Inhibition of myostatin promotes myogenic differentiation of rat bone marrow-derived mesenchymal stromal cells

Cooling-promoted myogenic differentiation of murine bone marrow mesenchymal stem cells through TRPM8 activation in vitro

TRPM8 agonist has been reported to promote osteogenic differentiation of mesenchymal stem cells (MSCs), therefore we evaluated whether cooling-induced activation of TRPM8 promotes myogenic differentiation of MSCs. We used 5-azacytidine as a myogenic differentiation inducer in murine bone marrow-derived MSCs. Addition of menthol, a TRPM8 agonist, to the differentiation induction medium significantly, increased the percentage of MyoD-positive cells, a specific marker of myogenic differentiation. We performed intracellular Ca2+ imaging experiments using fura-2 to confirm TRPM8 activation by cooling stimulation. The results confirmed that intracellular Ca2+ concentration ([Ca2+ ]i) increases due to TRPM8 activation, and TRPM8 antagonist inhibits increase in [Ca2+ ]i at medium temperatures below 19°C. We also examined the effect of cooling exposure time on myogenic differentiation of MSCs using an external cooling stimulus set at 17°C. The results showed that 60 min of cooling had an acceleratory effect on differentiation (2.18 ± 0.27 times). We observed that the TRPM8 antagonist counteracted the differentiation-promoting effect of the cooling. These results suggest that TRPM8 might modulate the multiple differentiation pathways of MSCs, and that cooling is an effective way of activating TRPM8, which regulates MSCs differentiation in vitro.

The Efficacy of Naïve versus Modified Mesenchymal Stem Cells in Improving Muscle Function in Duchenne Muscular Dystrophy: A Systematic Review

As one of the most common genetic conditions, Duchenne muscular dystrophy (DMD) is a fatal disease caused by a recessive mutation resulting in muscle weakness in both voluntary and involuntary muscles and, eventually, in death because of cardiovascular failure. Currently, there is no pharmacologically curative treatment of DMD, but there is evidence supporting that mesenchymal stem cells (MSCs) are a novel solution for treating DMD. This systematic review focused on elucidating the therapeutic efficacy of MSCs on the DMD in vivo model. A key issue of previous studies was the material-choice, naïve MSCs or modified MSCs; modified MSCs are activated by culture methods or genetic modification. In summary, MSCs seem to improve pulmonary and cardiac functions and thereby improve survival regardless of them being naïve or modified. The improved function of distal skeletal muscles was observed only with primed MSCs treatment but not naïve MSCs. While MSCs can provide significant benefits to DMD mouse models, there is little to no data on the results in human patients. Due to the limited number of human studies, the differences in study design, and the insufficient understanding of mechanisms of action, more rigorous comparative trials are needed to elucidate which types of MSCs and modifications have optimal therapeutic potential.

Beneficial role of adipose-derived mesenchymal stem cells from microfragmented fat in a murine model of duchenne muscular dystrophy

INTRODUCTION

No etiologic therapy is available for Duchenne muscular dystrophy (DMD), but mesenchymal stem cells were shown to be effective in preclinical models of DMD. The objective of this study is to investigate the effect of microfragmented fat extracted on a murine model of DMD.

METHODS

Fat tissue was extracted from healthy human participants and injected IM into DMD mice. Histological analysis, cytokines, and force measurement were performed up to 4 weeks after injection.

RESULTS

Duchenne muscular dystrophy mice injected with microfragmented fat exhibited an improved muscle phenotype (decreased necrosis and fibrosis), a decrease of inflammatory cytokines, and increased strength.

DISCUSSION

Administration of microfragmented fat in key muscles may improve muscular phenotype in patients with DMD. Muscle Nerve, 2019.

BMSC Transplantation Aggravates Inflammation, Oxidative Stress, and Fibrosis and Impairs Skeletal Muscle Regeneration

Skeletal muscle contusion is one of the most common muscle injuries in sports medicine and traumatology. Bone marrow mesenchymal stem cell (BMSC) transplantation has been proposed as a promising strategy to promote skeletal muscle regeneration. However, the roles and underlying mechanisms of BMSCs in the regulation of skeletal muscle regeneration are still not completely clear. Here, we investigated the role of BMSC transplantation after muscle contusion. BMSCs were immediately transplanted into gastrocnemius muscles (GMs) following direct contusion. Comprehensive morphological and genetic analyses were performed after BMSC transplantation. BMSC transplantation exacerbated muscle fibrosis and inflammation, as evidenced by increased leukocyte and macrophage infiltration, increased inflammatory cytokines and chemokines, and increased matrix metalloproteinases. BMSC transplantation also increased muscle oxidative stress. Overall, BMSC transplantation aggravated inflammation, oxidative stress and fibrosis and impaired skeletal muscle regeneration. These results, shed new light on the role of BMSCs in regenerative medicine and indicate that caution is needed in the application of BMSCs for muscle injury.

