SPP1 and Myocardial fibrosis: In terms of the SLAY motif of OPN, the proangiogenic activity of the SVVYGLR peptide has been reported in transformed rat lung endothelial cells,23 in a dorsal air sac model,24 in animal models of heart failure25 and in myocardial fibrosis.26 Furthermore, the SLAY motif has been reported to bind to various integrins, such as αvβ3, α4β1, α4β7 or α9β1, in a cell-type-dependent manner but HUVEC.11, 12, 27, 28 As the SLAY motif is located adjacent to the RGD sequence, the RGD and SLAY motifs in OPNpt20 appear to compete for binding with αvβ3-integrin.