A Comparative Examination of the Clinical Outcome and Histological Appearance of Cryopreserved and Fresh Split-Thickness Skin Grafts

Abstract

The clinical use of frozen, human allogeneic skin grafts is considered a suitable alternative to freshly harvested allogeneic skin grafts when the latter are not available. However, limited functional and histological information exists regarding the effects of cryopreservation on allogeneic skin grafts, especially those across mismatched histocompatibility barriers. Thus, we performed a side-by-side comparative study of fresh vs frozen skin grafts, across both minor and major histocompatibility barriers, in a miniature swine model. Since porcine skin shares many physical and immunological properties with human skin, our findings have relevance to current clinical practices involving allogeneic grafting and may support future, temporary wound therapies involving frozen xenografts, comprised genetically modified porcine skin. Four miniature swine underwent harvest and grafting of split-thickness skin, with and without cryopreservation, in order to observe autologous grafts and grafts across minor and major histocompatibility barriers. A biopsy of the grafts was done at regular intervals for study of architecture, vascularization, and outcomes. All grafts vascularized without technical complications. Differences were noted in the early appearance of some fresh vs frozen grafts, but no significant difference was observed in overall survival times in any of the experimental groups. These results demonstrate that despite early observable differences in the healing process, cryopreservation and thawing does not significantly affect long-term graft survival or time to rejection, thus supporting the clinical and experimental use of fresh and frozen split-thickness skin grafts as comparable and interchangeable.

Conflict of interest statement

No conflict of interest exists for any authors

Figures

Figure 1

Experimental surgical schematic depicting the placement of autologous and allogeneic, fresh and frozen, split-thickness skin grafts for both experimental groups. Minor mismatched MHC experimental series, Group 1, is shown top. Grafts (from left to right): Fresh Autologous (control), Frozen Autologous (control), Fresh Allogeneic, and Frozen Allogeneic split thickness skin graft. Fully mismatched MHC experimental series, Group 2, shown bottom. Grafts (from left to right): Frozen Autologous (control), Fresh Allogeneic, and Frozen Allogeneic split thickness skin graft.

Figure 2

a – Experimentally obtained images illustrating the rejection time course of autologous and allogeneic, fresh and frozen, split-thickness skin grafts in minor mismatched MHC experimental series, Group 1. Horizontal legend denotes post-operative day (POD); vertical legend denotes skin graft type. b – Experimentally obtained images illustrating the rejection time course of autologous and allogeneic, fresh and frozen, split-thickness skin grafts in fully mismatched MHC experimental series, Group 2. Horizontal legend denotes post-operative day (POD); vertical legend denotes skin graft type.

Figure 2

a – Experimentally obtained images illustrating the rejection time course of autologous and allogeneic, fresh and frozen, split-thickness skin grafts in minor mismatched MHC experimental series, Group 1. Horizontal legend denotes post-operative day (POD); vertical legend denotes skin graft type. b – Experimentally obtained images illustrating the rejection time course of autologous and allogeneic, fresh and frozen, split-thickness skin grafts in fully mismatched MHC experimental series, Group 2. Horizontal legend denotes post-operative day (POD); vertical legend denotes skin graft type.

Figure 3

a – Histological images of fresh and frozen skin grafts, in minor mismatched MHC experimental series, Group 1. All images representative of post-operative day (POD) 4. Horizontal legend represents unique subject identifier; horizontal legend denotes skin graft type. b - Histological images of fresh and frozen skin grafts across a fully mismatched MHC experimental series, Group 2. All images representative of post-operative day (POD) 4. Horizontal legend represents unique subject identifier; horizontal legend denotes skin graft type.

Figure 3

a – Histological images of fresh and frozen skin grafts, in minor mismatched MHC experimental series, Group 1. All images representative of post-operative day (POD) 4. Horizontal legend represents unique subject identifier; horizontal legend denotes skin graft type. b - Histological images of fresh and frozen skin grafts across a fully mismatched MHC experimental series, Group 2. All images representative of post-operative day (POD) 4. Horizontal legend represents unique subject identifier; horizontal legend denotes skin graft type.