Activation of Wnt3a signaling promotes myogenic differentiation of mesenchymal stem cells in mdx mice

AIM

Duchenne muscular dystrophy (DMD) is an X-linked genetic muscular disorder with no effective treatment at present. Mesenchymal stem cell (MSC) transplantation has been used to treat DMD, but the efficiency is low. Our previous studies show that activation of Wnt3a signaling promotes myogenic differentiation of MSCs in vitro. Here we report an effective MSC transplantation therapy in mdx mice by activation of Wnt3a signaling.

METHODS

MSCs were isolated from mouse bone marrow, and pretreated with Wnt3a-conditioned medium (Wnt3a-CM), then transplanted into mdx mice. The recipient mice were euthanized at 4, 8, 12, 16 weeks after the transplantation, and muscle pathological changes were examined. The expression of dystrophin in muscle was detected using immunofluorescence staining, RT-PCR and Western blotting.

RESULTS

Sixteen weeks later, transplantation of Wnt3a-pretreated MSCs in mdx mice improved the characteristics of dystrophic muscles evidenced by significant reductions in centrally nucleated myofibers, the variability range of cross-sectional area (CSA) and the connective tissue area of myofibers. Furthermore, transplantation of Wnt3a-pretreated MSCs in mdx mice gradually and markedly increased the expression of dystrophin in muscle, and improved the efficiency of myogenic differentiation.

CONCLUSION

Transplantation of Wnt3a-pretreated MSCs in mdx mice results in long-term amelioration of the dystrophic phenotype and restores dystrophin expression in muscle. The results suggest that Wnt3a may be a promising candidate for the treatment of DMD.

CD44 promotes the migration of bone marrow-derived mesenchymal stem cells toward glioma

Previous in vivo and in vitro studies have shown that human mesenchymal stem cells (MSCs) exhibit tropism for gliomas. However, the mechanism underlying this directed migration remains unclear. The aim of the present study was to investigate the possible mechanism underlying platelet-derived growth factor-BB (PDGF-BB)-induced chemotactic migration of bone marrow-derived MSCs (BMSCs) toward glioma. Rat glioma C6 cell-conditioned medium was utilized to evaluate the chemotactic response of BMSCs toward glioma using an in vitro migration assay. Recombinant rat PDGF-BB was added to C6 cell-conditioned medium to assess its effect on the tropism of BMSCs. The effect of PDGF-BB on the expression levels of cluster of differentiation (CD)44 in BMSCs was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence assays. The results revealed that chemotactic migration was induced in BMSCs by rat glioma C6 cell-conditioned medium, which was enhanced by PDGF-BB treatment in a dose-dependent manner. Furthermore, RT-PCR and immunofluorescence assays showed that CD44 expression was upregulated in BMSCs following treatment with 40 ng/ml PDGF-BB for 12 h. Additionally, 3-h pretreatment with the anti-CD44 neutralizing antibody OX-50 was observed to attenuate the tropism of BMSCs toward glioma in the presence or absence of PDGF-BB. The results of the present study indicate that CD44 mediates the tropism of BMSCs toward glioma, and PDGF-BB promotes the migration of BMSCs toward glioma via the upregulation of CD44 expression in BMSCs. These findings suggest CD44 inhibition may be a potential therapeutic target for the treatment of glioma.

