Skin Rejection Research Articles

Depletion of Foxp3+ T Cells Abrogates Tolerance of Skin and Heart Allografts in Murine Mixed Chimeras Without the Loss of Mixed Chimerism

The relative contribution of central and peripheral mechanisms to the generation and maintenance of allograft tolerance is of considerable interest. Here, we present new evidence that regulatory T cells (Foxp3(+) ) maintain skin and heart allograft tolerance in mixed hematopoietic chimeric mice. Transient depletion of both donor- and recipient-derived Foxp3(+) cells was necessary and sufficient to induce decisive rejection of long-accepted skin and heart allografts. In contrast, stable hematopoietic chimerism remained, and there was no detectable induction of donor-specific reactivity to hematopoietic cells. Foxp3(+) cell depletion did not result in the rejection of skin grafts of only MHC-disparate donors (B6.C-H2(d) /bByJ), indicating that MHC antigens were not the target in the graft. We conclude that two different mechanisms of tolerance are present in mixed chimeras. Hematopoietic chimerism, resistant to Foxp3(+) depletion, is probably due to deletional tolerance to MHC antigens, as supported by previous studies. In contrast, regulatory tolerance mechanisms involving Foxp3(+) cells are required to control reactivity against non-MHC antigens not present on hematopoietic lineages.

Investigation of Major Factors That Cause Skin and Hide Rejection in Ethiopia: The Case of Tanneries in Addis Ababa and Modjo Towns

A study was conducted from May 2013 to September 2013 with the objective of identifying the major causes of skin and hide rejection on wet blue skins and hides in AA and Modjo tanneries. A total of 769 rejected skins and hides out of which 272 wet blue sheep skins, 275 goat wet blue skins and 222 cattle hides were examined for the major defects that cause rejection. For sheep skins ekek 110(40.3%), scratch 54(19.9%), wound 54(19.4%), scar 23(8.3%), flay cut, machine defect, and pox each 11(4.2% and putrefaction4(1.4%)) were major causes of sheep skin rejection.. In goats skin, scratch 95(34.7%) was the dominant cause of rejection followed by scar 62(22.7%), ekek 49(18.1%),, flying defect 22(8%) and pox14(5.3%). In cattle hide, putrefaction 98(44.2%), flying cuts 58(26.2%), ekek 33(14.8%),Scratch 20(9%), branding 6(2.5%)were major causes of hide rejection. In sheep skin diseases such as Ekek and scratch caused high rejection of skin and entailed serious economic loss in terms of foreign exchange earning to Ethiopia. Therefore, this main cause of sheep skin rejection and factors that cause rejections should be controlled. where as in goat skins serious issue is scratch responsible for rejection. This study revealed that ekek, scratch, wound and scar, putrefaction and flay cuts were major causes of skin and hide rejection and this suggests out of six major defects four (67%) are pre-slaughter defects and there need to be integrated efforts towards improved livestock extension and husbandry and better health care which are vital issues for production of better quality hide and skin.

Anti-CD28 Antagonism Using a Monovalent Fab Antibody for the Prolongation of Human Skin Allograft Survival.

Background. T cells play a principal detrimental role in alloresponses after transplantation. Costimulation through CD28 induces T cells activation, cytokine production, proliferation, and differentiation, whereas the absence of CD28 signalling leads to T cell apoptosis or anergy. Importantly, the development of effector or regulatory responses after initial antigen exposure may be influenced by the balance between CD28 and cytotoxic T lymphocyte antigen 4 (CTLA-4) costimulatory signalling. Influencing this balance by blocking costimulation through CD28 is theoretically advantageous to agonistic signaling through CTLA4 (for example using CTLA4-Ig) as this would not interfere with CTLA4 and PDL-1 co-inhibitory signaling. In the current study we have investigated the hypothesis that a non-activating monovalent anti-CD28 antibody would prevent rejection of human skin allografts in vivo. Methods. Using a humanised mouse system, we treated mice that had received human skin transplants with FR104 (5 mg/kg), CTLA4-Ig (10mg/kg) or vehicle control intravenously twice a week for three weeks. All mice were started on the treatment regimen three weeks post-adoptive transfer of allogeneic human peripheral blood mononuclear cells (PBMCs) to ensure adequate levels of human leukocyte chimerism. Results. FR104 significantly prolonged skin allograft survival in humanised mice compared with CTLA4-Ig (median survival time, MST=63 vs. 31 (p=0.002)) or Saline (MST=31). While FR104 treatment significantly impacted the level of human leukocyte chimerism in the peripheral blood, it remained above the required reconstitution level known to induce skin rejection. The number of graft infiltrating CD4+ (47.8±24.8 vs 83.3±5.1 cells/HPF, P<0.02) and CD8+ (50.0±11.9 vs 111±34.0 cells/HPF, P<0.04) cells was significantly reduced by FR104 treatment as compared to CTLA-4 Ig treatment. No differences were noted in the number of graft infiltrating Foxp3+ cells between FR104 and CTLA4-Ig groups. FR104 significantly suppressed the serum cytokine production of IL-2, IFNγ, TNFα and IL-10. Conclusion. FR104 is an effective immunosuppressant in vivo. By sparing CTLA-4 and PDL-1 coinhibitory signals, FR104 may theoretically lead to improved therapeutic responses compared with CTLA-4-Ig.

