Autologous skin reconstruction by combining epidermis and acellular dermal matrix tissue derived from the skin of giant congenital melanocytic nevi

Advancements of 3D bioprinting in regenerative medicine: Exploring cell sources for organ fabrication

3D bioprinting has unlocked new possibilities for generating complex and functional tissues and organs. However, one of the greatest challenges lies in selecting the appropriate seed cells for constructing fully functional 3D artificial organs. Currently, there are no cell sources available that can fulfill all requirements of 3D bioprinting technologies, and each cell source possesses unique characteristics suitable for specific applications. In this review, we explore the impact of different 3D bioprinting technologies and bioink materials on seed cells, providing a comprehensive overview of the current landscape of cell sources that have been used or hold potential in 3D bioprinting. We also summarized key points to guide the selection of seed cells for 3D bioprinting. Moreover, we offer insights into the prospects of seed cell sources in 3D bioprinted organs, highlighting their potential to revolutionize the fields of tissue engineering and regenerative medicine.

Tissue Engineering in Skin Substitute

Thermal injuries may cause significant damage to large areas of the skin. Extensive and deep burn wounds require specialized therapy. The optimal method in the strategy of treating extensive, full thickness burns (III°) is the use of autologous split thickness skin grafts STSG (Busuioc et al. Rom J Morphol Embryol 4:1061-1067, 2012; Kitala D, Kawecki M, Klama-Baryła A, Łabuś W, Kraut M, Glik J, Ryszkiel I, Kawecki MP, Nowak M. Allogeneic vs. Autologous Skin Grafts in the Therapy of Patients with Burn Injuries: A Restrospective, Open-label Clinical Study with Pair Matching. Adv Clin Exp Med. 2016 Sep-Oct;25(5):923-929.; Glik J, Kawecki M, Kitala D, Klama-Baryła A, Łabuś W, Grabowski M, Durdzińska A, Nowak M, Misiuga M, Kasperczyk A. A new option for definitive burn wound closure - pair matching type of retrospective case-control study of hand burns in the hospitalized patients group in the Dr Stanislaw Sakiel Center for Burn Treatment between 2009 and 2015. Int Wound J. 2017 Feb 21. https://doi.org/10.1111/iwj.12720 . [Epub ahead of print]; Prim et al. May 24Wound Repair Regen., 2017; Grossova et al. Mar 31Ann Burns Fire Disasters 30:5-8, 2017). The main limitation of that method is the inadequate amount of healthy, undamaged skin (donor sites), which could be harvested and used as a graft. Moreover, donor sites are an additional wounds that require analgesic therapy, leave scars during the healing process and they are highly susceptible to infection (1-6). It must be emphasized that in terms of the treatment of severe, deep and extensive burns, and there should be no doubt that the search for a biocompatible skin substitute that would be able to replace autologous STSG is an absolute priority. The above-mentioned necessitates the search for new treatment methods of severe burn wounds. Such methods could consider the preparation and application of bioengineered, natural skin substitutes. At present, as the clinical standard considered by the physicians may be use of available biological skin substitutes, e.g., human allogeneic skin, in vitro cultured skin cells, acellular dermal matrix ADM and revitalized ADMs, etc. (Busuioc et al. Rom J Morphol Embryol 4:1061-1067, 2012; Kitala D, Kawecki M, Klama-Baryła A, Łabuś W, Kraut M, Glik J, Ryszkiel I, Kawecki MP, Nowak M. Allogeneic vs. Autologous Skin Grafts in the Therapy of Patients with Burn Injuries: A Restrospective, Open-label Clinical Study with Pair Matching. Adv Clin Exp Med. 2016 Sep-Oct;25(5):923-929.; Glik J, Kawecki M, Kitala D, Klama-Baryła A, Łabuś W, Grabowski M, Durdzińska A, Nowak M, Misiuga M, Kasperczyk A. A new option for definitive burn wound closure - pair matching type of retrospective case-control study of hand burns in the hospitalised patients group in the Dr Stanislaw Sakiel Center for Burn Treatment between 2009 and 2015. Int Wound J. 2017 Feb 21. https://doi.org/10.1111/iwj.12720 . [Epub ahead of print]; Prim et al. May 24Wound Repair Regen., 2017; Grossova et al. Mar 31Ann Burns Fire Disasters 30:5-8, 2017; Łabuś et al. FebJ Biomed Mater Res B Appl Biomater 106:726-733, 2018).

