for proper muscular growth and development. Approaches validated by this work may point the way to an eventual therapeutic strategy to reverse DMD in humans.

Duchenne muscular dystrophy is a genetic disease caused by the lack of a protein called dystrophin that normally helps to support the structural integrity of muscle fibers, including those in the heart. Without the dystrophin protein, cells are weaker and degenerate more quickly. Over time, affected individuals boys, typically, as it is a recessive X-linked disorder lose their capacity to move independently.

Its really a devastating disease; it robs young boys of their capacity to be young boys, said Wagers, who is the Forst Family Professor of Stem Cell and Regenerative Biology, Co-Chair of the Department of Stem Cell & Regenerative Biology, and an Executive Committee Member of Harvard Stem Cell Institute. Though it is early days, Im hopeful that through this work we may identify and validate new avenues for therapy to completely rescue the proper expression and function of the dystrophin protein and regenerate healthy muscle tissue.

Researchers worldwide have pursued a variety of promising approaches such as cell and gene therapies, small-molecule therapies, and others to lessen or prevent the disease and improve patients quality of life.

The strategy pursued by the Wagers Lab at Harvard aims to fully correct the genetic template for dystrophin at its source, in the DNA of stem cells (satellite cells) that create and regenerate muscle cells. Combining cutting-edge CRISPR/Cas9 genome editing technologies with a deep knowledge of stem cell science and regenerative biology, this approach if successful might offer a permanent restoration of muscular function.

In skeletal muscle, muscle fibers are terminally post-mitotic, meaning they cannot divide and they cannot reproduce themselves, Wagers explains. If you lose muscle fibers, the only way to produce new muscle is from stem cells, specifically the satellite cells. The satellite cells are self-renewing, self-repairing, and ready to spring into action to create new muscle fibers. So we expect that a satellite cell with the corrected DMD gene would quite quickly and continuously propagate the edited gene throughout the muscle tissue.

At present, research conducted in mice has shown promising results. In June, the Wagers Lab published the results of editing stem cells in vivo, demonstrating that stem cell genes can be edited in living systems, not only in a dish. In that work, Wagers and her team delivered genome editing molecules to the cells using adeno-associated viruses (AAVs). Her lab has also successfully used gene editing in heart, muscle, and satellite cells to partially restore the function of the DMD gene that encodes dystrophin, by chopping out faulty sequences of code that are disrupting the proper reading frame.

The new stem-cell approach pursued in collaboration with Sarepta would build on these achievements and use more precise genome editing approaches, in animal models of DMD, to entirely replace genetic mutations in the DMD gene with correctly encoded sequences. The project will also explore alternate delivery methods and strategies to mitigate immune effects of in vivo genome editing.

This ambitious project will benefit greatly from the resources and insights of a company with deep clinical experience in the development of therapeutics for muscular dystrophy, said Vivian Berlin, Managing Director of Strategic Partnerships at Harvard OTD. Preclinical discoveries by Harvard researchers may open entirely new possibilities for lifesaving treatments in the long run, offering much-needed hope to patients and families in the future. Were grateful to be able to sustain the important momentum already established in Prof. Wagers lab, through this collaboration.

As we work to bring forward new treatments for patients with DMD, Sarepta is excited to support Prof. Wagers and her lab to accelerate the development of a gene editing approach, which has shown significant potential in early studies, said Louise Rodino-Klapac, Sareptas Senior Vice President of Gene Therapy. This multi-year collaboration is part of Sareptas broader commitment to pursuing all therapeutic modalities and advancing our scientific understanding of gene editing in order to maximize the potential of this approach to help patients.

Under the terms of the agreement between Harvard and Sarepta, the company will have the exclusive option to license any arising intellectual property for the purpose of developing products to prevent and treat human disease. As with any research agreement facilitated by OTD, the right of academic and other not-for-profit researchers to use the technology in further scholarly work is preserved.

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Stem Cell Therapy for Knees and Orthopedics | Riordan …

Posted: March 13, 2019 at 7:45 am

Dont rely on pain management to mask injuries. Explore biologic therapies with a group committed to the most minimally invasive procedures that help the body heal naturally and effectively.

Neil Riordan, PA, PhD is one of the early pioneers and experts in applied stem cell research. Dr. Riordan founded publicly traded company Medistem Laboratories (later Medistem Inc.) which was acquired by Intrexon in 2013.

