Can Losartan controlled release improve the bio-hybrid cardiac patch in preventing left ventricle pathological remodeling?

Objective  Cardiac patches (CP) are a promising alternative to prevent pathological remodeling initiated by a heart attack. In previous studies we demonstrated the efficacy of the biohybrid approach on rat chronic infarction model at 8 and 16 weeks from the injury. This study aims to further enhance the efficacy of the bio-hybrid approach by the controlled release of Losartan. The abstract presents the full in-vitro characterization of the scaffold that will be evaluated on a rat chronic infarction model.  Methods   The bio-hybrid CP was fabricated using double-stream electrospinning of Poly (ester-carbonate urethane) urea (PECUU) and cardiac extracellular-matrix (ECM) gel obtained from decellularized porcine hearts. Poly (D, L-lactide-co-glycolide) (PLGA) microparticles (MPs) loaded with drugs were embedded in the ECM-gel. Scanning electron Microscopy and digital image analysis was adopted to characterize the patch microstructure (e.g. fiber orientation, diameter and intersection density). Cell vitality and proliferation were evaluated with Alamar Blue for 14 days and histological staining (Masson's Trichrome, Hematoxylin & Eosin) performed at pre-set intervals. Patch topology, Young’s Modulus, and suture retention were measured via a dial indicator gauge - biquintic interpolation and uniaxial tensile testing (UTT), respectively. Biomaterial anisotropy was evaluated via biaxial tensile testing (BTT). Accelerated hydrolytic degradation tests were performed for 14 days. Losartan release was assessed over a 14-day period using a Franz Cell. C2C12 cell culture was adopted to assess cell infiltration. Results The custom-algorithm identified fiber orientation index of 0.65 and 0.77 (0.5 pure isotropy, 1 pure anisotropy) for the ECM-side and polymer-side, respectively, indicating a predominant fiber alignment of the polymer side towards a preferential direction. As rat native LV anisotropy dictates an OI of 0.8, the patch processing allowed to achieve physiologically relevant values of structural anisotropy. This was also confirmed by BTT and by UTT which demonstrated that the patch circumferential direction was stiffer (1.34MPa) than the longitudinal (0.89MPa). Process stability in terms of thickness homogeneity with average value of 390 µm was confirmed by the limited STD of 7.39 µm. Cell viability assays and H&E staining demonstrated that the patch is non-toxic and supports cell-growth and infiltration. Conclusions Results demonstrate our capacity to couple the biohybrid approach (polymer rich/control on mechanics, ECM rich/bioactivity) with physiologically relevant anisotropy and with the controlled release of Losartan. Future in-vivo evaluation on rat coronary ligation model will assess if and how controlled release can synergistically enhance cardiac patch efficacy in preventing pathological remodeling.