Number Of Pax7-positive Cells Research Articles

Lack of PKCθ Promotes Regenerative Ability of Muscle Stem Cells in Chronic Muscle Injury.

Duchenne muscular dystrophy (DMD) is a genetic disease characterized by muscle wasting and chronic inflammation, leading to impaired satellite cells (SCs) function and exhaustion of their regenerative capacity. We previously showed that lack of PKCθ in mdx mice, a mouse model of DMD, reduces muscle wasting and inflammation, and improves muscle regeneration and performance at early stages of the disease. In this study, we show that muscle regeneration is boosted, and fibrosis reduced in mdxθ−/− mice, even at advanced stages of the disease. This phenotype was associated with a higher number of Pax7 positive cells in mdxθ−/− muscle compared with mdx muscle, during the progression of the disease. Moreover, the expression level of Pax7 and Notch1, the pivotal regulators of SCs self-renewal, were upregulated in SCs isolated from mdxθ−/− muscle compared with mdx derived SCs. Likewise, the expression of the Notch ligands Delta1 and Jagged1 was higher in mdxθ−/− muscle compared with mdx. The expression level of Delta1 and Jagged1 was also higher in PKCθ−/− muscle compared with WT muscle following acute injury. In addition, lack of PKCθ prolonged the survival and sustained the differentiation of transplanted myogenic progenitors. Overall, our results suggest that lack of PKCθ promotes muscle repair in dystrophic mice, supporting stem cells survival and maintenance through increased Delta-Notch signaling.

Metformin alleviates muscle wasting post-thermal injury by increasing Pax7-positive muscle progenitor cells

BackgroundProfound skeletal muscle wasting and weakness is common after severe burn and persists for years after injury contributing to morbidity and mortality of burn patients. Currently, no ideal treatment exists to inhibit muscle catabolism. Metformin is an anti-diabetic agent that manages hyperglycemia but has also been shown to have a beneficial effect on stem cells after injury. We hypothesize that metformin administration will increase protein synthesis in the skeletal muscle by increasing the proliferation of muscle progenitor cells, thus mitigating muscle atrophy post-burn injury.MethodsTo determine whether metformin can attenuate muscle catabolism following burn injury, we utilized a 30% total burn surface area (TBSA) full-thickness scald burn in mice and compared burn injuries with and without metformin treatment. We examined the gastrocnemius muscle at 7 and 14 days post-burn injury.ResultsAt 7 days, burn injury significantly reduced myofiber cross-sectional area (CSA) compared to sham, p < 0.05. Metformin treatment significantly attenuated muscle catabolism and preserved muscle CSA at the sham size. To investigate metformin’s effect on satellite cells (muscle progenitors), we examined changes in Pax7, a transcription factor regulating the proliferation of muscle progenitors. Burned animals treated with metformin had a significant increase in Pax7 protein level and the number of Pax7-positive cells at 7 days post-burn, p < 0.05. Moreover, through BrdU proliferation assay, we show that metformin treatment increased the proliferation of satellite cells at 7 days post-burn injury, p < 0.05.ConclusionIn summary, metformin’s various metabolic effects and its modulation of stem cells make it an attractive alternative to mitigate burn-induced muscle wasting while also managing hyperglycemia.

PO-184 Effects of resistance training and aerobic training on Fibronectin of Skeletal Muscle Extracellular Matrix and Satellite Cell in Aging Mice

