Jean-Thomas Vilquin

Autologous skeletal myoblast transplantation for severe postinfarction left ventricular dysfunction

OBJECTIVESnThis phase I trial was designed to assess the feasibility and safety of autologous skeletal myoblast transplantation in patients with severe ischemic cardiomyopathy.nnnBACKGROUNDnExperimentally, myoblast grafting into postinfarction myocardial scars improves left ventricular function.nnnMETHODSnTen patients were included on the basis of the following criteria: 1) severe left ventricular dysfunction (ejection fraction < or = 35%); 2) the presence of a postinfarction akinetic and nonviable scar, as assessed by dobutamine echocardiography and 18-fluorodeoxyglucose positron emission tomography; and 3) an indication of coronary bypass in remote areas. Skeletal myoblasts were grown from a biopsy taken at the thigh.nnnRESULTSnAn average of 871 x 10(6) cells (86% of myoblasts) were obtained after a mean period of 16 days and implanted uneventfully across the scar at the time of bypass. Except for one patient whose early death was unrelated to the cell transplantation, all patients had an uncomplicated postoperative course. Four patients showed delayed episodes of sustained ventricular tachycardia and were implanted with an internal defibrillator. At an average follow-up of 10.9 months, the mean New York Heart Association functional class improved from 2.7 +/- 0.2 preoperatively to 1.6 +/- 0.1 postoperatively (p < 0.0001), and the ejection fraction increased from 24 +/- 1% to 32 +/- 1% (p < 0.02). A blinded echocardiographic analysis showed that 63% of the cell-implanted scars (14 of 22) demonstrated improved systolic thickening. One noncardiac death occurred 17.5 months after transplantation.nnnCONCLUSIONSnThese preliminary data suggest the feasibility and safety of autologous skeletal myoblast transplantation in severe ischemic cardiomyopathy, with the caveat of an arrhythmogenic potential. New-onset contraction of akinetic and nonviable segments suggests a functional efficacy that requires confirmation by randomized studies.

Myoblast transplantation for heart failure.

Intramyocardial skeletal muscle transplantation has been shown experimentally to improve heart function after infarction. We report success with this procedure in a patient with severe ischaemic heart failure. We implanted autologous skeletal myoblasts into the postinfarction scar during coronary artery bypass grafting of remote myocardial areas. 5 months later, there was evidence of contraction and viability in the grafted scar on echocardiography and positron emission tomography. Although this result is encouraging, it requires validation by additional studies.

Viability and differentiation of autologous skeletal myoblast grafts in ischaemic cardiomyopathy

Autologous skeletal myoblast transplantation might improve postinfarction ventricular function, but graft viability and differentiation (ie, proof of concept) has not been shown. A 72-year-old man had autologous cultured myoblasts from his vastus lateralis injected to an area of transmural inferior myocardial infarction in non-reperfused scar tissue. He showed improvement in symptoms and left-ventricular ejection fraction. When he died 17.5 months after the procedure, the grafted post-infarction scar showed well developed skeletal myotubes with a preserved contractile apparatus. 65% of myotubes expressed the slow myosin isoform and 33% coexpressed the slow and fast isoforms (vs 44% and 0.6%, respectively, in skeletal muscle). Myoblast grafts can survive and show a switch to slow-twitch fibres, which might allow sustained improvement in cardiac function.

Factors affecting functional outcome after autologous skeletal myoblast transplantation

BACKGROUNDnThis study assessed the extent to which the initial degree of functional impairment and the number of injected cells may influence the functional improvement provided by autologous skeletal myoblast transplantation into infarcted myocardium.nnnMETHODSnOne week after left coronary artery ligation, 44 rats received into the infarcted scar, autologous skeletal myoblasts expanded in vitro for 7 days (mean, 3.5 x 10(6), n = 21), or culture medium alone (controls, n = 23). Left ventricular function was assessed by two-dimensional echocardiography.nnnRESULTSnWhen transplanted hearts were stratified according to their baseline ejection fraction, a significant improvement occurred at 2 months in the less than 25% (from 21.4% to 37%), 25% to 35% (from 29% to 43.8%), and in the 35% to 40% (from 37.2% to 41.7%) groups, compared to controls (p = 0.048, 0.0057, and 0.034, respectively), but not in the more than 40% stratum. A significant linear relationship was found between the improvement in ejection fraction and the number of injected myoblasts, both at 1 and 2 months after transplantation (p < 0.0001).nnnCONCLUSIONSnAutologous myoblast transplantation is functionally effective over a wide range of postinfarct ejection fractions, including in the sickest hearts provided that they are injected with a sufficiently high number of cells.

