A promising strategy for treating peripheral ischemia involves the delivery of stem cells to promote angiogenesis through paracrine signaling. Treatment success depends on cell localization, retention, and survival within the mechanically dynamic intramuscular (IM) environment. Herein we describe an injectable, in situ-gelling hydrogel for the IM delivery of adipose-derived stem/stromal cells (ASCs), specifically designed to withstand the dynamic loading conditions of the lower limb and facilitate cytokine release from encapsulated cells. Copolymers of poly(trimethylene carbonate)-b-poly(ethylene glycol)-b-poly(trimethylene carbonate) diacrylate were used to modulate the properties of methacrylated glycol chitosan hydrogels crosslinked by thermally-initiated polymerization using ammonium persulfate and N,N,N′,N′-tetramethylethylenediamine. The scaffolds had an ultimate compressive strain over 75% and maintained mechanical properties during compressive fatigue testing at physiological levels. Rapid crosslinking (<3 min) was achieved at low initiator concentration (5 mM). Following injection and crosslinking within the scaffolds, human ASCs demonstrated high viability (>90%) over two weeks in culture under both normoxia and hypoxia. Release of angiogenic and chemotactic cytokines was enhanced from encapsulated cells under sustained hypoxia, in comparison to normoxic and tissue culture polystyrene controls. When delivered by IM injection in a mouse model of hindlimb ischemia, human ASCs were well retained in the scaffold over 28 days and significantly increased the IM vascular density compared to untreated controls.

治疗外周缺血的一种有前途的策略涉及通过旁分泌信号传递干细胞以促进血管生成。治疗的成功取决于细胞在机械动态肌内（IM）环境中的定位，保留和存活。在本文中，我们描述了可注射的原位凝胶化水凝胶，用于IM递送脂肪来源的干/基质细胞（ASC），特别设计用于承受下肢的动态负荷条件并促进细胞因子从包囊细胞中释放。聚的共聚物（三亚甲基碳酸酯） - b -聚（乙二醇） - b-聚碳酸三亚甲基酯用于调节过硫酸铵和N，N，N'，N'的热引发聚合反应交联的甲基丙烯酸二醇壳聚糖水凝胶的性能-四甲基乙二胺。支架的极限压缩应变超过75％，并在生理水平的压缩疲劳测试过程中保持机械性能。在低引发剂浓度（5 mM）下实现了快速交联（<3分钟）。在支架内注射和交联后，在常氧和低氧条件下，人类ASC在培养两周后均表现出较高的生存力（> 90％）。与常氧和组织培养的聚苯乙烯对照相比，持续缺氧条件下包封细胞的血管生成和趋化细胞因子释放增强。当通过IM注射在后肢缺血的小鼠模型中递送时，人ASC在28天内很好地保留在支架中，并且与未治疗的对照相比显着增加了IM血管密度。