Plasticity of oral mucosal cell sheets for accelerated and scarless skin wound healing

Collagen: The Superior Material for Full-Thickness Oral Mucosa Tissue Engineering

BACKGROUND

Tissue engineering has significantly progressed in developing full-thickness oral mucosa constructs designed to replicate the natural oral mucosa. These constructs serve as valuable in vitro models for biocompatibility testing and oral disease modeling and hold clinical potential for replacing damaged or lost oral soft tissue. However, one of the major challenges in tissue engineering of the oral mucosa is the identification of an appropriate scaffold with optimal porosity, interconnected porous networks, biodegradability, and biocompatibility. These characteristics facilitate cell migration, nutrient delivery, and vascularization. Various biomaterials have been investigated for constructing tissue-engineered oral mucosa models; collagen has demonstrated superior outcomes compared with other materials.

HIGHLIGHT

This review discusses the different types of tissue-engineered oral mucosa developed using various materials and includes articles published between January 2000 and December 2022 in PubMed and Google Scholar. The review focuses on the superiority of collagen-based scaffolds for tissue engineering of oral mucosa, explores in vitro applications, and discusses potential clinical applications.

CONCLUSION

Among the various scaffold materials used for engineering the connective tissue of the oral mucosa, collagen-based scaffolds possess excellent biological properties, offering high-quality oral mucosa constructs and high resemblance to the native human oral mucosa in terms of histology and expression of various differentiation markers.

Research progress in cell therapy for oral diseases: focus on cell sources and strategies to optimize cell function

In recent years, cell therapy has come to play an important therapeutic role in oral diseases. This paper reviews the active role of mesenchymal stem cells, immune cell sources, and other cells in oral disorders, and presents data supporting the role of cell therapy in oral disorders, including bone and tooth regeneration, oral mucosal disorders, oral soft tissue defects, salivary gland dysfunction, and orthodontic tooth movement. The paper will first review the progress of cell optimization strategies for oral diseases, including the use of hormones in combination with stem cells, gene-modified regulatory cells, epigenetic regulation of cells, drug regulation of cells, cell sheets/aggregates, cell-binding scaffold materials and hydrogels, nanotechnology, and 3D bioprinting of cells. In summary, we will focus on the therapeutic exploration of these different cell sources in oral diseases and the active application of the latest cell optimization strategies.

Reflecting the human lip in vitro: Cleft lip skin and mucosa keratinocytes keep their identities

OBJECTIVES

Cell models have shown great promise as tools for research, potentially providing intriguing alternatives to animal models. However, the original tissue characteristics must be maintained in culture, a fact that is often assumed, but seldom assessed. We aimed to follow the retention of the original tissue identities of cleft lip-derived skin and mucosa keratinocytes in vitro.

METHODS

Cleft lip-derived keratinocytes were isolated from discarded tissue along the cleft margins during cheiloplasty. Cell identities were assessed by immunohistochemistry and quantitative real-time PCR for tissue-specific markers and compared with native lip tissue. Moreover, keratinocytes were regularly analyzed for the retention of the original tissue characteristics by the aforementioned methods as well as by differentiation assays.

RESULTS

The various anatomical zones of the human lip could be distinguished using a panel of differentiation and functional-based markers. Using these markers, retention of the original tissue identities could be followed and confirmed in the corresponding primary keratinocytes in culture.

CONCLUSIONS

Our findings promote patient-derived cells retaining their original identities as astonishing and clinically relevant in vitro tools. Such cells allow a better molecular understanding of various lip-associated pathologies as well as their modeling in vitro, including but not restricted to orofacial clefts.

Engineering Heterogeneous Tumor Models for Biomedical Applications

Tumor tissue engineering holds great promise for replicating the physiological and behavioral characteristics of tumors in vitro. Advances in this field have led to new opportunities for studying the tumor microenvironment and exploring potential anti-cancer therapeutics. However, the main obstacle to the widespread adoption of tumor models is the poor understanding and insufficient reconstruction of tumor heterogeneity. In this review, the current progress of engineering heterogeneous tumor models is discussed. First, the major components of tumor heterogeneity are summarized, which encompasses various signaling pathways, cell proliferations, and spatial configurations. Then, contemporary approaches are elucidated in tumor engineering that are guided by fundamental principles of tumor biology, and the potential of a bottom-up approach in tumor engineering is highlighted. Additionally, the characterization approaches and biomedical applications of tumor models are discussed, emphasizing the significant role of engineered tumor models in scientific research and clinical trials. Lastly, the challenges of heterogeneous tumor models in promoting oncology research and tumor therapy are described and key directions for future research are provided.

