Conditioned medium from adipose mesenchymal stromal cells stimulated with pituitary adenylate cyclase-activating polypeptide (PACAP) mitigates RINm5F pancreatic β-cell dysfunction.

BACKGROUND: The regenerative potential of mesenchymal stromal cells (MSCs) is linked to their secretion of bioactive molecules that modulate cellular processes. Different immunomodulatory molecules enhance their secretory and functional capacity. PACAP reduces oxidative stress and apoptosis, while promoting proliferation and cell differentiation. It also regulates inflammation and the immune response, but its role in MSCs secretoma modulation remains poorly explored. This study aimed to evaluate the effect of conditioned medium (CM) derived from PACAP -preconditioned MSCs on the recovery of β-pancreatic cells from the RINm5F line exposed to oxidative damage. METHODS AND RESULTS: MSCs were obtained from adipose tissue of Sprague-Dawley rats. The concentration of PACAP to stimulate MSCs viability was determined by MTT assay. The mitochondrial metabolism of MSCs was significantly increased by PACAP at 0.1nM for 48 h. We evaluated the resulting CM protective effect in RINm5F cells exposed to oxidative damage by high glucose and streptozotocin (STZ). A dose-response curve was previously performed to select the CM concentration. Viability, mitochondrial membrane potential (MMP), radical oxygen species (ROS), apoptosis, glutathione peroxidase (GPx) activity and insulin secretion were all evaluated. RINm5F β-pancreatic cells treated with PACAP-preconditioned MSCs CM increased cells viability, restored MMP, reduced ROS and apoptosis caused by oxidative stress. In addition, we observed an increase in GPx antioxidant activity, and functional recovery of these cells was confirmed by increased insulin levels. CONCLUSIONS: CM from PACAP-MSCs reverses oxidative damage and apoptosis of RINm5F-pancreatic B cells caused by high glucose and STZ, probably by stimulating their antioxidant response, without ruling out other compensatory mechanisms.