Lack of galectin-1 results in defects in myoblast fusion and muscle regeneration.

Galectin-1 has been implicated in the development of skeletal muscle, being maximally expressed at the time of myofiber formation. Furthermore, in the presence of exogenous galectin-1, mononuclear myoblasts show increased fusion in vitro. In the current study, we have used the galectin-1 null mouse to elucidate the role of galectin-1 in skeletal muscle development and regeneration. Myoblasts derived from the galectin-1 mutant showed a reduced ability to fuse in vitro. In galectin-1 null mutants, there was evidence of a delay in muscle fiber development at the neonatal stage and muscle fiber diameter was reduced when compared with wild-type at the adult stage. Muscle regeneration was also compromised in the galectin-1 mutant with the process being delayed and a reduced fiber size being maintained. These results, therefore, show a definitive role for galectin-1 in fusion of myoblasts both in vitro, in vivo, and in regeneration after recovery from induced injury.     

miR-431 promotes differentiation and regeneration of old skeletal muscle by targeting Smad4

The myogenic capacity of myoblasts decreases in skeletal muscle with age. In addition to environmental factors, intrinsic factors are important for maintaining the regenerative potential of muscle progenitor cells, but their identities are largely unknown. Here, comparative analysis of microRNA (miRNA) expression profiles in young and old myoblasts uncovered miR-431 as a novel miRNA showing markedly reduced abundance in aged myoblasts. Importantly, elevating miR-431 improved the myogenic capacity of old myoblasts, while inhibiting endogenous miR-431 lowered myogenesis. Bioinformatic and biochemical analyses revealed that miR-431 directly interacted with the 3′ untranslated region (UTR) of Smad4 mRNA, which encodes one of the downstream effectors of TGF-β signaling. In keeping with the low levels of miR-431 in old myoblasts, SMAD4 levels increased in this myoblast population. Interestingly, in an in vivo model of muscle regeneration following cardiotoxin injury, ectopic miR-431 injection greatly improved muscle regeneration and reduced SMAD4 levels. Consistent with the finding that the mouse miR-431 seed sequence in the Smad4 3′ UTR is conserved in the human SMAD4 3′ UTR, inhibition of miR-431 also repressed the myogenic capacity of human skeletal myoblasts. Taken together, our results suggest that the age-associated miR-431 plays a key role in maintaining the myogenic ability of skeletal muscle with age.     

The consensus of the task force of the European Society of Cardiology concerning the clinical investigation of the use of autologous adult stem cells for repair of the heart.

A task force has been established by the European Society of Cardiology to investigate the role of progenitor/stem cell therapy in the treatment of cardiovascular disease. This article is the consensus of this group, of what clinical studies are needed in this field, and the challenges to be addressed in the translation of progenitor/stem cell biology to repair of the heart.     

长链非编码RNA在成肌分化中的作用

人类基因组90％可以发生转录,但98％的转录产物为不具有蛋白编码能力的非编码 RNA （ noncoding RNA, ncRNA）。长链非编码RNA （ long noncoding RNA, lncRNA）是指转录本超过200 nt的非编码RNA,曾一度被认为是转录的“噪音”,不具有任何生物学功能。然而,近年报道lncRNA广泛参与成肌分化,可在RNA水平通过多种方式调控成肌分化进程,是成肌分化的重要调节因子。     

Enhancing effects of anagliptin on myoblast differentiation and the expression of mitochondrial biogenetic factors in C2C12 mouse skeletal muscle cells

To investigate the regulatory effects of anagliptin, a DPP-IV inhibitor used to treat type 2 diabetes mellitus (T2DM), on myoblast differentiation and mitochondrial biogenesis in C2C12 mouse skeletal muscle cells. C2C12 myoblasts were differentiated into myotubes and then treated with anagliptin (10, 25, and 50 μmol/L) for 24 hours. In C2C12 myotubes, anagliptin treatment was significantly increased the expression of MHC, PGC1α, Sirt-1, NRF-1, and TFAM and the phosphorylation of AMPK and ACC in a concentration-dependent manner. Anagliptin also significantly increased the total ATP levels in the myotubes. These results suggest that anagliptin can help prevent skeletal muscle dysfunction in T2DM by promotion of myoblast differentiation and enhancement of energy production via upregulation of mitochondrial biogenetic factors and activation of the AMPK/ACC signalling pathway.     

