Impact of Needle Selection on Survival of Muscle-Derived Cells When Used for Laryngeal Injections.

Objective: To describe how differing injector needles and delivery vehicles impact Autologous Muscle-Derived Cell (AMDC) viability when used for laryngeal injection. Methods: In this study, adult porcine muscle tissue was harvested and used to create AMDC populations. While controlling cell concentration (1 × 107 cells/ml), AMDCs including Muscle Progenitor Cells (MPCs) or Motor Endplate Expressing Cells (MEEs) were suspended in either phosphate-buffered saline or polymerizable (in-situ scaffold forming) type I oligomeric collagen solution. Cell suspensions were then injected through 23- and 27-gauge needles of different lengths at the same rate (2 ml/min) using a syringe pump. Cell viability was measured immediately after injection and 24- and 48-hours post-injection, and then compared to baseline cell viability prior to injection. Results: The viability of cells post-injection was not impacted by needle length or needle gauge but was significantly impacted by the delivery vehicle. Overall, injection of cells using collagen as a delivery vehicle maintained the highest cell viability. Conclusion: Needle gauge, needle length, and delivery vehicle are important factors that can affect the viability of injected cell populations. These factors should be considered and adapted to improve injectable MDC therapy outcomes when used for laryngeal applications.

Human Muscle-Derived Cells Are Capable of Tenogenic Differentiation and Contribution to Tendon Repair.

BACKGROUND: It has been reported that the harvested hamstring tendon for autograft could be regenerated with well-oriented fibers and uniformly distributed spindle-shaped cells after removal. However, which cell type might participate in the repair process remains unknown. PURPOSE: To investigate the tenogenic differentiation potential of human muscle-derived cells (MDCs) both in vitro and in vivo. STUDY DESIGN: Controlled laboratory study. METHODS: Primary human MDCs and tenocytes were isolated from discarded materials during a peroneus longus tendon-harvesting procedure. Expression of tenogenic genes were evaluated and compared among MDCs, MDCs with tenogenic induction, and tenocytes. RNA sequencing was performed to evaluate the expression profile of differentiated MDCs. Human MDCs were implanted in a tendon injury model to investigate the in vivo tenogenic differentiation potential. Histologic and functional analyses were performed to evaluate the function of MDCs for tendon repair. RESULTS: The relative expression levels (in fold change) of tenogenic genes Col I, MKX, SCX, THBS4, and TNC in MDCs were significantly upregulated 11.5 ± 1.3, 957.1 ± 63.7, 19.1 ± 2.8, 61.9 ± 4.8, and 10.2 ± 2.8 after tenogenic induction, respectively. The expression profile of tenogenically differentiated MDCs was much closer to primary tenocytes. Activation of TGF-ß/Smad3 signaling significantly promoted the tenogenic differentiation ability of MDCs. Transplanted human MDCs were identified in regenerated tendon and expressed tenogenic genes. As for biomechanical properties, the failure loads in the Matrigel, transplantation, and uninjured groups were 7.2 ± 0.5, 11.6 ± 0.3, and 13.9 ± 0.7 N, while the stiffness values were 4.4 ± 1.3 × 103, 7.6 ± 0.8 × 103, and 10.9 ± 1.1 × 103 N/m. Plantarflexion force, histologic morphology, and motor function were also significantly improved after MDC transplantation in a tendon injury model. CONCLUSION: There exist cells with tenogenic differentiation potential in human skeletal muscles. Activation of TGF-ß/Smad3 signaling plays an important role in tenogenic differentiation for human MDCs. Human MDCs contribute to structural and functional repair for the injured tendon. MDCs are a potential cell source to participate in the repair process after tendon injury. CLINICAL RELEVANCE: The MDCs could be a promising cell source to repair tendon injury.

Skeletal Muscle-Derived Cell Implantation for the Treatment of Fecal Incontinence: A Randomized, Placebo-Controlled Study.

