Background: Spinal cord injury is a devastating clinical condition for which there are currently no effective therapeutic options. In the present study, we aim to investigate the effect of an administered injection of exosomes derived human urine stem cell (USC-Exo) embedded in hydrogel could improve the spinal cord functional recovery after injury and the underlying mechanism.Methods: Exosome were isolate from USC and identified by transmission electron Microscopy (TEM) and western blot. Functional assays in vitro were performed to assess the effects of USC-Exo on tube formation and migration, as well as their regulatory role in the PI3K/AKT signaling pathway activation. A locally administered injection of exosome embedded in hydrogel was used for SCI treatment. The effects of USC-Exo on functional recovery and the role of the candidate protein ANGPTL3 harboring in USC-Exo for promoting angiogenesis in SCI model was assessed.Results: In the current study, we demonstrate that a locally administered injection of USC-Exo embedded in hydrogel can pass the spinal cord blood brain barrier and deliver ANGPTL3 to the injured spinal cord region. In addition, the administration of human USC-Exo could enhance spinal cord neurological functional recovery by promoting angiogenesis. The results of mechanistic studies revealed that ANGPTL3 is enriched in (USC-Exo) and is required for their ability to promote angiogenesis. Functional studies further confirmed that the effects of USC-Exo on angiogenesis are mediated by the PI3K/AKT signaling pathway. Conclusion: Collectively, our results indicate that USC-Exo serve as a crucial regulator of angiogenesis by delivering ANGPTL3 and may represent a promising novel therapeutic agent for SCI repair.

Abstract Background: Spinal cord injury (SCI) is a devastating clinical diseasewithout effectivetherapeuticapproach recently. In this study, we aim to investigate the effect of locally injection with exosome derived human urine stem cell (USC) embedding with hydrogelcould improve the spinal cord functional recovery after injury and the underlying mechanism.Methods:Exosome were isolate from USC andidentified by transmission electron microscopy and western blot. Functional assays using human umbilical vein endothelial cell (HUVEC) in vitro were performed to assess the effects of USC-Exosdeliverythe angiopoietin-like protein 3 (ANGPTL3) on tube formation and migration as well as their regulatory role in the PI3K/AKT signaling pathway activation. In vivo experiment we locally injection with exosome derived USC embedding with hydrogel for treatment of SCI. The effects of USC-Exos on functional recovery in spinal cord injury mice were tested by measuring motor evoked potential, histological and neovascular numbers. Meanwhile, the role of the candidate protein ANGPTL3 in USC-Exo for promoting angiogenesisin SCI was assessed.Results:In current study, we demonstrate that when given locallyinjection with exosomederivedhuman urine stem cell (USC) embeddingwith hydrogelcould pass the spinal cord blood brain barrier and delivery the angiopoietin-like protein 3 (ANGPTL3) to the injured spinal cord region. In addition, the administration of exosome derived from human USC could enhance spinal cord neurological functional recovery by promoting angiogenesis.The mechanism studies revealed that ANGPTL3 are enriched in USCexosome(USC-Exo) and required for USC exosome promoting angiogenesis. Functional studies further confirmed the effects caused by exosome derived from USC on angiogenesis wasmediated by PI3K/AKT signaling pathway. Conclusion:Collectively, our results indicated that USC derived exosome serve as a critical regulator of angiogenesis by transferring ANGPTL3 and may represent a promising novel therapeutic agent for SCI repair.