Long-term (1 year) functional and histological results of autologous skeletal muscle cells transplantation in rat

BACKGROUNDnSeveral studies have demonstrated the short-term benefits of autologous skeletal muscle cell transplantation on postinfarction left ventricular function. The present experiments were designed to assess the long-term effects of the procedure.nnnMETHODS AND RESULTSnThirteen Wistar rats that had undergone skeletal muscle cell transplantation (n=6) or injection of control culture medium (n=7) in isoforms areas after myocardial infarction created by coronary artery ligation and survived for 1 year were functionally assessed by combining echocardiography and pressure-volume loops. At 1 year after transplantation, both contractile and relaxation indices were significantly improved in the skeletal muscle cell-grafted group compared with controls. One-year echocardiographic measurements of ejection fraction were similar to those recorded 2 months after the procedure. The stability of the functional outcome contrasted with a decrease in the number of histologically detectable skeletal myotubes over time. However, the proportion of the slow and composite (fast and slow) myosin isoforms expressed by skeletal muscle fibers still present after 1 year was greater than that found in animals sacrificed after 2 months.nnnCONCLUSIONnThe functional benefits of autologous skeletal muscle cell transplantation are sustained over time and are associated with either selection, preservation or an increased expression of slow myosin heavy chain isoforms. The discrepancy between maintenance of this improvement and the decay in the engrafted myotubes suggests protective mechanisms operative from the early post-transplantation stage and possibly involving modulation of extracellular matrix remodelling or paracrinally induced maturation of putative cardiac resident stem cells.

Characterization of distinct mesenchymal-like cell populations from human skeletal muscle in situ and in vitro

Human skeletal muscle is an essential source of various cellular progenitors with potential therapeutic perspectives. We first used extracellular markers to identify in situ the main cell types located in a satellite position or in the endomysium of the skeletal muscle. Immunohistology revealed labeling of cells by markers of mesenchymal (CD13, CD29, CD44, CD47, CD49, CD62, CD73, CD90, CD105, CD146, and CD15 in this study), myogenic (CD56), angiogenic (CD31, CD34, CD106, CD146), hematopoietic (CD10, CD15, CD34) lineages. We then analysed cell phenotypes and fates in short- and long-term cultures of dissociated muscle biopsies in a proliferation medium favouring the expansion of myogenic cells. While CD56(+) cells grew rapidly, a population of CD15(+) cells emerged, partly from CD56(+) cells, and became individualized. Both populations expressed mesenchymal markers similar to that harboured by human bone marrow-derived mesenchymal stem cells. In differentiation media, both CD56(+) and CD15(+) cells shared osteogenic and chondrogenic abilities, while CD56(+) cells presented a myogenic capacity and CD15(+) cells presented an adipogenic capacity. An important proportion of cells expressed the CD34 antigen in situ and immediately after muscle dissociation. However, CD34 antigen did not persist in culture and this initial population gave rise to adipogenic cells. These results underline the diversity of human muscle cells, and the shared or restricted commitment abilities of the main lineages under defined conditions.

Current advances in cell therapy strategies for muscular dystrophies

Introduction: Muscular dystrophies are a heterogeneous group of genetic diseases characterized by muscle weakness, wasting and degeneration. Cell therapy consists of delivering myogenic precursor cells to damaged tissue for the complementation of missing proteins and/or the regeneration of new muscle fibres. Areas covered: We focus on human candidate cells described so far (myoblasts, mesoangioblasts, pericytes, myoendothelial cells, CD133+ cells, aldehyde-dehydrogenase-positive cells, mesenchymal stem cells, embryonic stem cells, induced pluripotent stem cells), gene-based strategies developed to modify cells prior to injection, animal models (dystrophic and/or immunodeficient) used for pre-clinical studies, and clinical trials that have been performed using cell therapy strategies. The approaches are reviewed in terms of feasibility, hurdles, potential solutions and/or research areas from where the solution may come and potential application in terms of types of dystrophies and targets. Expert opinion: Cell therapy for muscular dystrophies should be put in the context of which dystrophy or muscle group is targeted, what tools are available at hand, but even more importantly what can cell therapy bring as compared with and/or in combination with other therapeutic strategies. The solution will probably be the right dosage of these combinations adapted to each dystrophy, or even to each type of mutation within a dystrophy.

