Immortalized Human Retinal Microvascular Endothelial Cells-hTERT

Endothelial UNC5B Regulates Blood‑Retinal Barrier Homeostasis

The blood‑retinal barrier (BRB), a critical component of the retinal neurovascular unit (NVU), is essential for maintaining retinal homeostasis. UNC5B, an endothelial receptor, has been implicated in vascular and neural regulation, but its role in BRB and NVU homeostasis remains unclear. The present study aimed to investigate the function of endothelial UNC5B in maintaining BRB integrity and NVU homeostasis, using both in vitro cell cultures, and in vivo DR and RVO mouse models.

UNC5B was knocked down in immortalized human retinal microvascular endothelial cells (HRMECs) by transfection with lentivirus-encapsulated UNC5B shRNA (Fig. 1A-C). PI/calcein-AM staining showed that cell death was significantly increased after UNC5B knockdown (Fig. 1D). Functional assays demonstrated that transcellular transport was elevated after UNC5B knockdown (Fig. 1G), and the paracellular leakage of monolayer endothelial cells was also increased (Fig. 1H). On the basis of these results, it was inferred that UNC5B serves a key role in maintaining endothelial cell barrier function.

Given the protective role of UNC5B in retinal endothelial cells, it was evaluated whether endothelial-specific overexpression preserved the integrity of the BRB in DR mice. The results showed that specific UNC5B overexpression in the endothelial cells of DR mice significantly reduced retinal vascular leakage (Fig. 2A), alleviated the formation of acellular capillaries and preserved pericyte number (Fig. 2B) and coverage (Fig. 2C). These findings highlighted the therapeutic potential of targeting endothelial-cell UNC5B to maintain the BRB integrity in DR.