SDSU Heart Institute and Biology Department, San Diego State University, CA 92182, USA.
Circ Res. 2012 Apr 27;110(9):1169-73. doi: 10.1161/CIRCRESAHA.112.267716. Epub 2012 Mar 22.
Cardiac progenitor cells (CPCs) in the adult heart are used for cell-based treatment of myocardial damage, but factors determining stemness, self-renewal, and lineage commitment are poorly understood. Immortal DNA strands inherited through asymmetric chromatid segregation correlate with self-renewal of adult stem cells, but the capacity of CPCs for asymmetric segregation to retain immortal strands is unknown. Cardioprotective kinase Pim-1 increases asymmetric cell division in vivo, but the ability of Pim-1 to enhance asymmetric chromatid segregation is unknown.
We aimed to demonstrate immortal strand segregation in CPCs and the enhancement of asymmetric chromatid distribution by Pim-1 kinase.
Asymmetric segregation is tracked by incorporation of bromodeoxyuridine. The CPC DNA was labeled for several generations and then blocked in second cytokinesis during chase to determine distribution of immortal versus newly synthesized strands. Intensity ratios of binucleated CPCs with bromodeoxyuridine of ≥70:30 between daughter nuclei indicative of asymmetric chromatid segregation occur with a frequency of 4.57, and asymmetric chromatid segregation is demonstrated at late mitotic phases. Asymmetric chromatid segregation is significantly enhanced by Pim-1 overexpression in CPCs (9.19 versus 4.79 in eGFP-expressing cells; P=0.006).
Asymmetric segregation of chromatids in CPCs is increased nearly two-fold with Pim-1 kinase overexpression, indicating that Pim-1 promotes self-renewal of stem cells.
成年心脏中的心肌祖细胞（CPCs）可用于基于细胞的心肌损伤治疗，但决定干细胞特性、自我更新和谱系分化的因素知之甚少。通过不对称染色单体分离遗传的不朽 DNA 链与成年干细胞的自我更新相关，但 CPCs 进行不对称分离以保留不朽链的能力尚不清楚。保护心脏的激酶 Pim-1 增加体内细胞的不对称分裂，但 Pim-1 增强不对称染色单体分离的能力尚不清楚。
我们旨在证明 CPCs 中的不朽链分离和 Pim-1 激酶增强的不对称染色单体分布。
通过掺入溴脱氧尿苷来追踪不对称分离。将 CPC DNA 标记几个代，然后在第二次细胞分裂期间阻断追踪，以确定不朽和新合成链的分布。双核 CPC 中溴脱氧尿苷的比值≥70:30 的子核指示不对称染色单体分离的频率为 4.57，并且在晚期有丝分裂阶段证明了不对称染色单体分离。在 CPC 中过表达 Pim-1 可显著增强不对称染色单体分离（9.19 与 eGFP 表达细胞中的 4.79 相比；P=0.006）。
Pim-1 激酶过表达使 CPCs 中染色单体的不对称分离增加近两倍，表明 Pim-1 促进了干细胞的自我更新。