Objective To investigate the effects of resistance and aerobic training on the content of fibronectin in skeletal muscle extracellular matrix and satellite cell in 9-month-old BALB/c mice, and then explore the effect of fibronectin content change on satellite cell and its intrinsic mechanism, which will provide a new research perspective and theoretical evidence for delaying sarcopenia.&#x0D; Methods 27 one-month-old BALB / c mice of SPF grade were purchased and fed for natural aging. At 9 months of age, the mice were divided into three groups randomly. Group R was resistance exercise training group (n=9), group A was aerobic exercise training group (n=9), and group C was control group (n=9). The load ladder model for resistance training in group R, the pyramid training program for 9 week training, 5 sets of load ladder training every time. 2 min for rest between sets, 1 min for rest between repetitions, 3 times a week. The treadmill training for aerobic training in group A for 9 weeks, the speed of 0.8km/h, 40min every time, 3 times a week. There is no training in group C. During the training, mouse grip strength was tested by the BIOSEB grip instrument once a week. After exercise intervention, the blood of mice was taken from the eyeball, and the gastrocnemius muscles were removed and placed in -80℃ temperature refrigerator to be freezed for tested . Immunofluorescence was used to detect FN and Pax7; The Real-time PCR was used to detect mRNA of FN, Sdc4, Fzd7, Wnt7a, c-Jun, Pax7; Western Blotting was used to detect the FN, sdc4, Fzd7, Wnt7a, c-Jun, p-c-Jun, Pax7 protein content.&#x0D; Results (1) Body weight, grip strength and skeletal muscle mass of mice: The body weight of group C and group R were significantly decreased after 9 weeks to compared with group A (P &lt;0.05; P &lt;0.05). The grip strength of group R and A was significantly increased in the ninth week to compared with group C, (P &lt;0.01; P &lt;0.05); The grip strength of group R and A in the ninth week were significantly higher than that in the first week (P &lt;0.01; P &lt;0.01)；&#x0D; (2) FN in skeletal muscle extracellular matrix and it’s receptor Sdc4: The integrated optical density (IOD) of FN in group R was higher than that in group C and group A, but there was no significant difference among the three groups. The FN mRNA in group R was significantly increased to compared with group A (P&lt;0.05). The FN protein content in group R was significantly increased to compared with group C and group A (P &lt;0.01; P &lt;0.01). There was no significant difference in the expression of Sdc4 mRNA in gastrocnemius muscle among the three groups. Compared with group C, the Sdc4 protein content was significantly down-regulated in both group R and group A (P&lt;0.01; P&lt;0.05).&#x0D; (3) Wnt7a/PCP signaling pathway: The Wnt7a mRNA and Wnt7a protein content in the gastrocnemius muscle of group R were significantly increased to compared with group C (P&lt;0.05; P&lt;0.01)). Compared with group A, Wnt7a protein content in group R was also significantly increased (P&lt;0.05). There was no significant difference in Fzd7 mRNA in gastrocnemius muscle among the three groups; but the Fzd7 protein content in group R was significantly increased to compared with group A (P&lt;0.05). The c-Jun mRNA in group R was significantly increased to compared with group C and A (P&lt;0.05; P&lt; 0.05). The content of c-Jun protein in group R was significantly increased to compared with group C and group A (P&lt;0.01; P&lt;0.01). The content of p-c-Jun protein in group R was significantly increased to compared with group C (P&lt;0.05). &#x0D; (4) Pax7 : The number of Pax7 positive cells in group R was higher than that in group C and group A, but there was no significant difference among the three groups. Pax7 mRNA in group R and group A were significantly lower than that in group C (P&lt;0.05; P&lt;0.01), but Pax7 protein content in group R was significantly higher than group C and group A (P &lt;0.05; P &lt;0.05)&#x0D; Conclusions (1) Exercise can improve muscle strength of aging mice.&#x0D; (2) Resistance training can promote FN in skeletal muscle extracellular matrix and improve skeletal muscle extracellular matrix components of aging mice.&#x0D; (3) Resistance exercise training can promote Pax7 expression through the increase of FN and up-regulation of Wnt7a / PCP signaling pathway, thus make it possible for satellite cell proliferation.

Recombinant human insulin-like growth factor-1 promotes hyperplasia of muscle fibers of urethral rhabdosphincter in rats by activating satellite cells in situ

