Comparison of juvenile and adult myasthenia gravis in a French cohort with focus on thymic histology.

Myasthenia gravis (MG) is an autoimmune disease characterized by muscle fatigability due to acetylcholine receptor (AChR) autoantibodies. To better characterize juvenile MG (JMG), we analyzed 85 pre- and 132 post-pubescent JMG (with a cutoff age of 13) compared to 721 adult MG patients under 40 years old using a French database. Clinical data, anti-AChR antibody titers, thymectomy, and thymic histology were analyzed. The proportion of females was higher in each subgroup. No significant difference in the anti-AChR titers was observed. Interestingly, the proportion of AChR+ MG patients was notably lower among adult MG patients aged between 30 and 40 years, at 69.7%, compared to over 82.4% in the other subgroups. Thymic histological data were examined in patients who underwent thymectomy during the year of MG onset. Notably, in pre-JMG, the percentage of thymectomized patients was significantly lower (32.9% compared to more than 42.5% in other subgroups), and the delay to thymectomy was twice as long. We found a positive correlation between anti-AChR antibodies and germinal center grade across patient categories. Additionally, only females, particularly post-JMG patients, exhibited the highest rates of lymphofollicular hyperplasia (95% of cases) and germinal center grade. These findings reveal distinct patterns in JMG patients, particularly regarding thymic follicular hyperplasia, which appears to be exacerbated in females after puberty.

Enzyme-controlled, nutritive hydrogel for mesenchymal stromal cell survival and paracrine functions.

Culture-adapted human mesenchymal stromal cells (hMSCs) are appealing candidates for regenerative medicine applications. However, these cells implanted in lesions as single cells or tissue constructs encounter an ischemic microenvironment responsible for their massive death post-transplantation, a major roadblock to successful clinical therapies. We hereby propose a paradigm shift for enhancing hMSC survival by designing, developing, and testing an enzyme-controlled, nutritive hydrogel with an inbuilt glucose delivery system for the first time. This hydrogel, composed of fibrin, starch (a polymer of glucose), and amyloglucosidase (AMG, an enzyme that hydrolyze glucose from starch), provides physiological glucose levels to fuel hMSCs via glycolysis. hMSCs loaded in these hydrogels and exposed to near anoxia (0.1% pO2) in vitro exhibited improved cell viability and angioinductive functions for up to 14 days. Most importantly, these nutritive hydrogels promoted hMSC viability and paracrine functions when implanted ectopically. Our findings suggest that local glucose delivery via the proposed nutritive hydrogel can be an efficient approach to improve hMSC-based therapeutic efficacy.

In Vivo Myoblasts Tracking Using the Sodium Iodide Symporter Gene Expression in Dogs.

Stem cell-based therapies are a promising approach for the treatment of degenerative muscular diseases; however, clinical trials have shown inconclusive and even disappointing results so far. Noninvasive cell monitoring by medicine imaging could improve the understanding of the survival and biodistribution of cells following injection. In this study, we assessed the canine sodium iodide symporter (cNIS) reporter gene as an imaging tool to track by single-photon emission computed tomography (SPECT/CT) transduced canine myoblasts after intramuscular (IM) administrations in dogs. cNIS-expressing cells kept their myogenic capacities and showed strong 99 mTc-pertechnetate (99 mTcO4 -) uptake efficiency both in vitro and in vivo. cNIS expression allowed visualization of cells by SPECT/CT along time: 4 h, 48 h, 7 days, and 30 days after IM injection; biopsies collected 30 days post administration showed myofiber's membranes expressing cNIS. This study demonstrates that NIS can be used as a reporter to track cells in vivo in the skeletal muscle of large animals. Our results set a proof of concept of the benefits NIS-tracking tool may bring to the already challenging cell-based therapies arena in myopathies and pave the way to a more efficient translation to the clinical setting from more accurate pre-clinical results.

Aldehyde dehydrogenases contribute to skeletal muscle homeostasis in healthy, aging, and Duchenne muscular dystrophy patients.

