In Vivo Response of Acellular Porcine Pericardial for Tissue Engineered Transcatheter Aortic Valves

Figures

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  Figure 1. Macroscopic examination of tissue scaffolds. (A) Native porcine aortic valve cusps show severe inflammation (red arrow). (B) Acellular porcine pericardium showing no signs of inflammation. (C) MSC-seeded acellular porcine pericardium showed an area of neovascularization after 8 weeks (yellow arrow).

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  Figure 2. Inflammation, recellularization, and neovascularization of pericardium and cusp after 8 weeks. Hematoxylin and Eosin (400 µm) showed inflammatory cell invasion of the native aortic cusp (A) along the periphery (arrow). Progressive recellularization and neovascularization was observed in (B) acellular pericardium and (C) MSC-seeded pericardium. TEM (5 µm) analysis showed macrophage infiltration (arrow) observed in (D) native cusp. (F) Blood vessels (arrow) containing red blood cells were observed in MSC-seeded pericardium. TEM (1 µm) showed uniformity of collagen fiber architecture in all samples (G–I) with mild ECM distortion.

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  Figure 3. Masson’s Trichrome and picrosirius red staining confirmed collagen deposition in pericardium and cusp after 8 weeks. Collagen was evenly distributed in all pericardial samples; however, there was an observable increase of muscle fibers in the (A) native porcine aortic cusp (arrows). Collagen denoted with blue staining was appreciated in the (A) native cusp, (B) acellular pericardium, and (C) MSC-seeded pericardium.

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  Figure 4. Immunohistochemistry for CD3 and CD163 after 8 weeks. Severe inflammation was observed in (A) native cusp (arrow), mild inflammation in (C) MSC-seeded pericardium (arrow), and no inflammation observed in (B) acellular pericardium. CD 163 staining specific marker of M2 macrophages showed increased expression in (D) native porcine aortic cusps (arrow) compared to (E) acellular porcine pericardium and (F) MSC-seeded pericardium.

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  Figure 5. Immunohistochemistry for CD31 and CD34 after 8 weeks. CD 31 staining showed progressive angiogenesis in both acellular (B,E) and MSC-seeded (C,F) samples (arrows) over the time. CD 34 staining was progressively positive in all samples which showed progressive angiogenesis in all scaffolds.

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  Figure 6. Immunohistochemistry for αSMA and Vimentin After 8 Weeks. Alpha smooth muscle was expressed in (B) acellular pericardium and (C) MSC-seeded pericardium. Vimentin positive cells were primarily present in (D) native cusp (yellow asterisk). The recruitment of vimentin positive cells started after 8 weeks in the (E) acellular and (F) MSC-seeded pericardium.

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  Figure 7. Biomechanical testing. Top. Engineering stress versus strain curves of the native cusps (C) at 1, 4 and 8 weeks subcutaneous implantation in rats. Bottom. Bar charts of the mean tensile stress and tangent modulus with error bars for acellular pericardium (P) at 1, 4 and 8 weeks subcutaneous implantation in rats. Significant differences between different tissues at the respect weeks is indicated with a star. There was a significant difference in both tensile stress and tangent modulus between 1 and 4 weeks but not 4 and 8 weeks.