Tissue Inhibitor of Metalloproteinase 4 Regulates Vascular Homeostasis during Injury and Repair

Tissue inhibitor of metalloproteinase 4 (TIMP4) is a least studied TIMP type recognized for the ability to inhibit metalloproteinases (MMPs). Our recent single-cell RNAseq showed that TIMP4 is abundantly expressed in the capillary and arteriolar endothelial cells of mice. However, its role in regulating vascular homeostasis, particularly in the context of vascular injury and repair, remain largely unexplored. In this study, we found that endothelium-targeted overexpression of TIMP4 in vivo enhanced vascular permeability during acute lung injury, while blocking TIMP4 improved survival, reduced inflammatory cell infiltration, and attenuated endothelial barrier disruption in mice after acute lung injury induced by LPS or polymicrobial sepsis, demonstrating a detrimental role of TIMP4 expression during acute lung injury. However, TIMP4 increased following ischemic injury of the hindlimb from mice. Overexpressing TIMP4 improved angiogenesis, perfusion recovery, and improved vascular repair, while knockdown showed opposite effects to delay vascular repair, suggesting that TIMP4 is protective to facilitate angiogenesis and vascular repair after hindlimb ischemia. Mechanistically, we find that TIMP4 acts as a VE-cadherin binding protein in response to VEGF signaling, which is independent of its inhibition of MMP. In human endothelial cells, TIMP4 is required for VEGF induced migration, angiogenesis, and hyperpermeability in vitro. TIMP4 facilitated VEGFA-induced Src activation and VE-cadherin phosphorylation, internalization, and degradation. In addition, VEGF facilitates the recruitment of TIMP4 to the membrane which is dependent on VE-cadherin. TIMP4 also directly binds to the ecto-domain of VE-cadherin. Our study identified TIMP4 as a VE-cadherin interacting protein which facilitates VEGF signaling and is required for VEGF function in endothelial cells. TIMP4 may play a divergent role in regulating homeostasis of microvascular endothelial cells in different contexts of organ injury and repair. This study is supported by Hong Kong Research Grant Council grants 14115524, 14107822, YCRG C4004-23Y, T12-101/23-N This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.