Involvement of Male-Specific Minor Histocompatibility Antigen H-Y in Epidermal Equivalent Allograft Rejection

This study describes the involvement of male-specific minor histocompatibility antigen H-Y in vitro cultured epidermal equivalent (EE) rejection. Male and female Balb/c or C3H/HeN keratinocytes were isolated and cultured separately. Male EE were grafted onto adult male (isografts) and adult female (H-Y allografts) mice. As controls, Balb/c EE were grafted onto adult C3H/HeN (complete allografts) mice. Fourteen, 21, and 30 days postgrafting, histological studies showed well-organized cutaneous tissues with complete basement membranes (laminin and type IV collagen deposition) in H-Y allografts compared to the isografts. This cutaneous organization was altered 150 days postgrafting, which is a sign of the H-Y EE allograft rejection. Complete allografts were totally rejected 21 days postgrafting. Immunological studies revealed leucocyte infiltration of H-Y allografts. Significant infiltration was detected even 150 days postgrafting. Leucocyte phenotyping revealed the presence of Mac-1+, CD8+ and CD4+ cells in the H-Y allografts. Humoral immune analysis revealed the presence of circulating anti-H-Y allogeneic keratinocyte cytotoxic antibodies in female recipient sera. Our data suggest that male-specific minor histocompatibility antigen H-Y induces cellular and humoral activation of the recipient immune system even after grafting EE free of cutaneous active immune cells such as T lymphocytes and Langerhans cells.

Histological Comparison of Implanted Cadaveric and Porcine Dermal Matrix Grafts

OBJECTIVES: Histological comparison of human-based (AlloDerm) and porcine-based (ENDURAGen) dermal matrices regarding tissue incorporation and neovascularization as potential soft tissue augmentation materials.

STUDY DESIGN: In vivo, rat model.

METHODS: Subcutaneous implantation of 1-mm thick, 1 cm X 1 cm pieces of AlloDerm, ENDURAGen, and meshed ENDURAGen was performed in 24 Sprague Dawley rats. Implant materials were harvested at 4 (n = 12) and 8 weeks (n = 12). Histological quantification of soft tissue ingrowth and microvascular density was performed following hematoxylin-eosin staining and CD34 immunohistochemistry, respectively.

RESULTS: AlloDerm showed significantly greater soft tissue in-growth and microvascular density compared with both ENDURAGen and meshed ENDURAGen at 4 and 8 weeks ( P < 0.001).

CONCLUSIONS: Although these results may differ in human host tissues, AlloDerm seems to be a more suitable dermal matrix implant than ENDURAGen for cases in which tissue incorporation and neovascularization are sought for the optimal outcome based on this animal model.

Skin Graft Fixation with Negative-Pressure Dressings

The tie-over bolster dressing is the most commonly used method for securing skin grafts. However, it requires surgical skill and experience to make a skin graft adhere closely to a grafting site when the site has a complicatedly curved surface. The lack of appropriate tension and pressure on the skin graft may produce hematoma, dislocation, or wrinkles in the graft. The grafting site for the dorsum of a hand is particularly complicated and irregular and requires delicate changes in pressure when the tie-over bolster dressing is used for sites supported and not supported by bones. We have obtained a high survival rate at such difficult sites by managing skin grafts with negative-pressure dressings. This paper describes the details of the technique with case reports. We have used this technique for skin graft fixation in 10 patients and confirmed its high utility as evidenced by a survival rate of 95% or higher of the grafted areas. Unlike existing techniques that apply pressure on skin grafts, this technique applies a negative pressure to the space between the skin graft and the grafting site to remove hematomas and pull the whole skin graft onto the grafting site with uniform force for adhesion.

Targeting of the hNC16A collagen domain to dendritic cells induces tolerance to human type XVII collagen

Antibodies, specific to murine DEC205, can be used to target antigens to dendritic cells. The immunodominant domain of human type XVII collagen, hNC16A, was fused to this antibody (DEC-hNC16A) and was administered as expression plasmid by gene gun transfection with the aim of inducing tolerance to human type XVII collagen in a skin transplantation model. Mice transfected with DEC-hNC16A were challenged with skin grafts from transgenic mice engineered to express human type XVII collagen. Graft survival was either prolonged or grafts were accepted infinitely (33% and 16%, respectively) upon treatment with DEC-hNC16A while 100% of grafts were rejected in untreated controls. Graft acceptance was associated with the absence of a CD4+ infiltrate and a dense CD8+ T-cell infiltrate and was not strictly dependent on antibody production. Our results show that DEC-hNC16A targets dendritic cells in vivo leading to prolonged survival of transgenic skin grafts. This indicates that DEC205-targeting may be used for the induction of tolerance to skin antigens, which would increase the chances of successful skin gene therapy of epidermolysis bullosa patients.

Use of autologous skin equivalents with artificial dermal matrix (integra) in donor site coverage in radial forearm free flaps: preliminary cases

PURPOSE

The radial forearm flap is one of the most commonly used methods for intraoral reconstruction in oral carcinoma surgery. One of its disadvantages is the residual functional and unaesthetic defect in the donor site. The objective of this report is to describe preliminary cases of a novel method to cover such donor sites based on the use of autologous skin equivalents (ASEs) and an artificial dermal matrix (Integra, Prim, Barcelona, Spain).

MATERIALS AND METHODS

The donor sites of 2 patients were treated with the artificial dermal matrix after raising a radial forearm flap. A skin biopsy and a blood sample were taken to construct an ASE. After 3 weeks, the ASE was applied over the dermal template and left to heal. The functional and esthetic results were recorded.

RESULTS

Good functional and esthetic results were achieved, with correct wrist motility, although a natural skin color could not be achieved. Neither the Integra nor the ASE was rejected. Total wound coverage was achieved at 4 months, and completely normal skin was observed at 6 months.

CONCLUSIONS

This technique of combining an artificial dermal matrix with an ASE could be an alternative method to cover the donor sites of radial forearm flaps.

Squamous cell carcinoma arising in a skin flap: case report and review on malignant transformations in skin grafts and microvascular cutaneous flaps

OBJECTIVES

Sufficient closure of intraoral defects can be challenging. Various methods of tissue transfer have been presented in the literature. From skin grafts to microvascular flaps, most techniques used for intraoral reconstruction use skin to line out the oral cavity to guarantee an epithelial surface. Native mucosa tolerates the moist environment of the oral cavity, whereas skin flaps do to just a certain extent. This may lead to chronic inflammation of the flap-skin. Under rare circumstances, these histologic changes can enhance the risk for malignant transformation of the skin graft.

CASE REPORT

We present a case of a patient who derived a squamous cell carcinoma in the skin island of a jump flap raised from the abdominal wall 30 years earlier. The flap was used to close a very wide palatal cleft. The patient had no history of malignancy, smoking, drinking, or other risk factors.

DISCUSSION

To the authors' knowledge, this is the first report on carcinoma in a skin flap in a patient without any history of intraoral malignancy. Although malignant transformations of skin grafts are very rare and usually appear years after the reconstruction, one should be aware that the moist environment can lead to chronic inflammation of the dermis of flap. This fact may increase the risk of malignant transformation in a skin graft.

