Myoprotective effects of bFGF on skeletal muscle injury in pressure-related deep tissue injury in rats

Trichostatin A reverses rocuronium resistance in burn-injured rats

AIMS

This study aimed to investigate whether the histone deacetylase HDAC4 inhibitor, trichostatin A (TSA), could reverse resistance to non-depolarizing muscle relaxants (NDMRs) caused by burn injuries.

MATERIALS AND METHODS

A rat burn injury model was established, in which TSA was administered to inhibit HDAC4 expression. The potency of rocuronium was assessed through tension tests, and the levels of HDAC4 and myogenin proteins were determined using Western blot. Additionally, siRNA was utilized to explore the effects of HDAC4 knockdown on rocuronium potency and protein expression.

RESULTS

The burn injuries increased the IC50 of rocuronium, which was reversed by TSA treatment. Furthermore, HDAC4 and myogenin protein expression levels were increased significantly in burned legs, a phenomenon that TSA effectively counteracted. HDAC4 knockdown decreased rocuronium IC50 and lowered HDAC4 and myogenin protein expression in the subsequent burn injuries.

CONCLUSION

The HDAC4 inhibitor TSA has the ability to mitigate NDMR resistance in skeletal muscle via the HDAC4-myogenin pathway after burn injuries.

Advance in topical biomaterials and mechanisms for the intervention of pressure injury

Pressure injuries (PIs) are localized tissue damage resulting from prolonged compression or shear forces on the skin or underlying tissue, or both. Different stages of PIs share common features include intense oxidative stress, abnormal inflammatory response, cell death, and subdued tissue remodeling. Despite various clinical interventions, stage 1 or stage 2 PIs are hard to monitor for the changes of skin or identify from other disease, whereas stage 3 or stage 4 PIs are challenging to heal, painful, expensive to manage, and have a negative impact on quality of life. Here, we review the underlying pathogenesis and the current advances of biochemicals in PIs. We first discuss the crucial events involved in the pathogenesis of PIs and key biochemical pathways lead to wound delay. Then, we examine the recent progress of biomaterials-assisted wound prevention and healing and their prospects.

Porous Se@SiO2 nanoparticles improve oxidative injury to promote muscle regeneration via modulating mitochondria

Background: Acute skeletal muscle injuries are common among physical or sports traumas. The excessive oxidative stress at the site of injury impairs muscle regeneration. The authors have recently developed porous Se@SiO₂ nanoparticles (NPs) with antioxidant properties. Methods: The protective effects were evaluated by cell proliferation, myogenic differentiation and mitochondrial activity. Then, the therapeutic effect was investigated in a cardiotoxin-induced muscle injury rat model. Results: Porous Se@SiO₂ NPs significantly protected the morphological and functional stability of mitochondria, thus protecting satellite cells from H₂O₂-induced damage to cell proliferation and myogenic differentiation. In the rat model, intervention with porous Se@SiO₂ NPs promoted muscle regeneration. Conclusion: This study reveals the application potential of porous Se@SiO₂ NPs in skeletal muscle diseases related to mitochondrial dysfunction.

Tazarotene gel promotes healing of deep tissue injury in mice

We investigated the efficacy and molecular mechanisms of tazarotene gel for healing deep tissue injury (DTI). We used male C57BL/6J mice to establish a DTI model. Animals were divided randomly into control, tazarotene gel and purilon gel groups. We injected 100 ul tazarotene gel, purilon gel or saline every 48 h for 20 days. Hematoxylin and eosin staining was used to observe pathological changes on days 14 and 21. The mRNA and protein expression of VEGF-α, TGF-β1 and HIF-1α were detected by qRT-PCR and western blot, respectively. Wound sites exhibited accelerated healing by 20 days in the tazarotene gel group. Fewer inflammatory cells and more granulation tissue were found in both experimental groups compared to controls. The mRNA and protein expression of VEGF-α and TGF-β1 in the experimental groups were increased compared to the control group by day 14. Expression of HIF-1α in the experimental groups was significantly less than in the controls. Tazarotene gel promoted wound healing independent of the HIF-1α/VEGF signalling pathway during tissue repair of DTI. Tazarotene and purilon gels exhibited similar macroscopic healing of wounds and expression of genes and proteins.

