Increased chromatin accessibility following 1α,25-dihydroxyvitamin D3 treatment in human endometrial stromal cells

Vitamin D signaling has recognized roles in female reproductive physiology, but its effects at the chromatin level in endometrial stromal cells are still unclear. Here, we investigated how the active form of vitamin D, 1α,25-dihydroxyvitamin D 3 , or calcitriol, influences the accessible chromatin landscape of human endometrial stromal cells. Assay for transposase-accessible chromatin using sequencing (ATAC-seq) was performed on T-HESCs treated with either a vehicle or 1,25(OH) 2 D 3 . Ligand treatment increased overall chromatin accessibility, shown by higher ATAC-seq signal intensity, while causing only minor changes in the total number of called peaks. Peak annotation revealed that accessible regions were spread across both promoter-proximal and distal genomic areas. Integrating this data with CUT&RUN and RNA sequencing showed that most vitamin D-responsive cistromic modifications and transcripts were linked to nearby open chromatin, though fewer were associated with regions that were significantly differentially accessible. These results suggest that 1,25(OH) 2 D 3 -dependent transcription mainly occurs within a permissive, pre-accessible chromatin environment. This study offers new evidence that active vitamin D influences the epigenomic landscape of human endometrial stromal cells, establishing the chromatin-based molecular response to a chemically-defined VDR ligand, 1,25(OH) 2 D 3 , relevant to stromal differentiation and preparation for decidualization. Highlights First evidence suggesting the direct impact of active vitamin D, 1α,25-dihydroxyvitamin D 3 , 1,25(OH) 2 D 3 , enhanced the signal intensity of chromatin accessibility in human endometrial stromal cells Most accessible chromatin regions were shared between vehicle and ligand-treated human endometrial stromal cells 1,25(OH) 2 D 3 -responsive transcription occurs largely within pre-accessible chromatin in human endometrial stromal cells Assay for transposase-accessible chromatin sequencing (ATAC-seq) defines a chromatin-level pharmacologic response to a chemically defined VDR ligand in human endometrial stromal cells