Jeong Seung Yeon, Choi Jun Hee, Allen Paul D, Lee Eun Hui
Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea.
Department of Medical Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Republic of Korea.
Cells. 2024 Dec 23;13(24):2136. doi: 10.3390/cells13242136.
Injured or atrophied adult skeletal muscles are regenerated through terminal differentiation of satellite cells to form multinucleated muscle fibers. Transplantation of satellite cells or cultured myoblasts has been used to improve skeletal muscle regeneration. Some of the limitations observed result from the limited number of available satellite cells that can be harvested and the efficiency of fusion of cultured myoblasts with mature muscle fibers (i.e., terminal differentiation) upon transplantation. However, the possible use of immature myotubes in the middle of the terminal differentiation process instead of satellite cells or cultured myoblasts has not been thoroughly investigated. Herein, myoblasts (Mb) or immature myotubes on differentiation day 2 (D2 immature myotubes) or 3 (D3 immature myotubes) were transferred to plates containing D2 or D3 immature myotubes as host cells. The transferred Mb/immature myotubes on the plates were further co-differentiated with host immature myotubes into mature myotubes in six conditions: Mb-to-D2, D2-to-D2, D3-to-D2, Mb-to-D3, D2-to-D3, and D3-to-D3. Among these six co-differentiation conditions, the D2-to-D3 co-differentiation condition exhibited the most characteristic myotube appearance and the greatest availability of Ca for skeletal muscle contraction. Compared with non-co-differentiated control myotubes, D2-to-D3 co-differentiated myotubes presented increased MyoD and myosin heavy chain II (MyHC II) expression and increased myotube width, accompanied by parallel and swirling alignment. These increases correlated with functional increases in both electrically induced intracellular Ca release and extracellular Ca entry due to the increased expression of ryanodine receptor 1 (RyR1), sarcoplasmic/endoplasmic reticulum Ca-ATPase 1a (SERCA1a), and stromal interaction molecule 1 (STIM1). These increases were not detected in any of the other co-differentiation conditions. These results suggest that in vitro-cultured D2-to-D3 co-differentiated mature myotubes could be a good alternative source of satellite cells or cultured myoblasts for skeletal muscle regeneration.
受损或萎缩的成年骨骼肌通过卫星细胞的终末分化得以再生，从而形成多核肌纤维。卫星细胞或培养的成肌细胞移植已被用于改善骨骼肌再生。观察到的一些局限性源于可收获的卫星细胞数量有限，以及培养的成肌细胞在移植后与成熟肌纤维融合（即终末分化）的效率。然而，在终末分化过程中期使用未成熟肌管而非卫星细胞或培养的成肌细胞的可能性尚未得到充分研究。在此，将成肌细胞（Mb）或分化第2天（D2未成熟肌管）或第3天（D3未成熟肌管）的未成熟肌管转移至含有D2或D3未成熟肌管作为宿主细胞的培养皿中。平板上转移的Mb/未成熟肌管在六种条件下与宿主未成熟肌管进一步共同分化为成熟肌管：Mb-to-D2、D2-to-D2、D3-to-D2、Mb-to-D3、D2-to-D3和D3-to-D3。在这六种共同分化条件中，D2-to-D3共同分化条件表现出最典型的肌管外观以及骨骼肌收缩时最大的钙可用性。与未共同分化的对照肌管相比，D2-to-D3共同分化的肌管呈现出MyoD和肌球蛋白重链II（MyHC II）表达增加以及肌管宽度增加，并伴有平行和漩涡状排列。这些增加与电诱导的细胞内钙释放和细胞外钙内流的功能增加相关，这是由于兰尼碱受体1（RyR1）、肌浆网/内质网钙ATP酶1a（SERCA1a）和基质相互作用分子1（STIM1）表达增加所致。在任何其他共同分化条件下均未检测到这些增加。这些结果表明，体外培养的D2-to-D3共同分化的成熟肌管可能是卫星细胞或培养的成肌细胞用于骨骼肌再生的良好替代来源。
