Sulfasalazine, a potent cystine-glutamate transporter inhibitor, enhances osteogenic differentiation of canine adipose-derived stem cells

Cystine-glutamate transporter (xCT) is a plasma membrane transporter that imports cystine and indirectly contributes to the oxidative stress resistance associated with increased intracellular glutathione levels. Canine adipose-derived stem cells (CADSCs) include an xCT-positive subpopulation and show relatively low expression of osteogenic markers during in vitro osteogenic differentiation. Sulfasalazine (SSZ), a drug used to treat rheumatoid arthritis, suppresses xCT expression in cancer cells. In this study, we found that the SSZ treatment at 100 µM significantly suppressed xCT mRNA expression in CADSCs but did not significantly affect cell proliferation under the same conditions. Additionally, this treatment decreased the intracellular glutathione concentration. During in vitro osteogenic differentiation, the SSZ treatment at 50 µM and 100 µM significantly increased alizarin red staining and its quantification, as well as the concentration-dependent osteogenic differentiation markers (BMP1 and SPP) mRNA expression. Our results suggested that SSZ enhances the osteogenic differentiation potential of CADSCs and can potentially exhibit a superior therapeutic profile in canine bone regenerative medicine.