BACKGROUND: Aldehyde dehydrogenases (ALDHs) are key players in cell survival, protection, and differentiation via the metabolism and detoxification of aldehydes. ALDH activity is also a marker of stem cells. The skeletal muscle contains populations of ALDH-positive cells amenable to use in cell therapy, whose distribution, persistence in aging, and modifications in myopathic context have not been investigated yet. METHODS: The Aldefluor® (ALDEF) reagent was used to assess the ALDH activity of muscle cell populations, whose phenotypic characterizations were deepened by flow cytometry. The nature of ALDH isoenzymes expressed by the muscle cell populations was identified in complementary ways by flow cytometry, immunohistology, and real-time PCR ex vivo and in vitro. These populations were compared in healthy, aging, or Duchenne muscular dystrophy (DMD) patients, healthy non-human primates, and Golden Retriever dogs (healthy vs. muscular dystrophic model, Golden retriever muscular dystrophy [GRMD]). RESULTS: ALDEF+ cells persisted through muscle aging in humans and were equally represented in several anatomical localizations in healthy non-human primates. ALDEF+ cells were increased in dystrophic individuals in humans (nine patients with DMD vs. five controls: 14.9 ± 1.63% vs. 3.6 ± 0.39%, P = 0.0002) and dogs (three GRMD dogs vs. three controls: 10.9 ± 2.54% vs. 3.7 ± 0.45%, P = 0.049). In DMD patients, such increase was due to the adipogenic ALDEF+ /CD34+ populations (11.74 ± 1.5 vs. 2.8 ± 0.4, P = 0.0003), while in GRMD dogs, it was due to the myogenic ALDEF+ /CD34- cells (3.6 ± 0.6% vs. 1.03 ± 0.23%, P = 0.0165). Phenotypic characterization associated the ALDEF+ /CD34- cells with CD9, CD36, CD49a, CD49c, CD49f, CD106, CD146, and CD184, some being associated with myogenic capacities. Cytological and histological analyses distinguished several ALDH isoenzymes (ALDH1A1, 1A2, 1A3, 1B1, 1L1, 2, 3A1, 3A2, 3B1, 3B2, 4A1, 7A1, 8A1, and 9A1) expressed by different cell populations in the skeletal muscle tissue belonging to multinucleated fibres, or myogenic, endothelial, interstitial, and neural lineages, designing them as potential new markers of cell type or of metabolic activity. Important modifications were noted in isoenzyme expression between healthy and DMD muscle tissues. The level of gene expression of some isoenzymes (ALDH1A1, 1A3, 1B1, 2, 3A2, 7A1, 8A1, and 9A1) suggested their specific involvement in muscle stability or regeneration in situ or in vitro. CONCLUSIONS: This study unveils the importance of the ALDH family of isoenzymes in the skeletal muscle physiology and homeostasis, suggesting their roles in tissue remodelling in the context of muscular dystrophies.

Long-Term Engraftment (16 Years) of Myoblasts in a Human Infarcted Heart.

We report the case of a patient who had undergone injections of myoblasts in an infarct area 16 years before being referred for heart transplantation. The pathological examination of the explanted heart found persisting myotubes embedded in fibrosis. This finding supports the ability of myoblasts to survive in harsh environments, which can make them appealing candidates for transplantation in diseases requiring supply of new myogenic cells. Stem Cells Translational Medicine 2018;7:705-708.

[Cell therapies for cardiopathies: the shift of paradigms]. / Thérapies cellulaires des cardiopathies - Évolution du paradigme.

Heart failure is a major concern for public health systems, and several approaches of cellular therapy are being investigated with the goal of improving the function of these failing hearts. Many cell types have been used (skeletal myoblasts, hematopoietic, endothelial or mesenchymal progenitors, cardiac cells…), most often in the indication of post-ischemic heart failure rather than in the indication of genetic dilated cardiomyopathy. It is easier, indeed, to target a restricted area than the whole myocardium. Several clinical trials have reported slight but encouraging functional benefits, but their interpretations were frequently limited by the small sizes of cohorts, and by the biological variabilities inherent to the patients status and to the biology of the cells. These trials also shed light on unexpected mechanisms of action of the cells, which are changing the concepts and methodologies of the studies. The functional benefits observed would be due, indeed, to the secretion of trophic factors by the cells, instead of their true structural and mechanical integration within the myocardial tissue. Accordingly, the new generations of clinical trials aim at improving the size and homogeneity of the patient cohorts to increase the statistical power. On the other hand, several studies are associating or conditionning cells with biomaterials or cocktails of cytokines to improve their survival and their biological efficacy. In parallel, bio-engineering investigates several ways to support cells in vitro and in vivo, to sustain the architectural structure of the failing myocardium, to produce ex vivo some true substitutive cardiac tissue, or to purely replace the cells by their active secreted products. Several therapeutic devices should emerge from these researches, and the choice of their respective use will be ultimately guided by the medical indication.