[A murine model with murine cytomegalovirus infection resulting in colon inflammation after allogeneic skin transplantation]

To provide a reliable animal model for study of human CMV disease in gastrointestinal track, we tried to infect with murine cytomegalovirus (MCMV) in mice that were received allogenetic skin transplantation under immunosuppression. (1) Skin transplantation was performed between 18 donor C57BL/6 mice and 72 recipient BALB/c mice. (2) All recipient mice were then given Cyclosporine at 12 mg/kg daily for 2 weeks by intraperitoneal injection. Mice were randomly divided into 3 groups. Two experimental groups were received MCMV-infected mouse embryonic fibroblasts (MEF) at 10(4) PFU and 10(5) PFU respectively, and the control group received MEF only. We observed any possibly pathophysiological behavior changes and recorded the changes in body weight. The mice were sacrificed at 5d, 9d, 14d, 21d post infection and colon tissue was collected for analysis.

RESULTS

Mice infected with MCMV at 10(5) PFU group showed anorexia, lethargy and degression in locomotor activity. This group of mice showed significant decrease in body weight than that of other groups. Colon tissues were collected 14 days after infection. Histological examination revealed that the mucous layer became thinner in the proximal colon and increased number of lymphoid follicles in distal colon in infected animals. The changes in the mucosal structure was most prominent in the group 10(5) PFU MCMV. Viral DNA was present in the colon by in situ hybridization for IE1 gene, and viral gB transcript was positive by RT-PCR. One of the viral major proteins, pp65, was widely distributed in the colon by immunohistochemistry. These data demonstrated that MCMV established infection in colon of the mice after allogenetic skin transplantation. Electron microscopy showed that there were herpes virus particles in the colon tissue.

CONCLUSION

Infection with MCMV in mouse after allogenetic skin transplantation by nasal cavity inoculation resulted in the pathological changes in colon tissue similar to that of inflammation in human colon. The small animal model of colon inflammation may provide a platform for further study of pathogenesis as well as medical intervention of HCMV involved inflammation of human bowel.

NOD-scid IL2rgamma(null) mouse model of human skin transplantation and allograft rejection

BACKGROUND

Transplantation of human skin on immunodeficient mice that support engraftment with functional human immune systems would be an invaluable tool for investigating mechanisms involved in wound healing and transplantation. Nonobese diabetic (NOD)-scid interleukin-2 gamma chain receptor (NSG) readily engraft with human immune systems, but human skin graft integrity is poor. In contrast, human skin graft integrity is excellent on CB17-scid bg (SCID.bg) mice, but they engraft poorly with human immune systems.

METHODS

Human skin grafts transplanted onto immunodeficient NSG, SCID.bg, and other immunodeficient strains were evaluated for graft integrity, preservation of graft endothelium, and their ability to be rejected after engraftment of allogeneic peripheral blood mononuclear cells.

RESULTS

Human skin transplanted onto NSG mice develops an inflammatory infiltrate, consisting predominately of host Gr1(+) cells, that is detrimental to the survival of human endothelium in the graft. Treatment of graft recipients with anti-Gr1 antibody reduces this cellular infiltrate, preserves graft endothelium, and promotes wound healing, tissue development, and graft remodeling. Excellent graft integrity of the transplanted skin includes multilayered stratified human epidermis, well-developed human vasculature, human fibroblasts, and passenger leukocytes. Injection of unfractionated, CD4 or CD8 allogeneic human peripheral blood mononuclear cell induces a rapid destruction of the transplanted skin graft.

CONCLUSIONS

NSG mice treated with anti-Gr1 antibody provide a model optimized for both human skin graft integrity and engraftment of a functional human immune system. This model provides the opportunity to investigate mechanisms orchestrating inflammation, wound healing, revascularization, tissue remodeling, and allograft rejection and can provide guidance for improving outcomes after clinical transplantation.

Dissociation between peripheral blood chimerism and tolerance to hindlimb composite tissue transplants: preferential localization of chimerism in donor bone

BACKGROUND

Mixed chimerism induces donor-specific tolerance to composite tissue allotransplants (CTAs). In the present studies, we used a nonmyeloablative conditioning approach to establish chimerism and promote CTA acceptance.

METHODS

Wistar Furth (RT1A(u)) rats were conditioned with 600 to 300 cGy total body irradiation (TBI, day-1), and 100 x 10(6) T-cell-depleted ACI (RT1A(abl)) bone marrow cells were transplanted on day 0, followed by a 11-day course of tacrolimus and one dose of antilymphocyte serum (day 10). Heterotopic osteomyocutaneous flap transplantation was performed 4 to 6 weeks after bone marrow transplantation.

RESULTS

Mixed chimerism was initially achieved in almost all recipients, but long-term acceptance of CTA was only achieved in rats treated with 600 cGy TBI. When anti-alphabeta-T-cell receptor (TCR) monoclonal antibody (mAb) (day-3) was added into the regimens, donor chimerism was similar to recipients preconditioned without anti-alphabeta-TCR mAb. However, the long-term CTA survival was significantly improved in chimeras receiving more than or equal to 300 cGy TBI plus anti-alphabeta-TCR mAb. Higher levels of donor chimerism were associated with CTA acceptance. The majority of flap acceptors lost peripheral blood chimerism within 6 months. However, donor chimerism persisted in the transplanted bone at significantly higher levels compared with other hematopoietic compartments. The compartment donor chimerism may be responsible for the maintenance of tolerance to CTA. Long-term acceptors were tolerant to a donor skin graft challenge even in the absence of peripheral blood chimerism.

CONCLUSIONS

Mixed chimerism established by nonmyeloablative conditioning induces long-term acceptance of CTA, which is associated with persistent chimerism preferentially in the transplanted donor bone.

Use of Homologous Acellular Dermal Matrix for Abdominal Wall Reconstruction in Rats

Homologous acellular dermal matrix graft (HADMG) has been used for the reconstructions of bowel, bladder, or urethra, but its suitability in the reconstruction of abdominal wall has not been tested. Therefore an experimental study was performed to evaluate the use of HADMG for the reconstruction of abdominal wall defects in weanling rats. Thirty weanling Wistar rats were used. A patch of abdominal wall 20 x 20 mm in dimension was removed. The defects were reconstructed with HADMGs that were derived from rat skin and prepared through a detergent enzymatic method. The reconstructed abdominal walls were evaluated as hernia rate and graft take ratio, excised and prepared for histological examination at 21 (n = 10), 40 (n = 10), and 90 (n = 10) days postoperation. The healing of repaired abdominal walls was uneventful. Histological evaluation demonstrated the migration of fibroblasts and neovascularization within the HADMG. Hernia in four rats were developed at 90 days. Neither significant wound contraction nor inflammation was seen at 21, 40, and 90 days after surgery in wounds receiving HADMGs. Thus, the use of a HADMG for reconstructing the abdominal wall in weanling rats has not given rise to any complications. HADMG has progressively remodeled into fibrous tissue. It appears to represent an important alternative substitute for the reconstruction of abdominal wall.

In vitro and in vivo immunosuppressive characteristics of hepatocyte growth factor-modified murine mesenchymal stem cells

BACKGROUND

Previous data have proven that hepatocyte growth factor (HGF) is able to maintain the survival of mesenchymal stem cells (MSCs), rendering HGF gene modification as an optional strategy for MSC therapy. However, the question about whether gene-transferred MSCs (MSC/HGFs) exhibit more potent immunosuppressive activity remains elusive.

