Abstract 194: Increasing Expression of Connexin43 in Bone Marrow Stem Cells Enhances Their Protective Effects on the Infarcted Heart

Abstract

Introduction: Coupling of stem cells (SCs) injected into the infarcted heart to endogenous cells that survived injury may enhance SC survival and engraftment and improve their protective effects. Connexin43 (Cx43) gap junctions are some of the first proteins expressed by differentiating SCs transplanted into the heart after myocardial infarction (MI), suggesting that cell coupling is critical for SC survival and differentiation. Hypothesis: Overexpression of Cx43 in SCs will enhance their ability to engraft, differentiate, and improve cardiac function and survival after transplant into the infarcted heart. Methods: Adult mouse SCs isolated from compact bone were sorted for c-kit surface marker using magnetic beads. SCs were transduced with PLL3.7 lentivirus encoding the Cx43 gene (GJA1) at MOI=300 to produce overexpression, which was confirmed by Western analysis on SC lysates. MI was induced in 12-week-old male C57BL/6 mice by ligating the left anterior descending coronary artery, and 40,000 SCs in 20 uL saline were administered immediately after MI via intramyocardial injection. A total of 69 animals were used: 18 received Cx43 SCs, 30 received non-transduced SCs (NTSC), 11 received only saline, and 10 underwent sham surgery. Echocardiography was performed 1 and 2 weeks post-MI. Results: Animals receiving Cx43 SCs had improved survival (90.0%) versus NTSC (76.7%) and saline controls (70.0%). The Cx43 SC group displayed improved ejection fraction versus NTSC and saline controls at 1 week (48.7% v. 43.3%, p=0.04; 30.1%, p<0.0001) and 2 weeks post-MI (45.7% v. 40.4%, p=0.08; 26.8%, p=0.0004). Similar improvements in fractional shortening, stroke volume, and cardiac output were observed. Administration of Cx43 SC and NTSC attenuated remodeling with no difference between the two groups. Both decreased end-diastolic and systolic volumes, increased thickness of the infarct-related anterior wall, and decreased heart weight (HW), HW/body weight and HW/tibia length ratios at 1 and 2 weeks post-MI. Conclusion: All SCs improved survival and cardiac function, and attenuated remodeling. Transplantation of Cx43 SCs improved survival and cardiac function even more than NTSCs, suggesting that Cx43 may play a crucial role in engraftment and differentiation.