The rapid inactivation of porcine skin by applying high hydrostatic pressure without damaging the extracellular matrix

A high-hydrostatic pressure device for nevus tissue inactivation and dermal regeneration for reconstructing skin defects after giant congenital melanocytic nevus excision: a clinical trial

Background

A novel treatment has been developed to reconstruct large skin defects caused by the excision of giant congenital melanocytic nevi. It involves the reimplantation of high-hydrostatic pressurized nevus tissue as a cell-inactivated autologous scaffold for dermal regeneration, followed by the implantation of cultured epithelial autografts on the regenerated dermis. Because this treatment has shown promise in a first-in-human clinical trial which used a prototype pressure machine, a novel pressure device was specifically designed for clinical use.

Methods

In a prospective investigator-initiated clinical trial involving three patients, we evaluated the safety and efficacy of the skin regeneration treatment using a pressure device. All three patients underwent surgical excision of the nevus tissue, primary reimplantation of the inactivated nevus tissue, and secondary implantation of cultured epithelial autografts.

Results

Engraftment of inactivated nevus tissue and cultured epithelial autografts was successful in all three cases, with over 90% epithelialization at 8 weeks post-surgery. No serious adverse events or device malfunction were observed during the trial.

Conclusion

The novel pressure device safely and effectively enabled dermal regeneration using the nevus tissue as an autologous scaffold. This innovative approach offers several advantages, including reduced invasiveness due to minimal sacrifice of normal skin for skin grafting and high curative potential resulting from full-thickness removal of the nevus tissue.

Development of a novel regenerative therapy for malignant bone tumors using an autograft containing tumor inactivated by high hydrostatic pressurization (HHP)

Surgical resection of malignant bone tumors leads to significant defects in the normal surrounding tissues that should be reconstructed to avoid amputation. Our research aimed to inactivate osteosarcoma (OS)-affected bone to obtain autologous bone grafts for bone defect reconstruction using a novel therapy called high hydrostatic pressurization (HHP) therapy. The key points are complete tumor death and preservation of the non-denatured native extracellular matrix (ECM) and bone tissue by HHP. Previously, we found that HHP at 200 MPa for 10 min can completely inactivate cells in normal skin and skin tumors, including malignant melanoma and squamous cell carcinoma while maintaining their original biochemical properties and biological components. Based on our previous research, this study used HHP at 200 MPa for 10 min to eradicate OS. We prepared an OS cell line (LM8), pressurized it at 200 MPa for 10 min, and confirmed its inactivation through morphological observation, WST-8 assay, and live/dead assay. We then injected OS cells with or without HHP into the bone marrow of the murine tibia, after which we implanted tumor tissues with or without HHP into the anterior surface of the tibia. After HHP, OS cells did not proliferate and were assessed using a live/dead assay. The pressurized cells and tumors did not grow after implantation. The pressurized bone was well prepared as tumor-free autologous bone tissues, resulting in the complete eradication of OS. This straightforward and short-pressing treatment was proven to process the tumor-affected bone to make a transplantable and tumor-free autologous bone substitute.

Application of decellularized vascular matrix in small-diameter vascular grafts

Coronary artery bypass grafting (CABG) remains the most common procedure used in cardiovascular surgery for the treatment of severe coronary atherosclerotic heart disease. In coronary artery bypass grafting, small-diameter vascular grafts can potentially replace the vessels of the patient. The complete retention of the extracellular matrix, superior biocompatibility, and non-immunogenicity of the decellularized vascular matrix are unique advantages of small-diameter tissue-engineered vascular grafts. However, after vascular implantation, the decellularized vascular matrix is also subject to thrombosis and neoplastic endothelial hyperplasia, the two major problems that hinder its clinical application. The keys to improving the long-term patency of the decellularized matrix as vascular grafts include facilitating early endothelialization and avoiding intravascular thrombosis. This review article sequentially introduces six aspects of the decellularized vascular matrix as follows: design criteria of vascular grafts, components of the decellularized vascular matrix, the changing sources of the decellularized vascular matrix, the advantages and shortcomings of decellularization technologies, modification methods and the commercialization progress as well as the application prospects in small-diameter vascular grafts.

A Novel Treatment for Giant Congenital Melanocytic Nevi Combining Inactivated Autologous Nevus Tissue by High Hydrostatic Pressure and a Cultured Epidermal Autograft: First-in-Human, Open, Prospective Clinical Trial

BACKGROUND

Giant congenital melanocytic nevi are large skin lesions associated with a risk of malignant transformation. The authors developed a novel treatment to reconstruct full-thickness skin defects by combining an inactivated nevus as the autologous dermis and a cultured epidermal autograft. The first-in-human trial of this treatment was performed.