MATERIALS AND METHODS

Murine MSCs were isolated, culture-expanded and transfected by an adenovirus carrying human HGF cDNA (Ad-HGF). The transfection efficiency was evaluated by measuring HGF concentrations in the culture supernatants. An MHC-incompatible skin grafting model (C57BL-->BALB/c) was used to observe if MSC/HGF transfusion could prolong the survival time of skin transplants compared to MSCs. Furthermore, their inhibitory effects on the proliferation of T lymphocytes elicited by Con A and the activation of CD11b+ cells in mixed lymphocyte reaction were compared with carboxyfluorescein diacetate succinmidyl ester labeling and flow cytometric techniques.

RESULTS

Ad-HGF was able to transfect mouse MSCs at high efficiency and administration of MSC/HGFs remarkably prolonged the mean survival time of skin grafts (16.73 +/- 0.57 days, p<0.01), compared with mice receiving MSCs (14.27 +/- 0.63 days), or saline (10.92 +/- 0.73 days). However, the presence of MSC/HGFs exhibited little additive impact on the suppression of T lymphocyte proliferation and activation of CD11b-positive and -negative cells in comparison with MSCs, though the inhibitory effects were evidently greater than with NIH3T3 cells and their Ad-HGF-modified counterparts.

CONCLUSION

MSC/HGFs inhibit in vitro immune responses in a pattern similar to MSCs, but this gene modification might have beneficial effects for transplanted cells and damaged tissue.

The use of fibrin glue for fixation of acellular human dermal allograft in septal perforation repair

OBJECTIVES

Acellular human dermal allograft used as an interpositional graft between mucoperichondrial flaps has been shown to be effective in the repair of septal perforations. The material is typically sutured to the septum, but this can be technically difficult. We describe a technique in which fibrin glue is used to secure the acellular human dermal allograft for septal perforation repair.

STUDY DESIGN

A retrospective case series of 5 patients who underwent this procedure are reviewed.

METHODS

Five patients with preexisting septal perforations underwent septal repair using fibrin glue to secure the interpositional acellular human dermal allograft. The graft was first placed between the mucoperichondrial flaps, and 1/3 cm(3) of fibrin glue was applied to both sides. One side was then covered with a bipedicled mucosal flap and compressed for 5 minutes to allow for fixation.

RESULTS

The use of fibrin glue compared with conventional suturing decreased the length of the procedure by approximately 30 minutes. At the 3-month postoperative examination, all 5 patients were found to have successful outcomes.

CONCLUSION

The use of fibrin glue for fixation of the acellular human dermal allograft in septal perforation repair is technically less difficult and reduces the length of the procedure, and we believe it reduces graft migration when compared with conventional suturing techniques.

Maximal inflammatory response benefits syngeneic skin graft acceptance

OBJECTIVE AND DESIGN

We investigated the influence of acute inflammation in skin isograft acceptance.

METHODS

Two mouse lines selected for maximal (AIRMAX) or minimal inflammatory response (AIRMIN) were transplanted with syngeneic skin. Cellular infiltrates and cytokine production were measured 1, 3, 7 or 14 days post-transplantation. The percentage of CD4+CD25+Foxp3+ cells in the lymph nodes was also evaluated.

RESULTS

Grafts were totally accepted in 100% of AIRMAX and in 26% of AIRMIN mice. In the latter, partial acceptance was observed in 74% of the animals. Emigrated cells were basically PMN and were enhanced in AIRMAX transplants. IL-10 production by graft infiltrating cells showed no interline differences. IFN-gamma was increased in AIRMIN grafts at day 14 and lower percentages of CD4+CD25+Foxp3+ cells in the lymph nodes were observed in these mice.

CONCLUSIONS

Our data suggest that differences in graft acceptance might be due to a lack of appropriate regulation of the inflammatory response in AIRMIN mice compromising the self/non-self recognition.

Wound healing effect of acellular artificial dermis containing extracellular matrix secreted by human skin fibroblasts

In this study, an acellular artificial dermis, composed of human collagen and glycosaminoglycan (GAG) secreted by cultured human fibroblasts on a bovine collagen sponge, was developed. Much of the newly secreted extracellular matrix (ECM) remained after the cell removal process. The main theme of this study focused on the matrix, rather than the viable cell components of the skin, as the major dermal deficit in the wound. Both the acellular artificial and bioartificial dermises, containing viable cells with ECM, were significantly less soluble than the collagen sponge, and the relative GAG content in the bioartificial and acellular artificial dermises was approximately 115-120% of the chondroitin-6-sulfate (CS) content found in the collagen sponge. In the group receiving the collagen sponge, the wound area gradually decreased to approximately 10% of its original area, while in the groups receiving the bioartificial and acellular artificial dermises, the wound area also gradually decreased to approximately 60 and 50%, respectively, of the original size over the 5 weeks after grafting. Both the bioartificial and acellular artificial dermises formed thicker, denser collagen fibers; more new blood vessel formation was observed in both cases. The basement membrane of the regenerated epidermal-dermal junction was thicker and more linear in the acellular artificial dermis graft than in the collagen sponge graft. In conclusion, the wound healing effects of acellular artificial dermis are no less than those of the bioartificial dermis, and much better than the collagen sponge graft with respect to wound contraction, angiogenesis, collagen formation, and basement membrane repair.

Inactivation of T-cell receptor-mediated integrin activation prolongs allograft survival in ADAP-deficient mice

BACKGROUND

Signaling through the T cell receptor (TCR) leads to profound changes in the function and properties of T cells, including integrin activation. Adhesion and degranulation promoting adapter protein (ADAP) is an adapter protein linking T cell receptor stimulation to integrin activation. We aim to clarify how disruption of TCR-mediated integrin activation affects alloreactive immune responses.

METHODS

In vitro T cell proliferation and the cytokine production was determined. In vivo cytotoxic T lymphocyte (CTL) activity was measured as well. Allogenic skin and heart transplantation was used to test the in vivo role of ADAP in alloimmune responses. Histology and flow cytometry was applied to analyze the graft infiltrating lymphocytes.

RESULTS

Upon stimulation with allogenic dendritic cells ADAP-deficient T cells displayed impaired proliferative responses compared to wild type (WT) T cells. This was accompanied by significantly decreased production of the cytokine interleukin-2. In contrast, the in vivo CTL activity in ADAP-deficient mice was comparable to that of WT mice. Consistently, we observed a prolongation of fully major histocompatibility complex (MHC)-mismatched heart transplants in ADAP deficient mice. Protection of allogenic heart grafts in ADAP-deficient mice was accompanied by a decrease in the infiltration, proliferation and activation of T cells in the allograft. However, no effect was observed after fully MHC-mismatched skin transplantation.

CONCLUSIONS

We have shown that although ADAP is dispensable for the rejection of allografts, ADAP function plays an important role for the efficacy of graft rejection. ADAP's main function appears to affect the induction phase of the immune response.

Inhibition of Terminal Complement Components in Presensitized Transplant Recipients Prevents Antibody-Mediated Rejection Leading to Long-Term Graft Survival and Accommodation

Ab-mediated rejection (AMR) remains the primary obstacle in presensitized patients following organ transplantation, as it is refractory to anti-T cell therapy and can lead to early graft loss. Complement plays an important role in the process of AMR. In the present study, a murine model was designed to mimic AMR in presensitized patients. This model was used to evaluate the effect of blocking the fifth complement component (C5) with an anti-C5 mAb on prevention of graft rejection. BALB/c recipients were presensitized with C3H donor skin grafts 7 days before heart transplantation from the same donor strain. Heart grafts, transplanted when circulating anti-donor IgG Abs were at peak levels, were rejected in 3 days. Graft rejection was characterized by microvascular thrombosis and extensive deposition of Ab and complement in the grafts, consistent with AMR. Anti-C5 administration completely blocked terminal complement activity and local C5 deposition, and in combination with cyclosporine and short-term cyclophosphamide treatment, it effectively prevented heart graft rejection. These recipients achieved permanent graft survival for >100 days with normal histology despite the presence of systemic and intragraft anti-donor Abs and complement, suggesting ongoing accommodation. Furthermore, double-transplant experiments demonstrated that immunological alterations in both the graft and the recipient were required for successful graft accommodation to occur. These data suggest that terminal complement blockade with a functionally blocking Ab represents a promising therapeutic approach to prevent AMR in presensitized recipients.

