目的 严重肢体缺血（Critical limb ischemia, CLI）是外周动脉疾病（Peripheral arterial disease, PAD）的终末期，预后较差，主要由动脉硬化闭塞症（Arteriosclerosis, ASO）、 血栓闭塞性脉管炎（Thromboangitis obliterans, TAO）和糖尿病足（Diabetic foot, DF） 引起。但目前国内外间充质干细胞移植的相关报道较少，本研究旨在评估脐带间充 质干细胞（Umbilical cord mesenchymal stem cell, UC-MSC）移植治疗严重下肢缺血 的安全性和有效性。 方法 本研究为单中心、前瞻性、单臂临床研究，入组患者为在2015年5月至2023 年12月期间就诊于中国医学科学院血液学医院的38例CLI患者，通过向CLI患者 下肢肌肉注射UC-MSC评估其安全性和有效性。 结果 共有36名患者在UC-MSC治疗后12个月时完成随访，其中4名患者死亡， 6 名患者截肢，死亡率为11.1%，截肢率为16.7%，1年无截肢生存率为72.2 %。在 治疗后12个月，患者的疼痛强度（Verbal rating scale, VRS）较基线相比显著降低 （1.62 ± 1.02 vs 2.79 ± 0.41, p<0.001），溃疡愈合率为72.2%，冷感改善率为63.9%， 38.9%的患者皮温较基线水平有改善；血清白介素-6（Interleukin 6, IL-6）和白介素-8（Interleukin 8, IL-8）较基线显著升高（28.25±10.20 vs. 13.65±8.46, p＜0.001）、 （137.29±67.79 vs. 55.40±26.20, p＜0.001）；CD3+CD4+T 淋巴细胞和 CD3 CD16+/CD56+NK 细胞较基线减少且具有统计学意义（42.57±6.07 vs. 40.35±6.29, p=0.024）、（13.47±3.60 vs. 11.20±4.42, p=0.005）；CD3+T cell、CD19+B cell 和 CD4+/CD8+较基线减少，但无统计学差异。 结论 UC-MSC 在 CLI 患者的治疗中降低患者截肢率，改善肢体疼痛，发挥免疫 调节作用并有效促进溃疡愈合，初步证明是一项安全有效的替代疗法。 

Objective Critical limb ischemia (CLI) is the end-stage of peripheral arterial disease (PAD), with poor prognosis, mainly caused by arteriosclerosis obliterans (ASO), thromboangiitis obliterans (TAO), and diabetic foot (DF). However, there are few relevant reports on mesenchymal stem cell transplantation at home and abroad. This study aims to evaluate the safety and effectiveness of umbilical cord mesenchymal stem cell (UC-MSC) transplantation in the treatment of critical limb ischemia. Methods This study is a single-center, prospective and single-arm clinical trial. A total of 38 CLI patients who visited the Institute of Hematology & Blood Diseases Hospital between May 2015 and December 2023 were enrolled. The safety and efficacy of UC MSC were evaluated by intramuscular injection of UC-MSC into the lower limbs of CLI patients. Results A total of 36 patients completed the follow-up at 12 months after UC-MSC treatment. Among them, 4 patients died and 6 patients underwent amputation, with a mortality rate of 11.1%, an amputation rate of 16.7%, and a 1-year amputation-free survival rate of 72.2%. At 12 months after treatment, the patients' pain intensity (verbal rating scale, VRS) were significantly lower than the baseline (1.62±1.02 vs 2.79±0.41, p<0.001). The ulcer healing rate was 72.2%, the cold sensation improvement rate was 63.9%, and 38.9% of the patients had improved skin temperature compared with the baseline. Serum Interleukin 6 (IL-6) and Interleukin 8 (IL-8) were significantly higher than the baseline (28.25±10.20 vs. 13.65±8.46, p＜0.001), (137.29±67.79 vs. 55.40±26.20, p＜0.001). CD3+CD4+T lymphocytes and CD3－CD16+/CD56+NK cells were significantly reduced compared with the baseline (42.57±6.07 vs. 40.35±6.29, p=0.024), (13.47± 3.60 vs. 11.20±4.42, p=0.005). CD3+T cells, CD19+B cells, and CD4+/CD8+ were reduced compared with the baseline, but there was no statistical difference. Conclusion UC-MSC can reduce the amputation rate, alleviate limb pain, exert immunomodulatory effects, and effectively promote ulcer healing in the treatment of patients with critical lower limb ischemia, which preliminarily proves to be a safe and effective alternative therapy.