RNA sequencing of aortic tissue of Klotho knock-out mice treated with a minimal and a high magnesium diet

Klotho knock-out mice are an important model for CKD-induced calcification. In CKD, serum magnesium (Mg2+) inversely correlates with vascular calcification. This study aims to determine the effects of Mg2+ on aortic calcification in Klotho knock-out mice. Klotho knock-out mice were treated with either a minimal or a high Mg2+ diet from birth. After eight weeks, serum biochemistry was studied and organs were harvested. Protective effects of Mg2+ were characterized by RNA-sequencing of aortic tissue. Micro-CT analysis was performed to study bone integrity. High Mg2+ diet prevented vascular calcification and reduced aortic gene expression of Runx2 and matrix Gla protein, demonstrating the protective effect on pro-osteogenic signaling. Differential expression of inflammation and extracellular matrix remodeling genes accompany the beneficial effects of Mg2+ on calcification. High dietary Mg2+ did not affect serum parathyroid hormone, vitamin D3 and calcium. High Mg2+ intake prevented calcification despite increasing fibroblast growth factor-23 and phosphate concentration in knock-out mice. In addition, mice on the high Mg2+ diet had a 20% reduced femoral bone mineral density and increased osteoid formation indicating osteomalacia, while osteoclast activity was decreased in Klotho knock-out mice. In Saos-2 osteoblasts, Mg2+ supplementation reduced mineralization independent of osteoblastic matrix production, alkaline phosphatase activity and maturation markers alpha-1 type-I collagen and sclerostin. In conclusion, high dietary Mg2+ prevents calcification in Klotho knock-out mice. These effects are potentially mediated by reduction of inflammatory and extracellular matrix remodeling pathways in the aorta. Mg2+ treatment is promising to prevent vascular calcification, but the risk for osteomalacia should be considered. Overall design: Both wild-type (n=6 for each diet) and Klotho knock-out (n=6 for each diet) mice were treated with either a minimal (0.05% w/w) or a high magnesium diet (0.48% w/w) and treated for 8 weeks from brith to ensure maximal exposure. After 8 weeks the mice were sacrificed and the aorta was harvested, cleaned and snap-frozen in liquid nitrogen. Samples were homogenized in TRIreagent for RNA isolation and RNA was sequenced at BaseClear Leiden B.V. The Netherlands. Wild-type mice on a minimal magnesium diet served as control group for the analysis.