A study of using tissue-engineered skin reconstructed by candidate epidermal stem cells to cover the nude mice with full-thickness skin defect

OBJECTIVE

To study and explore the feasibility of using candidate epidermal stem cells with reconstruct tissue-engineered skin for a skin defect.

METHODS

After the candidate epidermal stem cells were selected directly by rapid adhesion to type IV collagen within 10min from keratinocytes isolated from foreskin epidermis, the TES was constructed by seeding large-scale cultured candidate epidermal stem cells onto a fibroblast-containing dermal substrate, then grafted onto athymic immunodeficient mice with full-thickness skin defects. All specimens were harvested after 1 week, 2 weeks and 4 weeks of transplantation to evaluate by gross, histological, transmission electron microscopic and immunohistochemical techniques its potential to reconstitute a full-thickness skin defect.

RESULTS

The transplanted skin developed a well-differentiated epidermis composed of stratum basale, prickle cell layer, granular layer and stratum corneum and clearly defined dermis with the morphological features of intact skin. The continuous and integral basement membrane zone (BMZ) was established; hemidesmosomes, basal lamina and anchoring fibrils were detected. In the dermis, the collagen of dermal substitute degraded gradually and fibroblasts were aligned in order; lymphocytes, organelle debris, differentiated microvasculature and hyperactive collagen fibrillogenesis were observed. The immunohistochemistry suggested that the keratinocytes of the TES were originated from the human candidate epidermal stem cells and not from the mice. The constructed TES was similar to the uninjured skin in morphological features, which suggested the constructed TES by combining cultured candidate epidermal stem cells with the dermal substrate could satisfy the need for the restoration of skin defects.

Homeostatic expansion permits T cells to re-enter the thymus and deliver antigen in a tolerogenic fashion

We previously have shown that delivery of alloantigen on T cells can be used to induce tolerance through central deletion. Here, we analyzed the requirements for tolerance induced by T cells. Adoptively transferred allogeneic T cells undergo extensive homeostatic proliferation in the periphery of lethally irradiated hosts receiving a syngeneic bone marrow transplant, and acquire a memory-like cell surface phenotype. Analysis of the kinetics of thymic re-entry of transferred T cells revealed that T cells undergo homeostatic proliferation in the periphery prior to re-entry into the thymus. Prevention of homeostatic proliferation results in a failure of transferred T cells to re-enter the thymus. In the absence of homeostatic proliferation, adoptively transferred T cells were unable to induce tolerance. These date suggest that homeostatic proliferation of T cells resulting in an activated cell surface phenotype is required for thymic re-entry and is mechanistically linked to the ability of T cells to induce tolerance.

New insights in CD28-independent allograft rejection

CD28 costimulatory blockade induces tolerance in most murine transplant models but fails to do so in stringent transplant models, such as skin transplantation. The precise immunological mechanisms of CD28-independent rejection remain to be fully defined. Using two novel mouse strains in which both CD28 and either CD4 or CD8 are knocked out (CD4(-/-)CD28(-/-) or CD8(-/-)CD28(-/-) mice), we examined mechanisms of CD28-independent CD4(+) or CD8(+) T-cell-mediated allograft rejection. CD4(-/-)CD28(-/-) and CD8(-/-)CD28(-/) deficient mice rejected fully allogeneic skin allografts at a tempo comparable with that in wild-type mice. Rejection proceeded despite significant reduction in alloreactive T-cell clone sizes suggesting the presence of a subset of T cells harnessing alternate CD28-independent costimulatory pathways. Blockade of CD40-CD154 and CD134-CD134L, but not ICOS-B7h pathways in combination significantly prolonged allograft survival in CD8(-/-)CD28(-/-) recipients and to a lesser extent in CD4(-/-)CD28(-/-) recipients. Prolongation in allograft survival was associated with reduced effector-memory T-cell generation, decreased allospecific Th1 cytokine generation and diminished alloreactive T-cell proliferation in vivo. In aggregate, the data identify these two pathways as critical mediators of CD28-independent rejection by CD4(+) and to a lesser extent CD8(+) T cells, and provide novel mechanistic insights into functions of novel T-cell co-stimulatory pathways in vivo.

Absence of C4d Deposition in Human Composite Tissue (Hands and Face) Allograft Biopsies: An Immunoperoxidase Study

Deposition of the C4d complement degradation product has been shown to be a marker of antibody-mediated rejection of solid organ allografts, including kidney, heart, liver, and lung. We investigated whether C4d deposition also would be useful in monitoring rejection in human composite tissue allografts. A total of 60 mucocutaneous formalin-fixed, paraffin-embedded and four frozen biopsy specimens from four patients with composite tissue allografts (three hands, one face) taken during a period of 7 days to 7 years after graft were immunostained for C4d by an immunoperoxidase and an immunofluorescence technique, respectively. C4d deposition was not found in any of the specimens studied, even though several of them showed pathological signs of rejection. No human leukocyte antigen alloantibodies were detected in any of the patients during the study period. These results suggest that humoral rejection occurs rarely, if at all, in the setting of human composite tissue allografts.

A pathogenic role for IgE in autoimmunity: bullous pemphigoid IgE reproduces the early phase of lesion development in human skin grafted to nu/nu mice

Bullous pemphigoid (BP) is an autoimmune disease characterized by subepidermal blistering. Based on previous work, IgG autoantibodies directed against BP180 are thought to be the primary pathogenic agent in BP. In addition to these IgG autoantibodies, however, most BP patients produce IgE class autoantibodies that also react with BP180, and total IgE levels are often elevated in this disease. To directly test whether BP IgE is pathogenic, 6 ng of total IgE isolated from two BP and two normal sera were injected into human skin grafted onto athymic, nude mice. Twenty-four hours after injection, erythematous, elevated plaques were observed in all human skin grafts receiving BP IgE (n=11), but not control IgE (n=9). Histologic and ultrastructural examination of the lesions showed engorgement of blood vessels and a dermal infiltrate composed of neutrophils, eosinophils, and mast cells, many of which were degranulated. At a higher dose of BP IgE (47 ng), histological separation of the epidermis from the dermis was observed in two of the three grafts. The BP IgE-induced erythematous plaques were reminiscent of those clinically seen in BP. This provides early evidence of a direct demonstration of a pathogenic role for IgE class autoantibodies in a human autoimmune disease.

