No abstract

Although cellular transplantation has been shown to promote improvements in cardiac function following injury, poor cell survival following transplantation continues to limit the efficacy of this therapy. We have previously observed that transplantation of muscle-derived stem cells (MDSCs) improves cardiac function in an acute murine model of myocardial infarction to a greater extent than myoblasts. This improved regenerative capacity of MDSCs is linked to their increased level of antioxidants such as glutathione (GSH) and superoxide dismutase. In the current study, we demonstrated the pivotal role of antioxidant levels on MDSCs survival and cardiac functional recovery by either reducing the antioxidant levels with diethyl maleate or increasing antioxidant levels with N-acetylcysteine (NAC). Both the anti- and pro-oxidant treatments dramatically influenced the survival of the MDSCs in vitro. When NAC-treated MDSCs were transplanted into infarcted myocardium, we observed significantly improved cardiac function, decreased scar tissue formation, and increased numbers of CD31(+) endothelial cell structures, compared to the injection of untreated and diethyl maleate-treated cells. These results indicate that elevating the levels of antioxidants in MDSCs with NAC can significantly influence their tissue regeneration capacity.

Stem cells are classically defined by their multipotent, long-term proliferation, and self-renewal capabilities. Here, we show that increased antioxidant capacity represents an additional functional characteristic of muscle-derived stem cells (MDSCs). Seeking to understand the superior regenerative capacity of MDSCs compared with myoblasts in cardiac and skeletal muscle transplantation, our group hypothesized that survival of the oxidative and inflammatory stress inherent to transplantation may play an important role. Evidence of increased enzymatic and nonenzymatic antioxidant capacity of MDSCs were observed in terms of higher levels of superoxide dismutase and glutathione, which appears to confer a differentiation and survival advantage. Further when glutathione levels of the MDSCs are lowered to that of myoblasts, the transplantation advantage of MDSCs over myoblasts is lost when transplanted into both skeletal and cardiac muscles. These findings elucidate an important cause for the superior regenerative capacity of MDSCs, and provide functional evidence for the emerging role of antioxidant capacity as a critical property for MDSC survival post-transplantation. INTRODUCTIONMyogenic cell transplantation has been proposed as a promising therapeutic approach in the treatment of skeletal and cardiac muscle injury. Early studies of myoblast transplantation into dystrophic skeletal muscle yielded limited regeneration of dystrophin-expressing muscle fibers (Beauchamp et al., 1994;Gussoni et al., 1997;Qu-Petersen et al., 2002). Similarly, given the limited regenerative ability of cardiac muscle, cell transplantation has been proposed as an alternative to heart transplantation (Assmus et al., 2006;Lunde et al., 2006;Schachinger et al., 2006).A major obstacle in both cardiac and skeletal myogenic therapies is the poor rate of engraftment of myogenic cells after transplantation (Taylor et al., 1998;Oshima et al., 2005). In skeletal muscle, numerous groups have observed a rapid inflammatory response that appears to contribute to rapid cell loss and limit therapeutic success (Beauchamp et al., 1994;Gussoni et al., 1997;Beauchamp et al., 1999). Multiple groups have postulated that the small number of injected cells that survive transplantation in both cardiac and skeletal muscle may represent a special subpopulation of stem-like cells (Qu et al., 1998;Beauchamp et al., 1999;Qu-Petersen et al., 2002).For these reasons, our group attempted to isolate this putative subpopulation of cells using a modified preplate technique. This procedure was initially developed to purify myoblasts from nonmyogenic cells, including fibroblasts, of whole tissue preparations based on the differential adhesion characteristics of the cells to a collagen coated flask (Rando and Blau, 1994). Our group modified this technique to isolate various populations of myogenic cells, including a population of early adhering preplate (EP) cells and a late adhering preplate (LP) cell population from which a subpopulation of long-term proliferating (LTP) cells,...