Lymphoid neogenesis in skin of human hand, nonhuman primate, and rat vascularized composite allografts.

The mechanisms of skin rejection in vascularized composite allotransplantation (VCA) remain incompletely understood. The formation of tertiary lymphoid organs (TLO) in hand transplantation has been recently described. We assess this phenomenon in experimental and clinical VCA rejection. Skin biopsies of human (n=187), nonhuman primate (n=11), and rat (n=15) VCAs were analyzed for presence of TLO. A comprehensive immunohistochemical assessment (characterization of the cell infiltrate, expression of adhesion molecules) including staining for peripheral node addressin (PNAd) was performed and correlated with rejection and time post-transplantation. TLO were identified in human, nonhuman primate, and rat skin samples. Expression of PNAd was increased in the endothelium of vessels upon rejection in human skin (P=0.003) and correlated with B- and T-lymphocyte numbers and LFA-1 expression. PNAd expression was observed at all time-points after transplantation and increased significantly after year 5. In nonhuman primate skin, PNAd expression was found during inflammatory conditions early and late after transplantation. In rat skin, PNAd expression was strongly associated with acute rejection and time post-transplantation. Lymphoid neogenesis and TLO formation can be uniformly found in experimental and human VCA. PNAd expression in vascular endothelium correlates with skin rejection and T- and B-cell infiltration.

Insights from computational modeling in inflammation and acute rejection in limb transplantation.

Acute skin rejection in vascularized composite allotransplantation (VCA) is the major obstacle for wider adoption in clinical practice. This study utilized computational modeling to identify biomarkers for diagnosis and targets for treatment of skin rejection. Protein levels of 14 inflammatory mediators in skin and muscle biopsies from syngeneic grafts [n = 10], allogeneic transplants without immunosuppression [n = 10] and allografts treated with tacrolimus [n = 10] were assessed by multiplexed analysis technology. Hierarchical Clustering Analysis, Principal Component Analysis, Random Forest Classification and Multinomial Logistic Regression models were used to segregate experimental groups. Based on Random Forest Classification, Multinomial Logistic Regression and Hierarchical Clustering Analysis models, IL-4, TNF-α and IL-12p70 were the best predictors of skin rejection and identified rejection well in advance of histopathological alterations. TNF-α and IL-12p70 were the best predictors of muscle rejection and also preceded histopathological alterations. Principal Component Analysis identified IL-1α, IL-18, IL-1β, and IL-4 as principal drivers of transplant rejection. Thus, inflammatory patterns associated with rejection are specific for the individual tissue and may be superior for early detection and targeted treatment of rejection.