METHODS

Patients with melanocytic nevi that were not expected to be closed by primary closure were recruited. The full-thickness nevus of the target was removed and inactivated by high hydrostatic pressurization at 200 MPa for 10 minutes. The inactivated nevus was sutured to the original site, and a cultured epidermal autograft was grafted onto it 4 weeks later. Patients were followed for up to 52 weeks.

RESULTS

Ten patients underwent reimplantation of the pressurized nevus, and one patient dropped out. The recurrence of nevus at 52 weeks was not detected by pathological diagnosis in any patients. The L* value at 52 weeks was significantly higher than that of the target nevus. One patient received skin grafting due to contracture of the reconstructed skin. The epithelized area of the reconstructed skin, as the percentage of the original target nevus, was 55.5 ± 19.4 percent at 12 weeks and 85.0 ± 32.4 percent at 52 weeks.

CONCLUSIONS

The inactivated nevus caused inflammation and contracture for several months. However, no recurrence was observed, and combination therapy using an inactivated nevus with a cultured epidermal autograft may therefore be a novel treatment of giant congenital melanocytic nevi.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Hydrostatic pressure can induce apoptosis of the skin

We previously showed that high hydrostatic pressure (HHP) treatment at 200 MPa for 10 min induced complete cell death in skin and skin tumors via necrosis. We used this technique to treat a giant congenital melanocytic nevus and reused the inactivated nevus tissue as a dermis autograft. However, skin inactivated by HHP promoted inflammation in a preclinical study using a porcine model. Therefore, in the present study, we explored the pressurization conditions that induce apoptosis of the skin, as apoptotic cells are not believed to promote inflammation, so the engraftment of inactivated skin should be improved. Using a human dermal fibroblast cell line in suspension culture, we found that HHP at 50 MPa for ≥ 36 h completely induced fibroblast cell death via apoptosis based on the morphological changes in transmission electron microscopy, reactive oxygen species elevation, caspase activation and phosphatidylserine membrane translocation. Furthermore, immunohistochemistry with terminal deoxynucleotidyl transferase dUTP nick-end labeling and cleaved caspase-3 showed most cells in the skin inactivated by pressurization to be apoptotic. Consequently, in vivo grafting of apoptosis-induced inactivated skin resulted in successful engraftment and greater dermal cellular density and macrophage infiltration than our existing method. Our finding supports an alternative approach to hydrostatic pressure application.

Long-term observation of airway reconstruction using decellularized tracheal allografts in micro-miniature pigs at growing stage

Introduction

Decellularized tissue exhibits cell matrix-like properties, along with reduced antigenicity. We explored the potential of decellularized allogeneic trachea to restore the upper respiratory tract, focusing on pediatric application. This study specifically aimed at long-term observation of tissue regeneration using a micro-miniature pig model.

Methods

Artificial defects (15 × 15 mm) in the subglottis and trachea of micro-miniature pigs were repaired by transplantation of either allogeneic decellularized or fresh (control) tracheal patches. Pigs were evaluated in situ, by bronchoscopy, every three months, and sacrificed for histological examination at six and twelve months after transplantation.

Results

No airway symptom was observed in any pig during the observation period. Bronchoscopy revealed the tracheal lumen to be restored by fresh grafts, showing an irregular surface with remarkable longitudinal compression; these changes were mild after restoration with decellularized grafts. Histologically, while fresh graft patches were denatured and replaced by calcified tissue, decellularized patches remained unchanged throughout the observation period. There were regeneration foci of cartilage adjacent to the grafts, and some foci joined the decellularized graft uniformly, suggesting the induction of tracheal reconstitution.

Conclusion

Allogeneic decellularized tracheal tissue could serve as a promising biomaterial for tracheal restoration, especially for pediatric patients at the growing stage.

