Global epigenetic immunohistochemical markers reveal developmental connections of distinct cell types during fetal development

The prenatal development of the human retina is a complex process orchestrated by several epigenetic mechanisms. This study investigated some global epigenetic markers (histone H3, histone H4, 5-methylcytosine, 5-hydroxymethylcytosine) during the fetal development of the human retina in 34 human eyes from 11 to 38 weeks of gestation. Immunohistochemical staining was performed to assess the distribution and intensity of the selected epigenetic markers across developmental stages. For the general retinal staining intensity, a score from 0 to 3 was used, whereas for the percentage of stained retinal nuclei, a score from 0 to 4 was applied. The two scores were multiplied resulting in the final staining score. The mean of the two graders was used for statistical analysis. Staining patterns were analyzed with regard to regional disparities (central versus periphery), distinctions among retinal cell layers, individual cell types, and changes over time. The immunohistochemical staining reaction varied across developmental stages, showing regional disparities and distinctions among retinal cell layers and individual cell types. We observed consistent trends of decreasing staining scores for histone 3 and 4 acetylation and DNA methylation decrease with advancing gestational age. Significant differences among trimesters indicated dynamic epigenetic changes during fetal retinal development. Morphological analysis revealed distinct staining patterns that correlated with cellular morphology and differentiation levelsGganglion cells, amacrine cells, and Müller cells demonstratednotable similarities in staining patterns with regard to the developmental stage. Furthermore, differences between central and peripheral retina diminished with age. The study provides novel insights into the epigenetic regulation of retinal development in humans and underscores the importance of analyzing the epigenome at the cellular level for a comprehensive understanding. Understanding these epigenetic processes may pave the way for further investigations on retinal development and the communication between different cell types.