Dystrophin-positive muscle fibers following C2 myoblast transplantation into mdx nude mice

To determine when and how the dystrophin-positive muscle fibers are formed after myoblast transplantation into dystrophin-negative muscles, the tibialis anterior (TA) muscle from mdx nude mouse was chronologically examined after C2 myoblast transplantation by immunohistochemical and glucose 6-phosphate isomerase (GPI) isoenzyme analyses. The host TA muscle transplanted with C2 myoblasts became necrotic with accumulation of basic fibroblast growth factor in the necrotic areas. This may stimulate concomitant proliferation of the host satellite cells and C2 myoblasts. Small dystrophinpositive muscle fibers appeared in the necrotic areas 3 days after transplantation. This TA muscle contained two different kinds of homodimer GPI isoenzymes but did not contain the heterodimer, suggesting rare fusion of host and donor cells. The dystrophin-positive muscle fibers in the necrotic areas rapidly increased in number and in size by 7 days, but they were smaller than the original host muscle fibers. They had central nuclei, indicating that they were regenerating fibers. The presence of heterodimer GPI isoenzyme in these muscles indicated that the regenerating fibers were mosaic host/donor muscle fibers. The dystrophin-positive muscle fibers are probably formed first by fusion of donor cells with each other and then later by the fusion of host satellite and donor cells.     

Engineered three-dimensional rabbit oral epithelial-mesenchymal-muscular hybrid sheets

Regenerative muscles are required for swallowing and mastication, and are important for functional recovery from diseases involving oral muscular defects. Therefore, we generated three-layer hybrid sheets, similar to oral mucosal structures containing submucosal muscles, using rabbit oral mucosa epithelial, mesenchymal, and myoblastic progenitor cells, and examined the structural proteins. Each cell type was obtained from rabbit oral mucosa using enzymatic digestion. Isolated mesenchymal and myoblastic cells were multi-differentiated into osteoblasts, adipocytes, and chondrocytes or myotubes. Isolated epithelial cells were cultured on collagen gels containing isolated mesenchymal cells for 2 weeks, and these epithelial–mesenchymal cell sheets were laminated onto myoblastic cell sheets. The engineered hybrid sheets were multi-stratified in the epithelial and myoblastic layers in a time-dependent manner, expressing intermediate cytoskeletal filament proteins of epithelium and muscle. Hybrid sheets also expressed extracellular matrix basement membrane proteins. Immature cell markers for epithelial and myoblastic cells were observed continuously in hybrid sheet cultures. We established engineered three-dimensional rabbit oral mucosa hybrid sheets containing each immature cell type in vitro.     

In vitro evaluation of human myoblast function after exposure to cobalt and chromium ions

The replacement of a native hip joint by a metal-on-metal prosthesis may induce deleterious inflammatory side effects that are associated with the release of wear particles and metal ions. These events are referred to the adverse reaction to metal debris (ARMD) and the adverse local tissue reaction (ALTR). While wear particles seem involved in ARMD, the role of metal ions in ALTR and their impact on myoblasts, located in the prosthesis vicinity, has not been fully identified. To clarify this issue we investigated, using an in vitro culture system, the effect of cobalt and/or chromium ions (Co²⁺ and/or Cr³⁺) on human myoblast proliferation, cellular differentiation, and inflammatory marker expression. Freshly isolated human myoblasts were cultured in media supplemented with graded concentrations of Co²⁺ and/or Cr³⁺. Co²⁺ induced a concentration-dependent decrease of both myoblast viability and myogenic differentiation while Cr³⁺ did not. Co²⁺ or Co²⁺/Cr³⁺ also induced the upregulation of ICAM-1, whereas HLA-DR expression was unaffected. Moreover, allogenic monocytes induced the synergistic increase of Co²⁺-induced ICAM-1 expression. We also found that Co²⁺ stabilized HIF-1α and increased TLR4, tumor necrosis factor-alpha (TNF-α), and interleukin 1β (IL-1β) expression in a dose and time-dependent manner in human myoblasts. This study showed that Co²⁺, but not Cr³⁺, was toxic toward myoblasts and induced, in the surviving cells, expression of inflammatory markers such as ICAM-1, TLR4, TNF-α, and IL-1β. This suggests that Co²⁺, most efficiently in the presence of monocytes, may be a key inducer of ALTR, which may, if severe and long-lasting, eventually result in prosthesis loosening.     