Transcriptome analysis of gene expression changes upon enzymatic dissociation in skeletal myoblasts

Single-cell RNA-sequencing analysis is one of the most effective tools for understanding specific cellular states. The use of single cells or pooled cells in RNA-seq analysis requires the isolation of cells from a tissue or culture. Although trypsin or more recently cold-active protease (CAP) has been used for cell dissociation, the extent to which the gene expression changes are suppressed has not been clarified. To this end, we conducted detailed profiling of the enzyme-dependent gene expression changes in mouse skeletal muscle progenitor cells, focusing on the enzyme treatment time, amount and temperature. We found that the genes whose expression was changed by the enzyme treatment could be classified in a time-dependent manner and that there were genes whose expression was changed independently of the enzyme treatment time, amount and temperature. This study will be useful as reference data for genes that should be excluded or considered for RNA-seq analysis using enzyme isolation methods.     

注射携人IGF-1基因的成肌细胞对小鼠损伤骨骼肌内源性mIGF-1表达的影响

目的:研究携人胰岛素样生长因子-1(human insulin-like growth factor-1,hIGF-1)基因的成肌细胞移植损伤小鼠体内后,内源性mIGF-1 mRNA及mIGF-1因子的表达情况。方法:雄性C3H小鼠(20~30g,7~11周)共76只随机分为3组:A组(转基因成肌细胞移植组)、B组(空白成肌细胞移植组)、C组(生理盐水对照组),每组24只。另4只鼠作正常对照。A、B、C各组小鼠于右下肢腓肠肌内侧面中段实施钝性打击,打击伤后第3天分别于致伤部位注入1×106个转基因成肌细胞、等量的空白成肌细胞或100μl生理盐水;打击伤后第2、5、10、15、20、30天,于各组中随机抽取4只小鼠处死,取右侧腓肠肌中段进行检测,以real time RT-PCR和免疫组化染色检测mIGF-1的表达。结果:(1)各组小鼠体内均有mIGF-1 mRNA的表达、mIGF-1免疫组化染色阳性;(2)A组小鼠mIGF-1 mRNA的表达和mIGF-1因子的分泌明显高于B、C组。结论:携hIGF-1基因的成肌细胞移植入钝挫伤的小鼠体内后,可促进mIGF-1 mRNA的表达和mIGF-1因子的分泌。     

差速贴壁及克隆化培养人胚成肌细胞及其移植恒河猴的实验性研究

６个水囊引产４～５个月龄人胚肢体肌组织，采用０．１％Ⅱ型胶原酶和０．１２５％胰蛋白酶二步消化法，分离肌卫星细胞，在含胎肌条件培养液（ＨＦＭＥ）的培养基中，差速贴壁及克隆纯化，电镜及Ｄｅｓｍｉｎ免疫细胞化学鉴定纯度后，Ｒｕｂｂｅｒｐｏｌｉｃｅ刮除收集，按１．６×１０６个细胞／ｋｇ体重，间隔０．５ｃｍ点均匀移植于恒河猴肱二头肌组织中。结果表明，该方法培养的成肌细胞纯度达９６％以上，移植后血清肌浆酶ＬＤＨ及ＣＰＫ与移植前相近（Ｐ＞０．０５），肌组织活检未见明显坏死，表明成肌细胞移植无宿主肌纤维损伤作用；移植后１周ＣＤ４／ＣＤ８比值大于２，补体Ｃ４短暂下降，但Ｔａｃ各值未超过移植前，２周后ＣＤ４／ＣＤ８比值恢复到正常水平，表明恒河猴对移植人的成肌细胞有排异反应，但可以耐受。移植后１周肌组织中可以检出Ｄｅｓｍｉｎ（＋）成肌细胞生长及移植后２周的ＡＯ（＋）的嗜碱性再生肌纤维，此后早期呈ＨＬＡ－ＤＲ（＋）的ＣＤ３（＋）、ＣＤ８（＋）细胞几尽消退。