Myostatin Attenuation In Vivo Reduces Adiposity, but Activates Adipogenesis

A potentially novel approach for treating obesity includes attenuating myostatin as this increases muscle mass and decreases fat mass. Notwithstanding, conflicting studies report that myostatin stimulates or inhibits adipogenesis and it is unknown whether reduced adiposity with myostatin attenuation results from changes in fat deposition or adipogenesis. We therefore quantified changes in the stem, transit amplifying and progenitor cell pool in white adipose tissue (WAT) and brown adipose tissue (BAT) using label-retaining wild-type and mstn(-/-) (Jekyll) mice. Muscle mass was larger in Jekyll mice, WAT and BAT mass was smaller and label induction was equal in all tissues from both wild-type and Jekyll mice. The number of label-retaining cells, however, dissipated quicker in WAT and BAT of Jekyll mice and was only 25% and 17%, respectively, of wild-type cell counts 1 month after induction. Adipose cell density was significantly higher in Jekyll mice and increased over time concomitant with label-retaining cell disappearance, which is consistent with enhanced expansion and differentiation of the stem, transit amplifying and progenitor pool. Stromal vascular cells from Jekyll WAT and BAT differentiated into mature adipocytes at a faster rate than wild-type cells and although Jekyll WAT cells also proliferated quicker in vitro, those from BAT did not. Differentiation marker expression in vitro, however, suggests that mstn(-/-) BAT preadipocytes are far more sensitive to the suppressive effects of myostatin. These results suggest that myostatin attenuation stimulates adipogenesis in vivo and that the reduced adiposity in mstn(-/-) animals results from nutrient partitioning away from fat and in support of muscle.

Correlation between in vitro expansion-related cell stiffening and differentiation potential of human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are an attractive cell source for tissue regeneration, given their self-renewal and multilineage potential. However, they are present in only small percentages in human bone marrow, and are generally propagated in vitro prior to downstream use. Previous work has shown that hMSC propagation can lead to alterations in cell behavior and differentiation potency, yet optimization of differentiation based on starting cell elastic modulus is an area still under investigation. To further advance the knowledge in this field, hMSCs were cultured and routinely passaged on tissue-culture polystyrene to investigate the correlation between cell stiffening and differentiation potency during in vitro aging. Local cell elastic modulus was measured at every passage using atomic force microscopy indentation. At each passage, cells were induced to differentiate down myogenic and osteogenic paths. Cells induced to differentiate, as well as undifferentiated cells were assessed for gene and protein expression using quantitative polymerase chain reaction and immunofluorescent staining, respectively, for osteogenic and myogenic markers. Myogenic and osteogenic cell potential are highly reliant on the elastic modulus of the starting cell population (of undifferentiated cells), and this potential appears to peak when the innate cell elastic modulus is close to that of differentiated tissue. However, the latent expression of the same markers in undifferentiated cells also appears to undergo a correlative relationship with cell elastic modulus, indicating some endogenous effects of cell elastic modulus and gene/protein expression. Overall, this study correlates age-related changes with regards to innate cell stiffening and gene/protein expression in commercial hMSCs, providing some guidance as to maintenance and future use of hMSCs in future tissue engineering applications.

Epigallocatechin-3-gallate suppresses the lipid deposition through the apoptosis during differentiation in bovine bone marrow mesenchymal stem cells

Epigallocatechin gallate (EGCG), a major component of tea, has known effects on obesity, fatty liver, and obesity-related cancer. We explored the effects of EGCG on the differentiation of bovine mesenchymal stem cells (BMSCs, which are multipotent) in a dose- and time-dependent manner. Differentiating BMSCs were exposed to various concentrations of EGCG (0, 10, 50, 100, and 200 µM) for 2, 4, and 6 days. BMSCs were cultured in Dulbecco's modified Eagle's medium (DMEM)/high-glucose medium with adipogenic inducers for 6 days, and the expression levels of various genes involved in adipogenesis were measured using real-time polymerase chain reaction (PCR) and Western blotting. We assessed apoptosis by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining of control and EGCG-exposed cells. We found that EGCG significantly suppressed fat deposition and cell viability (P < 0.05). The mRNA and protein levels of various adipogenic factors were measured. Expression of the genes encoding peroxisome proliferator-activated receptor gamma (PPARG), CCAAT/enhancer-binding protein alpha (CEBPA), fatty acid-binding protein 4 (FABP4), and stearoyl-CoA desaturase (SCD) were diminished by EGCG during adipogenic differentiation (P < 0.05). We also found that EGCG lowered the expression levels of the adipogenic proteins encoded by these genes (P < 0.05). EGCG induced apoptosis during adipogenic differentiation (P < 0.05). Thus, exposure to EGCG potentially inhibits adipogenesis by triggering apoptosis; the data suggest that EGCG inhibits adipogenic differentiation in BMSCs.