Activation of adenosine 2A receptors attenuates allograft rejection and alloantigen recognition

The current studies investigated the in vitro and in vivo effect of adenosine 2A receptor (A(2A)R) agonists to attenuate allogenic immune activation. We performed MLRs with spleen T lymphocytes and APCs isolated from wild-type and A(2A)R knockout mice of both C57BL/6 and BALB/c background strains. Two-way MLR-stimulated T cell proliferation was reduced by ATL313, a selective A(2A)R agonist in a dose-responsive manner (approximately 70%; 10 nM), an effect reversed by the A(2A)R antagonist ZM241385 (100 nM). By one-way MLRs, we observed that ATL313's inhibitory effect was due to effects on both T cells and APCs. ATL313 suppressed the activation markers CD25 and CD40L and the release of inflammatory cytokines IFN-gamma, RANTES, IL-12P(70), and IL-2. ATL313 also increased negative costimulatory molecules programmed death-1 and CTLA-4 expressed on T cells. In lymphocytes activated with anti-CD3e mAb, ATL313 inhibited the phosphorylation of Zap70, an effect that was reversed by the protein kinase A inhibitor H-89. In skin transplants, allograft survival was enhanced with ATL313, an effect blocked by ZM241385. These results indicate that A(2A)R agonists attenuate allogenic recognition by action on both T lymphocytes and APCs in vitro and delayed acute rejection in vivo. We conclude that A(2A)R agonists may represent a new class of compounds for induction therapy in organ transplantation.

Tertiary lymphoid tissues generate effector and memory T cells that lead to allograft rejection

Tertiary lymphoid tissues are lymph node-like cell aggregates that arise at sites of chronic inflammation. They have been observed in transplanted organs undergoing chronic rejection, but it is not known whether they contribute to the rejection process by supporting local activation of naïve lymphocytes. To answer this question, we established a murine transplantation model in which the donor skin contains tertiary lymphoid tissues due to transgenic expression of lymphotoxin-alpha(RIP-LT alpha), whereas the recipient lacks all secondary lymphoid organs and does not mount primary alloimmune responses. We demonstrate in this model that RIP-LT alpha allografts that harbor tertiary lymphoid tissues are rejected, while wild-type allografts that lack tertiary lymphoid tissues are accepted. Wild-type allografts transplanted at the same time as RIP-LT alpha skin or 60 days later were also rejected, suggesting that tertiary lymphoid tissues, similar to secondary lymphoid organs, generate both effector and memory immune responses. Consistent with this observation, naive T cells transferred to RIP-LT alpha skin allograft but not syngeneic graft recipients proliferated and differentiated into effector and memory T cells. These findings provide direct evidence that tertiary lymphoid structures perpetuate the rejection process by supporting naïve T-cell activation.

IgE basement membrane zone antibodies induce eosinophil infiltration and histological blisters in engrafted human skin on SCID mice

Bullous pemphigoid (BP) is characterized by the deposition of IgG in the basement membrane zone, infiltration of eosinophils, and blister formation. The purpose of this study was to evaluate a potential role of IgE basement membrane antibodies in the histological findings of BP. LABD97 is a component of the shed ectodomain of bullous pemphigoid antigen 2. We have developed an IgE hybridoma to LABD97 antigen. This hybridoma was injected subcutaneously in SCID mice with engrafted human skin. A subcutaneous hybridoma secreting IgE antibodies developed. An IgE mouse hybridoma to trinitrophenyl was used as a control. Human grafts and mouse skin were examined grossly over 21 days, histologically, and immunopathologically at day 21 after injection of the hybridoma. A visible subcutaneous tumor developed in 10-14 days. Erythema and intense scratching developed 2-3 days before the tumor in test mice, but not in controls. At day 21, 16/16 test mice developed intense eosinophil infiltration and degranulation of the human mast cells within the grafts and 13/16 developed histological, but not clinically visible, basement membrane blisters. Human skin grafts of control mice and normal mouse skin on the test mice and control mice did not develop any histological abnormalities. IgE antibodies to LABD97 recapitulate the histological inflammatory process seen in BP.

Fitness of cell-mediated immunity independent of repertoire diversity

Fitness of cell-mediated immunity is thought to depend on TCR diversity; however, this concept has not been tested formally. We tested the concept using JH(-/-) mice that lack B cells and have TCR Vbeta diversity <1% that of wild-type mice and quasimonoclonal (QM) mice with oligoclonal B cells and TCR Vbeta diversity 7% that of wild-type mice. Despite having a TCR repertoire contracted >99% and defective lymphoid organogenesis, JH(-/-) mice rejected H-Y-incompatible skin grafts as rapidly as wild-type mice. JH(-/-) mice exhibited T cell priming by peptide and delayed-type hypersensitivity, although these responses were less than normal owing either to TCR repertoire contraction or defective lymphoid organogenesis. QM mice with TCR diversity contracted >90%, and normal lymphoid organs rejected H-Y incompatible skin grafts as rapidly as wild type mice and exhibited normal T cell priming and normal delayed-type hypersensitivity reactions. QM mice also resisted Pneumocystis murina like wild-type mice. Thus, cell-mediated immunity can function normally despite contractions of TCR diversity >90% and possibly >99%.

The ubiquitous cellular transcriptional factor USF targets the varicella-zoster virus open reading frame 10 promoter and determines virulence in human skin xenografts in SCIDhu mice in vivo

Varicella-zoster virus (VZV) open reading frame 10 (ORF10) is a determinant of virulence in SCIDhu skin xenografts but not in human T cells in vivo. In this analysis of the regulation of ORF10 transcription, we have identified four ORF10-related transcripts, including a major 1.3-kb RNA spanning ORF10 only and three other read-through transcripts. Rapid-amplification-of-cDNA-ends experiments indicated that the 1.3-kb transcript of ORF10 has single initiation and termination sites. In transient expression assays, the ORF10 promoter was strongly stimulated by the major VZV transactivator, IE62. Deletion analyses revealed approximate boundaries for the full ORF10 promoter activity between -75 and -45 and between +5 and -8, relative to the ORF10 transcription start site. The recombinant virus POKA10-Deltapro, with the ORF10 promoter deletion, blocked transcription of ORF10 and also of ORF9A and ORF9 mRNAs, whereas expression of read-through ORF9A/9/10 and ORF9/10 transcripts was increased, compensating for the loss of the monocistronic mRNAs. The cellular factor USF bound specifically to its consensus site within the ORF10 promoter and was required for IE62 transactivation, whereas disrupting the predicted TATA boxes or Oct-1 binding elements had no effect. The USF binding site was disrupted in the recombinant virus, POKA10-proDeltaUSF, and no ORF10 protein was produced. Both ORF10 promoter mutants reduced VZV replication in SCIDhu skin xenografts. These observations provided further evidence of the contribution of the ORF10 protein to VZV pathogenesis in skin and demonstrated that VZV depends upon the cellular transcriptional factor USF to support its virulence in human skin in vivo.

Protective Effects of Monoclonal Antibody to Intercellular Adhesion Molecule-1 in Venous Ischemia-Reperfusion Injury: Experimental Study in Rats

Flaps with venous occlusion have a decreased survival rate compared with arterial occlusion. It seems that several factors are involved in the etiology of total venous occlusion, including free radicals, edema, thrombosis, and reperfusion injury. In the present study, the authors evaluated the blockage of polymorphonuclear leukocyte endothelial adhesion by using a monoclonal antibody to the intercellular adhesion molecule 1 (ICAM-1) ligand to prevent venous ischemia-reperfusion injury in rat epigastric island flaps. A skin flap (3 x 4 cm) supplied by the superficial epigastric artery and vein was harvested unilaterally in 40 male Wistar rats. Total venous occlusion of the skin flap was achieved. Arterial inflow was left intact. Rats were randomly divided into four groups (n = 10). In Group 1; rats were intravenously pretreated with 0.5 ml of 0.9 percent normal saline 15 min before applying a venous clamp, and the flaps were subjected to 6 hr of venous ischemia. In Group 2; rats were intravenously pretreated with 0.05 mg of monoclonal antibody to the intercellular adhesion molecule 1 (0.20 mg/kg) in 0.5 ml of 0.9 percent normal saline 15 min before applying the venous clamp, and the flaps were subjected to venous ischemia as in Group 1. In Group 3; rats were pretreated as in Group 1, and the flaps were subjected to 8 hr of venous ischemia. In Group 4; rats were pretreated as in Group 2, and the flaps were subjected to 8 hr of venous ischemia. The flaps were assessed histologically and by measuring viable and non-viable areas on postoperative day 7. Flap measurements revealed that blocking the action of ICAM-1 IN VIVO by administering monoclonal antibody significantly attenuated ischemic injury after 6 or 8 hr of venous occlusion.