Biofunctional hydrogels for skeletal muscle constructs

Hydrogel scaffolds encapsulating C2C12 mouse skeletal muscle cells have been engineered as in vitro constructs towards regenerative medicine therapies for the enhancement and inducement of functional skeletal muscle formation. Previous work has largely involved two‐dimensional (2D) muscle strips, naturally occurring hydrogels and incomplete examination of the effects of the scaffold and/or biological functionalization on myogenic differentiation in a controllable manner. The goal of this study was to identify key properties in functionalized poly(ethylene glycol) (PEG)–maleimide (MAL) synthetic hydrogels that promote cell attachment, proliferation and differentiation for the formation of multinucleated myotubes and functional skeletal muscle tissue constructs. Significant differences in myoblast viability were observed as a function of cell seeding density, polymer weight percentage and bioadhesive ligands. The identified optimized conditions for cell survival, required for myotube development, were carried over for differentiation assays. PEG hydrogels (5% weight/volume), functionalized with 2.0 mm RGD adhesive peptide and crosslinked with protease‐cleavable peptides, incubated for 3 days before supplementation with 2% horse serum, significantly increased expression of differentiated skeletal muscle markers by 50%; 17% more multinucleated cells and a 40% increase in the number of nuclei/differentiated cell compared to other conditions. Functionality of cell‐laden hydrogels was demonstrated by a 20% decrease in the extruded length of the hydrogel when stimulated with a contractile agent, compared to 7% for a saline control. This study provided strategies to engineer a three‐dimensional (3D) microenvironment, using synthetic hydrogels to promote the development of differentiated muscle tissue from skeletal muscle progenitor cells to form contractile units. Copyright © 2014 John Wiley & Sons, Ltd.     

Systematic review of plasma-membrane ecto-ATP synthase: A new player in health and disease

This review summarizes recent studies on plasma-membrane ecto-ATP synthase from structural and functional standpoints to possible pathophysiological roles. This review discusses significant new contributions and perspectives in the area of ecto-ATP synthase since the topic was last reviewed in 2015. Following an extensive summary of the cell types in which the ecto-ATP synthase is present, its structural and functional mechanism are discussed and physiological and pathological roles of the ecto-ATP synthase are reviewed and evaluated. Attempts to define the possible role of ecto-ATP synthase as possible target for anti-cancer and anti-obesity interventions are discussed.     

犬成年骨骼肌成肌细胞的培养纯化、鉴定及生长特性的研究

目的建立简便、有效的成年犬骨骼肌成肌细胞（skeletal myoblast cells，SMCS）体外分离培养、纯化和鉴定的方法，并观察犬SMCs的生长特性。方法采用机械分解法与IA型胶原酶和胰蛋白酶的二步酶消化法相结合，分离消化法培养获取犬SMCs，用DMEM培养液培养，以Ficoll梯度液纯化，进行Desmin免疫组化鉴定，并观察细胞形态、生长特性。结果犬SMCs培养后经台盼蓝检查成活率达95％以上，在接种后4～5d增殖达高峰，细胞生长旺盛；Fiooll分离纯化的SMCs纯度较高；Desmin免疫细胞化学染色有97％的SMCs胞浆呈阳性反应。结论改良方法获得的SMCs具有良好的增殖、分化能力；采用FicollU纯化以血清培养，即可获得高产量高纯度的SMCs。     

Modulation of the microenvironment by growth factors regulates the in vivo growth of skeletal myoblasts

OBJECTIVES

To investigate the optimal microenvironment for efficient myoblast transplantation in vivo.

MATERIALS AND METHODS

The effects of co‐culture with growth factors, including basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), insulin‐like growth factor‐I) and platelet‐derived growth factor (PDGF), on in vitro growth, migration and proteolytic activity of mouse skeletal myoblasts were investigated. Myoblasts were co‐injected with growth factors into the subcutis and bladder wall of nude mice, and its impact on the growth patterns of myoblasts in vivo assessed.

