(717d) Generation of a Heart Patch Using a Blend of Native Heart Matrix, Chitosan and Polycaprolactone

Introduction: One common cardiac defect, tetralogy of Fallot, generally requires surgical placement of a patch or baffle across the right ventricular outflow tract (RVOT) in an area that consists of myocardial tissue. Various types of biocompatible polymers or decellularized matrices have been attractive candidates for cardiac patch applications, including Dacron, Gore-Tex®, and autologous or bovine pericardium^1-2. However, these constructs have significant drawbacks in cardiac patching, including the absence of growth potential, loss of mechanical strength over time, and inability to grow with the patient as well as an increased risk of infection and aneurysm. To improve these drawbacks, we have investigated a multi-layered scaffold manufactured by forming a gelatin (typeA)-chitosan hydrogel around a self-assembled polycaprolactone core³. In this study, decellularized porcine heart myocardium (HM) powder was blended with chitosan and formed a hydrogel. Cardiac specific decellularized matrices can provide the improvement of mimicking the native biochemical and composition of native extracellular matrix⁴. Chitosan allows structural stability, mechanical properties conducive to cell invasion and function, and controllable biodegradation rate³.

Materials and Methods: Polycaprolactone matrix (10% in glacial acetic acid) was formed by self-assembly in aqueous media. Chitosan (C) solutions (2% in ddH₂O with 0.5 M acetic acid) were mixed with decellularized porcine heart myocardium solution (HM) (2% in ddH₂O) or type-A gelatin (G) solutions (2% in ddH₂O) respectively and emulsified using sonicator at 37°C for 30 min. 250 mL blended solutions were poured into custom-made Teflon moulds in between PCL matrices and lyophilized at -50°C for 24 hours followed by freezing with the dry ice. Formed hydrogels were neutralized using 100% ethanol and rehydrated using phosphate buffered saline (PBS). Hydrogels were assessed to test surface characteristics, mechanical properties, and cellular attachment, gene expressions and electrophysiological characteristics of neonatal rat ventricular myocytes (NRVM) isolated from 1 to 3 day old Sprague-Dawley rats.

Results and Discussion: Effects of different blending ratios of HM to chitosan (1:1, 1:2, 1:3, 1:4) on pore size, compressive modulus, NRVM adhesion and viability were characterized to identify the optimal blending ratio. 25% HM and 75% chitosan blended hydrogel (HM/C13) showed similar pore sizes and stiffness as G/C11 hydrogels which had the optimal environment for NRVM from our previous research³. Further, NRVM cultured on HM/C13 formed a 3-D formation after 7 days of culturing with ~82% of viability. Gene expression analysis results indicated that NRVM cultured on HM/C13 hydrogel had significantly higher a-myosin heavy chain (MYH6) expression (Fig. B), and faster conduction velocity (4.05±2.59 cm/s of G/C11and 9.30±3.99 cm/s of HM/C13; p<0.05, n=5) compared to cells on G/C11 samples.

Conclusions: The results of this study demonstrate that mixtures of heart myocardium and chitosan hydrogel has sufficient mechanical strength, can maintain cardiomyocyte viability, and improved cell maturation for use in a cardiac patch application. The best results in terms of cell spreading and viability and scaffold integrity resulted from a blend of 25% HM-75% chitosan. In summary, this novel hydrogel shows significant potential for use of cardiac patch to repair full-thickness RVOT defects.

Acknowledgements: We would like to thank Dr. Jessica DeQuach and Dr. Karen Christman at University of California, San Diego for donating decellularized porcine heart myocardium powder.

References: ¹Jenkins, K. J. et al., Circulation 2007, 115 (23), 2995-3014. ²Kochupura, P. et al., Circulation 2005, 112 (9), I144-I149. ³Pok S, etc. Acta Biomater. 2013;9:5630-42. ⁴Singelyn JM, etc. J Cardiovasc Transl Res 2010;3:478-86.