Objective To observe the activation of satellite cells of urethral rhabdosphincter of Sprague-Dawley (SD) rats after local injetion of human recombinant insulin-like growth factor-1. Methods 20 male SD rats were randomly divided into four groups: control group, and low, medium, and high-dose group (n=5 in each group). Recombinant human insulinlikegrowth factor-1 (rhIGF-1) in doses of 20, 50, 100 μg/μl was locally injected into the urethral wall of rats in low, medium, and high-dose rhIGF-1 group, and the same volume of saline was given to rats in control group. After 4 weeks, the rats were sacrificed. The newly formed myofibers were determined by hematoxylin-eosin (HE) staining and the activation of satellite cells were detected by immunohistochemical staining with satellite cell specific anti-c-Met antibody and anti-pax7 antibody. Results HE staining showed the number of newly formed muscle fibers in control group, 20 μg/μl group, 50 μg/μl group and 100 μg/μl group were (0.82±0.75), (1.33±0.62), (2.00±0.74), (2.67±0.98), respectively; immunofluorescence staining showed the number of pax7 positive muscle fibers were (27.00±2.65), (37.87±9.46), (61.83±11.66), (64.27±9.28), respectively; the mean fluorescence intensity of c-Met were (7.41±2.00), (15.39±4.96), (21.60±4.26), (24.04±3.13), respectively. Compared with control group, new muscle fibers increased significantly in 50 μg/μland 100 μg/μl group (P values were 0.004 and 0.000, respectively). The number of pax7 positive cells also increased significantly in these two groups (P values were 0.000 and 0.000, respectively). However, there was no significant difference between 20 μg/μl group and control group in the number of new muscle fibers and pax7 positive cells (P=0.487 and 0.425, respectively). The mean fluorescence intensity of c-Met in three treated groups were higher than that in control group (P=0.000, 0.000 and 0.000, respectively). Conclusion Local injection of human recombinant insulin-like growth factor-1 in urethral wall activates muscle satellite cells, promoting it to proliferate and differentiate into new muscle fibers, causing the hypertrophy of urethral rhabdosphincter of SD rats. Key words: Recombinant insulin-like growth factor-1; Skeletal muscle satellite cells; Urethral rhabdosphincter

The effect of low intensity shockwave treatment (Li-SWT) on human myoblasts and mouse skeletal muscle

BackgroundTransplanting myogenic cells and scaffolds for tissue engineering in skeletal muscle have shown inconsistent results. One of the limiting factors is neovascularization at the recipient site. Low intensity shockwave therapy (Li-SWT) has been linked to increased tissue regeneration and vascularization, both integral to survival and integration of transplanted cells. This study was conducted to demonstrate the response of myoblasts and skeletal muscle to Li-SWT.MethodPrimary isolated human myoblasts and explants were treated with low intensity shockwaves and subsequently cell viability, proliferation and differentiation were tested. Cardiotoxin induced injury was created in tibialis anterior muscles of 28 mice, and two days later, the lesions were treated with 500 impulses of Li-SWT on one of the legs. The treatment was repeated every third day of the period and ended on day 14 after cardiotoxin injection.. The animals were followed up and documented up to 21 days after cardiotoxin injury.ResultsLi-SWT had no significant effect on cell death, proliferation, differentiation and migration, the explants however showed decreased adhesion. In the animal experiments, qPCR studies revealed a significantly increased expression of apoptotic, angiogenic and myogenic genes; expression of Bax, Bcl2, Casp3, eNOS, Pax7, Myf5 and Met was increased in the early phase of regeneration in the Li-SWT treated hind limbs. Furthermore, a late accumulative angiogenic effect was demonstrated in the Li-SWT treated limbs by a significantly increased expression of Angpt1, eNOS, iNOS, Vegfa, and Pecam1.ConclusionTreatment was associated with an early upregulation in expression of selected apoptotic, pro-inflammatory, angiogenic and satellite cell activating genes after muscle injury. It also showed a late incremental effect on expression of pro-angiogenic genes. However, we found no changes in the number of PAX7 positive cells or blood vessel density in Li-SWT treated and control muscle. Furthermore, Li-SWT in the selected doses did not decrease survival, proliferation or differentiation of myoblasts in vitro.