Analysis of skin graft survival using green fluorescent protein transgenic mice

Skin grafting has become a basic and established operation technique; however, it is not clear how skin grafts adapt to recipient beds and replace their functions. In this study, we analyzed the origin of cells in adapted transplants by using green fluorescent protein (GFP) transgenic mice, which emits green fluorescence in the whole body. The dorsal skins of GFP transgenic mice were transplanted to the back of wild-type mice. Similarly, wild-type skins were transplanted to the back of GFP transgenic mice. Since transplantation with full thickness back skin was not successful due to severe immunorejection, tail skins, which contain fewer epidermal Langerhans cells, were used for the experiments. Six months after transplantation, immunohistochemical analysis of the grafts revealed that tissues derived from ectodermal origin such as the epidermis, hair follicles, and sebaceous glands survived in transplanted grafts, but that other tissues such as the dermis, nerves and blood vessels are partly replaced by tissues from recipient beds. Our results further demonstrated that transplantation analyses with GFP transgenic mice could be a useful approach to study the origin of cells in transplants.

Culture of keratinocytes for transplantation without the need of feeder layer cells

Patients with large burn wounds have a limited amount of healthy donor skin. An alternative for the autologous skin graft is transplantation with autologous keratinocytes. Conventionally, the keratinocytes are cultured with mouse feeder layer cells in medium containing fetal calf serum (FCS) to obtain sufficient numbers of cells. These xenobiotic materials can be a potential risk for the patient. The aim of the present study was to investigate if keratinocytes could be expanded in culture without the need of a feeder layer and FCS. Keratinocytes were cultured on tissue culture plastic with or without collagen type IV coating in medium containing Ultroser G (serum substitute) and keratinocyte growth factor (KGF). An in vitro skin equivalent model was used to examine the capacity of these cells to form an epidermis. Keratinocytes in different passages (P2, P4, and P6) and freshly isolated cells were studied. Keratinocytes grown on collagen type IV were able to form an epidermis at higher passage numbers than cells grown in the absence of collagen type IV (P4 and P2, respectively). In both cases the reconstructed epidermis showed an increased expression of Ki-67, SKALP, involucrin, and keratin 17 compared to normal skin. Only 50,000 keratinocytes grown on collagen type IV in P4 were needed to form 1 cm2 epidermis, whereas 150,000 of freshly isolated keratinocytes were necessary. Using this culture technique sufficient numbers of keratinocytes, isolated from 1 cm2 skin, were obtained to cover 400 cm2 of wound surface in 2 weeks. The results show that keratinocytes can be cultured without the need of a fibroblast feeder layer and FCS and that these cells are still able to create a fully differentiated epidermis. This culture technique can be a valuable tool for the treatment of burn wounds and further development of tissue engineered skin.

Effectiveness of negative pressure closure in the integration of split thickness skin grafts: a randomized, double-masked, controlled trial

OBJECTIVES

To determine the effectiveness of the negative pressure closure (NPC) technique in the integration of split-thickness skin grafts (STSG) to the recipient site.

METHODS

Randomized, double-masked, controlled trial.

SETTING

A tertiary burn unit.

PATIENT CHARACTERISTICS

Between May 2003 and October 2004, 60 patients having wounds with skin loss which hindered primary closure, were incorporated to this study. We excluded patients with > or =20% of total body surface burns, polytraumatized, surgical contraindications, those who were enlisted in other clinical trials, and those who rejected the informed consent.

INTERVENTIONS

In all the patients, surgical cleaning of the recipient site and STSG were performed after which they were randomly assigned between 2 groups: a group that received a NPC dressing and were connected to the central aspiration system at -80 mm Hg versus a control group with similar dressing but without connection to negative pressure. Loss of STSG area at the fourth postoperative day, days of hospital stay.

RESULTS

Sixty patients were included. The median loss of the STSG in the NPC group was 0.0 cm versus 4.5 cm in the control group (P = 0.001). The median hospital stay was of 13.5 days in the NPC group versus 17 days in the control group (P < 0.001).

CONCLUSIONS

The use of NPC significantly diminishes the loss of STSG area, as well as shortens the days of hospital stay. Therefore, it should be routinely used for these kinds of procedures.

Delayed reepithelialization and scarring deregulation following drug-induced toxic epidermal necrolysis

A 51-year-old Caucasian woman developed severe drug-induced toxic epidermal necrolysis (TEN) due to allopurinol. The withdrawal of the culprit drug was unfortunately delayed, and dramatic retardation of reepithelialization was observed. At that stage of disease evolution, an inflammatory cell infiltrate was present in the dermis. Coverage of eroded lesions by frozen cultured keratinocyte allografts failed to hasten reepithelialization compared to ungrafted sites. This unusual protracted TEN evolution was followed by the development of extensive hypertrophic and keloid scars. Several biopsies were taken over 6 months. The histologic presentation of the grafted and ungrafted eroded scar tissues looked similar. Both the number and size of the Factor XIIIa-positive dermal dendrocytes, as well as the number of alpha-actin-positive myofibroblasts showed a marked increase between weeks 2 and 12 after grafting. They were reduced after 6 months when the scarring process was stabilized. alpha1 [IV] collagen was never expressed over the eroded scars. Similar to burn patients, delayed reepithelialization might be a risk factor for abnormal scarring in TEN. Cultured keratinocyte allograft apparently offered no improvement in reepithelialization and did not prevent abnormal scarring in this TEN patient.

IL-12 Instructs Skin Homing of Human Th2 Cells

Distinct pattern of homing receptors determines the tissue preference for T cells to exert their effector functions. This homing competence is mostly determined early during T cell activation of naive T cells. In contrast, mechanisms governing the acquisition of particular homing receptors by T cells of the memory phenotype remain enigmatic. Th2 cell-mediated allergic diseases tend to flare during infections despite that these infections prime APCs to produce the prototypic Th1 cell-differentiating cytokine IL-12. In this study, we investigate the effect of IL-12 on the regulation of cutaneous lymphocyte Ag (CLA) on differentiated Th2 cells and consequences of this expression for allergic inflammation. Upon activation with IL-12, CLA- Th2 cells rapidly up-regulated IL-12Rbeta2 chain, alpha(1-3)-fucosyltransferase VII, and CLA molecules. IL-12-mediated CLA expression on Th2 cells was functional because it mediated rolling of these Th2 cells on E-selectin in vitro and migration into human skin grafts in SCID mice. CLA induction occurred immediately after exposure to IL-12 and was independent of IFN-gamma expression. In accordance, the transcription factor mediating IFN-gamma expression, T-bet, does not directly affect CLA expression. However, CLA expression was further enhanced after IL-12 treatment of T-bet+ -transfected Th2 cells in agreement with an increased IL-12 responsiveness of these cells caused by T-bet. The finding that IL-12 conferred skin-homing potential to already differentiated Th2 cells before inducing a switch in their cytokine production profile may explain the observed exacerbation of allergic skin diseases following bacterial infections.