Cell therapy for muscular dystrophies: advances and challenges

Purpose of reviewCell therapy is considered a potential therapeutic avenue for the treatment of skeletal muscle diseases. Heterologous and autologous approaches have been attempted in the context, respectively, of generalized degenerative disease and of localized repairs. Cell transplantation trials, however, have been hampered by poor survival and limited migratory ability of the cells. This article reviews recent problems including the identification of new putative cellular candidates, the combination of complementary genetic or pharmacological therapeutic approaches, and the set up of clinical trials. Recent findingsDeeper investigations identified anoikis, oxidative stress, fusion inability and some administration methodologies as causes of early massive cell death. It was proposed to adapt the injection strategies or to combine them with genetic modifications of the cells or pharmacological interventions on the environment to improve the success of implantation. New myogenic cell types have been identified, mainly in the family of perivascular cells, which can be administered systemically. New concepts have emerged regarding the correction of gene expression (use of lentiviral vectors, set-up of exon skipping, direct DNA repair, etc.). SummaryInitial cell transplantation trials dedicated to the repair of striated muscles in muscular dystrophies produced mitigated results and underlined some limitations of cellular candidates under study. The research and identification of new stem cell candidates, the invention of new molecular strategies for correction of gene expression, the development of complementary approaches to improve transplantation success, have been justified by the unmet medical needs. These efforts led to new preclinical and clinical trials based on these concepts.

Distinction Between Two Populations of Islet-1-Positive Cells in Hearts of Different Murine Strains

Islet-1 expression identifies populations of progenitor cells in embryonic, fetal, and newborn murine hearts that are able to give rise to all cardiac cell lineages ex vivo and in vivo. Using systematic immunohistochemistry, we investigated whether islet-1-positive cells are present in adult mouse heart from the perspective of their potential therapeutic utility. The presence, localization, and nature of islet-1-positive cells were assessed in mice of different strains, ages, and conditions. Islet-1-positive cells were present in mouse heart from postnatal day 1 to young adulthood. Depending on the strain, these cells were organized in either 1 or 2 types of clusters localized to restricted areas, at a distance of 6%-35% of the heart length from the base. The first type of cluster was present in all strains and consisted of neural crest-derived cells that formed cardiac ganglia. The number of cells remained stable (a few hundred) from neonatal up to adult ages, and variations were noted between strains regarding their long-term persistency. The second type of cluster was essentially present in 129SvJ or Balb/C strains and absent from the other strains tested (C57BL/6J, C3H, SJL). It consisted of cells expressing highly ordered sarcomeric actin, consistent with their having cardiomyocyte identity. These cells disappeared in animals older than 4 months. Neither the number nor the type of islet-1-positive cells varied with time in a mouse model of dilated cardiomyopathy. Our studies demonstrate that islet-1-positive cells are relatively few in number in adult murine heart, being localized in restricted and rather inaccessible areas, and can represent both neural crest and cardiomyocyte lineages.

Transplantation of Human Myoblasts in SCID Mice as a Potential Muscular Model for Myotonic Dystrophy

Myotonic dystrophy (DM), the most frequent hereditary myopathy in adults, is characterized clinically by muscle weakness, myotonia, and systemic symptoms. Although the specific genetic basis for DM has been established, less is known about the cellular defects responsible for its pleiotropic manifestations. DM pathogenesis studies are presently limited due to the absence of animal models. In the present study, we transplanted myoblasts of DM patients into the Tibialis anterior of Severe Combined Immunodeficient (SCID) mice to determine whether this approach could reproduce the muscular characteristics of DM. One to 4 months after transplantation, a variable number of innervated human muscle fibers, recognized by an antibody specific for the human dystrophin, were found in the transplanted muscles. The CTG expansion was retained in human muscle fibers as determined by Southern blot analysis. Although the histological characteristics of DM were absent in these fibers, electromyographic recording showed typical myotonic discharges in muscles transplanted with DM myoblasts. The specificity of the myotonic runs was demonstrated by its inhibition by apamin, a drug that specifically blocks DM myotonia. We conclude that transplantation of myoblasts from DM patients into SCID mice represents a potential in vivo model for basic studies of this disease.