A novel serum: Electrophoresis method to prepare acellular corneal matrix as an artificial corneal scaffold

INTRODUCTION

The aim of this study was to develop a novel decellularization method in order to obtain an ideal scaffold with good biocompatibility.

METHODS

The porcine corneas were treated with human serum for 5 days or serum-electrophoresis respectively. The electrophoresis (100 V/cm) was performed in sterilized buffer containing 40-mM tris base, 18-mM glacial acetic acid, and antibiotics for 1 h at 4°C. The properties of artificial corneal scaffolds were characterized by morphological and histological examinations. The biocompatibility and biological safety were examined by subcutaneous implant test and lamellar keratoplasty.

RESULTS AND CONCLUSIONS

The transparency and appearance of serum-electrophoresis acellular porcine corneal matrix were better than serum acellular porcine corneal matrix. DNA and α-gal in serum-electrophoresis acellular porcine corneal matrix were more efficiently removed than those in serum acellular porcine corneal matrix (p < 0.05). The subcutaneous and corneal implantation experiments showed serum-electrophoresis acellular porcine corneal matrix had better biocompatibility compared to serum acellular porcine corneal matrix (p < 0.01). This novel serum-electrophoresis decellularization method may be valuable for preparation of xenogenic corneal tissue for clinical application.

Limitations of recellularized biological scaffolds for human transplantation

A shortage of donor organs for transplantation and the dependence of the recipients on immunosuppressive therapy have motivated researchers to consider alternative regenerative approaches. The answer may reside in acellular scaffolds generated from cadaveric human and animal tissues. Acellular scaffolds are expected to preserve the architectural and mechanical properties of the original organ, permitting cell attachment, growth, and differentiation. Although theoretically, the use of acellular scaffolds for transplantation should pose no threat to the recipient's immune system, experimental data have revealed significant immune responses to allogeneic and xenogeneic transplanted scaffolds. Herein, we review the various factors of the scaffold that could trigger an inflammatory and/or immune response, thereby compromising its use for human transplant therapy. In addition, we provide an overview of the major cell types that have been considered for recellularization of the scaffold and their potential contribution to triggering an immune response.

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.

Extracellular vesicles derived from mesenchymal cells: perspective treatment for cutaneous wound healing in pediatrics

AIM

We evaluated the effects of the intradermal injection of extracellular vesicles (EVs) derived from adipose stem cells (ASC-EVs) and bone marrow cells (BM-EVs) in an experimental cutaneous wound repair model.

METHODS

Mesenchymal stem cells (MSCs) were in vitro expanded from adipose (ASC) or BM tissues (BM-MSC) of rabbits. EVs were separated from the supernatants of confluent ASC and BM-MSCs. Two skin wounds were induced in each animal and treated with MSC or EV injections. Histological examination was performed postinoculation.

RESULTS

EV-treated wounds exhibited a better restoration compared with the counterpart MSC treatment. ASC-EV-treated wounds were significantly better than BM-EVs (p = 0.036).

CONCLUSION

EV topical inoculation provides restored architecture during cutaneous wound healing and represents a promising solution for regenerative medicine in children.

Acellular Cauda Equina Allograft as Main Material Combined with Biodegradable Chitin Conduit for Regeneration of Long-Distance Sciatic Nerve Defect in Rats

Autologous nerve grafting (ANG), the gold standard treatment for peripheral nerve defects, still has many restrictions. In this study, the acellular cauda equina allograft (ACEA), which consists of biodegradable chitin conduit and acellular cauda equina, is developed. The cauda equina is able to complete decellularization more quickly and efficiently than sciatic nerves under the same conditions, and it is able to reserve more basal lamina tube. In vitro, ACEA shows superior guidance capacity for the regeneration of axons and migration of Schwann cells compared to acellular sciatic nerve allograft (ASNA) in dorsal root ganglion culture. In vivo, ACEA is used to bridge 15 mm long-distance defects in rat sciatic nerves. On day 21 after transplantation, the regenerative distance of neurofilaments in the grafting segment is not significantly different between the ACEA and ANG groups. At week 12, ACEA group shows better sciatic nerve repair than chitin conduit only and ASNA groups, and the effect is similar to that in the ANG group as determined by gait analysis, neural electrophysiological, and histological analyses. The above results suggest that the ACEA has the potential to become a new biological material as a replacement for autografting in the treatment of long-distance nerve defects.