Perforator artery based flap debulking: an alternative method

The postoperative bulky appearance of a musculocutaneous flap constitutes aesthetic problems that could necessitate secondary operations. Three patients who were reconstructed with free musculocutaneous flaps were re-operated at the postoperative sixth month. The fasciocutaneous flaps were elevated based on perforator arteries, and the excess skin, dermal, and adipose tissues were excised. There were no complications in the follow-up. This one-staged, perforator artery based flap debulking is proposed as an efficient and alternative method.

Human Skin Preserved Long-Term in Anhydric Pulverized Sodium Chloride Retains Cell Molecular Structure and Resumes Function After Transplantation

BACKGROUND

Human skin is needed to cover large areas of the body lost through burns, trauma, and extensive maxillofacial surgery. Contemporary methods of skin storage are limited by the period of preservation to a few days. Our previous findings showed that fixation and storage of human skin in anhydric sodium chloride at room temperature for weeks or months preserves its morphological and molecular structure. In this study, we examined whether skin grafts preserved in sodium chloride may be successfully transplanted.

METHODS

Skin was harvested from lower limbs of patients during elective surgery, placed in containers with anhydric salt powder, and kept at 22 degrees C for 3 to 12 weeks. Desalination and rehydration took place before transplantation. Desalinated fragments were transplanted onto the dorsum of scid mice.

RESULTS

All grafts were accepted by recipients. Three weeks after transplantation, keratinocytes synthesized keratins 10, 16, and 17 and expressed antigens specific for stem (p63) and transient (CD29) cells. Moreover, they proliferated vigorously, their basal layer cells incorporated bromdeoxyuridine and expressed proliferative cell nuclear antigen. Isolated from transplants and cultured in vitro, they remained viable and produced enzymes. Dermis retained its structure and expressed fibroblast-specific antigen. All graft cells remained human leukocyte antigen I.

CONCLUSION

Human skin preserved in anhydric sodium chloride at room temperature for months can be successfully transplanted to scid mice. We propose the concept of "spore-like" keratinocyte stem cells to explain the long-term ex vivo survival of keratinocytes. The mechanism of survival of fibroblasts remains to be determined.

Lymphopenia-Induced Homeostatic Proliferation of CD8+T Cells Is a Mechanism for Effective Allogeneic Skin Graft Rejection following Burn Injury

Burn patients are immunocompromised yet paradoxically are able to effectively reject allogeneic skin grafts. Failure to close a massive burn wound leads to sepsis and multiple system organ failure. Immune suppression early (3 days) after burn injury is associated with glucocorticoid-mediated T cell apoptosis and anti-inflammatory cytokine responses. Using a mouse model of burn injury, we show CD8+ T cell hyperresponsiveness late (14 days) after burn injury. This is associated with a CD8+ T cell pro- and anti-inflammatory cytokine secretion profile, peripheral lymphopenia, and accumulation of a rapidly cycling, hyperresponsive memory-like CD8+CD44+ IL-7R- T cells which do not require costimulation for effective Ag response. Adoptive transfer of allospecific CD8+ T cells purified 14 days postburn results in enhanced allogeneic skin graft rejection in unburned recipient mice. Chemical blockade of glucocorticoid-induced lymphocyte apoptosis early after burn injury abolishes both the late homeostatic accumulation of CD8+ memory-like T cells and the associated enhanced proinflammatory CD8+ T cell response, but not the late enhanced CD8+ anti-inflammatory response. These data suggest a mechanism for the dynamic CD8+ T cell response following injury involving an interaction between activation, apoptosis, and cellular regeneration with broad clinical implications for allogeneic skin grafting and sepsis.

Anti-mouse CD154 antibody treatment facilitates generation of mixed xenogeneic rat hematopoietic chimerism, prevents wasting disease and prolongs xenograft survival in mice

BACKGROUND

The induction of xenogeneic hematopoietic chimerism is an attractive approach for overcoming the host response to xenografts, but establishing xenogeneic chimerism requires severe myeloablative conditioning of the recipient. The goal of this study was to determine if co-stimulation blockade would facilitate chimerism and xenograft tolerance in irradiation-conditioned concordant recipients.

METHODS

Wistar Furth rat bone marrow (BM) cells were injected into irradiation-conditioned C57BL/6 mice with or without co-administration of anti-mouse CD154 monoclonal antibody (mAb). Chimerism was quantified by flow cytometry, and mice were transplanted with WF rat skin and islet xenografts.

RESULTS

Blockade of CD40-CD154 interaction facilitated establishment of xenogeneic chimerism in mice conditioned with 600 cGy irradiation. Anti-CD154 mAb was not required for establishment of chimerism in mice treated with 700 cGy. However, mice irradiated with 700 cGy but not treated with anti-CD154 mAb developed a "graft-versus-host disease (GVHD)-like" wasting syndrome and died, irrespective of their development of chimerism. Xenogeneic chimeras established with irradiation and anti-CD154 mAb treatment exhibited prolonged skin and, in many cases, permanent islet xenograft survival. Chimerism was unstable and eventually lost in most recipients. Skin xenografts were rejected even in mice that remained chimeric, whereas most islet xenografts survived to the end of the observation period.

CONCLUSIONS

Blockade of host CD40-CD154 interaction facilitates the establishment of xenogeneic chimerism and prevents wasting disease and death. Chimerism permits prolonged xenograft survival, but chimerism generated in this way is unstable over time. Skin xenografts are eventually rejected, whereas most islet xenografts survive long term and perhaps permanently.

Keratin expression in cultured skin substitutes suggests that the hyperproliferative phenotype observed in vitro is normalized after grafting

Cultured skin substitutes, consisting of fibroblasts and keratinocytes in a biopolymer matrix, are an adjunctive treatment for full thickness burn wounds. Previous studies revealed that cultured skin substitutes in vitro exhibit a gene expression profile similar to hyperproliferative skin or wounded normal skin. In the present study, we sought to determine whether this hyperproliferative phenotype is maintained after healing of grafted cultured skin in vivo. Immunohistochemistry was used to localize multiple keratin proteins in native human skin, and in cultured skin substitutes in vitro and after grafting to athymic mice. Keratin 6, keratin 16, and keratin 17, which are known to be upregulated during keratinocyte activation and in hyperproliferative epidermis, were highly expressed in cultured skin substitutes in vitro. These proteins were low or undetectable in native human skin, and were reduced in cultured skin after grafting. Conversely, keratin 15, which is downregulated in activated keratinocytes, was not detected in cultured skin substitutes in vitro but was upregulated after grafting to mice. The results confirm previous observations suggesting a hyperproliferative or activated phenotype in cultured skin substitutes in vitro, similar to wounded native skin. After grafting to athymic mice, the expression patterns suggest a normalization of cultured skin substitutes to a phenotype more closely resembling uninjured human skin.