BACKGROUND AND AIMS: Fecal incontinence (FI) improvement following injection of autologous skeletal muscle-derived cells has been previously suggested. This study aimed to test the efficacy and safety of said cells through a multicenter, placebo-controlled study, to determine an appropriate cell dose, and to delineate the target patient population that can most benefit from cell therapy. METHODS: Patients experiencing FI for at least 6 months were randomized to receive a cell-free medium or low or high dose of cells. All patients received pelvic floor electrical stimulation before and after treatment. Incontinence episode frequency (IEF), FI quality of life, FI burden assessed on a visual analog scale, Wexner score, and parameters reflecting anorectal physiological function were all assessed for up to 12 months. RESULTS: Cell therapy improved IEF, FI quality of life, and FI burden, reaching a preset level of statistical significance in IEF change compared with the control treatment. Post hoc exploratory analyses indicated that patients with limited FI duration and high IEF at baseline are most responsive to cells. Effects prevailed or increased in the high cell count group from 6 to 12 months but plateaued or diminished in the low cell count and control groups. Most physiological parameters remained unaltered. No unexpected adverse events were observed. CONCLUSIONS: Injection of a high dose of autologous skeletal muscle-derived cells followed by electrical stimulation significantly improved FI, particularly in patients with limited FI duration and high IEF at baseline, and could become a valuable tool for treatment of FI, subject to confirmatory phase 3 trial(s). (ClinicalTrialRegister.eu; EudraCT Number: 2010-021463-32).

FATP1 Exerts Variable Effects on Adipogenic Differentiation and Proliferation in Cells Derived From Muscle and Adipose Tissue.

In livestock, intramuscular adipose tissue is highly valued whereas adipose tissue in other depots is considered as waste. Thus, genetic factors that favor fat deposition in intramuscular compartments over that in other adipose depots are highly desirable in meat-producing animals. Fatty acid transport 1 (FATP1) has been demonstrated to promote cellular fatty acid uptake and metabolism; however, whether it also influences cellular lipid accumulation remains unclear. In the present study, we investigated the effects of FATP1 on the differentiation and proliferation of adipocytes in five types of cells derived from muscle and adipose tissue and estimated the effects of FATP1 on intramuscular fat (IMF) deposition. We showed that FATP1 is mainly expressed in heart and muscle tissue in buffaloes as well as cells undergoing adipogenic differentiation. Importantly, we found that FATP1 promoted the adipogenic differentiation of muscle-derived cells (buffalo myocytes and intramuscular preadipocytes and mouse C2C12 cells) but did not affect, or even inhibited, that of adipose-derived cells (buffalo subcutaneous preadipocytes and mouse 3T3-L1 cells, respectively). Correspondingly, our results further indicated that FATP1 promotes IMF deposition in mice in vivo. Meanwhile, FATP1 was found to enhance the proliferative activity of all the assessed cells, except murine 3T3-L1 cells. These results provide new insights into the potential effects of FATP1 on IMF deposition, especially regarding its positive effects on meat quality in buffaloes and other livestock.

The effect of skeletal muscle-derived cells implantation on stress urinary incontinence and functional urethral properties in female patients.

OBJECTIVE: To evaluate improvement of stress urinary incontinence (SUI) and functional status of the urethra after autologous skeletal-muscle derived cell (aSMDC) implantation. METHODS: Phase I-II, open, non-randomized, single-center study of ultrasound guided aSMDC implantation (dosed at 0.2 × 106  cells/2 mL) into the external urethral sphincter to treat SUI. RESULTS: A total of 38 patients were treated and followed for 2 years. SUI measured by Incontinence Episode Frequency score, short pad test, quality of life, patient's and clinician's perception significantly improved and remained improved after 2 years. However, urodynamic urethral properties in general did not improve at 1-year after treatment. Subgroup analysis revealed that addition of an adjuvant functional electrical stimulation therapy discontinued 4 weeks after injection in the compliant group, gave better urodynamic values and maintained the long-term SUI improvement at 2 years. CONCLUSION: The aSMDC injection was safe and well-tolerated by patients. The status of SUI improved and with it the quality of life of patients, even if this was not necessarily reflected in the urodynamic urethral properties. Electrical stimulation, as an adjuvant therapy, could have an essential role in the success of the therapy. CLINICAL REGISTRATION: Clinical study was registered under Eudra-CT number: 2010-021867-34 at European Clinical Trial Database (EudraCT), accessible at: EudraCT (europa.eu).