High Hydrostatic Pressure Therapy Annihilates Squamous Cell Carcinoma in a Murine Model

Cutaneous squamous cell carcinoma (cSCC) is one of the most common skin cancers. In the treatment of cSCC, it is necessary to remove it completely, and reconstructive surgery, such as a skin graft or a local or free flap, will be required, depending on the size, with donor-site morbidity posing a burden to the patient. The high hydrostatic pressure (HHP) technique has been developed as a physical method of decellularizing various tissues. We previously reported that HHP at 200 MPa for 10 min could inactivate all cells in the giant congenital melanocytic nevus, and we have already started a clinical trial using this technique. In the present study, we explored the critical pressurization condition for annihilating cSCC cells in vitro and confirmed that this condition could also annihilate cSCC in vivo. We prepared 5 pressurization conditions in this study (150, 160, 170, 180, and 190 MPa for 10 min) and confirmed that cSCC cells were killed by pressurization at ≥160 MPa for 10 min. In the in vivo study, the cSCC cells inactivated by HHP at 200 MPa for 10 min were unable to proliferate after injection into the intradermal space of mice, and transplanted cSCC tissues that had been inactivated by HHP showed a decreased weight at 5 weeks after implantation. These results suggested that HHP at 200 MPa for 10 min was able to annihilate SCC, so HHP technology may be a novel treatment of skin cancer.

Exploration of the Pressurization Condition for Killing Human Skin Cells and Skin Tumor Cells by High Hydrostatic Pressure

High hydrostatic pressure (HHP) is a physical method for inactivating cells or tissues without using chemicals such as detergents. We previously reported that HHP at 200 MPa for 10 min was able to inactivate all cells in skin and giant congenital melanocytic nevus (GCMN) without damaging the extracellular matrix. We also reported that HHP at 150 MPa for 10 min was not sufficient to inactivate them completely, while HHP at 200 MPa for 10 min was able to inactivate them completely. We intend to apply HHP to treat malignant skin tumor as the next step; however, the conditions necessary to kill each kind of cell have not been explored. In this work, we have performed a detailed experimental study on the critical pressure and pressurization time using five kinds of human skin cells and skin tumor cells, including keratinocytes (HEKas), dermal fibroblasts (HDFas), adipose tissue-derived stem cells (ASCs), epidermal melanocytes (HEMa-LPs), and malignant melanoma cells (MMs), using pressures between 150 and 200 MPa. We pressurized cells at 150, 160, 170, 180, or 190 MPa for 1 s, 2 min, and 10 min and evaluated the cellular activity using live/dead staining and proliferation assays. The proliferation assay revealed that HEKas were inactivated at a pressure higher than 150 MPa and a time period longer than 2 min, HDFas and MMs were inactivated at a pressure higher than 160 MPa and for 10 min, and ASCs and HEMa-LPs were inactivated at a pressure higher than 150 MPa and for 10 min. However, some HEMa-LPs were observed alive after HHP at 170 MPa for 10 min, so we concluded that HHP at a pressure higher than 180 MPa for 10 min was able to inactivate five kinds of cells completely.

Simple and efficient method for consecutive inactivation-cryopreservation of porcine skin grafts

We previously reported that inactivation treatment by high hydrostatic pressurization (HHP) has potential utility as a novel skin regeneration therapy for various skin tumors. In this study, we evaluated whether glycerol-cryopreservation could be applied in order to preserve inactivated skin by HHP using a porcine model. Twenty full-thickness skin grafts (1.5 × 1.5 cm) were prepared from a minipig. The skin samples were inactivated by the HHP in normal saline or glycerol/fructose solution, followed by cryopreservation for 5 weeks at - 80 °C in each same solution. Another 10 grafts immediately after inactivation were prepared as non-cryopreserved controls. Nine grafts in each group were randomly implanted on the fascia of a host pig and removed at 1, 4 and 11 weeks after grafting. All grafts showed engraftment macroscopically. Hematoxylin eosin staining showed the cellular components in all areas of the dermis at 4 and 11 weeks after grafting, and immunohistochemical staining for CD31 showed the presence of capillaries in the grafts in all groups. The surface and cross-sectional areas of grafts in the normal saline solution cryopreserved group decreased between 1 and 11 weeks, whereas these areas in the glycerol cryopreserved group did not decrease significantly. Glycerol cryopreservation may therefore be a simple and efficient method for preserving porcine skin inactivated by HHP.