Composite Vascularized Skin/Bone Transplantation Models for Bone Marrow-Based Tolerance Studies

There is an ongoing need to understand the mechanisms of bone marrow-based allograft tolerance. This is important in clarifying the diverse variables influencing the ultimate outcome of the solid organ and composite tissue transplants. To establish bone marrow transplantation as a routine clinical application, further experimental studies should be conducted to overcome the obstacles related to the bone marrow transplantation. These obstacles include graft versus host disease, immunocompetence, and toxicity of the conditioning regimens. For these purposes, novel experimental models are needed. In an attempt to provide a reliable research tool for bone marrow-based tolerance induction studies, we introduced different experimental models of modified vascularized skin/bone marrow (VSBM) transplantation technique for tolerance induction, monitoring, and maintenance studies. In this skin/bone transplantation model, the technical feasibility of concurrent or consecutive transplantation of the combination of bilateral vascularized skin, vascularized bone marrow, or vascularized skin/bone marrow transplants was investigated. Isograft transplantations were performed between genetically identical Lewis (LEW, RT1) rats. Five different experimental designs in 5 groups of 5 animals each were studied. Group I: Bilateral vascularized skin (VS) transplantation; group II: bilateral vascularized skin/bone transplantation; group III: vascularized skin transplantation on one side and vascularized skin/bone transplantation on the contralateral side; group IV: vascularized bone transplantation on one side and vascularized skin/bone transplantation on the contralateral side; group V: vascularized bone transplantation on one side and vascularized skin transplantation on the contralateral side. Successful transplantations were performed in all groups. The survival of the isograft transplants was evaluated clinically and histologically. All skin flaps remained pink and pliable and grew new hair. The viability of the compact bone, bone marrow and skin at 100 days posttransplant was confirmed by histologic evaluation, and bone marrow revealed active hematopoiesis. Bilateral skin/bone transplantation model may serve as an experimental tool to study new strategies in tolerance induction by altering the amount of the immunogenic load in the form of skin transplant and bone marrow delivery in the vascularized form, allowing for expedited engraftment of stem and progenitor cells.

Perforator flaps in head and neck surgery

A 'perforator flap' is a flap of skin or subcutaneous tissue that is based on the dissection of a 'perforating vessel'. Over the past few years a large number of 'perforator flaps' have been devised and described. By reducing any muscle harvest and trauma to a minimum, perforator flaps aim to minimize donor site morbidity whilst providing the reconstructive surgeon with more versatility than other flap types. The principal perforator flaps are discussed, particularly those employed in head and neck reconstruction including 'free style perforator flaps'. Methods of locating perforating vessels for the use of perforator flaps are described. The technique of perforator flap harvest is illustrated as exemplified in the anterolateral thigh perforator flap. Advantages in the use of this flap for head and neck reconstruction are discussed and are compared with that of non-perforator flaps, particularly the Radial Forearm Flap. The role of the primary thinning of perforator flaps is discussed. The versatility of the anterolateral flap is discussed, which may well supersede the Radial Forearm Flap as the principal soft tissue flap used in head and neck surgery.

The HPV xenograft severe combined immunodeficiency mouse model

The permissive propagation of papillomaviruses outside their natural hosts has not been possible, which is an important restriction to the study of human papillomavirus (HPV) infections and associated diseases. Since the mid-1980s, several models have been described that rely on the growth of HPV in susceptible human xenografts implanted in immunodeficient mice. The severe combined immunodeficiency (SCID) mouse has been particularly suited to this approach, and to reproduce reliably the macroscopic, microscopic, and molecular features of naturally occurring lesions. We describe two common methods that permit growth and propagation of HPV in subcutaneous (heterotopic) or cutaneous (orthotopic) human skin grafts implanted in the SCID mouse.

Effector and Memory CD8+ T Cells Can Be Generated in Response to Alloantigen Independently of CD4+ T Cell Help

There is now considerable evidence suggesting that CD8(+) T cells are able to generate effector but not functional memory T cells following pathogenic infections in the absence of CD4(+) T cells. We show that following transplantation of allogeneic skin, in the absence of CD4(+) T cells, CD8(+) T cells become activated, proliferate, and expand exclusively in the draining lymph nodes and are able to infiltrate and reject skin allografts. CD44(+)CD8(+) T cells isolated 100 days after transplantation rapidly produce IFN-gamma following restimulation with alloantigen in vitro. In vivo CD44(+)CD8(+) T cells rejected donor-type skin allografts more rapidly than naive CD8(+) T cells demonstrating the ability of these putative memory T cells to mount an effective recall response in vivo. These data form the first direct demonstration that CD8(+) T cells are able to generate memory as well as effector cells in response to alloantigen during rejection in the complete absence of CD4(+) T cells. These data have important implications for the design of therapies to combat rejection and serve to reinforce the view that CD8(+) T cell responses to allografts require manipulation in addition to CD4(+) T cell responses to completely prevent the rejection of foreign organ transplants.

Skin cell isolation and expansion for cell transplantation is limited in patients using tobacco, alcohol, or are exhibiting diabetes mellitus

The aim of this exploratory study was to investigate the isolation and expansion of keratinocytes and fibroblasts from donors with certain medical histories. Biopsies were taken from donors (N=32) falling into one or more of the following categories: a history of heavy smoking and/or alcohol abuse, drug abuse, diabetes mellitus or steroid treatment. Cells from donors who did not fall into any of the above-mentioned categories were used as controls. Proliferation and growth behaviour of cells were analyzed by measurement of passage duration, absorbance (MTT-assay) and light microscopy. Donors with a specific medical history required larger biopsy areas than the control group for isolating a sufficient number of fibroblasts and keratinocytes. Times to confluence were significantly prolonged and absorbances (MTT) were significantly reduced in several donor groups when compared to control cultures. Biopsies from donors with steroid treatment, drug abuse and combined nicotine and alcohol abuse could not be established beyond passage 0 degrees or 1 degree, respectively. We conclude that isolation and expansion of skin cells from donors with certain medical histories may require larger biopsies, prolonged expansion times or may even result in failure. These findings may therefore be of clinical importance in the field of autologous skin cell transplantation.

DNA Damage and Tumor Surveillance: One Trigger for Two Pathways

Biological evolution ensures that several backup mechanisms always exist to prevent the failure of cellular processes of critical importance for life. This notion applies to processes aimed at preventing cancer development. Recent research suggests that the DNA damage response, activated in one of the earliest cellular responses to transformation, may elicit two independent tumor surveillance mechanisms. The first, and most well known, is activation of the proapoptotic molecule p53 and subsequent cellular suicide. The second, reported in a recent study, is induction of the expression of ligands for the activating immune receptor NKG2D. That DNA damage induces two independent tumor surveillance responses demonstrates how one tumor surveillance mechanism may be assisted by another to secure efficient protection against early tumorigenesis. The results also support the immunosurveillance theory of cancer and suggest that it may operate at very early stages of tumorigenesis.

Microdialyse et monitorage des lambeaux libres à palette cutanée en chirurgie maxillo-faciale

The development of in vivo microdialysis has made it possible to monitor cutaneous free flaps in maxillo-facial surgery. A microprobe inserted in the free flap dermis collects a microdialysate enabling measurement of dermal metabolites such as glucose, lactate, pyruvate, or glycerol. The monitoring curves are predictive of ischemia-related tissue injury. Hourly measurements provide a reliable method for early diagnosis of venous or arterial thrombosis. Revision surgery can then be undertaken if needed to repair microanastomoses before clinical alteration. This technique has been compared with validated flaps monitoring systems such as temperature probe, transcutaneous oxygen tension monitoring, and laser Doppler flowmetry. Microdialysis has several advantages: objective measurements, different curves for venous and arterial thrombosis, early diagnosis. Accessibility to oral cavity or pharyngeal flaps requires careful clinical analysis (microprobe fixation, anatomy and choice of flap).