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.

Reconstruction of the tendon-bone insertion with decellularized tendon-bone composite grafts: comparison with conventional repair.

PURPOSE: Injuries involving the tendon-bone interface (TBI) are difficult to address. Standard techniques typically lead to diminished strength of the healed insertion site. We hypothesized that these injuries would benefit from being reconstructed with decellularized composite grafts replacing both tendon and bone. To test this hypothesis, decellularized grafts were compared with conventional pullout repairs in an in vivo animal model. METHODS: We harvested 48 Achilles TBI grafts from rats and decellularized them. Tendon-bone interface graft reconstruction and pullout repairs were compared using a pair-matched design. Biomechanical properties were evaluated at 2, 4, 8, and 12 weeks. We evaluated histological analysis of insertion morphology and collagen type I/III content. RESULTS: There was a significant increase in ultimate failure load (35 ± 11 vs 24 ± 7 N) and ultimate tensile stress (1.5 ± 0.3 vs 1.0 ± 0.4 N/mm(2)) of the TBI grafts compared with pullout repairs at 2 weeks. These differences remained at 4 weeks. At 12 weeks, both TBI grafts and pullout repairs were as strong as native tissue and not significantly different from each other. Histology showed a more organized extracellular matrix in the TBI graft group at the early time points. Repopulation of the decellularized grafts increased over time. At 12 weeks, the insertion points of both groups were richly populated with cells that possessed morphologies similar to those found in native TBI. CONCLUSIONS: This study showed that decellularized TBI grafts were stronger compared with conventional pullout repairs at 2 and 4 weeks but were comparable at 12 weeks. A more organized extracellular matrix and different collagen composition in the early time points may explain the observed differences in strength. CLINICAL RELEVANCE: In the future, decellularized TBI grafts may be used to reconstruct tendon-bone insertion tears in multiple areas including the flexor tendon system.

Implanted cell-dense prevascularized tissues develop functional vasculature that supports reoxygenation after thrombosis.

Achieving adequate vascularization within implanted engineered tissues is a significant obstacle to maintaining viability and functionality. In vitro prevascularization of engineered tissues has been explored as a potential solution to this challenge. The traditional paradigm of in vitro prevascularization is to implant an engineered tissue with a preformed vascular network that is perfused after anastomosis with the host circulation. We investigated the efficacy of this strategy by implanting cell-dense prevascularized tissues created via cell-mediated contraction and composed of collagen and a collagen-fibrin mixture into dorsal window chambers surgically prepared on immunocompromised mice. We found that host-implant anastomosis takes place in 2-6 days and that perfusion of vessels within the implants is subsequently restricted by thrombosis. However, by day 7, a functional vascular network composed of host and implant vessels developed. Prevascularization enhanced intra-implant pO2 significantly as early as 2 days postimplantation, reaching a maximum of 55 mmHg by day 8, which was significantly greater than the maximum within cellularized control tissues (18 mmHg). By day 14, collagen tissues supported ∼ 0.51 × 10(9) implanted and host-derived cells per mL. Our findings elucidate key features of in vitro prevascularization that can be used toward the design of larger and more functionally complex engineered tissues.

Xenoenxerto (pele da Tilápia-do-Nilo) e hidrofibra com prata no tratamento das queimaduras de II grau em adultos / Nile tilapia skin xenograft versus silver-based hydrofiber dressing in the treatment of second-degree burns in adults

Introdução: Estudos recentes apontam a utilização do curativo biológico com base em animais aquáticos como biomaterial na medicina regenerativa, apresentando boa aderência ao leito das feridas. O objetivo foi avaliar a eficácia da utilização da pele da Tilápia-do-Nilo (Oreochromis niloticus) como curativo biológico oclusivo, no manejo/tratamento de queimaduras de 2º grau em adultos. Métodos: Estudo clínico com 30 pacientes aleatoriamente tratados com pele da Tilápia-do-Nilo (n = 15) e hidrofibra com prata Aquacel Ag® (n =1 5). Resultados: Em relação à duração, o tratamento com a pele da Tilápiado-Nilo obteve uma média de dias de tratamento (9,6 ± 2,4) similar ao material comparativo (10,7 ± 4,5). Quanto ao relato de dor durante a troca de curativos, não houve diferença estatisticamente significante (p > 0,68) entre os grupos. Após a troca do curativo, não houve inferioridade no registro do valor na escala analógica de dor, em que 66,7% dos tratados com pele da Tilápia-do-Nilo relataram diminuição dos eventos álgicos. Constatou-se ainda que 60% dos pacientes tratados com a pele da Tilápia-do-Nilo não tiveram seus curativos substituídos em qualquer momento do tratamento. Para o curativo Aquacel AG®, 53,3% dos pacientes tiveram mais de uma substituição de curativos. Conclusões: Com base na pesquisa, pode-se concluir que a pele da Tilápia-do-Nilo é eficaz como curativo biológico oclusivo. Houve similaridade entre os grupos para a média de dias de tratamento (completa cicatrização da ferida) e para o relato de dor durante a realização do curativo. Também, a não inferioridade relacionada a dor após os curativos e suas trocas (quando existentes) e na quantidade de substituições destes.

Introduction: Recent studies have suggested the use of biological dressings made of aquatic animals as biomaterials in regenerative medicine since they demonstrate good adherence to the wound bed. The objective of this study was to evaluate the efficacy of Nile tilapia skin (Oreochromis niloticus) as an occlusive biological dressing in the management and treatment of second-degree burns in adults. Methods: This clinical study included 30 patients randomly treated with Nile tilapia skin (n = 15) or Aquacel Ag® silver-based hydrofiber dressing (n = 15). Results: The Nile tilapia skin yielded a similar mean treatment time (9.6 ± 2.4 days) to that of the comparative material (10.7 ± 4.5 days). There was no statistically significant intergroup difference (p > 0.68) in pain during dressing changes. No disadvantage in pain was noted, as 66.7% of patients treated with Nile Tilapia skin reported a decrease in pain events. Moreover, 60% of the patients treated with the Nile Tilapia skin did not require dressing replacement at any time during treatment. For the Aquacel AG® dressing, 53.3% of the patients required more than one dressing replacement. Conclusions: Our findings suggest that the Nile tilapia skin is as effective as an occlusive biological dressing. The average treatment time (complete wound healing) and pain reports during dressing changes were similar between groups. Furthermore, pain after and number of dressing exchanges (when performed) were not worse.