Autologous Muscle-Derived Cell Therapy for Swallowing Impairment in Patients Following Treatment for Head and Neck Cancer.

OBJECTIVES/HYPOTHESIS: To evaluate the safety and potential efficacy of autologous muscle-derived cells (AMDCs) for the treatment of swallowing impairment following treatment for oropharynx cancer. STUDY DESIGN: Prospective, phase I, open label, clinical trial. METHODS: Oropharynx cancer survivors disease free ≥2 years post chemoradiation were recruited. All patients had swallowing impairment but were not feeding tube dependent (Functional Oral Intake Scale [FOIS] ≥ 5). Muscle tissue (50-250 mg) was harvested from the vastus lateralis and 150 × 106 AMDCs were prepared (Cook MyoSite Inc., Pittsburgh, PA). The cells were injected into four sites throughout the intrinsic tongue musculature. Participants were followed for 24 months. The primary outcome measure was safety. Secondary endpoints included objective measures on swallowing fluoroscopy, oral and pharyngeal pressure, and changes in patient-reported outcomes. RESULTS: Ten individuals were enrolled. 100% (10/10) were male. The mean age of the cohort was 65 (±8.87) years. No serious adverse event occurred. Mean tongue pressure increased significantly from 26.3 (±11.1) to 31.8 (±9.5) kPa (P = .017). The mean penetration-aspiration scale did not significantly change from 5.6 (±2.1) to 6.8 (±1.8), and the mean FOIS did not significantly change from 5.4 (±0.5) to 4.6 (±0.7). The incidence of pneumonia was 30% (3/10) and only 10% (1/10) experienced deterioration in swallowing function throughout 2 years of follow-up. The mean eating assessment tool (EAT-10) did not significantly change from 24.1 (±5.57) to 21.3 (±6.3) (P = .12). CONCLUSION: Results of this phase I clinical trial demonstrate that injection of 150 × 106 AMDCs into the tongue is safe and may improve tongue strength, which is durable at 2 years. A blinded placebo-controlled trial is warranted. LEVEL OF EVIDENCE: 3 Laryngoscope, 132:523-527, 2022.

[Experimental study on early repair of peripheral nerve defect in mice by transplantation of muscle-derived cells].