No abstract

BackgroundDespite the initial promise of myoblast transfer therapy to restore dystrophin in Duchenne muscular dystrophy patients, clinical efficacy has been limited, primarily by poor cell survival post-transplantation. Murine muscle derived stem cells (MDSCs) isolated from slowly adhering cells (SACs) via the preplate technique, induce greater muscle regeneration than murine myoblasts, primarily due to improved post-transplantation survival, which is conferred by their increased stress resistance capacity. Aldehyde dehydrogenase (ALDH) represents a family of enzymes with important morphogenic as well as oxidative damage mitigating roles and has been found to be a marker of stem cells in both normal and malignant tissue. In this study, we hypothesized that elevated ALDH levels could identify murine and human muscle derived cell (hMDC) progenitors, endowed with enhanced stress resistance and muscle regeneration capacity.Methodology/Principal FindingsSkeletal muscle progenitors were isolated from murine and human skeletal muscle by a modified preplate technique and unfractionated enzymatic digestion, respectively. ALDHhi subpopulations isolated by fluorescence activate cell sorting demonstrated increased proliferation and myogenic differentiation capacities compared to their ALDHlo counterparts when cultivated in oxidative and inflammatory stress media conditions. This behavior correlated with increased intracellular levels of reduced glutathione and superoxide dismutase. ALDHhi murine myoblasts were observed to exhibit an increased muscle regenerative potential compared to ALDHlo myoblasts, undergo multipotent differentiation (osteogenic and chondrogenic), and were found predominately in the SAC fraction, characteristics that are also observed in murine MDSCs. Likewise, human ALDHhi hMDCs demonstrated superior muscle regenerative capacity compared to ALDHlo hMDCs.ConclusionsThe methodology of isolating myogenic cells on the basis of elevated ALDH activity yielded cells with increased stress resistance, a behavior that conferred increased regenerative capacity of dystrophic murine skeletal muscle. This result demonstrates the critical role of stress resistance in myogenic cell therapy as well as confirms the role of ALDH as a marker for rapid isolation of murine and human myogenic progenitors for cell therapy.

Copper films of different thicknesses of 0.2, 0.5, 1 and 2 microns were electroplated on top of the adhesion-promoting barrier layers on <100> single crystal silicon wafers. Controlled Cu grain growth was achieved by annealing films in vacuum.The Cu film microstructure was characterized using Atomic Force Microscopy and Focused Ion Beam Microscopy. Elastic modulus of 110 to 130 GPa and hardness of 1 to 1.6 GPa were measured using the continuous stiffness option (CSM) of the Nanoindenter XP. Thicker films appeared to be softer in terms of the lower modulus and hardness, exhibiting a classical Hall-Petch relationship between the yield stress and grain size. Lower elastic modulus of thicker films is due to the higher porosity and partially due to the surface roughness. Comparison between the mechanical properties of films on the substrates obtained by nanoindentation and tensile tests of the freestanding Cu films is made.

Abstract:A non-contact galvanometer-based optical scanning system for diffuse correlation tomography was developed for monitoring bone graft healing in a murine femur model. A linear image reconstruction algorithm for diffuse correlation tomography was tested using finite-element method based simulated data and experimental data from a femur or a tube suspended in a homogeneous liquid phantom. Finally, the non-contact system was utilized to monitor in vivo blood flow changes prior to and one week after bone graft transplantation within murine femurs. Localized blood flow changes were observed in three mice, demonstrating a potential for quantification of longitudinal blood flow associated with bone graft healing.

Intramuscular injection of bone morphogenetic proteins (BMPs) has been shown to induce ectopic bone formation. A chondrogenic phase is typically observed in this process, which suggests that there may exist a chondrogenic subpopulation of cells residing in skeletal muscle. Two prospective cell populations were isolated from rat skeletal muscle: fascia-derived cells (FDCs), extracted from gluteus maximus muscle fascia (epimysium) and muscle-derived cells (MDCs) isolated from the muscle body. Both populations were investigated for their cell surface marker profiles (flowcytometry analysis), proliferation rates as well as their myogenic and chondrogenic potentials. The majority of FDCs expressed mesenchymal stromal cell markers but not endothelial cell markers. FDCs underwent chondrogenic differentiation after BMP4 treatment in vitro, but not myogenic differentiation. Although MDCs showed chondrogenic potential, they expressed the myogenic cell marker desmin and readily underwent myogenic differentiation in vitro; however, the chondrogenic potential of the MDCs is confounded by the presence of FDC-like cells residing in the muscle perimysium and endomysium. To clarify the role of the muscle-derived myogenic cells in chondrogenesis, mixed pellets with varying ratios of FDCs and L6 myoblasts were formed and studied for chondrogenic potential. Our results indicated that the chondrogenic potential of the mixed pellets decreased with the increased ratio of myogenic cells to FDCs supporting the role of FDCs in chondrogenesis. Taken together, our results suggest that non-myogenic cells residing in the fascia of skeletal muscle have a strong chondrogenic potential and may represent a novel donor cell source for cartilage regeneration and repair.