Characterization of a functionally active primary microglial cell culture from the pig retina

Retinal inflammation is an integral component of many retinal diseases including diabetic retinopathy (DR), age-related macular degeneration (AMD) and retinopathy of prematurity (ROP). Inflammation is commonly initiated and perpetuated by myeloid-derived immune cells. In the retina, microglial cells are resident macrophages with myeloid origins, which acts as the first responders involved in the innate immune system. To understand the disease pathogenesis, the use of isolated retinal cell culture model is vital for the examination of multiple cellular responses to injury or trauma. The pig retina resembles human retina in terms of tissue architecture, vasculature, and topography. Additionally, it is a better model than the rodent retina because of the presence of the pseudomacula. In the present study, we sought to establish and characterize pig retinal primary microglial cell (pMicroglia) culture. We used pig eyes from the local abattoir and optimized pMicroglia cultures using multiple cell culture conditions and methods. The best results were obtained by seeding cells in DMEM-high glucose media for 18 days followed by shaking of the culture plate. The resulting pMicroglia were characterized by cellular morphology, phenotype, and immunostaining with Iba-1, CD68, P2Y12, CD163, CD14, and Isolectin GS-IB4. Generated pMicroglia were found functionally active in phagocytosis assay and responsive to lipopolysaccharides (LPS) in dose-dependent production of IL-1β. Furthermore, they showed increased secretion of pro-inflammatory cytokines with LPS treatment. Thus, we report a novel and reproducible method for the isolation of primary microglial cells from pig eyes, which may be useful for studying retinal diseases.