Dr. Riordan has published more than 70 scientific articles in international peer-reviewed journals. In the stem cell arena, his colleagues and he have published more than 20 articles on multiple sclerosis, spinal cord injury, heart failure, rheumatoid arthritis, Duchenne muscular dystrophy, autism, and Charcot-Marie-Tooth syndrome.

In addition to his scientific journal publications, Dr. Riordan has authored two books about mesenchymal stem cell therapy: Stem Cell Therapy: A Rising Tide: How Stem Cells Are Disrupting Medicine and Transforming Lives and MSC (Mesenchymal Stem Cells): Clinical Evidence Leading Medicines Next Frontier. Dr. Riordan has also written two scientific book chapters on the use of non-controversial stem cells from placenta and umbilical cord.

Learn more about Dr. Riordan

Board-Certified Orthopaedic Surgeon, Fellowship Trained in Adult Hip and Knee Reconstruction, and Orthopaedic Surgery. Also specializes in Total Joint Replacement, Revision Total Joint Arthroplasty, Computer Assisted Surgery, MAKOplasty, Minimally Invasive Joint Replacement and Arthroscopy, and Regenerative Medicine

Dr. Mittal is a native Texan who grew up in the Dallas/Fort Worth area. After attending Baylor University on a full academic scholarship, he attended one of the best medical schools in the United States, University of Texas Southwestern in Dallas. In medical school he cultivated his growing interest in Orthopaedic surgery, and subsequently accepted a much sought after Orthopaedic residency position at John Peter Smith Hospital in Fort Worth. His desire to perform total joint replacement surgery led him to the highly acclaimed fellowship program at Charlotte Orthopaedic Specialists (now OrthoCarolina) in Charlotte, North Carolina where thousands of joint replacements are performed each year.

In addition to his work at Riordan Medical Institute and The Orthopaedic Center in Tulsa, Oklahoma, Dr. Mittal was instrumental in the adoption of computer navigation and the MAKOplasty RIO Robotic Arm with Hillcrest Hospital where he continues to perform surgeries. He has quickly established himself as an innovator and advocate of advanced orthopaedic care with skills in computer navigation, MAKOplasty, mobile-bearing knee replacements and alternate bearing hip replacements. Dr. Mittal is different from other CAS & MAKOplasty users in his ability to use the navigation software and RIO robotic arm to truly customize the hip or knee prosthesis to fit the patient, in terms of sizing, alignment and ligament balancing.

Dr. Mittal has an avid interest in fitness training and sports. In his free time, he enjoys traveling and spending time with his family and friends.

Learn more about Dr. Mittal

Dr. Rudy Herrera is an ACGME fellowship-trained, board-certified interventional pain management physician. He obtained his medical degree from the University of Texas Health Science Center at San Antonio. His residency occurred at the highly competitive Family Medicine program at John Peter Smith (JPS) Health Network in Fort Worth.

Following residency, Dr. Herrera was one of four selected into the Sports Medicine Fellowship program at JPS Health Network. He continued his training in interventional pain management in an ACGME accredited pain fellowship that was a joint venture between UT Southwestern Medical Center and JPS Health Network.

In addition to administering stem cell therapy for orthopedic conditions at RMI (spinal discs, knees, hips, and shoulders), Dr. Herrera specializes in the evaluation, treatment and prevention of complex pain syndromes: osteoarthritis, back and neck pain, cancer pain, pelvic and abdominal pain, chronic pain, complex regional pain syndrome (reflex sympathetic dystrophy), fibromyalgia, headaches, neuropathic pain, shingles, phantom limb pain, post herpetic neuralgia and sports related injuries.

Learn more about Dr. Herrera

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Stem Cell Therapy for Neuromuscular Diseases | InTechOpen