Water absorption by decellularized dermis

Water absorption by decellularized dermis was investigated and compared with biopolymer and synthetic polymer hydrogels (glutaraldehyde-crosslinked gelatin and crosslinked poly(acrylamide) hydrogel, respectively). Porcine dermis was decellularized in an aqueous sodium dodecyl sulfate (SDS) solution. Histological evaluation revealed that the SDS-treated dermis has much larger gaps between collagen fibrils than non-treated dermis, and that water absorption depends on these gaps. Decellularized dermis has low water absorptivity and the absorption obeys Fick's second law. During absorption, the water diffusion rate decreases with time and occurs in two steps. The first is rapid absorption into the large gaps, followed by slow absorption by the collagen fiber layer. Because of the gaps, decellularized dermis can absorb more water than native dermis and shows different water absorption behavior to glutaraldehyde-crosslinked gelatin and crosslinked poly(acrylamide) hydrogels.

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.

Atomic force microscopy in the production of a biovital skin graft based on human acellular dermal matrix produced in-house and in vitro cultured human fibroblasts

The most efficient method in III° burn treatment is the use of the autologous split thickness skin grafts that were donated from undamaged body area. The main limitation of this method is lack of suitable donor sites. Tissue engineering is a useful tool to solve this problem. The goal of this study was to find the most efficient way of producing biovital skin substitute based on in house produced acellular dermal matrix ADM and in vitro cultured fibroblasts. Sixty samples of sterilized human allogeneic skin (that came from 10 different donors) were used to examine the influence of decellularizing substances on extracellular matrix and clinical usefulness of the test samples of allogeneic human dermis. Six groups of acellular dermal matrix were studied: ADM-1 control group, ADM-2 research group (24 h incubation in 0.05% trypsin/EDTA solution), ADM-3 research group (24 h incubation in 0.025% trypsin/EDTA solution), ADM-4 research group (24 h incubation in 0.05% trypsin/EDTA solution and 4 h incubation in 0,1% SDS), ADM-5 research group (24 h incubation in 0.025% trypsin/EDTA solution and 4 h incubation in 0,1% SDS), and ADM-6 research group (24 h incubation in 0,1% SDS). Obtained ADMs were examined histochemically and by atomic force microscopy (AFM). ADMs were settled by human fibroblasts. The number of cultured cells and their vitality were measured. The obtained results indicated that the optimal method for production of living skin substitutes is colonization of autologous fibroblasts on the scaffold prepared by the incubation of human allogeneic dermis in 0.05% trypsin/EDTA. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 726-733, 2018.

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.

Mesenchymal stromal cells for cutaneous wound healing in a rabbit model: pre-clinical study applicable in the pediatric surgical setting

Objective

Mesenchymal stromal cells (MSCs) expanded in vitro have been proposed as a potential therapy for congenital or acquired skin defects in pediatrics. The aim of this pre-clinical study was to investigate the effects of intradermal injections of MSC in experimental cutaneous wound repair comparing allogeneic and autologous adipose stem cells (ASCs) and autologous bone marrow-mesenchymal stromal cells (BM-MSCs).

Methods

Mesenchymal stromal cells were in vitro expanded from adipose and BM tissues of young female New Zealand rabbits. MSCs were characterized for plastic adhesion, surface markers, proliferation and differentiation capacity. When an adequate number of cells (ASCs 10 × 10⁶ and BM-MSCs 3 × 10⁶, because of their low rate of proliferation) was reached, two skin wounds were surgically induced in each animal. The first was topically treated with cell infusions, the second was used as a control. The intradermal inoculation included autologous or allogeneic ASCs or autologous BM-MSCs. For histological examination, animals were sacrificed and wounds were harvested after 11 and 21 days of treatment.

Results

Rabbit ASCs were isolated and expanded in vitro with relative abundance, cells expressed typical surface markers (CD49e, CD90 and CD29). Topically, ASC inoculation provided more rapid wound healing than BM-MSCs and controls. Improved re-epithelization, reduced inflammatory infiltration and increased collagen deposition were observed in biopsies from wounds treated with ASCs, with the best result in the autologous setting. ASCs also improved restoration of skin architecture during wound healing.

Conclusion

The use of ASCs may offer a promising solution to treat extended wounds. Pre-clinical studies are however necessary to validate the best skin regeneration technique, which could be used in pediatric surgical translational research.