Effect of FK506 Ointment (Protopic) on Rat Skin Allograft Model

ObjectiveFK-506 (tacrolimus) is a well known immunosuppressive agent used to prevent allograft rejection. The need for chronic allograft immunosuppression and the consequent harmful systemic effects preclude the use of tissue allograft as a routine surgical reconstructive option. This study assessed the effects of FK-506 ointment (Protopic) therapy versus subcutaneous injection of FK-506 (Prograf) on rat skin graft model. MethodsDonor Wistar rat dorsal skin was grafted to recipient Sprague-Dawley rats. Animals groups were divided into 2 groups: Group I was treated with intravenous injection of FK-506, and group II was treated with FK-506 ointment for 2 weeks after surgery. Graft appearance challenges were assessed. ResultsFK506 ointment could prolong the median allograft survival time (16.7 days) compared with group I (15.8). Hematoxylin-eosin staining performed on the allo-skin biopsy samples obtained from both group I and II animals at 2 weeks after graft revealed moderate degree of skin rejection accompanied by mixed lymphocyte infiltration. Tacrolimus mean blood levels were much lower in group II (<0.2 ng/mL) than in group I (0.45 ng/mL) ConclusionsImmunosuppressive FK506 ointment therapy has similar effect to intravenous injection and it could be a useful therapy in the prevention of skin allograft rejection.

Altered Glycosylation in Donor Mice Causes Rejection of Strain-Matched Skin and Heart Grafts

Differential protein glycosylation in the donor and recipient can have profound consequences for transplanted organs, as evident in ABO-incompatible transplantation and xenotransplantation. In this study, we investigated the impact of altered fucosylation on graft acceptance by using donor mice overexpressing human α1,2-fucosyltransferase (HTF). Skin and heart grafts from HTF transgenic mice were rapidly rejected by otherwise completely matched recipients (median survival times 16 and 14 days, respectively). HTF skin transplanted onto mice lacking T and B cells induced an natural killer cell-mediated innate rejection crisis that affected 50-95% of the graft at 10-20 days. However, in the absence of adaptive immunity, the residual graft recovered and survived long-term (>100 days). Experiments using "parked" grafts or MHC class II-deficient recipients suggested that indirect rather than direct antigen presentation plays a role in HTF skin graft rejection, although the putative antigen(s) was not identified. We conclude that altered glycosylation patterns on donor tissue can trigger a powerful rejection response comprising both innate and adaptive components. This has potential implications for allotransplantation, in light of increasing recognition of the variability of the human glycome, and for xenotransplantation, where carbohydrate remodeling has been a lynchpin of donor genetic modification.

English

Sheep and goats are important contributors to food production in Ethiopia providing meat, milk and income generation for the country. Skins are the most important items to generate foreign currency for developing countries like Ethiopia. However, the huge resource potential of sheep and goats populations of the country are constrained and threatened by compound effect of diseases, poor management and malnutrition. Parasitic skin diseases caused by ectoparasites such as mange mites, lice, keds and ticks are among these threats resulting in serious economic loss to the tanning industry and the country as a whole. The economic impact of ectoparasitism in Ethiopia is not well documented. Tanneries reported that 35% of sheep skin and 56% of goats&rsquo; skin are rejected due to external parasites, and out of the reject groups of the processed skin, about 80 to 90% defects were believed to be due to external parasites. The estimated economic loss due to drop in quality of sheep and goat skin is around USD 25.8 million per year. It also takes time before disease affected animals after treatment could return to their normal body condition. Currently, ectoparasites are among major causes in decreased production, reproduction of these animals as well as leather quality deterioration, down grading and rejection of skins. As many as one-quarter to one third of all skins processed at tanneries in Ethiopia have various defects and are unsuitable for export purposes where most of these defects occur in the pre-slaughter stage of production while the animals are alive and are directly related to parasitic skin diseases. Information available so far in Ethiopia indicate that parasitic skin diseases of small ruminants are widely distributed in different agro-climatic areas, causing serious economic loss to the farming community, tanning and leather industry at large, seriously hampering the income generation and foreign currency flow to the country. The extent of the problem has increased continuously during the past few years, threatening the small ruminant population, health, production and reproduction that warrants cost effective control measures. Key words: Control, Ethiopia, ectoparasites, small ruminants, tanning industry.

