骨髓间充质干细胞通过上调EPO表达减轻缺氧损伤引起的PC12细胞凋亡

 目的：观察骨髓间充质干细胞（BM-MSCs）对氯化钴（CoCl2）诱导的PC12细胞缺氧损伤及凋亡的影响并探讨其作用机制。方法：将PC12细胞分为以下几组：空白对照组、CoCl2处理组、BM-MSCs-siCTL+CoCl2处理组和BM-MSCs-siEPO +CoCl2处理组。应用MTT、流式细胞术（FCM）及Hoechst  33258染色法检测BM-MSCs对CoCl2诱导的细胞活性下降及凋亡的影响。采用逆转录PCR（RT-PCR）和Western blotting检测BM-MSCs的促红细胞生成素（EPO）表达情况。同时通过RT-PCR法检测PC12细胞的Bcl-2与Bax表达情况。此外应用分光光度法检测caspase-9和-3活性。结果：MTT结果显示BM-MSCs共培养能够提高PC12细胞活力, 0.6 mmol/L CoCl2单独处理组24 h和48 h细胞存活率仅为（43.0±6.4）%和（33.8±5.7）%，1∶15细胞比BM-MSCs共培养24 h和48 h后细胞存活率明显上升，分别为（77.9±3.8）%和（75.2±9.7）%（P＜0.01）。RT-PCR 和Western blotting显示0.6 mmol/L CoCl2处理24 h和48 h明显诱导BM-MSCs的EPO表达上调，而EPO siRNA可完全抑制BM-MSCs的EPO表达（P＜0.01）。FCM及Hoechst 33258结果表明CoCl2处理能诱导PC12细胞损伤及凋亡，BM-MSCs-siCTL与PC12细胞共培养可有效抑制CoCl2的细胞毒性作用，减少细胞缺氧性损伤及凋亡，而EPO siRNA可明显阻断BM-MSCs的抗细胞凋亡作用（P＜0.01）。 RT-PCR结果显示BM-MSCs共培养组PC12细胞的Bcl-2表达较CoCl2处理组明显升高，而Bax表达较CoCl2处理组明显降低；EPO siRNA明显抑制BM-MSCs介导的Bcl-2表达升高和Bax表达降低（P＜0.01）。分光光度法结果显示BM-MSCs-siCTL共培养组的caspase-9和-3活性较CoCl2处理组明显降低，而BM-MSCs-siEPO共培养组的caspase-9和-3活性较BM-MSCs-siCTL共培养组明显增加（P＜0.01）。结论：BM-MSCs共培养能抑制CoCl2诱导的PC12细胞凋亡，其细胞保护作用的机制可能与其上调EPO的表达有关。

Bone marrow-derived mesenchymal stem cells protect against hypoxia-induced injury and apoptosis of PC12 cells via up-regulation of erythropoietin expression

AIM： To investigate the effects of bone marrow-derived mesenchymal stem cells (BM-MSCs) on cobalt chloride (CoCl2)-induced injury and apoptosis of PC12 cells. METHODS：PC12 cells were divided into control group, CoCl2 group, BM-MSCs-siCTL+CoCl2 group and BM-MSCs-siEPO+CoCl2 group. The viability of the PC12 cells was measured by MTT assay. Flow cytometry and Hoechst 33258 staining were used to determine the apoptotic rate and the changes of chromatin distribution in PC12 cells. The expression of erythropoietin (EPO) in BM-MSCs was measured by RT-PCR and Western blotting. The mRNA expression of Bcl-2 and Bax in PC12 cells was detected by RT-PCR. Caspase-9 and caspase-3 assay kits were used to detect the activity of caspase-9 and caspase-3. RESULTS：The viability of PC12 cells treated with CoCl2 for 24 h and 48 h decreased to （43.0±6.4）% and （33.8±5.7）%, respectively, while 1∶15 ratio of BM-MSCs co-culture increased the cell viability to （77.9±3.8）% and （75.2±9.7）%,respectively. The expression of EPO in BM-MSCs was up-regulated after treated with 0.6 mmol/L CoCl2 for 24 h and 48 h, while EPO siRNA significantly abrogated the EPO expression in BM-MSCs. BM-MSCs-siCTL co-culture significantly inhibited the apoptosis of PC12 cells induced by CoCl2. However, EPO siRNA the protective effect of BM-MSCs. Compared with CoCl2 treatment group, BM-MSCs co-culture induced remarkable increase in the expression of Bcl-2 and decrease in the expression of Bax in PC12 cells, which was reversed by EPO siRNA. BM-MSCs-siCTL co-culture remarkably abrogated the CoCl2  induced up-regulation of caspase-9 and -3, while BM-MSCs-siEPO co-culture significantly reversed the down-regulation of caspase-9 and -3 induced by BM-MSCs-siCTL co-culture. CONCLUSION：BM-MSCs protect PC12 cells from apoptosis induced by CoCl2. The protective effect of BM-MSCs might be executed by up-regulating the expression of EPO.