Vitamin D Reduces Myofibroblast Formation and Collagen 1 Expression Through Upregulating eNOS Expression in Kidney Fibrosis Model in Mice

Introduction: Kidney fibrosis lead to myofibroblast formation with vascular remodeling and activation of Endothelin-1 (ET-1) and eNOS pathways. Vitamin D has reno-protective effect, however its role in ET-1 and eNOS pathways haven't been elucidated yet. Objective: Investigate the role of vitamin D in kidney fibrosis model through attenuating vascular remodeling and ET-1/eNOS pathway. Methods: We performed Unilateral Ureteral Obstruction (UUO) in right kidney of male Swiss Webster mice (8 weeks old, 30-50 grams, n=25), which were divided into three groups: sham operation (SO) group, UUO group, and UUO with i.p injection of 0.5 μg/Kg BW of Calcitriol/VitD (UUOD) group. Mice were terminated at day 7 post operation, right kidneys were harvested and used for paraffin making, immunostaining, and RNA extraction. Paraffin sections were deparaffinized and stained with Sirius Red (SR) to quantify lumen area and Lumen/Wall area ratio (LWAR). Immunostaining was done for quantification of myofibroblast number. Reverse Transcriptase PCR (RTPCR) was done to examine preproEndothelin-1 (ppET-1) and endothelial NOS (eNOS) mRNA expression. Results: UUO induced a significant increase of myofibroblast cell number, that was indicated by positive staining of a-SMA. Meanwhile, it was lower in UUOD group. RTPCR revealed higher expression of Collagen 1 mRNA in UUO group compared to SO group. In the meantime, Vitamin D downregulated Collagen 1 mRNA expression compared to UUO group. UUO and UUOD groups demonstrated significantly higher expression of ET-l mRNA compared to SO with no significant difference between UUO and UUOD group. eNOS in UUO group was slightly higher in UUO group compared to SO with UUOD group was significantly higher than SO and UUO group. Conclusion: Vitamin D attenuates kidney fibrosis through attenuating myofibroblast formation, vascular remodeling and upregulating eNOS.