Background. Aging is a major risk factor for cardiovascular disease. Cysteine protease cathepsin K (CatK) has been implicated in the process of angiogenesis, but the exact roles of individual CatK in vessel formation during aging are poorly understood. Methods and Results. To study the putative role of CatK in ischemia-induced angiogenesis, we applied a hindlimb ischemia model to aged wild-type (CatK^+/+) and CatK-deficient (CatK^−/−) mice. A serial laser Doppler blood-flow analysis revealed that the recovery of the ischemic/normal blood-flow ratio in the aged CatK^−/−mice was impaired throughout the follow-up period. On postoperative day 14, CatK deficiency had also impaired capillary formation. CatK deficiency reduced the levels of cleaved Notch1, phospho-Akt, and/or vascular endothelial growth factor (VEGF) proteins in the ischemic muscles and bone marrow-derived c-Kit⁺ cells. A flow cytometry analysis revealed that CatK deficiency reduced the numbers of endothelial progenitor cell (EPC)-like CD31⁺/c-Kit⁺ cells in the peripheral blood as well as the ischemic vasculature. In vitro experiments, CatK^−/− impaired bone-derived c-Kit⁺ cellular functions (migration, invasion, proliferation, and tubulogenesis) in aged mice. Our findings demonstrated that aging impaired the ischemia-induced angiogenesis associated with the reductions of the production and mobilization of CD31⁺/c-Kit⁺ cells in mice. Conclusions. These findings established that the impairment of ischemia-induced neovascularization in aged CatK^−/− mice is due, at least in part, to the reduction of EPC mobilization and the homing of the cells into vasculature that is associated with the impairment of Notch1 signaling activation at advanced ages.

中文翻译：

---

组织蛋白酶 K 缺乏会损害老年小鼠缺血诱导的新生血管形成。

背景。衰老是心血管疾病的主要危险因素。半胱氨酸蛋白酶组织蛋白酶 K (CatK) 与血管生成过程有关，但人们对单个 CatK 在衰老过程中血管形成中的确切作用知之甚少。方法和结果。为了研究 CatK 在缺血诱导的血管生成中的假定作用，我们将后肢缺血模型应用于老年野生型 (CatK ^+/+ ) 和 CatK 缺陷 (CatK ^-/- ) 小鼠。一系列激光多普勒血流分析显示，老年 CatK 的缺血/正常血流比率恢复^-/-小鼠在整个随访期间受损。术后第 14 天，CatK 缺乏也损害了毛细血管的形成。CatK 缺乏降低了缺血性肌肉和骨髓来源的 c-Kit ⁺细胞中切割的 Notch1、磷酸-Akt 和/或血管内皮生长因子 (VEGF) 蛋白的水平。流式细胞术分析显示，CatK 缺乏减少了外周血和缺血性脉管系统中内皮祖细胞 (EPC) 样 CD31 ⁺ /c-Kit ^{+细胞的数量。}体外实验，CatK ^-/-受损的骨源性 c-Kit ⁺老年小鼠的细胞功能（迁移、侵袭、增殖和肾小管发生）。我们的研究结果表明，衰老损害了与小鼠中 CD31 ⁺ /c-Kit ⁺细胞的产生和动员减少相关的缺血诱导的血管生成。结论。这些发现证实，老年 CatK ^-/-小鼠缺血诱导的新血管形成受损至少部分是由于 EPC 动员减少和细胞归巢到与 Notch1 信号激活受损相关的脉管系统。在高龄。