One-step fabrication of cell sheet-laden hydrogel for accelerated wound healing

Full-thickness skin wounds are have continued to be reconstructive challenges in dermal and skin appendage regeneration, and skin substitutes are promising tools for addressing these reconstructive procedures. Herein, the one-step fabrication of a cell sheet integrated with a biomimetic hydrogel as a tissue engineered skin for skin wound healing generated in one step is introduced. Briefly, cell sheets with rich extracellular matrix, high cell density, and good cell connections were integrated with biomimetic hydrogel to fabricate gel + human skin fibroblasts (HSFs) sheets and gel + human umbilical vein endothelial cells (HUVECs) sheets in one step for assembly as a cell sheet-laden hydrogel (CSH). The designed biomimetic hydrogel formed with UV crosslinking and ionic crosslinking exhibited unique properties due to the photo-generated aldehyde groups, which were suitable for integrating into the cell sheet, and ionic crosslinking reduced the adhesive force toward the substrate. These properties allowed the gel + cell sheet film to be easily released from the substrate. The cells in the harvested cell sheet maintained excellent viability, proliferation, and definite migration abilities inside the hydrogel. Moreover, the CSH was implanted into a full-thickness skin defects to construct a required dermal matrix and cell microenvironment. The wound closure rate reached 60.00 ± 6.26% on the 2nd day, accelerating mature granulation and dermis formation with skin appendages after 14 days. This project can provide distinct guidance and strategies for the complete repair and regeneration of full-thickness skin defects, and provides a material with great potential for tissue regeneration in clinical applications.

The preclinical and clinical progress of cell sheet engineering in regenerative medicine

Cell therapy is an accessible method for curing damaged organs or tissues. Yet, this approach is limited by the delivery efficiency of cell suspension injection. Over recent years, biological scaffolds have emerged as carriers of delivering therapeutic cells to the target sites. Although they can be regarded as revolutionary research output and promote the development of tissue engineering, the defect of biological scaffolds in repairing cell-dense tissues is apparent. Cell sheet engineering (CSE) is a novel technique that supports enzyme-free cell detachment in the shape of a sheet-like structure. Compared with the traditional method of enzymatic digestion, products harvested by this technique retain extracellular matrix (ECM) secreted by cells as well as cell-matrix and intercellular junctions established during in vitro culture. Herein, we discussed the current status and recent progress of CSE in basic research and clinical application by reviewing relevant articles that have been published, hoping to provide a reference for the development of CSE in the field of stem cells and regenerative medicine.

New insights into balancing wound healing and scarless skin repair

Scars caused by skin injuries after burns, wounds, abrasions and operations have serious physical and psychological effects on patients. In recent years, the research of scar free wound repair has been greatly expanded. However, understanding the complex mechanisms of wound healing, in which various cells, cytokines and mechanical force interact, is critical to developing a treatment that can achieve scarless wound healing. Therefore, this paper reviews the types of wounds, the mechanism of scar formation in the healing process, and the current research progress on the dual consideration of wound healing and scar prevention, and some strategies for the treatment of scar free wound repair.

Cancer-Associated Fibroblasts: The Origin, Biological Characteristics and Role in Cancer-A Glance on Colorectal Cancer

Simple Summary

Tumor microenvironment is a major contributor to tumor growth, metastasis and resistance to therapy. It consists of many cancer-associated fibroblasts (CAFs), which derive from different types of cells. CAFs detected in different tumor types are linked to poor prognosis, as in the case of colorectal cancer. Although their functions differ according to their subtype, their detection is not easy, and there are no established markers for such detection. They are possible targets for therapeutic treatment. Many trials are ongoing for their use as a prognostic factor and as a treatment target. More research remains to be carried out to establish their role in prognosis and treatment.