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

We previously reported that high hydrostatic pressure (HHP) of 200 MPa for 10 minutes could induce cell killing. In this study, we explored whether HHP at 200 MPa or HHP at lower pressure, in combination with hyposmotic distilled water (DW), could inactivate the skin, as well as cultured cells. We investigated the inactivation of porcine skin samples 4 mm in diameter. They were immersed in either a normal saline solution (NSS) or DW, and then were pressurized at 100 and 200 MPa for 5, 10, 30, or 60 min. Next, we explored the inactivation of specimens punched out from the pressurized skin 10×2 cm in size. The viability was evaluated using a WST-8 assay and an outgrowth culture. The histology of specimens was analyzed histologically. The mitochondrial activity was inactivated after the pressurization at 200 MPa in both experiments, and no outgrowth was observed after the pressurization at 200 MPa. The arrangement and proportion of the dermal collagen fibers or the elastin fibers were not adversely affected after the pressurization at 200 MPa for up to 60 minutes. This study showed that a HHP at 200 MPa for 10 min could inactivate the skin without damaging the dermal matrix.

Decellularization of porcine carotid by the recipient's serum and evaluation of its biocompatibility using a rat autograft model

Recently, decellularized tissues for organ transplantation and regeneration have been actively studied in the field of tissue engineering. In the decellularization process, surfactants such as sodium dodecyl sulfate (SDS) have been most commonly used to remove cellular components from the tissue. However, the residual surfactant may be cytotoxic in vivo and has been reported to hinder remodeling after implantation. In addition, treatment with surfactants may destroy the important extracellular matrix (ECM) structure that allows the decellularized tissue to function as a scaffold for cells. In this study, decellularized tissues with high biocompatibility were created using the recipient's serum. By immersing a heterogeneous tissue in serum conditioned to activate the complement system and DNase I, its cellular components could be removed. Compared to an SDS-treated graft, the serum-treated graft preserved the native structure of its ECM. When subcutaneously implanted into an isogenic inbred rat, the graft treated with the recipient's serum resulted in less immunorejection than did the SDS-treated graft.

Complete cell killing by applying high hydrostatic pressure for acellular vascular graft preparation

Pressure treatment has been developed in tissue engineering application. Although the tissue scaffold prepared by a ultrahydrostatic pressure treatment has been reported, an excessive pressure has a potential to disrupt a structure of extracellular matrix through protein denaturation. It is important to understand the suitable low-pressure condition and mechanisms for cell killing. In this study, cellular morphology, mitochondria activity, and membrane permeability of mammalian cells with various pressure treatments were investigated with in vitro models. When the cells were treated with a pressure of 100 MPa for 10 min, cell morphology and adherence were the same as an untreated cells. Dehydrogenase activity in mitochondria was almost the same as untreated cells. On the other hand, when the cells were treated with the pressure of more than 200 MPa, the cells did not adhere, and the dehydrogenase activity was completely suppressed. However, green fluorescence was observed in the live/dead staining images, and the cells were completely stained as red after above 500 MPa. That is, membrane permeability was disturbed with the pressure treatment of above 500 MPa. These results indicated that the pressure of 200 MPa for 10 min was enough to induce cell killing through inactivation of mitochondria activity.

Transcriptional profiling of epidermal barrier formation in vitro

BACKGROUND

Barrier function is integral to the health of epithelial tissues. Currently, there is a broad need to develop and improve our knowledge with regard to barrier function for reversal of mild skin irritation and dryness. However, there are few in vitro models that incorporate modulations of both lipids and epidermal differentiation programs for pre-clinical testing to aid in the understanding of barrier health.

OBJECTIVE

We have generated a reconstituted epidermis on a decellularized dermis (DED) and characterized its barrier properties relative to human epidermis in order to determine its utility for modeling barrier formation and repair.

METHODS

We followed the process of epidermal differentiation and barrier formation through immunocytochemistry and transcriptional profiling. We examined barrier functionality through measurements of surface pH, lipid composition, stratum corneum water content, and the ability to demonstrate topical dose-dependent exclusion of surfactant.

RESULTS

Transcriptional profiling of the epidermal model during its formation reveals temporal patterns of gene expression associated with processes regulating barrier function. The profiling is supported by gradual formation and maturation of a stratum corneum and expression of appropriate markers of epidermis development. The model displays a functional barrier and a water gradient between the stratum corneum and viable layers, as determined by confocal Raman spectroscopy. The stratum corneum layer displays a normal acidic pH and an appropriate composition of barrier lipids.

CONCLUSION

The epidermal model demonstrates its utility as an investigative tool for barrier health and provides a window into the transcriptional regulation of multiple aspects of barrier formation.