Myoblasts and embryonic stem cells differentially engraft in a mouse model of genetic dilated cardiomyopathy.

The functional and architectural benefits of embryonic stem cells (ESC) and myoblasts (Mb) transplantations into infarcted myocardium have been investigated extensively. Whereas ESC repopulated fibrotic areas and contributed to myocardial regeneration, Mb exerted their effects through paracrine secretions and scar remodeling. This therapeutic perspective, however, has been less explored in the setting of nonischemic dilated cardiomyopathies (DCMs). Our aim was to compare the integration and functional efficacy of ESC committed to cardiac fate by bone morphogenic protein 2 (BMP-2) pretreatment and Mb used as gold standard following their transplantation into the myocardium of a mouse model of laminopathy exhibiting a progressive and lethal DCM. After 4 and 8 weeks of transplantation, stabilization was observed in Mb-transplanted mice (P = 0.008) but not in groups of ESC-transplanted or medium-injected animals, where the left ventricular fractional shortening (LVFS) decreased by 32 ± 8% and 41 ± 8% respectively. Engrafted differentiated cells were consistently detected in myocardia of mice receiving Mb, whereas few or no cells were detected in the hearts of mice receiving ESC, except in two cases where teratomas were formed. These data suggest that committed ESC fail to integrate in DCM where scar tissue is absent to provide the appropriate niche, whereas the functional benefits of Mb transplantation might extend to nonischemic cardiomyopathy.

A novel genetic variant in the transcription factor Islet-1 exerts gain of function on myocyte enhancer factor 2C promoter activity.

AIMS: The transcription factor Islet-1 (ISL1) is a marker of cardiovascular progenitors and is essential for mammalian cardiogenesis. An ISL1 haplotype has recently been associated with congenital heart disease. In this study we evaluated whether ISL1 variants are associated with hypertrophic (HCM), dilated (DCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), or with Emery-Dreifuss muscular dystrophy (EDMD). METHODS AND RESULTS: The six exon and intron boundaries of ISL1 were screened for genetic variants in a cohort of 454 index cases. Eleven exonic variants were identified in HCM, DCM, ARVC, and/or EDMD. Out of the five novel variants, two are located in the 5'-untranslated region, two are silent (p.Arg171Arg and p.Asn189Asn), and one is a missense (p.Asn252Ser). The latter was identified in the homozygous state in one DCM patient, and in the heterozygous state in 11 relatives, who did not present with DCM but often with cardiovascular features. This variant was found in one HCM patient also carrying a MYH7 mutation and in 3/96 North-African Caucasian control individuals, but was absent in 138 European Caucasian control individuals. We investigated the effect of the ISL1 wild type and p.Asn252Ser mutant on myocyte enhancer factor 2C (Mef2c) promoter activity, an established ISL1 target. Mef2c promoter activity was ∼4-fold higher in the presence of wild-type and ∼6-fold higher in the presence of mutant ISL1 in both HEK and CHO cells. CONCLUSION: This study describes a new gain-of-function p.Asn252Ser variant in the human ISL1 gene, which could potentially lead to greater activation of downstream targets involved in cardiac development, dilation, and hypertrophy.

Cell therapy for muscular dystrophies: advances and challenges.

PURPOSE OF REVIEW: Cell 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 FINDINGS: Deeper 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.). SUMMARY: Initial 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.

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.

Aldehyde dehydrogenase activity identifies a population of human skeletal muscle cells with high myogenic capacities.