Abstract

The therapeutic approaches to cancer remain a considerable target for all scientists around the world. Although new cancer treatments are an everyday phenomenon, cancer still remains one of the leading mortality causes. Colorectal cancer (CRC) remains in this category, although patients with CRC may have better survival compared with other malignancies. Not only the tumor but also its environment, what we call the tumor microenvironment (TME), seem to contribute to cancer progression and resistance to therapy. TME consists of different molecules and cells. Cancer-associated fibroblasts are a major component. They arise from normal fibroblasts and other normal cells through various pathways. Their role seems to contribute to cancer promotion, participating in tumorigenesis, proliferation, growth, invasion, metastasis and resistance to treatment. Different markers, such as a-SMA, FAP, PDGFR-β, periostin, have been used for the detection of cancer-associated fibroblasts (CAFs). Their detection is important for two main reasons; research has shown that their existence is correlated with prognosis, and they are already under evaluation as a possible target for treatment. However, extensive research is warranted.

Exosomes Derived From Umbilical Cord Mesenchymal Stem Cells Treat Cutaneous Nerve Damage and Promote Wound Healing

Wound repair is a key step in the treatment of skin injury caused by burn, surgery, and trauma. Various stem cells have been proven to promote wound healing and skin regeneration as candidate seed cells. Therefore, exosomes derived from stem cells are emerging as a promising method for wound repair. However, the mechanism by which exosomes promote wound repair is still unclear. In this study, we reported that exosomes derived from umbilical cord mesenchymal stem cells (UC-MSCs) promote wound healing and skin regeneration by treating cutaneous nerve damage. The results revealed that UC-MSCs exosomes (UC-MSC-Exo) promote the growth and migration of dermal fibroblast cells. In in vitro culture, dermal fibroblasts could promote to nerve cells and secrete nerve growth factors when stimulated by exosomes. During the repair process UC-MSC-Exo accelerated the recruitment of fibroblasts at the site of trauma and significantly enhanced cutaneous nerve regeneration in vivo. Interestingly, it was found that UC-MSC-Exo could promote wound healing and skin regeneration by recruiting fibroblasts, stimulating them to secrete nerve growth factors (NGFs) and promoting skin nerve regeneration. Therefore, we concluded that UC-MSC-Exo promote cutaneous nerve repair, which may play an important role in wound repair and skin regeneration.

The Bigger Picture: Why Oral Mucosa Heals Better Than Skin

Wound healing is an essential process to restore tissue integrity after trauma. Large skin wounds such as burns often heal with hypertrophic scarring and contractures, resulting in disfigurements and reduced joint mobility. Such adverse healing outcomes are less common in the oral mucosa, which generally heals faster compared to skin. Several studies have identified differences between oral and skin wound healing. Most of these studies however focus only on a single stage of wound healing or a single cell type. The aim of this review is to provide an extensive overview of wound healing in skin versus oral mucosa during all stages of wound healing and including all cell types and molecules involved in the process and also taking into account environmental specific factors such as exposure to saliva and the microbiome. Next to intrinsic properties of resident cells and differential expression of cytokines and growth factors, multiple external factors have been identified that contribute to oral wound healing. It can be concluded that faster wound closure, the presence of saliva, a more rapid immune response, and increased extracellular matrix remodeling all contribute to the superior wound healing and reduced scar formation in oral mucosa, compared to skin.

A Scarless Healing Tale: Comparing Homeostasis and Wound Healing of Oral Mucosa With Skin and Oesophagus

Epithelial tissues are the most rapidly dividing tissues in the body, holding a natural ability for renewal and regeneration. This ability is crucial for survival as epithelia are essential to provide the ultimate barrier against the external environment, protecting the underlying tissues. Tissue stem and progenitor cells are responsible for self-renewal and repair during homeostasis and following injury. Upon wounding, epithelial tissues undergo different phases of haemostasis, inflammation, proliferation and remodelling, often resulting in fibrosis and scarring. In this review, we explore the phenotypic differences between the skin, the oesophagus and the oral mucosa. We discuss the plasticity of these epithelial stem cells and contribution of different fibroblast subpopulations for tissue regeneration and wound healing. While these epithelial tissues share global mechanisms of stem cell behaviour for tissue renewal and regeneration, the oral mucosa is known for its outstanding healing potential with minimal scarring. We aim to provide an updated review of recent studies that combined cell therapy with bioengineering exporting the unique scarless properties of the oral mucosa to improve skin and oesophageal wound healing and to reduce fibrotic tissue formation. These advances open new avenues toward the ultimate goal of achieving scarless wound healing.

