Macrophage matrix metalloproteinase-2/-9 gene and protein expression following adhesion to ECM-derived multifunctional matrices via integrin complexation

Macrophages are commonly observed at the biomaterial–tissue interface and interact with the extracellular matrix (ECM) mainly by integrin receptors to play a critical role in ECM turnover by secreting matrix metalloproteinases (MMPs). To investigate β1 and β3 containing integrin-mediated adhesion and subsequent MMP-2/-9 protein and gene expression in human blood-derived monocytes, biofunctional peptides immobilized onto flexible polyethylene glycol (PEG) arms were grafted onto a gelatin-based interpenetrating network (IPN). Adherent monocyte density was dramatically greater in the presence of RGD immobilized onto flexible PEG arms of the gelatin-based IPN. Pretreatment of monocytes with either anti-integrin β1 or β3 led to a significant decrease in adherent cell density on RGD-PEG-grafted IPNs. MMP-2 and MMP-9 protein and MMP-9 mRNA expression increased in the presence of IPNs initially, independent of ligand identity. Anti-integrin β1 or β3 antibody pretreatment of monocytes led to a general decrease in MMP-2/-9 protein expression. These results demonstrate the importance of β1 and β3 containing integrins in mediating monocyte adhesion onto RGD immobilized onto flexible PEG arms of the IPN. The results also reveal that MMP-2/-9 protein and gene expression is influenced by the presence of gelatin and not the ligands immobilized on the PEG arms of the IPN.