To reconstitute skin: theme and variations

Single-Cell Suspensions of Cultured Human Keratinocytes in Fibrin–Glue Reconstitute the Epidermis

To overcome common disadvantages of standard cultured epidermal sheet grafts (CEG) we have developed a new technique of transplanting cultured human keratinocytes suspended as single cells in a fibrin–glue matrix (Keratinocyte–fibrin–glue suspension—KFGS). In an athymic mouse model with reproducible standardized full thickness wounds this new technique was compared directly to CEG. Reepithelialization was similar in both groups, but reconstitution of the dermo-epidermal junction zone, as shown by electron microscopy and immunohistochemistry was significantly enhanced by the fibrin–glue suspension technique. The new KFGS technique is earlier available than sheet grafts, is able to transfer actively proliferative single keratinocytes, and simplifies the application.

Use of porcine acellular dermal matrix as a dermal substitute in rats

OBJECTIVE

To examine porcine acellular dermal matrix (ADM) as a xenogenic dermal substitute in a rat model.

SUMMARY BACKGROUND DATA

Acellular dermal matrix has been used in the treatment of full-thickness skin injuries as an allogenic dermal substitute providing a stable wound base in human and animal studies.

METHODS

Xenogenic and allogenic ADMs were produced by treating porcine or rat skin with Dispase and Triton X-100. Full-thickness skin defects (225 mm2) were created on the dorsum of rats (n = 29), porcine or rat ADMs were implanted in them, and these were overlain with ultrathin split-thickness skin grafts (STSGs). In two adjacent wounds, 0.005- or 0.017-inch-thick autografts were implanted. In other experiments, the antimicrobial agent used during ADM processing (azide or a mixture of antibiotics) and the orientation of the implanted ADM (papillary or reticular side of ADM facing the STSG) were studied. Grafts were evaluated grossly and histologically for 30 days after surgery.

RESULTS

Significant wound contraction was seen at 14, 20, and 30 days after surgery in wounds receiving xenogenic ADM, allogenic ADM, and thin STSGs. Contraction of wounds containing xenogenic ADM was significantly greater than that of wounds containing allogenic ADM at 30 days after surgery. Graft take was poor in wounds containing xenogenic ADM and moderately good in those containing allogenic ADM. Wound healing was not significantly affected by the antimicrobial agent used during ADM preparation or by the ADM orientation.

CONCLUSION

Dispase-Triton-treated allogenic ADM was useful as a dermal substitute in full-thickness skin defects, but healing with xenogenic ADM was poor.

Long-term outcome of xenogenic dermal matrix implantation in immunocompetent rats

BACKGROUND

Acellular dermal matrix (ADM) has been used successfully in the treatment of full-thickness skin injuries as an allogenic dermal substitute. To assess the efficacy of xenogenic ADM in such wounds, we examined the long-term wound healing and immunological responses to porcine ADM in a rat model.

MATERIALS AND METHODS

Xenogenic and allogenic ADMs were produced by treating porcine (fresh or cryopreserved) or rat skin with dispase and Triton X-100. Full-thickness skin defects on the rat dorsum were implanted with porcine or rat ADMs and overlaid with split-thickness skin grafts (STSGs). Wounds were evaluated grossly and immunologically at 1, 6, and 12 months after surgery.

RESULTS

Extensive wound contraction was seen in wounds implanted with porcine ADM, but healing was significantly (P < 0.01) better in the rat ADM or STSG groups at 6 and 12 months postsurgery. Sera obtained from porcine ADM-implanted rats reacted strongly with porcine ADM and specifically with the papillary dermis and basal lamina. One month postsurgery, extensive inflammation but few intact mast cells were seen in wounds implanted with porcine ADM and significant (P < 0.02) levels of residual porcine ADM were detectable immunologically. Little inflammation was evident in the STSG or rat ADM groups at any time. Significant lymphocyte proliferation (P < 0.05) occurred in the 6- and 12-month groups in response to porcine, but not rat, ADM.

CONCLUSIONS

In wounds implanted with xenogenic ADM, a short-lived acute inflammatory response, long-lasting humoral and cell-mediated immune responses, and generally poor wound healing were observed.

Evaluation of transdermal penetration enhancers using a novel skin alternative

A novel alternative to animal skin models was developed in order to aid in the screening of transdermal penetration enhancers. The skin alternative consists of a dermal layer containing human fibroblasts dispersed in a collagen matrix and an epidermal layer of differentiated and stratified human keratinocytes. Skin alternatives were placed in modified Franz diffusion cells (receptor volume 12 mL, donor area 3.14 cm2, n = 5) and enhancer solution (0.4 M in propylene glycol (PG)) was applied. Following 1 h of pretreatment, 10 microL of saturated hydrocortisone (HC) solution in PG was applied, and the cells were occluded with Parafilm. Samples were removed from the receptor compartment over 24 h, replaced with fresh receptor solution, and analyzed for steroid content using HPLC. Skin HC content was also determined. Receptor concentration at 24 h (Q24) for full-thickness skin alternative (control) was 28.6 +/- 13.7 microM and permeability (P) was 8.3 x 10(-4) +/- 5.5 x 10(-4) cm h-1. Azone (1) produced a Q24 of 105.0 +/- 36.1 microM and a P of 11.3 x 10(-4) +/- 1.8 x 10(-4) cm h-1, while the novel penetration enhancer 1-dodecyl-2-pyrrolidinone (2) produced a Q24 of 164.8 +/- 61.2 microM and a P of 33.3 x 10(-4) +/- 6.6 x 10(-4) cm h-1. Compound 3 produced the highest values for all permeability parameters tested with a P of 48.0 +/- 36.8 cm h-1 and a Q24 of 186.1 +/- 45.1 microM. When compared to the control, compound 1 gave an enhancement ratio (ER) of 3.7 for Q24 and 1.4 for P. Compound 2 gives an ER 5.8 for Q24 and 4.0 for P. These enhancement ratios are similar to those found using HC and human skin.

HIV transmission by transplantation of allograft skin: a review of the literature

The fear of human immunodeficiency virus (HIV) transmission by means of allograft skin has led to a cautious approach to allograft donor selection. However, no irrefutable diagnostic test exists to determine the possible presence of HIV at the time of donation. In order to find ways of improving HIV donor screening practices for skin banks, we review the presence of HIV in human skin, explore the possible transmission of HIV by transplantation of human allograft skin, and discuss the reliability of existing HIV tests. The use of the polymerase chain reaction (PCR) as a sensitive detection system for HIV infection of skin biopsies, in combination with conventional routine HIV blood screening tests; could lower the risk of transmitting HIV to severely burned patients.