First Trimester Cord Perivascular Cells (FTM HUCPVCs) Home to Injured Cardiomyocytes and Promote MMP-Mediated Extracellular Remodeling Post Injury in Vitro and In Vivo Post Myocardial Infarct

Background: Following myocardial infarction, the reparative phase involves extracellular matrix (ECM) remodeling to replace necrotic myocytes with a collagen scar. An ideal therapeutic cell type should home to injury sites and effectively remodel ECM at injury sites. We aimed to investigate the homing properties of first trimester umbilical cord perivascular cells (FTM HUCPVCs) and MMP-based ECM remodelling using in vitro assays and in vivo, using a rat model of MI.
Methods: To assess homing properties of FTM HUCPVCs in vitro, primary rat cardiomyocytes were subjected to hypoxia (pO2=1%) and glucose deprivation in culture for 24h followed by labeled-FTM HUCPVCs seeded on MatrigelTM-coated trans-membrane inserts. Migration of FTM HUCPVCs was detected by florescent well scans. Neutralizing antibodies against SDF1, TNFα, MMP2 and MMP15 were used to inhibit MatrigelTM processing and chemotaxis of MSCs. In vivo model of myocardial infarction was established by left ventricular coronary artery ligation on 8 week old immunocompromised (Foxrnu) rats. 1 week post-MI, FTM-HUCPVCs, term-HUCPVCs or human BMSCs (n=6 per group) were injected into the injured myocardium (3X106 cells each). 2 weeks after cell implantation, animals were sacrificed. In situ gelatinase activity was assessed by fluorescent gelatinase substrate (DQ gelatin) on fixed cardiac tissue sections and the signal was quantified. 9 independent fields in 6 tissue sections per heart were analyzed. Statistical analysis was performed with ANOVA.
Results: MMP2 an MMP15 neutralizing antibodies significantly inhibited invasion of FTM-HUCPVCs towards injured cardiomyocytes in vitro (p<0.05). Serum-free culture conditions altered the trans-membrane migration of FTM-HUCPVCs in response to injured cardiomyocytes or soluble SDF1. Anti-TNFα antibody significantly inhibited trans-membrane migration of FTM-HUCPVCs expanded in either serum-containing (p<0.05) or serum-free (p<0.01) conditions. Purified TNF-α and SDF1 attracted FTM-HUCPVCs through basal membrane-like structures, however the effect was not significant. FTM-HUCPVC-treated scar tissue displayed significantly increased gelatinase signal when compared to term-HUCPVCs and bone marrow MSCs.
Conclusion: ECM processing and homing in response to injured cardiomyocytes appeared to be mediated by MMPs as well as cytokines, including SDF1 and TNFα, and altered by xeno-free conditions. These findings suggest that FTM-HUCPVCs could be an excellent candidate for post-MI cell therapy, and that the extent of MMP activity can be controlled by culture conditions. Our in vivo data also indicates that FTM-HUCPVCs have superior ECM processing in the scar tissue of infarcted hearts compared to older sources of MSCs.