The sustained release of basic fibroblast growth factor accelerates angiogenesis and the engraftment of the inactivated dermis by high hydrostatic pressure

We developed a novel skin regeneration therapy combining nevus tissue inactivated by high hydrostatic pressure (HHP) in the reconstruction of the dermis with a cultured epidermal autograft (CEA). The issue with this treatment is the unstable survival of CEA on the inactivated dermis. In this study, we applied collagen/gelatin sponge (CGS), which can sustain the release of basic fibroblast growth factor (bFGF), to the inactivated skin in order to accelerate angiogenesis. Murine skin grafts from C57BL6J/Jcl mice (8 mm in diameter) were prepared, inactivated by HHP and cryopreserved. One month later, the grafts were transplanted subcutaneously onto the back of other mice and covered by CGS impregnated with saline or bFGF. Grafts were harvested after one, two and eight weeks, at which point the engraftment was evaluated through the histology and angiogenesis-related gene expressions were determined by real-time polymerase chain reaction. Histological sections showed that the dermal cellular density and newly formed capillaries in the bFGF group were significantly higher than in the control group. The relative expression of FGF-2, PDGF-A and VEGF-A genes in the bFGF group was significantly higher than in the control group at Week 1. This study suggested that the angiogenesis into grafts was accelerated, which might improve the engraftment of inactivated dermis in combination with the sustained release of bFGF by CGSs.

Melanin pigments in the melanocytic nevus regress spontaneously after inactivation by high hydrostatic pressure

We report a novel treatment for giant congenital melanocytic nevi (GCMN) that involves the reuse of resected nevus tissue after high hydrostatic pressurization (HHP). However, the remaining melanin pigments in the inactivated nevus tissue pose a problem; therefore, we performed a long-term observation of the color change of inactivated nevus tissue after HHP. Pressurized nevus specimens (200 MPa group, n = 9) and non-pressurized nevus tissues (control group, n = 9) were subcutaneously implanted into nude mice (BALB/c-nu) and then harvested 3, 6, and 12 months later. Color changes of the nevus specimens were evaluated. In the 200 MPa group, the specimen color gradually regressed and turned white, and brightness values were significantly higher in the 200 MPa group than in the control group after 6 months. This indicated that melanin pigments in the pressurized nevus tissue had spontaneously degraded and regressed. Therefore, it is not necessary to remove melanin pigments in HHP-treated nevus tissue.

Caracterização histomorfológica do sistema tegumentar auricular de cateto - Pecari tajacu Linnaeus, 1758)

RESUMO A criopreservação de tecido somático derivado da pele de catetos consiste numa alternativa para a conservação da biodiversidade por meio da associação com a transferência nuclear. Nesse contexto, a manipulação de tecidos da pele é uma etapa crucial para o sucesso dessa biotécnica. Portanto, o objetivo do presente estudo, foi caracterizar o sistema tegumentar auricular periférico de catetos, visando aprimorar a conservação tecidual. Para tanto, fragmentos auriculares de oito animais foram avaliados quanto às camadas teciduais, aos componentes, à atividade proliferativa e à viabilidade metabólica, usando-se as colorações hematoxilina-eosina e tricrômico de Gomori, quantificação de AgNORs e microscopia eletrônica de transmissão. Assim, tamanhos de 104,2µm e 222,6µm foram observados para epiderme e derme, com uma proporção volumétrica de 36,6% e 58,7%, respectivamente. Além disso, na epiderme, foram evidenciadas as camadas basal (22,5µm), intermediárias (53,5µm) e córnea (28,2µm), com valores médios de 65,3 células epidermais, 43,4 melanócitos e 14,8 halos perinucleares. Já a derme apresentou 127 fibroblastos, com 2,5 AgNORs/nucléolo. Adicionalmente, a atividade metabólica foi de 0,243. Em conclusão, o sistema tegumentar auricular periférico de catetos possui algumas marcantes variações em relação a outros mamíferos, quanto ao número de camadas e espessura da epiderme, quantidade de células epidermais, melanócitos e parâmetros proliferativos.

The Alteration of the Epidermal Basement Membrane Complex of Human Nevus Tissue and Keratinocyte Attachment after High Hydrostatic Pressurization

We previously reported that human nevus tissue was inactivated after high hydrostatic pressure (HHP) higher than 200 MPa and that human cultured epidermis (hCE) engrafted on the pressurized nevus at 200 MPa but not at 1000 MPa. In this study, we explore the changes to the epidermal basement membrane in detail and elucidate the cause of the difference in hCE engraftment. Nevus specimens of 8 mm in diameter were divided into five groups (control and 100, 200, 500, and 1000 MPa). Immediately after HHP, immunohistochemical staining was performed to detect the presence of laminin-332 and type VII collagen, and the specimens were observed by transmission electron microscopy (TEM). hCE was placed on the pressurized nevus specimens in the 200, 500, and 1000 MPa groups and implanted into the subcutis of nude mice; the specimens were harvested at 14 days after implantation. Then, human keratinocytes were seeded on the pressurized nevus and the attachment was evaluated. The immunohistochemical staining results revealed that the control and 100 MPa, 200 MPa, and 500 MPa groups were positive for type VII collagen and laminin-332 immediately after HHP. TEM showed that, in all of the groups, the lamina densa existed; however, anchoring fibrils were not clearly observed in the 500 or 1000 MPa groups. Although the hCE took in the 200 and 500 MPa groups, keratinocyte attachment was only confirmed in the 200 MPa group. This result indicates that HHP at 200 MPa is preferable for inactivating nevus tissue to allow its reuse for skin reconstruction in the clinical setting.