RESULTS

There was dose‐dependent stimulation of in vitro myoblast growth after treatment with each of the four growth factors, but bFGF induced the most marked increase in the growth of myoblasts. Treatment of myoblasts with all types of growth factors also resulted in a dose‐dependent increase in the in vitro migration of myoblasts, and PDGF had the most prominent effect on myoblast migration. Increased secretion of matrix metalloproteinase‐9 (MMP‐9) in myoblasts induced by growth factors was proportional to their increased migration capacity, which was partly inhibited by SB‐3CT, an inhibitor of MMP‐9. The in vivo growth of myoblasts was significantly enhanced by co‐injection with all types of growth factor into both the subcutis and bladder wall, but this effect was most marked 1 and 2 weeks after co‐injection with bFGF and PDGF, respectively. Furthermore, there was synergistic in vivo growth of myoblasts by co‐injection of both bFGF and PDGF compared with that achieved with either agent alone.

CONCLUSIONS

These findings suggest that modulation of the microenvironment using growth factors, particularly bFGF and PDGF, could provide the optimum condition for effective myoblast transplantation in vivo.     

聚集蛋白基因在原代培养成肌细胞中的表达

目的研究神经源性聚集蛋白（agrin）基因在原代培养成肌细胞中的表达。方法原代培养成年大鼠的成肌细胞，免疫细胞化学方法进行鉴定，将agrin—Y428基因cDNA片段亚克隆入pCDNA3真核表达载体，重组子经脂质体介导转染成肌细胞，G418筛选，获得具有抗性的克隆，增殖后以逆转录一聚合酶链反应（RT—PCR）和免疫荧光的方法检测基因的转录和蛋白表达，并初步测定其生物学活性。结果原代培养8周后，90％以上仍为成肌细胞，转染神经源性agrin基因后，成肌细胞可以表达相应的mRNA和有功能活性的蛋白。结论原代培养的成肌细胞可以作为agrin基因转移的有效载体，可用于进一步肌肉功能减退的基因治疗中。     

CPUHY002对大鼠心肌细胞瞬时外向钾电流的影响

目的观察一种新合成的磷酸二酯酶Ⅲ(PDEⅢ)抑制剂CPUHY002对大鼠心肌细胞瞬时外向钾电流(Ito)的影响。方法采用全细胞膜片钳技术考察CPUHY002对急性分离大鼠心肌细胞和H9c2细胞系Ito的作用。结果在+50 mV下,CPUHY002对急性分离细胞和H9c2细胞系的Ito呈浓度依赖性抑制,其半数有效抑制浓度(IC50)分别为0.98μmol/L和0.91μmol/L;1μmol/L CPUHY002可使I-V曲线明显下移,Ito峰值分别下降(39.10±2.30)%和(47.32±2.06)%,激活曲线右移,失活曲线左移(未见于H9c2),恢复曲线无显著变化。结论 CPUHY002可浓度依赖性地抑制大鼠心肌细胞Ito。     

周期性牵张应力下成肌细胞面积、周长的变化研究

目的基于成熟的细胞力学加载和细胞图像处理、分析方法,从细胞层次上定量观察成肌细胞周期性牵张应力加载后的面积、周长的时间改建效应。方法通过4点加力装置给成肌细胞施与各种时间段的生理性牵张应力(0.1Hz,2000μstrain),在相差显微镜下观察并记录细胞形态变化;借助计算机细胞图像处理和分析系统对成肌细胞形态进行定量分析。结果加力组和对照组的成肌细胞面积、周长测量值在加力0.5、1.0、2.0h后,两者差异不大,加力4h后两者的差异开始出现,加力8h后两者的差异变得明显;随着加力时间的延长,加力组和对照组间细胞形态参数测量的差别越来越明显。而去除细胞力学刺激后,成肌细胞形态都出现回复趋势。结论连续加力时细胞形态面积、周长变化明显,而停止加力后细胞面积、周长有回复的趋势。