Intramuscular injection of mesenchymal stem cells activates anabolic and catabolic systems in mouse skeletal muscle

Skeletal muscle mass is critical for good quality of life. Mesenchymal stem cells (MSCs) are multipotent stem cells distributed across various tissues. They are characterized by the capacity to secrete growth factors and differentiate into skeletal muscle cells. These capabilities suggest that MSCs might be beneficial for muscle growth. Nevertheless, little is known regarding the effects on muscle protein anabolic and catabolic systems of intramuscular injection of MSCs into skeletal muscle. Therefore, in the present study, we measured changes in mechanistic target of rapamycin complex 1 (mTORC1) signaling, the ubiquitin–proteasome system, and autophagy-lysosome system-related factors after a single intramuscular injection of MSCs with green fluorescence protein (GFP) into mouse muscles. The intramuscularly-injected MSCs were retained in the gastrocnemius muscle for 7 days after the injection, indicated by detection of GFP and expression of platelet-derived growth factor receptor-alpha. The injection of MSCs increased the expression of satellite cell-related genes, activated mTORC1 signaling and muscle protein synthesis, and increased protein ubiquitination and autophagosome formation (indicated by the expression of microtubule-associated protein 1 light chain 3-II). These results suggest that the intramuscular injection of MSCs activated muscle anabolic and catabolic systems and accelerated muscle protein turnover.

[Effects and mechanism of hepatocyte growth factor-modified human adipose mesenchymal stem cells on wound healing of full-thickness skin defects in diabetic rats]

Objective: To investigate the effects and mechanism of hepatocyte growth factor (HGF)-modified human adipose mesenchymal stem cells (ADSCs) on the wound healing of full-thickness skin defects in diabetic rats. Methods: The experimental research method was adopted. The discarded abdominal adipose tissue was collected from a 35-year-old healthy female who underwent abdominal liposuction in the Department of Plastic Surgery of the First Affiliated Hospital of Air Force Medical University in December 2019. The long spindle-shaped primary ADSCs were obtained by collagenase digestion, and the third passage of cells were identified by flow cytometry to positively express ADSCs surface markers CD29 and CD90 and negatively express CD34 and CD45. The third passage of ADSCs were used for the subsequent experiments. ADSCs were transfected with lentivirus-mediated HGF for 4 h (obtaining HGF modified ADSCs) and then routinely cultured for 24 h. The cell morphology was observed under an inverted phase contrast microscope, and the transfection rate was calculated. Eighty-one male Sprague-Dawley rats aged 4 weeks were induced into diabetic rat model by high glucose and high fat diet combined with streptozotocin injection. A full-thickness skin defect wound of 1.5 cm×1.5 cm was made on the back of each rat. The injured rats were divided into phosphate buffer solution (PBS) group, ADSCs alone group, and HGF-modified ADSCs group according to the random number table, with 27 rats in each group. The rats were injected with the same volume of corresponding substances around the wound on post injury day (PID) 1, 3, and 7, respectively. Nine rats in each group were selected according to the random number table, the wound area of whom was measured on PID 0 (immediately), 3, 7, 10, and 14 (after injection on injection day), and the wound healing rates on PID 3, 7, 10, and 14 were calculated. Nine remaining rats in each group were sacrificed after injection on PID 3 and 7, respectively, and the skin tissue around the wound were collected. The mRNA expressions of inflammatory factors such as tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-10 on PID 3 and collagen type Ⅰ and Ⅲ on PID 7 were detected by real-time fluorescent quantitative reverse transcription polymerase chain reaction. The expression level of vascular endothelial growth factor (VEGF) was detected by enzyme-linked immunosorbent assay on PID 7. The protein expression of nuclear factor κb-p65 on PID 3 and phosphorylation level of protein kinase B (Akt) on PID 7 were detected by Western blotting. Data were statistically analyzed with analysis of variance for repeated measurement, one-way analysis of variance, least significant difference t test, and Bonferroni correction. Results: After 24 h of culture, the HGF-transfected human ADSCs showed good morphology, which was not different with the non-transfected ADSCs, and the transfection rate reached 90%. On PID 3, 7, 10, and 14, the wound healing rates of rats in HGF-modified ADSCs group were (31.5±1.0)%, (75.2±2.0)%, (92.2±1.3)%, and (99.1±1.8)%, respectively, being significantly higher than (21.4±1.3)%, (61.4±1.5)%, (80.1±2.1)%, and (92.4±1.8)% in PBS group and (25.1±2.1)%, (67.2±1.3)%, (89.3±1.4)%, and (95.1±2.1)% in ADSCs alone group (t=1.452, 0.393, 0.436, 0.211, 4.982, 3.011, 4.211, 7.503, P<0.05 or P<0.01). On PID 3, compared with those in PBS group and ADSCs alone group, the mRNA expressions of TNF-α and IL-1β and protein expression of nuclear factor κb-p65 in the skin tissue around the wound of rats in HGF-modified ADSCs group were significantly decreased (t=7.281, 17.700, 9.447, 6.231, 13.083, 7.783, P<0.01), and the mRNA expression of IL-10 in the skin tissue around the wound of rats in HGF-modified ADSCs group was significantly increased (t=-6.644, -6.381, P<0.01). On PID 7, compared with those in PBS group and ADSCs alone group, the mRNA expressions of collagen type Ⅰ and Ⅲ, the expression level of VEGF, and the phosphorylation level of Akt in the skin tissue around the wound of rats in HGF-modified ADSCs group were significantly increased (t=-5.126, -4.347, -5.058, -3.367, -10.694, -19.876, -4.890, -6.819, P<0.05 or P<0.01). Conclusions: HGF-modified human ADSCs can significantly promote the wound healing of full-thickness skin defects in diabetic rats. The mechanism may be related to the inhibition of TNF-α and IL-1β expression, the promotion of IL-10, collagen type Ⅰ and Ⅲ, and VEGF expression, which could be related to the inhibition of nuclear factor κB signaling pathway, and the promotion of Akt signaling pathway.