Posted: June 14, 2015 at 8:40 pm

1. Introduction

Neuromuscular disease is a very broad term that encompasses many diseases and aliments that either directly, via intrinsic muscle pathology, or indirectly, via nerve pathology, impair the functioning of the muscles. Neuromuscular diseases affect the muscles and/or their nervous control and lead to problems with movement. Many are genetic; sometimes, an immune system disorder can cause them. As they have no cure, the aim of clinical treatment is to improve symptoms, increase mobility and lengthen life. Some of them affect the anterior horn cell, and are classified as acquired (e.g. poliomyelitis) and hereditary (e.g. spinal muscular atrophy) diseases. SMA is a genetic disease that attacks nerve cells, called motor neurons, in the spinal cord. As a consequence of the lost of the neurons, muscles weakness becomes to be evident, affecting walking, crawling, breathing, swallowing and head and neck control. Neuropathies affect the peripheral nerve and are divided into demyelinating (e.g. leucodystrophies) and axonal (e.g. porphyria) diseases. Charcot-Marie-Tooth (CMT) is the most frequent hereditary form among the neuropathies and its characterized by a wide range of symptoms so that CMT-1a is classified as demyelinating and CMT-2 as axonal (Marchesi & Pareyson, 2010). Defects in neuromuscular junctions cause infantile and non-infantile Botulism and Myasthenia Gravis (MG). MG is a antibody-mediated autoimmune disorder of the neuromuscular junction (NMJ) (Drachman, 1994; Meriggioli & Sanders, 2009). In most cases, it is caused by pathogenic autoantibodies directed towards the skeletal muscle acetylcholine receptor (AChR) (Patrick & Lindstrom, 1973) while in others, non-AChR components of the postsynaptic muscle endplate, such as the muscle-specific receptor tyrosine kinase (MUSK), might serve as targets for the autoimmune attack (Hoch et al., 2001). Although the precise origin of the autoimmune response in MG is not known, genetic predisposition and abnormalities of the thymus gland such as hyperplasia and neoplasia could have an important role in the onset of the disease (Berrih et al., 1984; Roxanis et al., 2001).

Several diseases affect muscles: they are classified as acquired (e.g. dermatomyositis and polymyositis) and hereditary (e.g. myotonic disorders and myopaties) forms. Among the myopaties, muscular dystrophies are characterized by the primary wasting of skeletal muscle, caused by mutations in the proteins that form the link between the cytoskeleton and the basal lamina (Cossu & Sampaolesi, 2007). Mutations in the dystrophin gene cause severe form of hereditary muscular diseases; the most common are Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy (BMD). DMD patients suffer for complete lack of dystrophin that causes progressive degeneration, muscle wasting and death into the second/third decade of life. Beside, BMD patients show a very mild phenotype, often asymptomatic primarily due to the expression of shorter dystrophin mRNA transcripts that maintain the coding reading frame. DMD patients muscles show absence of dystrophin and presence of endomysial fibrosis, small fibers rounded and muscle fiber degeneration/regeneration. Untreated, boys with DMD become progressively weak during their childhood and stop ambulation at a mean age of 9 years, later with corticosteroid treatment (12/13 yrs). Proximal weakness affects symmetrically the lower (such as quadriceps and gluteus) before the upper extremities, with progression to the point of wheelchair dependence. Eventually distal lower and then upper limb weakness occurs. Weakness of neck flexors is often present at the beginning, and most patients with DMD have never been able to jump. Wrist and hand muscles are involved later, allowing the patients to keep their autonomy in transfers using a joystick to guide their wheelchair. Musculoskeletal contractures (ankle, knees and hips) and learning difficulties can complicate the clinical expression of the disease. Besides this weakness distribution in the same patient, a deep variability among patients does exist. They could express a mild phenotype, between Becker and Duchenne dystrophy, or a really severe form, with the loss of deambulation at 7-8 years. Confinement to a wheelchair is followed by the development of scoliosis, respiratory failure and cardiomyopathy. In 90% of people death is directly related to chronic respiratory insufficiency (Rideau et al., 1983). The identification and characterization of dystrophin gene led to the development of potential treatments for this disorder (Bertoni, 2008). Even if only corticosteroids were proven to be effective on DMD patient (Hyser and Mendell, 1988), different therapeutic approaches were attempted, as described in detail below (see section 7).

The identification and characterization of the genes whose mutations caused the most common neuromuscular diseases led to the development of potential treatments for those disorders. Gene therapy for neuromuscular disorders embraced several concepts, including replacing and repairing a defective gene or modifying or enhancing cellular performance, using gene that is not directly related to the underlying defect (Shavlakadze et al., 2004). As an example, the finding that DMD pathology was caused by mutations in the dystrophin gene allowed the rising of different therapeutic approaches including growth-modulating agents that increase muscle regeneration and delay muscle fibrosis (Tinsley et al., 1998), powerful antisense oligonucleotides with exon-skipping capacity (Mc Clorey et al., 2006), anti-inflammatory or second-messenger signal-modulating agents that affect immune responses (Biggar et al., 2006), agents designed to suppress stop codon mutations (Hamed, 2006). Viral and non-viral vectors were used to deliver the full-length - or restricted versions - of the dystrophin gene into stem cells; alternatively, specific antisense oligonucleotides were designed to mask the putative splicing sites of exons in the mutated region of the primary RNA transcript whose removal would re-establish a correct reading frame. In parallel, the biology of stem cells and their role in regeneration were the subject of intensive and extensive research in many laboratories around the world because of the promise of stem cells as therapeutic agents to regenerate tissues damaged by disease or injury (Fuchs and Segre, 2000; Weissman, 2000). This research constituted a significant part of the rapidly developing field of regenerative biology and medicine, and the combination of gene and cell therapy arose as one of the most suitable possibility to treat degenerative disorders. Several works were published in which stem cell were genetically modified by ex vivo introduction of corrective genes and then transplanted in donor dystrophic animal models.

