Therapeutic factors secreted by mesenchymal stem cells (MSCs) promote angiogenesis in vivo. However, delivery of MSCs in the absence of a cytoprotective environment offers limited efficacy due to low cell retention, poor graft survival, and the nonmaintenance of a physiologically relevant dose of growth factors at the injury site. The delivery of stem cells on an extracellular matrix (ECM)-based platform alters cell behavior, including migration, proliferation, and paracrine activity, which are essential for angiogenesis. We demonstrate the biophysical and biochemical effects of preconditioning human MSCs (hMSCs) for 96 h on a three-dimensional (3D) ECM-based microgel platform. By altering the macromolecular concentration surrounding cells in the microgels, the proangiogenic phenotype of hMSCs can be tuned in a controlled manner through cell-driven changes in extracellular stiffness and “outside-in” integrin signaling. The softest microgels were tested at a low cell dose (5 × 10⁴ cells) in a preclinical hindlimb ischemia model showing accelerated formation of new blood vessels with a reduced inflammatory response impeding progression of tissue damage. Molecular analysis revealed that several key mediators of angiogenesis were up-regulated in the low-cell-dose microgel group, providing a mechanistic insight of pathways modulated in vivo. Our research adds to current knowledge in cell-encapsulation strategies by highlighting the importance of preconditioning or priming the capacity of biomaterials through cell–material interactions. Obtaining therapeutic efficacy at a low cell dose in the microgel platform is a promising clinical route that would aid faster tissue repair and reperfusion in “no-option” patients suffering from peripheral arterial diseases, such as critical limb ischemia (CLI).

间充质干细胞（MSCs）分泌的治疗因子促进体内血管生成。然而，由于细胞滞留率低，移植物存活差以及在损伤部位不维持生理相关剂量的生长因子，在缺乏细胞保护环境的情况下递送MSCs的功效有限。干细胞在基于细胞外基质（ECM）的平台上的递送改变了细胞行为，包括迁移，增殖和旁分泌活性，这对于血管生成至关重要。我们展示了基于三维（3D）ECM的微凝胶平台上预处理人类MSC（hMSC）96 h的生物物理和生化作用。通过改变微凝胶中细胞周围的大分子浓度，hMSC的促血管生成表型可以通过细胞驱动的胞外硬度变化和“由内而外”的整合素信号传导以受控方式进行调节。在低细胞剂量（5×10）下测试了最柔软的微凝胶在临床前后肢缺血模型中显示^4个细胞），显示新血管的形成加快，炎症反应减少，阻止了组织损伤的进展。分子分析显示，低细胞剂量微凝胶组中血管生成的几个关键介质被上调，从而提供了体内调节途径的机理性见解。我们的研究通过强调预处理或通过细胞间相互作用来激发生物材料能力的重要性，从而增加了细胞封装策略的最新知识。在微凝胶平台上以低细胞剂量获得治疗效果是一种有前途的临床途径，该途径可帮助患有严重肢体缺血（CLI）等外周动脉疾病的“无选择”患者更快地进行组织修复和再灌注。