Growth factors improve the proliferation of Jeju black pig muscle cells by regulating myogenic differentiation 1 and growth-related genes

OBJECTIVE

The growth rate of pigs is related to differentiation and proliferation of muscle cells, which are regulated by growth factors and expression of growth-related genes. Thus, the objective of this study was to establish optimal culture conditions for Jeju black pig (JBP) muscle cells and determine the relationship of various factors involved in muscle growth with the proliferation of JBP muscle cells.

METHODS

Muscles were taken from the femur skeletal muscle of JBP embryos. After isolation of the muscle cells, cells were cultured in a 6-well plate under four different culture conditions to optimize culture conditions for JBP muscle cells. To analyze proliferation rate of JBP muscle cells, these muscle cells were seeded into 6-well plates at a density of 1.5×105 cells per well and cultured for 3 days. Western blot and quantitative real-time polymerase chain reaction were applied to verify the myogenic differentiation 1 (MyoD) expression and growth-related gene expression in JBP muscle cells, respectively.

RESULTS

We established a muscle cell line from JBP embryos and optimized its culture conditions. These muscle cells were positive for MyoD, but not for paired box 7. The proliferation rate of these muscle cells was significantly higher in a culture medium containing bFGF and epidermal growth factor + basic fibroblast growth factor (EGF+bFGF) than that without a growth factor or containing EGF alone. Treatment with EGF and bFGF significantly induced the expression of MyoD protein, an important transcription factor in muscle cells. Moreover, we checked the changes of expression of growth-related genes in JBP muscle cells by presence or absence of growth factors. Expression level of collagen type XXI alpha 1 gene was changed only when EGF and bFGF were added together to culture media for JBP muscle cells.

CONCLUSION

Concurrent use of EGF and bFGF increased the expression of MyoD protein, thus regulating the proliferation of JBP muscle cells and the expression of growth-related genes.

Single, high-dose local injection of bFGF improves thyroarytenoid muscle atrophy after paralysis

OBJECTIVES/HYPOTHESIS

Unilateral vocal fold paralysis (UVFP) induces hoarseness due to progressive atrophy of the denervated thyroarytenoid (TA) muscle. Therefore, treatments aimed at regenerating the atrophied TA muscle are required. Basic fibroblast growth factor (bFGF) is involved in muscle development and regeneration. This study aimed to elucidate the effects of bFGF injection on atrophied TA muscle.

STUDY DESIGN

Animal research.

METHODS

A recurrent laryngeal nerve-paralysis rat model was established, and low- (200 ng) or high-dose (2,000 ng) bFGF or saline (control) was injected into the TA muscle 28 days later. The larynges were excised on day 1, 3, 7, 14, and 28 after treatment. The cross-sectional area of the TA muscle in normal and paralyzed sides was compared, and the Ki67-positive (Ki67⁺ ) dividing cells, paired box 7-positive (Pax7⁺ ) satellite cells (SCs), and myogenic differentiation-positive (MyoD⁺ ) myoblasts were counted.

RESULTS

The TA muscle area of animals administered high-dose bFGF increased with time and was significantly larger than that of the saline-injected controls 28 days after treatment (P < .05). The counts of Ki67⁺ and Pax7⁺ cells were the highest on day 1, whereas the MyoD⁺ myoblast count was highest on day 7. These results suggest that bFGF administration into the denervated TA muscles compensated for the atrophied TA muscles by inducing proliferation of SCs and their differentiation to myoblasts.

CONCLUSIONS

A single injection of high-dose bFGF augmented regeneration and differentiation of the atrophied TA muscle by enhancing proliferation and differentiation of muscle SCs, suggesting its possible clinical application in humans with UVFP.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:159-165, 2020.