Aldehyde dehydrogenase 1A1 (ALDH) activity is one hallmark of human bone marrow (BM), umbilical cord blood (UCB), and peripheral blood (PB) primitive progenitors presenting high reconstitution capacities in vivo. In this study, we have identified ALDH(+) cells within human skeletal muscles, and have analyzed their phenotypical and functional characteristics. Immunohistofluorescence analysis of human muscle tissue sections revealed rare endomysial cells. Flow cytometry analysis using the fluorescent substrate of ALDH, Aldefluor, identified brightly stained (ALDH(br)) cells with low side scatter (SSC(lo)), in enzymatically dissociated muscle biopsies, thereafter abbreviated as SMALD(+) (for skeletal muscle ALDH(+)) cells. Phenotypical analysis discriminated two sub-populations according to CD34 expression: SMALD(+)/CD34(-) and SMALD(+)/CD34(+) cells. These sub-populations did not initially express endothelial (CD31), hematopoietic (CD45), and myogenic (CD56) markers. Upon sorting, however, whereas SMALD(+)/CD34(+) cells developed in vitro as a heterogeneous population of CD56(-) cells able to differentiate in adipoblasts, the SMALD(+)/CD34(-) fraction developed in vitro as a highly enriched population of CD56(+) myoblasts able to form myotubes. Moreover, only the SMALD(+)/CD34(-) population maintained a strong myogenic potential in vivo upon intramuscular transplantation. Our results suggest that ALDH activity is a novel marker for a population of new human skeletal muscle progenitors presenting a potential for cell biology and cell therapy.

The Myoblast Autologous Grafting in Ischemic Cardiomyopathy (MAGIC) trial: first randomized placebo-controlled study of myoblast transplantation.

BACKGROUND: Phase I clinical studies have demonstrated the feasibility of implanting autologous skeletal myoblasts in postinfarction scars. However, they have failed to determine whether this procedure was functionally effective and arrhythmogenic. METHODS AND RESULTS: This multicenter, randomized, placebo-controlled, double-blind study included patients with left ventricular (LV) dysfunction (ejection fraction < or = 35%), myocardial infarction, and indication for coronary surgery. Each patient received either cells grown from a skeletal muscle biopsy or a placebo solution injected in and around the scar. All patients received an implantable cardioverter-defibrillator. The primary efficacy end points were the 6-month changes in global and regional LV function assessed by echocardiography. The safety end points comprised a composite index of major cardiac adverse events and ventricular arrhythmias. Ninety-seven patients received myoblasts (400 or 800 million; n=33 and n=34, respectively) or the placebo (n=30). Myoblast transfer did not improve regional or global LV function beyond that seen in control patients. The absolute change in ejection fraction (median [interquartile range]) between 6 months and baseline was 4.4% (0.2; 7.3), 3.4% (-0.3; 12.4), and 5.2% (-4.4; 11.0) in the placebo, low-dose, and high-dose groups, respectively (P=0.95). However, the high-dose cell group demonstrated a significant decrease in LV volumes compared with the placebo group. Despite a higher number of arrhythmic events in the myoblast-treated patients, the 6-month rates of major cardiac adverse events and of ventricular arrhythmias did not differ significantly between the pooled treatment and placebo groups. CONCLUSIONS: Myoblast injections combined with coronary surgery in patients with depressed LV function failed to improve echocardiographic heart function. The increased number of early postoperative arrhythmic events after myoblast transplantation, as well as the capability of high-dose injections to revert LV remodeling, warrants further investigation.

Ex vivo generation of mature and functional human smooth muscle cells differentiated from skeletal myoblasts.

We described the ex vivo production of mature and functional human smooth muscle cells (SMCs) derived from skeletal myoblasts. Initially, myoblasts expressed all myogenic cell-related markers such as Myf5, MyoD and Myogenin and differentiate into myotubes. After culture in a medium containing vascular endothelial growth factor (VEGF), these cells were shown to have adopted a differentiated SMC identity as demonstrated by alphaSMA, SM22alpha, calponin and smooth muscle-myosin heavy chain expression. Moreover, the cells cultured in the presence of VEGF did not express MyoD anymore and were unable to fuse in multinucleated myotubes. We demonstrated that myoblasts-derived SMCs (MDSMCs) interacted with endothelial cells to form, in vitro, a capillary-like network in three-dimensional collagen culture and, in vivo, a functional vascular structure in a Matrigel implant in nonobese diabetic-severe combined immunodeficient mice. Based on the easily available tissue source and their differentiation into functional SMCs, these data argue that skeletal myoblasts might represent an important tool for SMCs-based cell therapy.