The effects of oral mucosa-derived heterotopic fibroblasts on cutaneous wound healing

An intriguing observation that has recently found support through clinical and experimental studies is that wounds of the oral mucosa tend to display faster healing and result in less scarring than in the skin. We aimed to investigate the potential of heterotopic oral mucosal fibroblasts in cutaneous wounds while determining the main differences between wounds conditioned with either the oral mucosa or dermis-derived human fibroblasts. A total of 48 nude mice were divided into four groups: control, sham, dermal fibroblast (DF), and oral fibroblast (OF). Fibroblasts were isolated, cultured, and seeded onto fibrin scaffolds for transfer to full-thickness dorsal wounds. Cell viability, wound area, healing rate, vascularization, cellular proliferation, dermal thickness, collagen architecture, and subtypes were evaluated. Both cell groups had a viability of 95% in fibrin gel prior to transfer. None of the wounds fully epithelialized on day 10, while all were epithelialized by day 21, which resulted in scars of different sizes and quality. Healing rate and scars were similar between the control and sham groups, whereas fastest healing and least scarring were noted in the OF group. Dermal thickness was highest in the DF group, which was also supported by highest levels of collagen types I and III. Proliferative cells and vascular density were highest in the OF group. DF result in healing through a thick dermal component, while oral fibroblasts result in faster healing and less scarring through potentially privileged angiogenic and regenerative gene expression.

Collagen Peptides Derived from Sipunculus nudus Accelerate Wound Healing

Marine collagen peptides have high potential in promoting skin wound healing. This study aimed to investigate wound healing activity of collagen peptides derived from Sipunculus nudus (SNCP). The effects of SNCP on promoting healing were studied through a whole cortex wound model in mice. Results showed that SNCP consisted of peptides with a molecular weight less than 5 kDa accounted for 81.95%, rich in Gly and Arg. SNCP possessed outstanding capacity to induce human umbilical vein endothelial cells (HUVEC), human immortalized keratinocytes (HaCaT) and human skin fibroblasts (HSF) cells proliferation and migration in vitro. In vivo, SNCP could markedly improve the healing rate and shorten the scab removal time, possessing a scar-free healing effect. Compared with the negative control group, the expression level of tumor necrosis factor-α, interleukin-1β and transforming growth factor-β1 (TGF-β1) in the SNCP group was significantly down-regulated at 7 days post-wounding (p < 0.01). Moreover, the mRNA level of mothers against decapentaplegic homolog 7 (Smad7) in SNCP group was up-regulated (p < 0.01); in contrast, type II TGF-β receptors, collagen I and α-smooth muscle actin were significantly down-regulated at 28 days (p < 0.01). These results indicate that SNCP possessed excellent activity of accelerating wound healing and inhibiting scar formation, and its mechanism was closely related to reducing inflammation, improving collagen deposition and recombination and blockade of the TGF-β/Smads signal pathway. Therefore, SNCP may have promising clinical applications in skin wound repair and scar inhibition.

Recent update on craniofacial tissue engineering

The craniofacial region consists of several different tissue types. These tissues are quite commonly affected by traumatic/pathologic tissue loss which has so far been traditionally treated by grafting procedures. With the complications and drawbacks of grafting procedures, the emerging field of regenerative medicine has proved potential. Tissue engineering advancements and the application in the craniofacial region is quickly gaining momentum although most research is still at early in vitro/in vivo stages. We aim to provide an overview on where research stands now in tissue engineering of craniofacial tissue; namely bone, cartilage muscle, skin, periodontal ligament, and mucosa. Abstracts and full-text English articles discussing techniques used for tissue engineering/regeneration of these tissue types were summarized in this article. The future perspectives and how current technological advancements and different material applications are enhancing tissue engineering procedures are also highlighted. Clinically, patients with craniofacial defects need hybrid reconstruction techniques to overcome the complexity of these defects. Cost-effectiveness and cost-efficiency are also required in such defects. The results of the studies covered in this review confirm the potential of craniofacial tissue engineering strategies as an alternative to avoid the problems of currently employed techniques. Furthermore, 3D printing advances may allow for fabrication of patient-specific tissue engineered constructs which should improve post-operative esthetic results of reconstruction. There are on the other hand still many challenges that clearly require further research in order to catch up with engineering of other parts of the human body.

