The Phenotypic Switch from Chondrocytes to Bone-Forming Cells Involves Asymmetric Cell Division and Apoptosis

We have investigated the early cellular events that take place during the phenotypic switch from hypertrophic chondrocytes to bone-forming cells in a) chondrocytes located inside intact lacunae after embryonic chick femurs had been cut through the hypertrophic cartilage and cultured for 1–15 days; and b) at the cartilage/marrow interface of femurs after short-term culture. Ultrastructural studies were combined with in situ methods localizing proliferating and apoptotic cells, and 3D-reconstructions of confocal images of the cartilage/marrow edge. The crucial event in the phenotypic switch was an asymmetric cell division which resulted in one daughter cell which underwent apoptosis and another viable daughter cell which subsequently differentiated to an osteogenic cell, i.e to a smaller basophilic cell that was positive for alkaline phosphatase, type I collagen, osteonectin, osteopontin, bone sialoprotein and osteocalcin and that, after 12–15 days in culture, could synthesize a mineralized bone matrix within intact lacunae. The present results suggest a mechanism whereby differentiated cells can change their phenotype. At least one mitotic division seems to be required to fix the commitment to the new phenotype.     

Schwann cells differentiated from spheroid-forming cells of rat subcutaneous fat tissue myelinate axons in the spinal cord injury

In the present study, we found that nestin-expressing spheroid cells derived from multipotent adipose stem cells of subcutaneous fat tissue could efficiently differentiate into Schwann cells (SCs) in vitro based on expression of SC markers such as A2B5, GFAP, O4, p75, S100, Sox10, Krox-20, and L1. The induced SC is engrafted to spinal cord injury lesions and formed a peripheral nervous system (PNS)-type myelin sheath on central nervous system (CNS) axons. PNS-type myelin sheath formation in repaired tissue was confirmed by transplantation of both induced PKH26-labeled SC and induced EGFP-expressing SC generated from EGFP transgenic rats. In addition to direct participation as myelin sheath-forming SC in repaired tissue, the induced SC also expressed several neurotrophic factors, as did native SC, which may suggest an additional role for induced SC in stimulation of endogenous healing responses. Thus, spheroid-forming cells from subcutaneous fat tissue demonstrated rapid and efficient induction into SC, and such cells show therapeutic promise for repair of damage to the CNS and PNS.     

氯沙坦抑制高糖及间歇性高糖诱导NRK-52E细胞的转分化作用

目的 探讨氯沙坦对高糖及间歇性高糖诱导大鼠肾小管导管上皮细胞株NRK-52E转分化的抑制作用。方法 实验分为空白组(0 mmol/L葡萄糖)、正常葡萄糖组(5 mmol/L葡萄糖)、高糖干预组(25 mmol/L葡萄糖)、间歇性高糖干预组(5 mmol/L葡萄糖/25 mmol/L葡萄糖交替)、氯沙坦干预组(10 μmol/L氯沙坦)、氯沙坦高糖干预组(10 μmol/L氯沙坦预处理后再高糖培养)、氯沙坦间歇性高糖干预组(10 μmol/L氯沙坦预处理后再间歇性高糖培养), 根据分组对NRK-52E细胞施加相应因素作用72 h后, 蛋白免疫印迹法检测转分化标志物转化生长因子β1(TGF-β1)、Ⅰ型胶原、金属蛋白酶2(MMP-2)、α平滑肌肌动蛋白(α-SMA)以及甲状旁腺素相关肽(PTHrP)在细胞中的表达, CM2H2DCFDA试剂盒检测细胞ROS含量。结果 高糖干预及间歇性高糖干预组TGF-β1、Ⅰ型胶原、MMP-2、α-SMA和PTHrP表达上调, ROS含量明显上升, 间歇性高糖作用更显著。应用氯沙坦干预后可以部分下调高糖或间歇性高糖诱导的TGF-β1、Ⅰ型胶原、MMP-2、α-SMA以及PTHrP表达, 降低细胞ROS含量。结论 氯沙坦可抑制高糖及间歇性高糖诱导的NRK-52E细胞转分化作用。