Diagnosing skin rejection in vascularized composite allotransplantation: advances and challenges

Refinements in microsurgical techniques coupled with advances in immunosuppressive and immunomodulatory protocols have enabled broader clinical application of vascularized composite allotransplantation (VCA) with encouraging immunological, functional, and esthetic results. However, skin rejection remains a significant obstacle and a serious complication for VCA recipients. Clinical and histopathological features of rejection in VCA have been described in a number of studies, which led to the development of an international consensus on the classification guidelines of rejection in the context of VCA. Nevertheless, currently available diagnostic modalities still have several limitations and shortcomings that can pose a significant diagnostic challenge, particularly when signs of rejection are found to be equivocal. In this review, we provide a critical analysis of these advances and challenges in diagnosing skin rejection. Specifically, we highlight the gaps in understanding of rejection mechanisms, the shortfalls in correlating cellular, molecular, and clinicopathologic markers with rejection grades, deficiencies in defining chronic rejection, and antibody-mediated rejection after VCA, as well as providing an outlook on novel concepts, such as the utilization of advanced computational analyses and cross-disciplinary diagnostic approaches.

Facial and Hand Allotransplantation

Vascularized composite allotransplantation (VCA) is a novel therapeutic option for treatment of patients suffering from limb loss or severe facial disfigurement. To date, 72 hand and 19 facial transplantations have been performed worldwide. VCA in hand and facial transplantation is a complex procedure requiring a multidisciplinary team approach and extensive surgical planning. Despite good functional outcome, courses after hand and facial transplantation have been complicated by skin rejection. Long-term immunosuppression remains a necessity in VCA for allograft survival. To widen the scope of these quality-of-life-improving procedures, minimization of immunosuppression to limit risks and side effects is needed.

Impact of sheep and goats ectoparasites on the tanning industry in Tigray Region, Ethiopia

A study was carried out to assess the effect of ectoparasites on the quality of processed skin and defects that cause downgrading and rejection of skins in pickled sheep and wet blue goat-skins at Wukro Sheba tannery in Tigray region. A total of 120 sheep and 120 goat pelts with known infestation by ectoparasites and ectoparasite free control pelts were purchased and processed in Sheba tannery and the corresponding skin defects were analyzed. Accordingly, three groups of 40 sheep pelts each (one group infested with M. ovinus, one group infested with Damalina ovis and a control group of ectoparasite free sheep pelts) and three groups of 40 goat pelts each (one group infested with sarcoptic mange, one group infested with Linognathus spp. and a control group of ectoparasite free goat pelts) were used. Defects observed at pickled stage include cockle, scratch, scar, technical defects due to flaying and old age. A strong association (P<0.001) was observed between cockle lesion and infestation of sheep pelts with D. ovis and Mellophagus ovinus and infestation of goat pelts with sarcoptic mange. Further more, the severity of infestation of sheep pelts with M. ovinus and D. ovis and infestation of goat pelts with sarcoptic mange were found to correlate significantly (P<0.001) with severity of cockle defect. Further investigation on 1000 pickled sheep and 1000 wet blue goat skins revealed that scratch defect was the dominant (43.4 % and 53 %), followed by cockle (35 % and 21.5 %), scar (7 % and 6.8 %) and knife cut (3.4 % and 6.2 %) in pickled sheep and wet blue goat skins, respectively. There was a significant difference (P<0.001) in proportion of cockle between pickled sheep and wet blue goat skins. In addition, a strong association (P<0.001) was observed between cockle and scratch, and cockle and scars on both pickled skins. The economic loss due to quality deterioration of exported skin in the study tannery was estimated to be 778,199.41 USD for pickled sheep and 247,677.61 USD for wet blue goat skins per annum. The growing threat of ectoparasites to small ruminant production and to the tanning industry needs well coordinated and urgent control intervention.Keywords: Ectoparasites, Goat, Sheep, Skin defects, Tigray Region, Ethiopia.

The Impact of Skin Type and Area on Skin Rejection in Limb Transplantation

Atypical manifestation of skin rejection observed in a series of hand transplant recipients suggests that appearance and mechanisms of rejection may vary and depend on skin type and location. We herein characterize skin rejection and inflammation at 3 defined areas of a rat hind-limb allograft. Allograft skin was harvested at the thigh, dorsum and planta pedis on postoperative day 5 and analyzed for histopathology, T-cell composition and expression of cytokines associated with skin inflammation. Isografts and naive animals served as controls. Histology of the allograft skin collected on day 5 showed a diffuse cell infiltrate in the dermis and at the dermal-epidermal interface in the thigh and dorsum, whereas in the planta pedis it was mainly located perivascularly in the dermis. At all areas, epidermal involvement such as apoptotic keratinocytes and infiltrating lymphocytes were observed. Isograft skin showed only very mild or no signs of inflammation at all 3 locations. No significant difference was obse...