OBJECTIVE: To investigate the mechanism of muscle-derived cells (MDCs) in repairing sciatic nerve defects in mice by observing the early growth of damaged peripheral nerves. METHODS: The hind limb skeletal muscles of mice carrying enhanced green fluorescent protein (EGFP) was collected to extract and culture EGFP-MDCs to P1 generation for later experiments. Five-mm-long nerve defects were created in the right sciatic nerves of C57BL/6 mice to establish a peripheral nerve defect model. The two stumps of sciatic nerve were bridged with 7-mm-long polyurethane (PUR) conduit. For the MDC group, EGFP-MDCs were injected into the PUR conduit. The PUR group without EGFP-MDCs was used as the negative control group. At 1 and 2 weeks after operation, the proximal and distal nerve stumps of the surgical side were collected to generally observe the early growth of nerve. Immunofluorescence staining of S100ß, the marker of Schwann cells, was performed on longitudinal frozen sections of nerve tissues to calculate the maximum migration distance of Schwann cells, and observe the source of the Schwann cells expressing S100ß. Immunofluorescence staining of phosphorylated erb-b2 receptor tyrosine kinase 2 (p-ErbB2) and phosphorylated focal adhesion kinase (p-FAK) in transverse frozen sections of nerve tissue was performed to calculate the positive rates of both proteins. RESULTS: The general observation showed that the proximal and distal stumps of the surgical side in PUR group were not connected at 1 and 2 weeks after operation, while the bilateral nerve stumps in the MDC group were connected at 2 weeks after operation. Immunofluorescence staining showed that the Schwann cells expressing S100ß in proximal and distal nerve stumps of PUR group and MDC group was not connected at 1 week after operation. At 2 weeks after operation, the Schwann cells expressing S100ß in the two nerve stumps of the MDC group were connected, but not in the PUR group. At 2 weeks after operation, the sum of the maximum migration distance of Schwann cells in the regenerated nerve in both two groups was significantly increased when compared with that in each group at 1 week after operation, and that of MDC group was significantly higher than that in the PUR group at both 1 and 2 weeks after operation, the differences were all significant ( P<0.05). At 1 week after operation, the positive rates of p-ErbB2 and p-FAK in the proximal nerve stump of MDC group were significantly higher than those in PUR group ( P<0.05). There was no significant difference in the positive rate of p-ErbB2 of proximal stump between the two groups at 2 weeks after operation ( t=0.327, P=0.747), while the positive rate of p-FAK of MDC group was significantly higher than that of PUR group ( t=4.470, P=0.000). At 1 and 2 weeks after operation, the positive rates of p-ErbB2 and p-FAK in the distal stump of MDC group were significantly higher than those in PUR group ( P<0.05). At 1 and 2 weeks after operation, part of Schwann cells expressing S100ß, which were derived from EGFP-MDCs, could be observed in the regenerated nerves of MDC group. CONCLUSION: MDCs can promote the phosphorylation of ErbB2 and FAK in the nerve stumps of mice, and promote the migration of Schwann cells. MDCs can be differentiated into cells expressing the Schwann cell marker S100ß, or as other cellular components, to involve in the early repair of peripheral nerves.

Effect of Muscle Cell Preservation on Viability and Differentiation of Hamstring Tendon Graft In Vitro.

Muscle tissue is often removed during hamstring tendon graft preparation for anterior cruciate ligament (ACL) reconstruction. The purpose of the study was to test whether preservation of muscle remnants on a tendon graft is beneficial to the graft healing process following ACL reconstruction. Co-culturing of tendon-derived cells (TDCs) and muscle-derived cells (MDCs) was performed at various ratios, and their potential for cell viability and multilineage differentiation was compared to a single TDC cell group. Ligamentous and chondrogenic differentiation was most enhanced when a small population of MDCs was co-cultured with TDCs (6:2 co-culture group). Cell viability and osteogenic differentiation were proportionally enhanced with increasing MDC population size. MDCs co-cultured with TDCs possess both the ability to enhance cell viability and differentiate into other cell lineages.

Generation of myogenic progenitor cell-derived smooth muscle cells for sphincter regeneration.

