Human and bovine osteopontin from milk and recombinant human osteopontin may stimulate intestinal proliferation and immune functions via various mechanisms revealed by microarray analysis

Abstract

Osteopontin (OPN) is a highly acidic phosphorylated glycoprotein, present at high concentration in human milk and low concentration in bovine milk and infant formula. Human OPN (hOPN) and bovine OPN (bOPN) have been demonstrated to be resistant to in vitro digestion. Thus, hOPN and bOPN may play important roles in intestinal and immunological development in infancy. hOPN, recombinant hOPN (rhOPN) and bOPN may function differently due to different post‐translational modifications and 63% amino acid identity between hOPN and bOPN. Therefore, we hypothesized that hOPN, rhOPN and bOPN are capable to stimulate intestinal proliferation and regulate immune functions via various mechanisms. BrdU assays showed that hOPN, rhOPN and bOPN significantly stimulated proliferation of human intestinal cells (HIEC). Compared with hOPN and rhOPN, a lower concentration was needed for proliferation effects exerted by bOPN. To screen for underlying mechanisms by which hOPN, rhOPN and bOPN stimulate intestinal proliferation, microarray assays (Illumina) were performed. Selected genes were verified by RT‐PCR with a high validation rate. Genes significantly regulated by hOPN, rhOPN, and bOPN were 243, 356, and 284 respectively of which only 50 genes were modulated by all. Genes tightly related to proliferation and immune function were significantly modified by hOPN, eg MAPK13, CCNE1, CdGAP, CXCL10, IL6ST and NFKB. Some of these genes were affected by rhOPN or bOPN, but not all. In summary, hOPN, rhOPN and bOPN are capable to stimulate intestinal proliferation and regulate immune functions but via various mechanisms.