Myostatin regulates tissue potency and cardiac calcium-handling proteins

Attenuating myostatin enhances striated muscle growth, reduces adiposity, and improves cardiac contractility. To determine whether myostatin influences tissue potency in a manner that could control such pleiotropic actions, we generated label-retaining mice with wild-type and mstn(-/-) (Jekyll) backgrounds in which slow-cycling stem, transit-amplifying, and progenitor cells are preferentially labeled by histone 2B/green fluorescent protein. Jekyll mice were born with fewer label-retaining cells (LRCs) in muscle and heart, consistent with increased stem/progenitor cell contributions to embryonic growth of both tissues. Cardiac LRC recruitment from noncardiac sources occurred in both groups, but lasted longer in Jekyll hearts, whereas heightened β-adrenergic sensitivity of mstn(-/-) hearts was explained by elevated SERCA2a, phospholamban, and β2-adrenergic receptor levels. Jekyll mice were also born with more adipose LRCs despite significantly smaller tissue weights. Reduced adiposity in mstn(-/-) animals is therefore due to reduced lipid deposition as adipoprogenitor pools appear to be enhanced. By contrast, increased bone densities of mstn(-/-) mice are likely compensatory to hypermuscularity because LRC counts were similar in Jekyll and wild-type tibia. Myostatin therefore significantly influences the potency of different tissues, not just muscle, as well as cardiac Ca²⁺-handling proteins. Thus, the pleiotropic phenotype of mstn(-/-) animals may not be due to enhanced muscle development per se, but also to altered stem/progenitor cell pools that ultimately influence tissue potency.

Decorin promotes myogenic differentiation and mdx mice therapeutic effects after transplantation of rat adipose-derived stem cells

BACKGROUND AIMS

Adipose-derived stem cells (ADSC) have been considered as attractive candidates for the treatment of Duchenne muscular dystrophy (DMD), but the rate of ADSC myogenesis is very low. Myostatin (Mstn), a negative regulator of myogenesis, is known to be responsible for limiting skeletal muscle regeneration. Decorin could bind Mstn and deactivate it. Decorin has been shown to improve myogenic differentiation in mdx mice. We hypothesized that inhibition of Mstn by using decorin may ameliorate myogenic differentiation of ADSC.

METHODS

Rat ADSC were transfected with the lentivirus-containing green fluorescence protein (GFP) and human decorin gene. The transfected ADSC were induced by 5-azacytidine (5-AzaC). The rates of myogenic differentiation and adipogenesis were detected. The transfected ADSC were injected into mdx mice and the expression of Mstn and decorin detected by Western blot. Dystrophin was detected after transfected ADSC transplantation by immunofluorescence staining and Western blot. Serum creatine kinase (CK) and histologic changes were also evaluated.

RESULTS

The optimal multiplicity of infection of ADSC was 10. Decorin improved muscle mass. In accordance with the increased muscle mass, dystrophin expression increased. Following the level of decorin increase, the Mstn expression decreased. Furthermore, serum CK and histologic changes in centrally nucleated fiber (CNF) decreased.

CONCLUSIONS

Improved myogenic differentiation of ADSC was observed by using decorin. This process was probably the result of decorin inhibiting Mstn. A new method of DMD therapy combining Mstn inhibition (using decorin) and ADSC transplantation is probably feasible.

Vascular potency of Sus scrofa bone marrow-derived mesenchymal stem cells: a progenitor source of medial but not endothelial cells

Short-term thrombotic occlusion and compliance mismatch hamper clinical use of synthetic small-diameter tissue engineered vascular grafts. It is felt that preconditioning of the graft with intimal (endothelial) and medial (vascular smooth muscle) cells contributes to patency of the graft. Autologous, non-vessel-derived cells are preferred because of systemic vascular pathology and immunologic concerns. We tested in a porcine model whether cultured bone marrow-derived mononuclear cells, also referred to as mesenchymal stem cells (MSC), are a potential source of intimal or medial cells in vascular tissue engineering. We show that MSC cultured in endothelial medium do not gain an endothelial phenotype or functional characteristics, even after enrichment for CD31, culturing under flow, treatment with additional growth factors (vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF)-2), or co-culture with microvascular endothelial cells (EC). On the other hand, we show that MSC cultured in MSC medium, but not in smooth muscle cell medium, show phenotypical and functional characteristics of vascular smooth muscle cells. We conclude that bone marrow-derived MSCs can be used as a bona fide source of medial, but not EC in small-diameter vascular tissue engineering.