Chapter Seven - MHC Class I Recognition by Monocyte-/Macrophage-Specific Receptors

The most important transplantation antigens in the discrimination between "self" and "nonself" are encoded by genes in the major histocompatibility complex (MHC) locus (H-2 in mice). It has been assumed that T lymphocytes are the effector cells for allograft rejection, as athymic nude rodents fail to reject allografts. In 1988, we i.p. transplanted Meth A (H-2D(d)K(d)) tumor cells into C57BL/6 (H-2D(b)K(b)) mice and found macrophages to be cytotoxic against the allografts. In 1996, several groups using CD4 or CD8 knockout mice reported that non-T cells were the effector cells for the rejection of skin or organ allografts. In 1998, we ascertained that macrophages were the effector cells of skin allograft rejection. Recently, we isolated cDNA clones encoding monocyte/macrophage MHC receptors (MMRs) for H-2D(d) and H-2K(d); established H-2D(d)- and/or H-2K(d)-transgenic mice and lymphoma cells; and found, using MMR-deficient mice, that MMR and T-cell receptor were essential for the rejection of transgenic skin and lymphoma, respectively.

On the Role of Dendritic Cells Versus Other Cells in Inducing Protective CD8+ T Cell Responses

Dendritic cells (and/or macrophages) are key transporters of antigen from extralymphatic tissue to secondary lymphatic organs. The phagocytized antigen is presented via MHC class II but not via class I, except for infections by intracellular viruses, bacteria, etc. (1–4). Class II-negative cells (e.g., fibroblasts) that get drained to secondary lymphatic organs (including spleen) induce MHC class I restricted CD8 T cells’ cell responses as efficiently as dendritic cells (5–7). So called crosspresentation is at least 105 times less efficient than direct presentation and therefore is practically not achievable under physiological conditions (5–8). If antigen accumulates in the endoplasmic (ER) reticulum because of transport problems, crosspresentation on to MHC class I can be demonstrated. This requires gigantic amounts of antigen accumulation in the ER, but this process has so far been difficult to quantitate in comparison to direct presentation (9). Positive demonstration of crosspresentation in experiments is sometimes based on use of excessive amounts of protein antigen (e.g., OVA) and/or the use of unphysiological (i.e., much too sensitive) detection method, e.g., using very high frequencies of transgenic T cells (e.g., OVA-specific tgCD8+ T cells). In some experiments, virus inactivation is not controlled properly, permitting abortive (but not virus productive) infections that seemingly suggest crosspresentation instead of direct presentation [e.g., Ref. (8)]. An insulin-producing allogeneic cell graft strictly transplanted under the kidney capsule is accepted for more than >200 days by the host, but is promptly rejected if at the time of transplantation, or a few days later, the same cells are also given i.p. or i.v. (10) Once accepted, the allogeneic strictly peripheral cell graft is highly resistant to rejection by a transplanted corresponding allogeneic skin graft (or dendritic cells). This skin graft is rejected in a primary fashion, signaling absence of direct or indirect priming by the original allogeneic cell graft indicating absence of priming by the original cell graft. This prompt skin rejection does not cause rejection of the insulin-producing cell graft (10). A strictly extralymphatic (7) tumor expressing a very strong and defined viral antigen (similar to insulin-producing self-beta-cells or allogeneic islet cells (10–12) can grow successfully to become lethal tumors. This depends on the condition that at the time of syngeneic tumor cell transplantation no (or too few) tumor cells escape/or drain to secondary lymphatic organs (7). This potentially early direct immunization is distinct from the late process of metastasis to secondary lymphatic organs that very often represent immune escape of tumor cells (e.g., MHC mutants, mutations of the T cell epitope, barrier formation by fibrin, coagulation, etc.)

