Supplementary Material for: Effect of youthful blood environment and its key factor SCF on renal interstitial fibrosis in elderly mice

Introduction: Youthful blood environment was shown to decelerate the aging process of kidney and to attenuate senile renal fibrosis in a young-old parabiotic animal model; in addition, we identified a stem cell factor (SCF) that is closely linked with the process. This research was to investigate the effect of youthful blood environment on senile renal interstitial fibrosis and the role of SCF. Methods: We bred SCF receptor c-Kit gene loss-of-function Wps/Wps mice and established a combination mice model that was subjected to unilateral ureteral obstructive (UUO) and parabiotic surgeries. Parabiotic mice were divided into isochronic parabiotic (young-young, Y-IP and old-old, O-IP) and heterochronic parabiotic (young-old, HP) groups. UUO surgery was performed in one of the parabiotic pairs in the IP group (Y-IPuuo and O-IPuuo) and in the elderly mice in the HP group (O-HPuuo). In order to study the role of SCF/c-kit on renal interstitial fibrosis, UUO surgery was performed in wildtype (WT) and Wps/Wps mice. Results: Fourteen days after UUO surgery, the kidney interstitial fibrosis area, kidney function, and the expressions of SCF/c-Kit, pNF-κB, and fibrosis-related proteins in the O-HPuuo group were significantly lower than those in the Ouuo and O-IPuuo groups. Compared with wildtype UUO mice, the expressions of pNF-κB and fibrosis-related proteins, and the kidney function were all significantly decreased in Wps/Wps UUO mice. Conclusion: Youthful blood environment downregulated the expressions of SCF/c-Kit in elderly UUO mice, and ameliorated UUO-induced kidney fibrosis and function loss.

引言：在年轻-老年联体共生动物模型中，年轻血液环境已被证实可延缓肾脏衰老进程，减轻老年性肾纤维化；此外，本研究鉴定出一种与该进程密切相关的干细胞因子（stem cell factor, SCF）。本研究旨在探究年轻血液环境对老年性肾间质纤维化的影响，以及SCF在该进程中的调控作用。
方法：本研究繁育了SCF受体c-Kit基因功能缺失型Wps/Wps小鼠，并构建了同时接受单侧输尿管梗阻（unilateral ureteral obstructive, UUO）与联体共生手术的复合小鼠模型。将联体共生小鼠分为同年代联体共生组（年轻-年轻组Y-IP与老年-老年组O-IP）以及异年代联体共生组（年轻-老年组HP）。在同年代联体共生组的一对联体小鼠中，对其中一只实施UUO手术（对应Y-IPuuo与O-IPuuo亚组）；在异年代联体共生组中，则对老年联体小鼠实施UUO手术（对应O-HPuuo亚组）。为探究SCF/c-Kit在肾间质纤维化中的作用，本研究对野生型（wildtype, WT）与Wps/Wps小鼠实施了UUO手术。
结果：UUO术后14天，O-HPuuo组的肾间质纤维化面积、肾功能水平，以及SCF/c-Kit、pNF-κB与纤维化相关蛋白的表达水平，均显著低于Ouuo组与O-IPuuo组。与野生型UUO小鼠相比，Wps/Wps UUO小鼠的pNF-κB与纤维化相关蛋白表达水平、肾功能水平均显著降低。
结论：年轻血液环境可下调老年UUO小鼠体内SCF/c-Kit的表达水平，并改善UUO诱导的肾脏纤维化及肾功能损伤。