Increased CD44 Expression in Endothelial Cells Induced by Advanced Glycation End Products Leads to Insufficient...

Pathological angiogenesis occurs in various diseases, including tumours, diabetes and wound healing. The endothelial cells lining these aberrant neovessels exhibit abnormal morphology, with loosely attached or absent pericytes and the basement membrane (BM) is often disrupted. Advanced glycation end products (AGEs) promote pathological angiogenesis in diabetic vascular complications, but whether the vascular BM structure is altered and the underlying molecular mechanisms remain unclear. By analysing single-cell RNA sequencing data (GSE204880) from the oxygen-induced retinopathy mouse model, this study found heterogeneous expression of type IV collagen (Col-IV) and laminin in endothelial cells, with enrichment of the AGE-RAGE pathway and BM-related pathways. Experimental results demonstrated that AGEs induce abnormal distribution of Col-IV in vascular BM, along with increased Col-IV levels in mouse serum and endothelial-pericyte co-culture supernatants, suggesting excessive BM degradation. Additionally, AGEs upregulated CD44 and matrix metalloproteinases 9 (MMP9) protein levels in retinal tissues and endothelial cells. Knockout/knockdown of CD44 or inhibition of MMP9, can both significantly alleviate BM structural disruption and abnormal angiogenesis. The down-regulation of CD44 expression or application of γ-secretase inhibitor DAPT attenuated AGEs-promoted MMP9 expression and secretion. Moreover, AGEs facilitated β-catenin nuclear translocation and its interaction with TCF4. When this interaction was blocked by LF3, AGEs-induced CD44 upregulation was reduced, and pathological angiogenesis and BM abnormalities were partially restored. These findings suggest that AGEs upregulate endothelial CD44 expression via β-catenin/TCF4 signalling pathway, which in turn promotes MMP9-mediated excessive degradation of BM components, leading to structural disorganisation and impaired vascular maturation in pathological angiogenesis.