Immunosuppression and Monitoring of Rejection in Hand Transplantation

Advances in vascularized composite allotransplantation over the last decade have achieved significant milestones in basic science and translational research, as well as clinically with highly encouraging functional and immunologic outcomes. However, certain immunologic challenges remain. In particular, although tolerance has been induced to nearly all components of a hand allograft in experimental models, the skin component may still be subject to acute rejection episodes. Currently, conventional immunosuppressive protocols have been successful at preventing allograft loss; however, they have not prevented episodes of acute skin rejection. Furthermore, the profound side effect profile of the life-long, high-dose, multidrug immunosuppression regimen that is necessary to maintain a viable graft alters the risk to benefit ratio of this non-life-saving procedure. Therefore, there must be a concerted effort in the scientific community to develop novel protocols to either minimize immunosuppression or to induce tolerance to the allograft to promote the widespread application of this life-changing procedure.

Macrophage MHC and T-Cell Receptors Essential for Rejection of Allografted Skin and Lymphoma

Skin or organ allograft rejection is dependent on noncytotoxic CD4(+) T cells, but the mechanisms of recognition and rejection remain elusive. Previously, we demonstrated C57BL/6 (H-2D(b)K(b)) macrophage-mediated, cell-to-cell contact-dependent, d haplotype-specific lysis of allografts (e.g., BALB/c skin and Meth A cells; H-2D(d)K(d)) in the rejection site and isolated two cDNA clones encoding receptors on macrophages for H-2D(d) and H-2K(d), macrophage major histocompatibility complex receptor (MMR) 1 and 2, respectively. To elucidate the role of MMR2 and T-cell receptors (TCRs) in graft rejection, we generated MMR2 knockout (KO) mice on a C57BL/6 background and transplanted D(d), K(d), or D(d)K(d) transgenic C57BL/6 skin or EL-4 lymphoma cells onto or into these KO mice. MMR2 KO mice lacking MMR2 mRNA or protein expression in their monocytes had no obvious abnormalities in terms of cell number in or composition of their lymphoid tissues or in T lymphocyte responses to alloantigen or nonalloantigen, whereas they failed to reject K(d) transgenic skin grafts. Surprisingly, they also lacked MMR1 mRNA and protein expression in their monocytes and failed to reject D(d) or D(d)K(d) transgenic skin grafts. However, they did reject skin grafts from mice expressing H-2I(d), minor H(d), or third-party major histocompatibility complex. On the contrary, D(d)-, K(d)-, or D(d)K(d)-EL-4 cells injected intradermally or intraperitoneally into MMR2 KO mice were rejected by TCR(αβ)(+)/CD8(+) T cells in a transgene number-dependent and MMR-independent manner. These results demonstrate that MMRs on monocytes/macrophages and TCRs on cytotoxic T lymphocytes in mice were essential for recognition and rejection of allografted skin and lymphoma, respectively.

Epicutaneous patch test—A new diagnostic option to prevent the rejection of silicone-covered cochlear implants in children

ObjectivesCochlear implantation (CI) is a revolutionary method for hearing rehabilitation in patients with severe or profound sensorineural hearing loss. One of the surgical complications may be the necrosis of the skin flap above the receiver-stimulator coil, resulting in device extrusion. Our aim was to find the plausible causes of the silicone covered implant rejection. Patients and methodsAuthors present four cases of cochlear implant rejection, briefly describe their dermato-surgical solutions and analyse their innovative method – the epicutanoeus patch testing with silicone samples. ResultsThey observed positive skin reaction in three of the four cases. ConclusionAuthors analyse the applicability and results of their surgical solutions and the epicutaneous testing in connection with the prevention of skin flap necrosis and rejection of silicone-covered cochlear implants.

A Single Center Experience of Abdominal Wall Graft Rejection After Combined Intestinal and Abdominal Wall Transplantation

We report our outcomes following combined intestinal and abdominal wall transplantation, focusing on the presentation and treatment of acute rejection of the abdominal wall vascularized composite allograft (VCA). Retrospective analysis of all patients with combined intestinal/VCA transplantation was undertaken. Graft abnormalities were documented photographically and biopsies taken, with histological classification of rejection according to Banff 2007 guidelines. We have performed five combined intestinal and abdominal wall transplants to date. Two patients developed erythematous, maculopapular to papular eruptions confined to the VCA, histologically confirmed as grade II/III rejection, yet with normal bowel on endoscopy. Both patients’ rashes resolved within 72 h of increasing immunosuppressive treatment. One patient later developed a recurrence of the rash, confirmed as skin rejection, but did not immediately seek medical attention. Treatment was therefore delayed, and mild intestinal rejection developed. We describe the rash associated with VCA rejection, and propose that while the skin of an abdominal wall VCA may reject independently of the intestinal allograft, delay in treatment of rejection episodes may result in rejection of the intestinal graft.