The response of muscle progenitor cells to cutaneous thermal injury

BackgroundSevere burn results in a systemic response that leads to significant muscle wasting. It is believed that this rapid loss in muscle mass occurs due to increased protein degradation combined with reduced protein synthesis. Alterations in the microenvironment of muscle progenitor cells may partially account for this pathology. The aim of this study was to ascertain the response of muscle progenitor cells following thermal injury in mice and to enlighten the cellular cascades that contribute to the muscle wasting.MethodsC57BL/6 mice received a 20% total body surface area (TBSA) thermal injury. Gastrocnemius muscle was harvested at days 2, 7, and 14 following injury for protein and histological analysis.ResultsWe observed a decrease in myofiber cross-sectional area at 2 days post-burn. This muscle atrophy was compensated for by an increase in myofiber cross-sectional area at 7 and 14 days post-burn. Myeloperoxidase (MPO)-positive cells (neutrophils) increased significantly at 2 days. Moreover, through Western blot analysis of two key mediators of the proteolytic pathway, we show there is an increase in Murf1 and NF-κB 2 days post-burn. MPO-positive cells were also positive for NF-κB, suggesting that neutrophils attain NF-κB activity in the muscle. Unlike inflammatory and proteolytic pathways, the number of Pax7-positive muscle progenitor cells decreased significantly 2 days post-burn. This was followed by a recovery in the number of Pax7-positive cells at 7 and 14 days, suggesting proliferation of muscle progenitors that accompanied regrowth.ConclusionOur data show a biphasic response in the muscles of mice exposed to burn injury, with phenotypic characteristics of muscle atrophy at 2 days while compensation was observed later with a change in Pax7-positive muscle progenitor cells. Targeting muscle progenitors may be of therapeutic benefit in muscle wasting observed after burn injury.

Ageing is associated with diminished muscle re‐growth and myogenic precursor cell expansion early after immobility‐induced atrophy in human skeletal muscle

Recovery of skeletal muscle mass from immobilisation-induced atrophy is faster in young than older individuals, yet the cellular mechanisms remain unknown. We examined the cellular and molecular regulation of muscle recovery in young and older human subjects subsequent to 2 weeks of immobility-induced muscle atrophy. Retraining consisted of 4 weeks of supervised resistive exercise in 9 older (OM: mean age) 67.3, range 61-74 yrs) and 11 young (YM: mean age 24.4, range 21-30 yrs) males. Measures of myofibre area (MFA), Pax7-positive satellite cells (SCs) associated with type I and type II muscle fibres, as well as gene expression analysis of key growth and transcription factors associated with local skeletal muscle milieu, were performed after 2 weeks immobility (Imm) and following 3 days (+3d) and 4 weeks (+4wks) of retraining. OM demonstrated no detectable gains in MFA (vastus lateralis muscle) and no increases in number of Pax7-positive SCs following 4wks retraining, whereas YM increased their MFA (P < 0.05), number of Pax7-positive cells, and had more Pax7-positive cells per type II fibre than OM at +3d and +4wks (P < 0.05). No age-related differences were observed in mRNA expression of IGF-1Ea, MGF, MyoD1 and HGF with retraining, whereas myostatin expression levels were more down-regulated in YM compared to OM at +3d (P < 0.05). In conclusion, the diminished muscle re-growth after immobilisation in elderly humans was associated with a lesser response in satellite cell proliferation in combination with an age-specific regulation of myostatin. In contrast, expression of local growth factors did not seem to explain the age-related difference in muscle mass recovery.

Skeletal muscle satellite cell content following acute resistance exercise with or without essential amino acid ingestion in young adults

Recent research shows that the number of Pax7 positive satellite cells increases between 24 to 48 hours following a bout of resistance exercise (RE). However, the behavior of Pax7 positive satellite cells during early postexercise recovery or with essential amino acid (EAA) ingestion has not been determined. Therefore, our aim was to determine whether the number of Pax7 positive satellite cells increase within 6 hours post RE and if this response is potentiated with EAA ingestion. Young (age=27±2 yrs) subjects were randomized into 2 groups consisting of either leg RE (n=5) or leg RE plus ingestion of 20 g of EAA 1 hour following exercise (n=4). Muscle biopsies were obtained from the vastus lateralis at baseline and at 6 hours post‐exercise. Immunohistochemical analysis of Pax7 was assessed via epifluorescent microscopy. We observed no change in the number of Pax7 positive cells from baseline (0.0705±0.012 cells/fiber) to 6 hours post RE (0.0684±0.016 cells/fiber; p = 0.92). Additionally, no change in Pax7 positive cells was noted 6 hours post RE with EAA ingestion (0.0601±0.018 cells/fiber) from baseline (p=0.74). We conclude that an increase in satellite cell content is not detectable during early postexercise recovery (i.e., within 6 hours following leg RE) with or without the ingestion of essential amino acids. Supported by NIH/NIAMS R01 AR049877, NIA P30AG024832, NIH 1UL1RR029876‐01.