A Porcine-Derived Acellular Dermal Scaffold That Supports Soft Tissue Regeneration: Removal of Terminal Galactose-α-(1,3)-Galactose and Retention of Matrix Structure

Abstract

Sub-optimal clinical outcomes after implantation of animal-derived tissue matrices may be attributed to the nature of the processing of the material or to an immune response elicited in response to xenogeneic epitopes. The ability to produce a porcine-derived graft that retains the structural integrity of the extracellular matrix and minimizes potential antigenic response to galactose-alpha-(1,3)-galactose terminal disaccharide (alpha-Gal) may allow the scaffold to support regeneration of native tissue. Dermal tissue from wild-type (WT-porcine-derived acellular dermal matrix [PADM]) or Gal-deficient (Gal(-/-) PADM) pigs was processed to remove cells and DNA while preserving the structural integrity of the extracellular matrix. In addition, the WT tissue was subjected to an enzymatic treatment to minimize the presence of alpha-Gal (Gal-reduced PADM). Extracellular matrix composition and integrity was assessed by histological, immunohistochemical (IHC), and ultrastructural analysis. In vivo performance was evaluated by implantation into the abdominal wall of Old World primates in an exisional repair model. Anti-alpha-Gal activity in the serum of monkeys implanted subcutaneously was assessed by ELISA. Minimal modification to the extracellular matrix was assessed by evaluation of intact structure as demonstrated by staining patterns for type I and type VII collagens, laminin, and fibronectin similar to native porcine skin tissues. Explants from the abdominal wall showed evidence of remodeling, notably fibroblast cell repopulation and revascularization, as early as 1 month. Serum ELISA revealed an initial anti-alpha-Gal induction that decreased to baseline levels over time in the primates implanted with WT-PADM, whereas no or minimal anti-Gal activity was detected in the primates implanted with Gal(-/-) PADM or Gal-reduced PADM. The combination of a nondamaging process, successful removal of cells, and reduction of xenogeneic alpha-Gal antigens from the porcine dermal matrix are critical for producing a material with the ability to remodel and integrate into host tissue and ultimately support soft tissue regeneration.

Decellularized Extracellular Matrix Derived from Porcine Adipose Tissue as a Xenogeneic Biomaterial for Tissue Engineering

“…The residual xenogeneic epitopes, such as cellular components and a-Gal epitopes, may be a major obstacle to its utility as a surgical material for tissue regeneration. 35 Therefore, new and more efficient decellularization techniques should be established to eliminate xenogeneic epitopes.…”

“…13 Recently, other groups reported methods for decellularization from human and porcine adipose tissue. 10,35 They utilized solvents for lipid removal such as isopropanol, in addition to physical, chemical, and enzymatic treatment. In this study, ECM was isolated from porcine adipose tissue by simple pulverization under high temperature and effectively decellularized after a relatively short exposure to NaCl, SDS, and enzymes.…”

Remodeling of Noncrosslinked Acellular Dermal Matrices in a Rabbit Model of Ventral Hernia Repair

“…Ansaloni et al [35], in a small series of patients implanted with Surgisis, also showed that all of them produced antibodies specific for alpha-gal with a peak between 2 and 6 weeks, showing decreasing levels 6 months after implantation. Another important study, using dermal tissue from wild-type [WT-porcine-derived acellular dermal matrix (PADM)] or Gal-deficient [Gal(-/-) PADM] pigs, stated that the combination of a nondamaging process, successful removal of cells, and reduction of xenogeneic alpha-Gal antigens from the porcine dermal matrix is critical for producing a material with the ability to remodel and integrate into host tissue and ultimately support soft tissue regeneration [36]. …”

Perspectives on whole-organ assembly: moving toward transplantation on demand

“…This immune activation does not appear to alter the host response to the scaffolds (37). If necessary, further reduction of the Gal epitope can be achieved by enzymatic cleavage during processing (38,39) or by obtaining tissues from genetically modified pigs that lack the Gal epitope (37,40). The attractive aspect of xenogeneic organs as a source of ECM is the availability of organs and the potential to secure healthy, pathogen-free tissue.…”

“…The persistence of intracellular proteins and cell surface antigens has been largely unexplored, with the exception of the Gal epitope in SIS and dermis (36,39) as well as actin and myosin in decellularized lungs (46,47).…”