BACKGROUND: Degeneration of smooth muscles in sphincters can cause debilitating diseases such as fecal incontinence. Skeletal muscle-derived cells have been effectively used in clinics for the regeneration of the skeletal muscle sphincters, such as the external anal or urinary sphincter. However, little is known about the in vitro smooth muscle differentiation potential and in vivo regenerative potential of skeletal muscle-derived cells. METHODS: Myogenic progenitor cells (MPC) were isolated from the skeletal muscle and analyzed by flow cytometry and in vitro differentiation assays. The differentiation of MPC to smooth muscle cells (MPC-SMC) was evaluated by immunofluorescence, flow cytometry, patch-clamp, collagen contraction, and microarray gene expression analysis. In vivo engraftment of MPC-SMC was monitored by transplanting reporter protein-expressing cells into the pyloric sphincter of immunodeficient mice. RESULTS: MPC derived from human skeletal muscle expressed mesenchymal surface markers and exhibit skeletal myogenic differentiation potential in vitro. In contrast, they lack hematopoietic surface marker, as well as adipogenic, osteogenic, and chondrogenic differentiation potential in vitro. Cultivation of MPC in smooth muscle differentiation medium significantly increases the fraction of alpha smooth muscle actin (aSMA) and smoothelin-positive cells, while leaving the number of desmin-positive cells unchanged. Smooth muscle-differentiated MPC (MPC-SMC) exhibit increased expression of smooth muscle-related genes, significantly enhanced numbers of CD146- and CD49a-positive cells, and in vitro contractility and express functional Cav and Kv channels. MPC to MPC-SMC differentiation was also accompanied by a reduction in their skeletal muscle differentiation potential. Upon removal of the smooth muscle differentiation medium, a major fraction of MPC-SMC remained positive for aSMA, suggesting the definitive acquisition of their phenotype. Transplantation of murine MPC-SMC into the mouse pyloric sphincter revealed engraftment of MPC-SMC based on aSMA protein expression within the host smooth muscle tissue. CONCLUSIONS: Our work confirms the ability of MPC to give rise to smooth muscle cells (MPC-SMC) with a well-defined and stable phenotype. Moreover, the engraftment of in vitro-differentiated murine MPC-SMC into the pyloric sphincter in vivo underscores the potential of this cell population as a novel cell therapeutic treatment for smooth muscle regeneration of sphincters.

Contemporary application of autologous muscle-derived cells for urinary sphincter regeneration.

OBJECTIVE: Stress urinary incontinence (SUI) remains a prevalent condition with substantial economic and quality-of-life impact. Treatment for incontinence historically culminates with invasive surgical procedures with recognized complication profiles. Innovative directions for SUI therapeutics are on the horizon, including the utilization of adult autologous muscle-derived cells for urinary sphincter regeneration (AMDC-USR). Herein, we visit fundamental concepts of innovative regenerative medicine technologies for urologic applications. METHODS: Synopsis of contemporary literature review regarding adult autologous muscle-derived cells for urinary sphincter regeneration is presented. RESULTS: Current published literature presents safety and efficacy data regarding AMDC-USR injection in 80 patients at 12-month follow-up. In these early studies, no long-term adverse events were reported and patients undergoing cellular injection at higher doses revealed at least 50% reduction in stress leaks and pad weight at 12-month follow-up. All dose groups demonstrated statistically significant improvement in patient-reported incontinence-specific quality-of-life scores at 12-month follow-up. Conclusions from the pooled analyses indicate that injection of AMDC-USR across a range of dosages appears safe. Efficacy data suggest a dose response with more patients responsive to the higher doses of AMDC-USR. CONCLUSION: Applications for utilization of autologous cellular therapies for treatment of SUI, and conceivably multiple additional indications, are approaching realization. Multiple Phase III randomized, placebo-controlled studies for AMDC-USR are concluding or ongoing to launch this regenerative option for the millions of patients who may ultimately benefit.

Skeletal muscle-derived cells repair peripheral nerve defects in mice.

Skeletal muscle-derived cells have strong secretory function, while skeletal muscle-derived stem cells, which are included in muscle-derived cells, can differentiate into Schwann cell-like cells and other cell types. However, the effect of muscle-derived cells on peripheral nerve defects has not been reported. In this study, 5-mm-long nerve defects were created in the right sciatic nerves of mice to construct a peripheral nerve defect model. Adult female C57BL/6 mice were randomly divided into four groups. For the muscle-derived cell group, muscle-derived cells were injected into the catheter after the cut nerve ends were bridged with a polyurethane catheter. For external oblique muscle-fabricated nerve conduit and polyurethane groups, an external oblique muscle-fabricated nerve conduit or polyurethane catheter was used to bridge the cut nerve ends, respectively. For the sham group, the sciatic nerves on the right side were separated but not excised. At 8 and 12 weeks post-surgery, distributions of axons and myelin sheaths were observed, and the nerve diameter was calculated using immunofluorescence staining. The number, diameter, and thickness of myelinated nerve fibers were detected by toluidine blue staining and transmission electron microscopy. Muscle fiber area ratios were calculated by Masson's trichrome staining of gastrocnemius muscle sections. Sciatic functional index was recorded using walking footprint analysis at 4, 8, and 12 weeks after operation. The results showed that, at 8 and 12 weeks after surgery, myelin sheaths and axons of regenerating nerves were evenly distributed in the muscle-derived cell group. The number, diameter, and myelin sheath thickness of myelinated nerve fibers, as well as gastrocnemius muscle wet weight and muscle area ratio, were significantly higher in the muscle-derived cell group compared with the polyurethane group. At 4, 8, and 12 weeks post-surgery, sciatic functional index was notably increased in the muscle-derived cell group compared with the polyurethane group. These criteria of the muscle-derived cell group were not significantly different from the external oblique muscle-fabricated nerve conduit group. Collectively, these data suggest that muscle-derived cells effectively accelerated peripheral nerve regeneration. This study was approved by the Animal Ethics Committee of Plastic Surgery Hospital, Chinese Academy of Medical Sciences (approval No. 040) on September 28, 2016.