Human Adipose-Derived Mesenchymal Stem Cells-Derived Exosomal microRNA-19b Promotes the Healing of Skin Wounds Through Modulation of the CCL1/TGF-β Signaling Axis

Introduction

Human adipose-derived mesenchymal stem cells (ADMSCs) with their secretory factors are able to induce collagen synthesis and fibroblast migration in the wound healing process. This study is launched to figure out the effect of human ADMSCs-derived exosomes on skin wound healing.

Methods

ADMSCs were extracted and ADMSCs-derived exosomes were identified. Skin damage models were established by treating HaCaT cells and human skin fibroblasts with H₂O₂. Next, the roles of ADMSCs and their derived exosomes were investigated. The exosomal miRNA then was analyzed, and the function of miRNA on the H₂O₂-induced cells was studied by miRNA suppression. Bioinformatics analysis, luciferase activity and RIP assays were implemented to find the target genes ofthe miRNA and the modulated pathways. A mouse skin damage model was induced to elucidate the effects of exosomes in vivo by injecting exosomes.

Results

H₂O₂ treatment significantly reduced the viability of HaCaT cells and increased their apoptosis rate. Co-culture with ADMSCs or their derived exosomes could improve the cell damage caused by H₂O₂. Meanwhile, H₂O₂ treatment promoted the internalization of exosomes. ADMSCs and their derived exosomes significantly increased miR-19b expression in the recipient cells, while inhibiting miR-19b resulted in a reduction in the therapeutic effect of ADMSCs-derived exosomes. Besides, miR-19b regulated the TGF-β pathway by targeting CCL1. The therapeutic effect of exosomes was further confirmed by a mouse model of skin damage.

Conclusion

Our study indicates that exosomal miR-19b derived from ADMSCs regulates the TGF-β pathway by targeting CCL1, thereby promoting the healing of skin wounds.

MMP-2 and TIMP-2 expression, quantitative analysis and biomechanical changes in scar hypertrophy after autologous free transplantation of rabbit oral mucosa and scrotal skin

This study aimed to investigate the long-term scar hypertrophy in the rabbit transplanted oral mucosa and scrotal skin with changed matrix environment, as well as the scar location expression, quantitative analysis of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-2 (TIMP-2) and biomechanical changes in the transplanted tissues. The split-thickness skin grafts were collected from the oral mucosas and scrotal skins of 30 male rabbits, and prepared into reelpipes for autologous transplantation into the rabbit back muscular tissues. Samples were collected to carry out elastic tensile mechanical detection and histological observation. The maximum longitudinal tensile displacement of scrotal skin before 8 weeks of transplantation was greater than that after 8 weeks of transplantation (P < 0.05). The expression intensities of MMP-2 and TIMP-2 in the oral mucosa and in scrotal skin at 2 W time point were higher than those at T _o time point (P < 0.05). The expression quantities of TIMP-2 in oral mucosa and scrotal skin during 8-24 W were higher than those of MMP-2 (P < 0.05). At 8 W time point, the TIMP-2/MMP-2 ratio in scrotal skin was higher than that in oral mucosa (P < 0.05). MMP-2 and TIMP-2 expression in normal oral mucosa and scrotal skin is weak, but their expression is remarkably up-regulated after 2 weeks of transplantation, revealing that scar formation was related to the high expression of MMP-2 and TIMP-2. At the 8th-24th weeks, the AOD values of TIMP-2 in oral mucosa and scrotal skin are apparently higher than those of MMP-2; moreover, the TIMP-2/MMP-2 ratio in scrotal skin at the 8th week was higher than that in oral mucosa, which can well explain the earlier scar formation in scrotal skin than in oral mucosa, and it also suggests that the different expression levels between TIMP-2 and MMP-2 may account for the important cause of scar formation.