Acellular porcine skin and allogeneic skin as wound-covering materials for extensive deep burns:a comparative study

Objective To evaluate the advantages of microskin graft using acellular porcine skin for treatment of extensive deep burns by comparing with that using allogeneic skin.Methods A retrospective analysis was conducted on 70 severe burn patients who were treated in the Second Affiliated Hospital of Kunming Medical University during Jan.1999 to Jan.2011.The patients were divided into the acellular porcine skin group and allogeneic skin group,each containing 35 patients.The survival rates of microskin grafts were determined at 4 weeks post-operation.Besides,the rejection of acellular porcine skin and allogeneic skin,changes of body temperature,white blood cell(WBC) count,lymphocyte and serum protein were observed at pre-and post-operation.Results(1) The survival rate was(71.5±6.6)% in acellular porcine skin group and(70.6±7.5)% in allogeneic skin group,with no significant difference found between the two groups(P0.05).(2) Acellular porcine skin group.At 3 days post-operation the acellular porcine skin was still attached to the wound,most of the skin was not discolorated,and small part of the skin became cinnamomeous.The acellular porcine skin was gradually separated from the auto-microskin at 3-4 weeks post operation,and there was small amount of exudates under the acellular porcine skin,which could be drained through a small cut.In the pressed area,there was still a small amount of exudates,but the acellular porcine skin was not dissolved and the microskin grafts survived and became confluent.(3) Allogeneic skin group.The allogeneic epidermal was rejected and was off from the wound at 3-14 days post transplantation,and at 10-30 days after transplantation the allogenic dermis became dry.During 25-60 days after transplantation,the allogenic dermis was completely stripped off,the microskin grafts became confluent,and the wound was healed.(4) The body temperature of the two groups was significantly descended after operation(P0.01).The temperature of acellular porcine skin group was significantly lower than that of allogeneic skin group at 14 day post-operation(P0.01).(5) The WBC count and percentage of neutrophils were also significantly decreased in both two groups after operation(P0.05),and WBC counts in the acellular porcine skin group was significantly lower than those in the allogeneic skin group at 7 and 14 days after operation(P0.05,P0.01).The peripheral blood lymphocytes were also significantly increased after operation(P0.01) and the lymphocytes in the acellular porcine skin group were significantly less than those in the allogeneic skin group at 14 days after operation(P0.01).Blood biochemistry results showed no significant differences in the protein levels between the two groups(P0.05).Conclusion Microskin graft using acellular porcine skin,instead of allogeneic skin,for extensive burn patients can inhibit systematic inflammatory response,improve the nutrition condition,and reduce the using of allogeneic skin.Acellular porcine skin might be a suitable alternative for allogeneic skin.

Histopathology of Chronic Rejection in a Nonhuman Primate Model of Vascularized Composite Allotransplantation

Chronic rejection of vascularized composite allografts (VCA) is an emerging phenomenon that may decrease long-term allograft survival and impair allograft function. Although intimal hyperplasia has been reported in human hand transplants, chronic changes in VCAs remain poorly described. We developed a nonhuman primate model of face transplantation to evaluate the effect of various immunosuppressive regimens on allograft survival that we have previously reported. Nineteen grafts were successfully transplanted and serially biopsied to assess for rejection. Five VCA grafts with long-term survival (>200 days) were weaned off immunosuppression. We performed additional histologic and immunohistochemical studies on previously collected samples. All five grafts developed features consistent with chronic rejection, including neointimal proliferation, transplant vasculopathy, vessel wall fibrosis, progressive luminal occlusion, and tertiary lymphoid follicles. Review of 186 serial allograft skin and subcutaneous tissue biopsies revealed that tertiary follicles and vascular changes developed in the absence of acute skin rejection. No relationship was found between alloantibody production and these changes. Recognition of these characteristics of VCA chronic rejection is important for diagnosis in clinical hand and face transplantation. Studies directed towards minimizing VCA chronic rejection responses may be required to improve long-term outcomes.