Skeletal muscle-derived cell implantation for the treatment of sphincter-related faecal incontinence.

BACKGROUND: In an earlier pilot study with 10 women, we investigated a new approach for therapy of faecal incontinence (FI) due to obstetric trauma, involving ultrasound-guided injection of autologous skeletal muscle-derived cells (SMDC) into the external anal sphincter (EAS), and observed significant improvement. In the current study, we tested this therapeutic approach in an extended patient group: male and female patients suffering from FI due to EAS damage and/or atrophy. Furthermore, feasibility of lower cell counts and cryo-preserved SMDC was assessed. METHODS: In this single-centre, explorative, baseline-controlled clinical trial, each patient (n = 39; mean age 60.6 ± 13.81 years) received 79.4 ± 22.5 × 106 cryo-preserved autologous SMDC. Changes in FI parameters, Fecal Incontinence Quality of Life (FIQL), anorectal manometry and safety from baseline to 1, 6 and 12 months post implantation were evaluated. RESULTS: SMDC used in this trial contained a high percentage of myogenic-expressing (CD56+) and muscle stem cell marker-expressing (Pax7+, Myf5+) cells. Intervention was well tolerated without any serious adverse events. After 12 months, the number of weekly incontinence episodes (WIE, primary variable), FIQL and patient condition had improved significantly. In 80.6% of males and 78.4% of females, the WIE frequency decreased by at least 50%; Wexner scores and severity of FI complaints decreased significantly, independent of gender and cause of FI. CONCLUSIONS: Injection of SMDCs into the EAS effectively improved sphincter-related FI due to EAS damage and/or atrophy in males and females. When confirmed in a larger, placebo-controlled trial, this minimal invasive procedure has the potential to become first-line therapy for FI. TRIAL REGISTRATION: EU Clinical Trials Register, EudraCT 2010-023826-19 (Date of registration: 08.11.2010).

Intraurethral co-transplantation of bone marrow mesenchymal stem cells and muscle-derived cells improves the urethral closure.

