Generation of vascularized retinal organoids containing microglia based on a PDMS microwell platform.

Retinal organoids (ROs) offer a biomimetic in vitro model for investigating human retinal development and disease. However, current ROs face several limitations, such as the absence of vascular networks and microglial cells (MGs). Here, we developed a vascularized retinal organoids (vROs) model by coculturing vascular organoids (VOs) with ROs in a V-bottom polydimethylsiloxane (PDMS) microwell platform. Through coculturing for 30 to 120 days, we observed the presence of tubular blood vessels at the center of vROs. Transcriptomic analysis revealed that the vascularization in ROs was associated with angiogenesis and immune response. Furthermore, we observed that MGs in VOs migrated and integrated into the vROs as VOs and ROs fused, with the vROs exhibiting responsiveness to inflammatory stimuli. The vROs expressed tight junction protein claudin-5 and displayed similar characteristics to the inner blood-retinal barrier (iBRB). These vRO models, which incorporate vascular structures and MGs, provide an alternate avenue for retinal vascular disease research and hold promise for future clinical applications.