Injectable hydrogel embedded with mesenchymal stem cells repairs severe spinal cord injury

Mesenchymal stem cell (MSC) transplantation was suggested as a promising approach to treat spinal cord injury (SCI). However, the heterogeneity of MSC and the lack of appropriate delivery methods impede its clinical application. To tackle these challenges, we first generated human MSCs derived from a single cell with a great homogeneity of batch quality and then developed a biocompatible injectable hydrogel to embed these cells to treat severe SCI. In a clinically relevant rat severe SCI model, we showed that the injection of MSCs with injectable hydrogel into the lesion site promoted robust functional recovery, while the intrathecal delivery of MSCs only resulted in limited therapeutic effects. Mechanistically, the hydrogel protected MSCs from the damage of harmful neuroinflammatory microenvironment in the spinal cord lesion. The hydrogel with the survived MSCs ameliorates the neuroinflammatory microenvironment of spinal cord lesion, preventing cavity formation and leads to the remnant of spared axons/tissues, which results in a better prognosis in the end. ### Competing Interest Statement Zhejiang University has filed a patent application related to this work, with X.W., Z. C., X.C, Y.Z., J.Y., S.J., Z. W., W.C. and T.Z. listed as inventors.