BACKGROUND: Cell therapy constitutes an attractive alternative to treat stress urinary incontinence. Although promising results have been demonstrated in this field, the procedure requires further optimization. The most commonly proposed cell types for intraurethral injections are muscle derived cells (MDCs) and mesenchymal stem/stromal cell (MSCs). The aim of this study was to evaluate the effects of MDC-MSC co-transplantation into the urethra. METHODS: Autologous transplantation of labeled MDCs, bone marrow MSCs or co-transplantation of MDC-MSC were performed in aged multiparous female goats (n = 6 in each group). The mean number of cells injected per animal was 29.6 × 106(± 4.3 × 106). PBS-injected animals constituted the control group (n = 5). Each animal underwent urethral pressure profile (UPP) measurements before and after the injection procedure. The maximal urethral closure pressure (MUCP) and functional area (FA) of UPPs were calculated. The urethras were collected at the 28th or the 84th day after transplantation. The marker fluorochrome (DID) was visualized and quantified using in vivo imaging system in whole explants. Myogenic differentiation of the graft was immunohistochemically evaluated. RESULTS: The grafted cells were identified in all urethras collected at day 28 regardless of injected cell type. At this time point the strongest DID-derived signal (normalized to the number of injected cells) was noted in the co-transplanted group. There was a distinct decline in signal intensity between day 28 and day 84 in all types of transplantation. Both MSCs and MDCs contributed to striated muscle formation if transplanted directly to the external urethral sphincter. In the MSC group those events were rare. If cells were injected into the submucosal region they remained undifferentiated usually packed in clearly distinguishable depots. The mean increase in MUCP after transplantation in comparison to the pre-transplantation state in the MDC, MSC and MDC-MSC groups was 12.3% (± 11.2%, not significant (ns)), 8.2% (± 9.6%, ns) and 24.1% (± 3.1%, p = 0.02), respectively. The mean increase in FA after transplantation in the MDC, MSC and MDC-MSC groups amounted to 17.8% (± 15.4%, ns), 15.2% (± 12.9%, ns) and 17.8% (± 2.5%, p = 0.04), respectively. CONCLUSIONS: The results suggest that MDC-MSC co-transplantation provides a greater chance of improvement in urethral closure than transplantation of each population alone.

Autologous muscle-derived cells for the treatment of female stress urinary incontinence: a 2-year follow-up of a Polish investigation.

AIMS: We evaluated the safety, feasibility and initial effects of therapy with muscle-derived cells (MDCs) for women with stress urinary incontinence (SUI). METHODS: MDCs were isolated from an upper-arm muscle biopsy from 16 women with SUI. Cells were isolated by enzymatic digestion and expanded in vitro for 8-10 weeks. A quantity of 0.6-25 × 10(6) of the obtained cells were injected transurethrally into the urethral rhabdosphincter of women under local anesthesia. The cells were placed circumferentially at the 9, 12, and 3 O'clock positions with endoscopic guidance. RESULTS: The initial results of the treatment of SUI with adult muscle-derived stem cells demonstrate the safety and feasibility of using these cells. The 2-year follow-up revealed a 75% success rate, with some patients achieving complete improvement (50%) and some patients achieving partial improvement (25%), suggesting that the prospects for this method are encouraging. CONCLUSIONS: Stem cell therapy promises to become a minimally invasive method for the regeneration of the urethral rhabdosphincter muscle. Injecting a small number of cells does not preclude obtaining the desired therapeutic result.

Mechanisms of muscle gene regulation in the electric organ of Sternopygus macrurus.

Animals perform a remarkable diversity of movements through the coordinated mechanical contraction of skeletal muscle. This capacity for a wide range of movements is due to the presence of muscle cells with a very plastic phenotype that display many different biochemical, physiological and morphological properties. What factors influence the maintenance and plasticity of differentiated muscle fibers is a fundamental question in muscle biology. We have exploited the remarkable potential of skeletal muscle cells of the gymnotiform electric fish Sternopygus macrurus to trans-differentiate into electrocytes, the non-contractile electrogenic cells of the electric organ (EO), to investigate the mechanisms that regulate the skeletal muscle phenotype. In S. macrurus, mature electrocytes possess a phenotype that is intermediate between muscle and non-muscle cells. How some genes coding for muscle-specific proteins are downregulated while others are maintained, and novel genes are upregulated, is an intriguing problem in the control of skeletal muscle and EO phenotype. To date, the intracellular and extracellular factors that generate and maintain distinct patterns of gene expression in muscle and EO have not been defined. Expression studies in S. macrurus have started to shed light on the role that transcriptional and post-transcriptional events play in regulating specific muscle protein systems and the muscle phenotype of the EO. In addition, these findings also represent an important step toward identifying mechanisms that affect the maintenance and plasticity of the muscle cell phenotype for the evolution of highly specialized non-contractile tissues.