Biomimetic hydrogel for rapid and scar-free healing of skin wounds inspired by the healing process of oral mucosa

Inspired by the wound healing characteristics of the oral mucosa, a biomimetic hydrogel was prepared to realize the rapid and scar-free healing of skin wounds. Through monitoring the healing process of injured oral mucosa, we find out that the combination of high, rapid and sequential expression of some growth factors and the sterile-moist microenvironment are crucial for re-epithelialization and precise control of the inflammation process. On the base of our findings, a hydrogel loaded with several functional compounds was prepared to achieve a comprehensive simulation of the oral mucosal trauma microenvironment for skin wound healing. After 7 days treatment, the skin wound area of the treated group was only about 20% of that of the untreated group, and the proportion of collagen type III and type I in the treated group was much higher than that of the untreated group, suggesting lighter scar hyperplasia. The comprehensive treatment strategy of sequential expression of growth factors in combination with maintaining of a sterile and humid environment is expected to have great application prospect in the field of chronic trauma repair and cosmetic surgery. STATEMENT OF SIGNIFICANCE: Long healing time and scar hyperplasia during wound healing have been a serious problem in the past decades of wound healing research. Oral cavity wound healing occurs in an environment that sustains ongoing physical trauma and is rich in bacteria. Despite this, injuries to the mucosal surface often heal faster than cutaneous wounds and leave less noticeable scars. Therefore, in recent years, many scholars have begun to study the healing mechanism of oral mucosa, which supports a new inspiration for the study of skin wound repair: whether the injured skin can achieve a rapid scar-free healing effect similar to oral mucosa? Imitating the biological process of oral mucosa wound healing would be a promising therapeutic strategy in wound healing. Therefore, inspired by the wound healing characteristics of the oral mucosa, a biomimetic gel was prepared to realize the rapid and scar-free healing of skin wounds. Through monitoring the healing process of injured oral mucosa, the combination of high, rapid and sequential expression of some growth factors and sterile-moist microenvironment was crucial for re-epithelialization and precise control of the inflammation process. The comprehensive treatment strategy of sequential expression of growth factors in combination with maintance of a sterile and humid environment implies its potential use in the field of chronic trauma repair and cosmetic surgery.

Unveiling Mesenchymal Stromal Cells' Organizing Function in Regeneration

Regeneration is a fundamental process attributed to the functions of adult stem cells. In the last decades, delivery of suspended adult stem cells is widely adopted in regenerative medicine as a leading means of cell therapy. However, adult stem cells cannot complete the task of human body regeneration effectively by themselves as far as they need a receptive microenvironment (the niche) to engraft and perform properly. Understanding the mechanisms underlying mammalian regeneration leads us to an assumption that improved outcomes of cell therapy require a specific microenvironment that is generated in damaged areas prior to stem cell delivery. To a certain extent, it may be achieved by the delivery of mesenchymal stromal cells (MSCs), not in dispersed form, but rather in self-organized cell sheets (CS) ⁻ tissue-like structures comprised of viable cells and microenvironment components: extracellular matrix and soluble factors deposited in the matrix. In this review, we highlight the potential role of MSCs as regeneration organizers and speculate that this function emerges in CS. This concept shifts our understanding of the therapeutic mechanism underlying a widely known CS-based delivery method for regenerative medicine.

Promotion of skin wound healing using prevascularized oral mucosal cell sheet

BACKGROUND

This study examined the potential use of our newly developed prevascularized oral mucosal cell sheet for the treatment of skin wounds.

METHODS

Mucosal cell sheets containing cultured keratinocytes and plasma fibrin without (K sheet) or with a mixture of fibroblasts and endothelial progenitor cells (PV sheet) were transplanted into full-thickness skin excisional wounds of nude mice.

RESULTS

This technique was successful for in vitro culture; expanding keratinocytes, fibroblasts, and endothelial progenitor cells; and generating prevascularized mucosal cell sheets. Cell sheets promoted in vivo wound healing with rapid wound closure and less scarring compared to controls. This result was more apparent in the PV than the K sheet (P < .05). Wounds covered with cell sheets showed less expression of TGFB1, ACTA2, and FN1 mRNAs than the controls (P < .05).

CONCLUSION

The prevascularized mucosal cell sheet showed in vivo efficacy and tissue plasticity in cutaneous wounds by promoting accelerated healing.