Stem cells received much attention because of their potential use in cell-based therapies for human disease such as leukaemia (Owonikoko et al., 2007), Parkinsons disease (Singh et al., 2007), and neuromuscular disorders (Endo, 2007; Nowak and Davies, 2004). The main advantage of stem cells rather than the other cells of the body is that they can replenish their numbers for long periods through cell division and, they can produce a progeny that can differentiate into multiple cell lineages with specific functions (Bertoni, 2008). The candidate stem cell had to be easy to extract, maintaining the capacity of myogenic conversion when transplanted into the host muscle and also the survival and the subsequent migration from the site of injection to the compromise muscles of the body (Price et al., 2007). With the advent of more sensitive markers, stem cell populations suitable for clinical experiments were found to derive from multiple region of the body at various stage of development. Numerous studies showed that the regenerative capacity of stem cells resided in the environmental microniche and its regulation. This way, it could be important to better elucidate the molecular composition cytokines, growth factors, cell adhesion molecules and extracellular matrix molecules - and interactions of the different microniches that regulate stem cell development (Stocum, 2001).

Several groups published different works concerning adult stem cells such as muscle-derived stem cells (Qu-Petersen et al., 2002), mesoangioblasts (Cossu and Bianco, 2003), blood- (Gavina et al., 2006) and muscle (Benchaouir et al., 2007)-derived CD133+ stem cells. Although some of them are able to migrate through the vasculature (Benchaouir et al., 2007; Galvez et al., 2006; Gavina et al., 2006) and efforts were done to increase their migratory ability (Lafreniere et al., 2006; Torrente et al., 2003a), poor results were obtained.

Embryonic and adult stem cells differ significantly in regard to their differentiation potential and in vitro expansion capability. While adult stem cells constitute a reservoir for tissue regeneration throughout the adult life, they are tissue-specific and possess limited capacity to be expanded ex vivo. Embryonic Stem (ES) cells are derived from the inner cell mass of blastocyst embryos and, by definition, are capable of unlimited in vitro self-renewal and have the ability to differentiate into any cell type of the body (Darabi et al., 2008b). ES cells, together with recently identified iPS cells, are now broadly and extensively studied for their applications in clinical studies.

Embryonic stem cells are pluripotent cells derived from the early embryo that are characterized by the ability to proliferate over prolonged periods of culture remaining undifferentiated and maintaining a stable karyotype (Amit and Itskovitz-Eldor, 2002; Carpenter et al., 2003; Hoffman and Carpenter, 2005). They are capable of differentiating into cells present in all 3 embryonic germ layers, namely ectoderm, mesoderm, and endoderm, and are characterized by self-renewal, immortality, and pluripotency (Strulovici et al., 2007).

hESCs are derived by microsurgical removal of cells from the inner cell mass of a blastocyst stage embryo (Fig. 1). The ES cells can be also obtained from single blastomeres. This technique creates ES cells from a single blastomere directly removed from the embryo bypassing the ethical issue of embryo destruction (Klimanskaya et al., 2006). Although maintaining the viability of the embryo, it has to be determined whether embryonic stem cell lines derived from a single blastomere that does not compromise the embryo can be considered for clinical studies. Cell Nuclear Transfer (SCNT): Nuclear transfer, also referred to as nuclear cloning, denotes the introduction of a nucleus from an adult donor cell into an enucleated oocyte to generate a cloned embryo (Wilmut et al., 2002).

ESCs differentiation. Differentiation potentiality of human embryonic stem cell lines. Human embryonic stem cell pluripotency is evaluated by the ability of the cells to differentiate into different cell types.

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Stem Cell Therapy for Neuromuscular Diseases | InTechOpen

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