Skeletal myoblast transplantation in ischemic heart failure: long-term follow-up of the first phase I cohort of patients.

BACKGROUND: Skeletal myoblast (SM) transplantation (Tx) in a post-myocardial infarction (MI) scar experimentally improves left ventricular (LV) ejection fraction (EF). Short-term follow-up (FU) studies have suggested that a similar benefit could clinically occur despite an increased risk of LV arrhythmias. METHODS AND RESULTS: We report the long-term FU of the first worldwide cohort of grafted patients (n = 9, 61.8+/-11.6 years, previous MI, EF < or = 35%) operated on (autologous SM Tx and bypass surgery) in 2000 to 2001 and evaluated before Tx, at 1 month (M1) and at a median FU of 52 (18 to 58) months after Tx (37 patient-years). NYHA class improved from 2.5+/-0.5 to 1.8+/-0.4 at M1 (P=0.004 versus baseline) and 1.7+/-0.5 at FU (P=not significant versus M1; P=0.0007 versus baseline). EF increased from 24.3+/-4% to 31+/-4.1% at M1 (+28%, P=0.001 versus baseline) and remained stable thereafter (28.7+/-8.1%, +18% versus baseline). There were 5 hospitalizations for heart failure in 3 patients at 28.6+/-9.9 months, allowing implant in 2 patients with a resynchronization pacemaker. An automatic cardiac defibrillator (ACD) was implanted in 5 patients for nonsustained (n =1) or sustained (n =4) ventricular tachycardia at 12.2+/-18.6 (1 to 45) months. Despite a beta-blocker/amiodarone combination therapy, there were 14 appropriate shocks for 3 arrhythmic storms in 3 patients at 6, 7, and 18 months after ACD implantation. CONCLUSIONS: In this cohort of severe heart failure patients both clinical status and EF stably improve over time with a strikingly low incidence of hospitalizations for heart failure (0.13/patient-years) and the arrhythmic risk can be controlled by medical therapy and/or on-request ACD implantation.

Mesenchymal stem cells in bone and cartilage repair: current status.

The progression of rheumatoid pathologies, degenerative diseases, traumatologies, and their cortege of increasing medical, social and economical needs, has mandated the development of tissue repair and engineering technologies in orthopedic medicine. Mesenchymal stem cells (MSCs) are multipotent cells that can be extracted from large and relatively easily accessible compartments of the body, especially the bone marrow, and such cells are able to differentiate into adipogenic, chondrogenic and osteogenic precursors. The concept of using MSCs to repair tissues has progressively evolved, and the goal of cell-mediated therapy is to prolong the natural physiological abilities of healing, or substitute them, when these are lacking, failing or progressing too slowly. In recent years, the first clinical trials on the utility of MSCs, with or without scaffolds and/or growth factors, have been initiated. In this review, the authors focus on findings from preclinical research, clinical trials and case reports involving bone and cartilage repairs. New perspectives are considered regarding uses of cell types, cell delivery approaches and growth factors. They also consider the stringent conditions, constraints and considerations necessary to take cell-mediated therapy from bench to bedside.

[The possible place of autologus cell therapy in facioscapulohumeral muscular dystrophy]. / Peut-on envisager une thérapie cellulaire autologue de la dystrophie musculaire facio-scapulo-humérale?