Treatment of intractable oral ulceration with an oral mucosa equivalent

The current use of steroids or pharmacological immunomodulators for the treatment of intractable oral ulceration is ineffective, necessitating newer cell-based therapeutic approaches. We examined the potential efficacy of an oral mucosa equivalent developed in this study in an in vivo model of repeat major oral ulceration mimicking the intractable oral ulceration observed clinically. Oral mucosal samples and plasma fibrin were obtained from Sprague-Dawley rats. The oral mucosa equivalents were prepared with cultured mucosal keratinocytes and plasma fibrin mixed with cultured fibroblasts. Ulcers were chemically induced on the rat buccal mucosa thrice in 3 weeks and covered with or without mucosa equivalents. Gross and microscopic findings and mRNA expression levels were compared between the ulcer control and mucosa equivalent groups. Oral mucosal keratinocytes and fibroblasts were cultured in vitro to achieve high viability and colony-forming efficiency. The equivalents showed epithelial and subepithelial structures similar to those of oral mucosa and exhibited high p63 positivity. In the in vivo study, ulceration was resolved earlier without significant granulation or scarring in the equivalent group than in control group (p < 0.05). Microscopic examinations revealed rapid re-epithelialization and less fibrosis in the equivalent group than in the control group (p < 0.05). Mucosa equivalent-covered ulcers showed histological characteristics similar to those of the normal buccal mucosa and exhibited lower expression of TGFB1, ACTA2, and FN1 mRNAs than the control group. The in vitro-engineered oral mucosa equivalent promotes ulcer healing without scarring and functional deficits. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1779-1785, 2019.

Use of a pre-vascularised oral mucosal cell sheet for promoting cutaneous burn wound healing

Pre-vascularised cell sheets have been used to promote early angiogenesis and graft survival. However, the use of pre-vascularised mucosal cell sheets for burn wounds has been rarely evaluated. Therefore, we examined the applicability of an oral pre-vascularised mucosal cell sheet that we had previously developed for the treatment of cutaneous burn wounds.

Methods: Mucosal keratinocytes, fibroblasts, and endothelial progenitor cells were isolated from the oral mucosa and peripheral blood and were expanded in vitro. Mucosal cell sheets were generated by seeding cultured keratinocytes onto a mixture of fibroblasts, endothelial cells, and fibrin. Third-degree burn wounds were created on the backs of rats and were covered with the cell sheets, skin grafts, or silastic sheets as a control. Gross and microscopic findings and gene expression profiles of wounds were compared among the groups.

Results: CD31-positive microvessels were observed in the fibrin-matrix layer of the cell sheet. In the cutaneous burn wound model, the cell sheets promoted wound healing, with accelerated wound closure and less scarring than with silastic sheets and skin grafts. The cell sheets had more microvessels and proliferating cells and less neutrophil infiltration and fibrotic features than the controls or skin grafts. The cell sheet induced higher mRNA expression of KRT14, VEGFA, IL10, and AQP3 and lower mRNA expression of TGFB1, IL6, ICAM1, ACTA2, and FN1 than did the controls or skin grafts.

Conclusions: The pre-vascularised mucosal cell sheet promotes cutaneous burn wound healing.

Development of an in vitro cell-sheet cancer model for chemotherapeutic screening

Epithelial cancer grows in vivo in a microenvironment that comprises tumour, stroma, and immune cells. A three-dimensional (3D) culture model might be able to mimic the tumour microenvironment in vivo; therefore, we developed a new 3D epithelial cancer model using in vitro cell-sheet engineering and compared the results of treatment with several chemotherapeutic drugs among the 3D cell-sheet model, spheroid culture, and 2D cell culture.

Methods: The cell sheet comprised keratinocytes and a plasma fibrin matrix containing fibroblasts. Cancer spheroids with or without cancer-associated fibroblasts (CAFs) were interposed between the keratinocytes and fibrin layer. Cell growth, viability, and hypoxia were measured using the cell counting kit-8, LIVE/DEAD assay, and propidium iodide and LOX-1 staining. The morphology, invasion, and mRNA and protein expression were compared among the different cell culture models.

Results: Enhanced resistance to sorafenib and cisplatin by cancer spheroids and CAFs was more easily observed in the 3D than in the 2D model. Invasion by cancer-CAF spheroids into the fibrin matrix was more clearly observed in the 3D cell sheet. The expansion of viable cancer cells increased in the 3D cell sheet, particularly in those with CAFs, which were significantly inhibited by treatment with 10 μM sorafenib or 20 μM cisplatin (P < 0.05). TGF-β1, N-cadherin, and vimentin mRNA and protein levels were higher in the 3D cell-sheet model.

Conclusions: The 3D cell sheet-based cancer model could be applied to in vitro observation of epithelial cancer growth and invasion and to anticancer drug testing.