An Exploratory Clinical Trial of a Novel Treatment for Giant Congenital Melanocytic Nevi Combining Inactivated Autologous Nevus Tissue by High Hydrostatic Pressure and a Cultured Epidermal Autograft: Study Protocol

Background

Giant congenital melanocytic nevi (GCMNs) are large brown to black skin lesions that appear at birth and are associated with a risk of malignant transformation. It is often difficult to reconstruct large full-thickness skin defects after the removal of GCMNs.

Objective

To overcome this difficulty we developed a novel treatment to inactivate nevus tissue and reconstruct the skin defect using the nevus tissue itself. For this research, we designed an exploratory clinical study to investigate the safety and efficacy of a novel treatment combining the engraftment of autologous nevus tissue inactivated by high hydrostatic pressurization with a cultured epidermal autograft (CEA).

Methods

Patients with congenital melanocytic nevi that were not expected to be closed by primary closure will be recruited for the present study. The target number of nevi is 10. The full-thickness nevus of the target is removed and pressurized at 200 MPa for 10 minutes. The pressurized and inactivated nevus is sutured to the original site. A small section of the patient’s normal skin is taken from around the nevus region and a CEA is prepared after a 3-week culturing process. The CEA is then grafted onto the engrafted inactivated nevus at four weeks after its retransplantation. The primary endpoint is the engraftment of the CEA at 8 weeks after its transplantation and is defined as being engrafted when the engraftment area of the inactivated nevus is 60% or more of the pretransplantation nevus area and when 80% or more of the transplanted inactivated nevus is epithelialized.

Results

The study protocol was approved by the Institutional Review Board of Kansai Medical University (No. 1520-2, January 5, 2016: version 1.3). The study opened for recruitment in February 2016.

Conclusions

This protocol is designed to show feasibility in delivering a novel treatment combining the engraftment of inactivated autologous nevus tissue and CEA. This is the first-in-man clinical trial of this treatment, and it should be a promising treatment of patients suffering from GCMN.

Trial Registration

University Hospital Medical Information Network: UMIN000020732; https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000022198 (Archived by WebCite at http://www.webcitation.org/6jLZH2vDN)

Verification of the Inactivation of Melanocytic Nevus in vitro Using a Newly Developed Portable High Hydrostatic Pressure Device

High hydrostatic pressure (HHP) technology is a physical method for inactivating tissue. We reported that nevus specimens were inactivated after HHP at 200 MPa and that the inactivated nevus could be used as autologous dermis for covering skin defects. In this study, we verified the inactivation of nevus specimens using a newly developed portable HHP device which will be used in a clinical trial. Nevus tissue specimens were obtained from 5 patients (mean age 7.2 years, range 1-19). We cultured fibroblasts and nevus cells from the tissue specimens and then evaluated their inactivation after HHP at 200 MPa by confirming the attachment of the suspensions and by the live/dead staining of the suspensions, through the dissociation of the cells on chamber slides and by the live/dead staining of the remaining cells. The cells were also quantitatively evaluated by WST-8 assay. We then confirmed the inactivation of the nevus specimens after HHP using explant culture. Our results indicated that fibroblasts and nevus cells were inactivated after HHP at 200 MPa, with the exception of a small percentage of green-colored cells, which reflected the remaining activity of the cellular esterases after HHP. No cells migrated from the nevus specimens after HHP at 200 MPa. We verified the inactivation of fibroblasts and nevus cells cultured from nevus specimens, and in the nevus samples themselves after pressurization at 200 MPa using this device. This device could be used in clinical trials for giant congenital melanocytic nevi and may thus become useful in various medical fields.