Facioscapulohumeral dystrophy (FSHD), one of the most common forms of muscular dystrophy, derives its name from the patients' selective, often asymmetric clinical distribution of muscle weakness. Interestingly, affected and non affected areas can coexist in the same patient for many years. The molecular hallmark is total deletion of the subtelomeric D4Z4 repeat on chromosome 4q. There is no specific treatment. Gene therapy is unlikely to be feasible, as no alterations have been found in the genes located in this subtelomeric region. Muscular dystrophies are characterized by the coexistence of genetically induced muscle degeneration and compensatory muscle regeneration by myoblast proliferation from satellite cells; muscle weakness and atrophy appears when this mechanism is overwhelmed. Cell therapy with autologous myoblasts would, in theory, be a simple way of boosting the regenerative process and of preventing or delaying muscle degeneration. This approach might also avoid the use of toxic immunotherapies. By using a recent very-high-yield cell culture method, we analyzed the proliferation and differentiation of myoblasts obtained from FSHD patients, both ex vivo and in vivo (by intramuscular injection to immunodeficient mice). Myoblasts were obtained by muscle biopsy from five FSHD patients harboring the D4Z4 deletion. We selected the vastus lateralis muscle, which exhibited no clinical, radiological or pathological signs of dystrophy. The growth characteristics of these cells were compared with those of cells from normal control muscles, based on the culture yield, phenotypic characterization with anti-CD56 and anti-desmin antibodies, and the capacity for differentiation (myotube production in vitro and human dystrophin expression one month after injection to Rag2 immunodeficient mice). Patients' cells recovered from 1 g of muscle biopsy specimen resembled control cells in terms of their growth kinetics, culture yield, and capacity to differentiate and produce mature muscle cells. These results indicate that myoblasts taken from unaffected muscle of patients with FSHD warrant testing in a human cell therapy trial.

Can cold or heat shock improve skeletal myoblast engraftment in infarcted myocardium?

OBJECTIVE: Cell death remains a major limitation of skeletal myoblast (SM) transplantation but the patterns of cell survival and proliferation in heart and their potential modulation by thermic stresses like heat shock (HS) and cryopreservation (Cryo) are still incompletely characterized. METHODS: To track SMs in situ, we developed a dual-marker system based on the semiconservative expression of the foreign soluble protein, beta-Galactosidase (beta-Gal) and the constitutive expression of the Y chromosome in a myocardial infarction model. Control medium or Lewis male rat SMs (fresh or subjected to Cryo or HS) were injected in Lewis female rats. RESULTS: There was a massive cell loss early after transplantation in the fresh group, which was only partially compensated for by a subsequent proliferation. Conversely, both Cryo and HS significantly improved early cell survival but blunted subsequent proliferation so that, at 15 days posttransplantation, the total number of engrafted donor-derived Y-positive cells did not differ significantly between the three groups. Most of them expressed a skeletal muscle phenotype. CONCLUSIONS: These data confirm the high death rate of in-scar transplanted myoblasts, demonstrate the ability of those that survive to proliferate and differentiate along the myogenic pathway but do not support the efficacy of either Cryo or HS for increasing the ultimate magnitude of myoblast engraftment.

Skeletal myoblast transplantation through a catheter-based coronary sinus approach: an effective means of improving function of infarcted myocardium.

AIMS: This study was designed to assess the functional effects of a transvenous coronary sinus technique of skeletal myoblast delivery in infarcted myocardium. METHODS AND RESULTS: An anterior myocardial infarction was created percutaneously in 14 sheep. Simultaneously, a muscle biopsy was harvested and expanded. Two weeks later, sheep were instrumented percutaneously with a dedicated catheter incorporating an extendable needle for puncture of the venous wall and, under endovascular ultrasound guidance, a microcatheter was advanced through the needle into the target scar for cell delivery. Following the baseline echocardiographic assessment of left ventricular (LV) function, sheep were randomly allocated to receive four-staged in-scar injections of either autologous cells (n=7) or culture medium (n=7). Two months later, LV function was reassessed blindly and hearts were explanted for subsequent histological and immunohistochemical analysis. There were no acute procedural complications. Baseline LV ejection fraction (EF) was significantly lower in transplanted sheep than in controls [38% (35-48) vs. 51% (38-55), respectively, P=0.03; median (range)]. Two months later, LVEF was significantly higher in the transplanted group than in controls [50% (47-56) vs. 39% (36-47), respectively, P=0.002]. Clusters of myoblasts were identified by histology and immunohistochemistry in three of the seven transplanted sheep. CONCLUSION: These data suggest the functional efficacy of the transvenous coronary sinus technique as a less invasive means of cell delivery to infarcted myocardium.