Vital, Porcine, Gal-Knockout Skin Transplants Provide Efficacious Temporary Closure of Full-Thickness Wounds: Good Laboratory Practice-Compliant Studies in Nonhuman Primates

Abstract

Vital, genetically engineered porcine skin transplants have long been regarded as a promising treatment option for severe burn wounds. The objective of this two-part, preclinical study was to evaluate the ability of vital, split-thickness skin xenotransplants derived from designated pathogen-free, alpha 1,3 galactosyltransferase knockout miniature swine to provide temporary wound closure of full-thickness wound defects intended to model severe and extensive, deep partial- and full-thickness burn wounds. In part 1 of the study, four full-thickness wound defects were introduced in four cynomolgus macaques recipients and, then engrafted with two xenografts and two allografts to achieve temporary wound closure. On POD-15, autografts were used to achieve definitive wound closure and were observed until POD-22. In part 2 of the study, four additional subjects each received two full-thickness wound defects, followed by two xenografts to achieve temporary wound closure, and were observed postoperatively for 30 days without further intervention. All grafts were assessed for signs of adherence to the wound bed, vascularity, and signs of immune rejection via gross clinical and histological methods. Xenograft and allograft comparators were equivalent in part 1, and later autografts were otherwise indistinguishable. In part 2, all xenotransplants demonstrated adherence, vascularity, and survival until POD-30. These were unexpected results that exceed previously published findings in similar models. Furthermore, the ensuing GLP-study report directly supported regulatory clearance, permitting a phase I clinical trial. This solution holds great promise as an alternative to human cadaver allograft, the current standard of care for the treatment of severe burns.

Immunological response in cynomolgus macaques to porcine α‐1,3 galactosyltransferase knockout viable skin xenotransplants—A pre‐clinical study

“…As previously reported, 28 Table 1). III 3 3 3 1 0 1 0 2001 2 100% re-epithelialized III-IV 3 3 3 2 0 1 0 2002 1 30% re-epithelialized III-IV 3 3 3 3 0 0 0 2002 2 30%re-epithelialized III-IV 3 3 3 3 0 0 0 2101 1 40% re-epithelialized II 3 3 2 3 0 0 0 2101 2 40% re-epithelialized III-IV 3 3 3 2 0 0 0 2102 1 20% re-epithelialized III-IV 3 3 3 3 0 0 0 2102 2 20% re-epithelialized II-III 3 3 3 3 These results are shown in Table 1.…”

“…44 Prior reports using earlier versions of GalT-KO materials 23,40 reported an average of 10-14 day survival, while true wild-type, GalT+ skin xenotransplants exhibited a clinical appearance of "white grafts" as early as POD-4, 22,[39][40][41] an indication of ischemic injury caused by preformed antibodies against porcine endothelial cell α-1,3-galactose epitope. 22 In contrast, all eight In contrast to our preceding study 28 Lastly, it could be posited that these findings could be attributed to the existence of subtle or nuanced variations of the immunological response to non-α-1,3-galactose porcine xenoantigens between species. In the majority of previous, similar studies, 22,23,39,40 baboon recipients were used instead of cynomolgus macaques.…”

“…One GalT‐KO miniature swine from the closed colony was selected as the donor source animal for all eight skin xenotransplants used in this study 36 . The preparation and procurement of the skin xenotransplants from the donor were previously described in detail 28 . The skin was procured under stringent aseptic conditions and sterile environment via air‐driven Zimmer dermatome (Medfix Solution, Inc, Tucson, AZ).…”

“…36 The preparation and procurement of the skin xenotransplants from the donor were previously described in detail. 28 The skin was pro- CryoStor CS5 media, 5 mL, (BioLife Solutions) was added to the vial, which was then sealed.…”

“…In our first article describing this pre‐clinical study, 28 the primary focus was reporting the clinical observations that all xenotransplants demonstrated survival, adherence, and vascularity until post‐operative day 30. Here, we present an extended analysis specific to the immunological response in recipients of vital skin xenotransplants, with a focus on the immune response to non‐α‐1,3‐galactose porcine xenoantigens and presence of various immune mediators associated with wound healing.…”