Microspheres of carboxymethyl chitosan, sodium alginate and collagen for a novel hemostatic in vitro study

To develop biocompatible composite microspheres for novel hemostatic use, we designed and prepared a novel biomaterial, composite microspheres consisting of carboxymethyl chitosan, sodium alginate, and collagen (CSCM). The ultra-structure of CSCM was investigated by scanning electron microscopy assay. In hemostatic function experiment, it was found that CSCM could facilitate platelet adherence, platelet aggregation, and platelet activation in vitro. Besides, the maximum swelling of CSCM submerged in PBS for 50 min was over 300% of that exhibited by commercial hemostatic compound microporous polysaccharide haemostatic powder (CMPHP). In addition, CSCM exhibited good biodegradability and non-cytotoxicity. These results demonstrated that CSCM may be useful in platelet plug formation, and this study would provide important information for further research on hemostasis experiment in vivo.

Inactivation of Human Nevus Tissue Using High Hydrostatic Pressure for Autologous Skin Reconstruction: A Novel Treatment for Giant Congenital Melanocytic Nevi

Giant congenital melanocytic nevi are intractable lesions associated with a risk of melanoma. High hydrostatic pressure (HHP) technology is a safe physical method for producing decellularized tissues without chemicals. We have reported that HHP can inactivate cells present in various tissues without damaging the native extracellular matrix (ECM). The objectives of this study were to inactivate human nevus tissue using HHP and to explore the possibility of reconstructing skin using inactivated nevus in combination with cultured epidermis (CE). Human nevus specimens 8 mm in diameter were pressurized by HHP at 100, 200, 500, and 1000 MPa for 10 min. The viability of specimens just after HHP, outgrowth of cells, and viability after cultivation were evaluated to confirm the inactivation by HHP. Histological evaluation using hematoxylin-eosin staining and immunohistochemical staining for type IV collagen was performed to detect damage to the ECM of the nevus. The pressurized nevus was implanted into the subcutis of nude mice for 6 months to evaluate the retention of human cells. Then, human CE was applied on the pressurized nevus and implanted into the subcutis of nude mice. The viability of pressurized nevus was not detected just after HHP and after cultivation, and outgrowth of fibroblasts was not observed in the 200, 500, and 1000 MPa groups. Human cells were not observed after 6 months of implantation in these groups. No apparent damage to the ECM was detected in all groups; however, CE took on nevus in the 200 and 500 MPa groups, but not in the 1000 MPa group. These results indicate that human nevus tissue was inactivated by HHP at more than 200 MPa; however, HHP at 1000 MPa might cause damage that prevents the take of CE. In conclusion, all cells in nevus specimens were inactivated after HHP at more than 200 MPa and this inactivated nevus could be used as autologous dermis for covering full-thickness skin defects after nevus removal. HHP between 200 and 500 MPa will be optimal to reconstruct skin in combination with cultured epidermal autograft without damage to the ECM.

Preparation of Inactivated Human Skin Using High Hydrostatic Pressurization for Full-Thickness Skin Reconstruction

We have reported that high-hydrostatic-pressure (HHP) technology is safe and useful for producing various kinds of decellularized tissue. However, the preparation of decellularized or inactivated skin using HHP has not been reported. The objective of this study was thus to prepare inactivated skin from human skin using HHP, and to explore the appropriate conditions of pressurization to inactivate skin that can be used for skin reconstruction. Human skin samples of 8 mm in diameter were packed in bags filled with normal saline solution (NSS) or distilled water (DW), and then pressurized at 0, 100, 150, 200 and 1000 MPa for 10 minutes. The viability of skin after HHP was evaluated using WST-8 assay. Outgrowth cells from pressurized skin and the viability of pressurized skin after cultivation for 14 days were also evaluated. The pressurized skin was subjected to histological evaluation using hematoxylin and eosin staining, scanning electron microscopy (SEM), immunohistochemical staining of type IV collagen for the basement membrane of epidermis and capillaries, and immunohistochemical staining of von Willebrand factor (vWF) for capillaries. Then, human cultured epidermis (CE) was applied on the pressurized skin and implanted into the subcutis of nude mice; specimens were subsequently obtained 14 days after implantation. Skin samples pressurized at more than 200 MPa were inactivated in both NSS and DW. The basement membrane and capillaries remained intact in all groups according to histological and immunohistological evaluations, and collagen fibers showed no apparent damage by SEM. CE took on skin pressurized at 150 and 200 MPa after implantation, whereas it did not take on skin pressurized at 1000 MPa. These results indicate that human skin could be inactivated after pressurization at more than 200 MPa, but skin pressurized at 1000 MPa had some damage to the dermis that prevented the taking of CE. Therefore, pressurization at 200 MPa is optimal for preparing inactivated skin that can be used for skin reconstruction.