Toward acellular xenogeneic heart valve prostheses: Histological and biomechanical characterization of decellularized and enzymatically deglycosylated porcine pulmonary heart valve matrices.

The use of decellularized xenogeneic heart valves might offer a solution to overcome the issue of human valve shortage. The aim of this study was to revise decellularization protocols in combination with enzymatic deglycosylation, in order to reduce the immunogenicity of porcine pulmonary heart valves, in means of cells, carbohydrates, and, primarily, Galα1-3Gal (α-Gal) epitope removal. In particular, the valves were decellularized with sodium dodecylsulfate/sodium deoxycholate (SDS/SD), Triton X-100 + SDS (Tx + SDS), or Trypsin + Triton X-100 (Tryp + Tx) followed by enzymatic digestion with PNGaseF, Endoglycosidase H, or O-glycosidase combined with Neuraminidase. Results showed that decellularization alone reduced carbohydrate structures only to a limited extent, and it did not result in an α-Gal free scaffold. Nevertheless, decellularization with Tryp + Tx represented the most effective decellularization protocol in means of carbohydrates reduction. Overall, carbohydrates and α-Gal removal could strongly be improved by applying PNGaseF, in particular in combination with Tryp + Tx treatment, contrary to Endoglycosidase H and O-glycosidase treatments. Furthermore, decellularization with PNGaseF did not affect biomechanical stability, in comparison with decellularization alone, as shown by burst pressure and uniaxial tensile tests. In conclusion, valves decellularized with Tryp + Tx and PNGaseF resulted in prostheses with potentially reduced immunogenicity and maintained mechanical stability.

Decellularization combined with enzymatic removal of N-linked glycans and residual DNA reduces inflammatory response and improves performance of porcine xenogeneic pulmonary heart valves in an ovine in vivo model.

BACKGROUND: Limited availability of decellularized allogeneic heart valve substitutes restricts the clinical application thereof. Decellularized xenogeneic valves might constitute an attractive alternative; however, increased immunological hurdles have to be overcome. This study aims for the in vivo effect in sheep of decellularized porcine pulmonary heart valves (dpPHV) enzymatically treated for N-glycan and DNA removal. METHODS: dpPHV generated by nine different decelluarization methods were characterized in respect of DNA, hydroxyproline, GAGs, and SDS content. Orthotopic implantation in sheep for six months of five groups of dpPHV (n = 3 each; 3 different decellularization protocols w/o PNGase F and DNase I treatment) allowed the analysis of function and immunological reaction in the ovine host. Allogenic doPHV implantations (n = 3) from a previous study served as control. RESULTS: Among the decellularization procedures, Triton X-100 & SDS as well as trypsin & Triton X-100 resulted in highly efficient removal of cellular components, while the extracellular matrix remained intact. In vivo, the functional performance of dpPHV was comparable to that of allogeneic controls. Removal of N-linked glycans and DNA by enzymatic PNGase F and DNase I treatment had positive effects on the clinical performance of Triton X-100 & SDS dpPHV, whereas this treatment of trypsin & Triton X-100 dpPHV induced the lowest degree of inflammation of all tested xenogeneic implants. CONCLUSION: Functional xenogeneic heart valve substitutes with a low immunologic load can be produced by decellularization combined with enzymatic removal of DNA and partial deglycosylation of dpPHV.

Effects of combined cryopreservation and decellularization on the biomechanical, structural and biochemical properties of porcine pulmonary heart valves.

UNLABELLED: Non-fixed, decellularized allogeneic heart valve scaffolds seem to be the best choice for heart valve replacement, their availability, however, is quite limited. Cryopreservation could prolong their shelf-life, allowing for their ideal match to a recipient. In this study, porcine pulmonary valves were decellularized using detergents, either prior or after cryopreservation, and analyzed. Mechanical integrity was analyzed by uniaxial tensile testing, histoarchitecture by histological staining, and composition by DNA, collagen (hydroxyproline) and GAG (chondroitin sulfate) quantification. Residual sodium dodecyl sulfate (SDS) in the scaffold was quantified by applying a methylene blue activation assay (MBAS). Cryopreserved decellularized scaffolds (DC) and scaffolds that were decellularized after cryopreservation (CD) were compared to fresh valves (F), cryopreserved native valves (C), and decellularized only scaffolds (D). The E-modulus and tensile strength of decellularized (D) tissue showed no significant difference compared to DC and CD. The decellularization resulted in an overall reduction of DNA and GAG, with DC containing the lowest amount of GAGs. The DNA content in the valvular wall of the CD group was higher than in the D and DC groups. CD valves showed slightly more residual SDS than DC valves, which might be harmful to recipient cells. In conclusion, cryopreservation after decellularization was shown to be preferable over cryopreservation before decellularization. However, in vivo testing would be necessary to determine whether these differences are significant in biocompatibility or immunogenicity of the scaffolds. STATEMENT OF SIGNIFICANCE: Absence of adverse effects on biomechanical stability of acellular heart valve grafts by cryopreservation, neither before nor after decellularization, allows the identification of best matching patients in a less time pressure dictated process, and therefore to an optimized use of a very limited, but best-suited heart valve prosthesis.