No / This volume highlights recent studies identifying epigenetic mechanisms as essential regulators of skin development, stem cell activity and regeneration. Chapters are contributed by leading experts and promote the skin as an accessible model system for studying mechanisms that control organ development and regeneration. The discussions contained throughout are of broad relevance to other areas of biology and medicine and can help inform the development of novel therapeutics for skin disorders as well as new approaches to skin regeneration that target the epigenome. Part of the highly successful Stem Cells and Regenerative Medicine series, Epigenetic Regulation of Skin Development and Regeneration uncovers the fundamental significance of epigenetic mechanisms in skin development and regeneration, and emphasizes the development of new therapies for a number of skin disorders, such as pathological conditions of epidermal differentiation, pigmentation and carcinogenesis. At least six categories of researchers will find this book essential, including stem cell, developmental, hair follicle or molecular biologists, and gerontologists or clinical dermatologists.

Skin is the largest organ of the body. Its integrity plays a crucial role in maintaining physiological homeostasis, protects against mechanical forces and infections, fluid imbalance, and thermal dysregulation. Numerous pathological states, such as diabetes mellitus, peripheral vascular disease, thermal injuries, or degloving lead to inadequate wound healing, necessitating medical intervention. Established wound healing techniques such as autologous and allogeneic skin grafts are inefficient due to the limited availability of donor tissues or probable immunogenic reactions. Current research in the field of tissue engineering aims to facilitate wound healing and restore skin functionality, focusing on key aspects of wound healing, such as extracellular matrix (ECM) reorganization, cell growth, and collagen synthesis/deposition. The research aims at developing and characterizing an in-vitro fibrin gel culture model system that stimulates the process of wound healing. The specific goal of this research is to investigate how the varied chemical composition of fibrin hydrogels can enhance fibroblast proliferation and promote accelerated collagen matrix formation, which is a significant step in tissue repair and regeneration.The fibrin gels are optimized by modulating the primary gel constituents (i.e. the concentrations of fibrin and thrombin). The ensuing hydrogels are characterized using Scanning Electron Microscope and compression testing to test for fiber size, porosity, elasticity, and mechanical properties. Cultured fibroblasts are used to investigate the effects of varying fibrin concentrations on cell-biomaterial interactions, including cell proliferation, cellular infiltration, and network formation. Furthermore, matrix formation and maturation as a function of fibrinogen concentration as defined by collagen matrix deposition, are also studied. Increasing the fibrinogen concentration, lead to an increase in elasticity and Young’s modulus, while a decrease in thrombin concentration generated a stronger fiber structure. Additionally, a decrease in fibrinogen concentration resulted in an increased proliferation rate of fibroblast cells, suggesting better cell adhesion and network formation within the gel substrate. These results were consistent and confirmed by quantifying a mature collagen matrix deposited by fibroblasts when subjected to ascorbic acid. In summary, this research investigates how the varied chemical composition of fibrin hydrogels can enhance fibroblast proliferation and promote accelerated collagen matrix formation, which is a significant step in tissue repair and regeneration. / Bioengineering

Large doses of recombinant growth factors formulated in solution form directly injected into the body is usual clinical practice in treating second-degree scald injuries, with promising results, but this approach creates side effects; furthermore, it may not allow appropriate levels of the factor to be sensed by the target injured tissue/organ in the specific time frame, owing to complications arising from regeneration. In this research, two delivery methods (infusion pumping and local topical application) were applied to deliver recombinant human erythropoietin (rHuEPO) for skin regeneration. First, rHuEPO was given in deep second-degree scald injury sites in mice by infusion pump. Vascularization was remarkably higher in the rHuEPO pumping group than in controls. Second, local topical application of rHuEPO gel was given in deep second-degree scald injury sites in rats. Histological analysis showed that epithelialization rate was significantly higher in the rHuEPO gel-treated group than in controls. Immunohistochemical studies showed that the rHuEPO gel-treated group showed remarkably higher expression of skin regeneration makers than the control group. An accurate method for visualization and quantification of blood vessel networks in target areas has still not been developed up to this point, because of technical difficulties in detecting such thin blood vessels. A method which utilizes a series of steps to enhance the image, removes noise from image background, and tracks the vessels edges for vessel segmentation and quantification has been used in this study. Using image analysis methods, we were able to detect the microvascular networks of newly formed blood vessels (less than 500 μm thickness), which participate in the healing process, providing not only nutrition and oxygen to grow tissues but also necessary growth factors to grow tissue cells for complete skin regeneration. The rHuEPO-treated group showed higher expression of stem cell markers (CD 31, CD 90, CD 71, and nestin), which actively contribute to in-wound-healing processes for new hair follicle generation as well as skin regeneration. Collectively, both rHuEPO group pumping into the systemic circulation system, and injection into the local injury area, prompted mice and rats to form new blood vessel networks in scald injury sites, which significantly participate in the scald healing process. These results may lead to the development of novel treatments for scald wounds.

Collective cell migration is critical for various physiological and pathological processes. In vitro wound healing assay has been widely used to study collective cell migration due to its technical simplicity and ability of revealing the complexity of collective cell migration. This project studies the function and importance of leader cells, the cells pulling cell monolayer migrating into free space, in endothelium and skin epithelial regeneration via plasma lithography enhanced in vitro wound healing assay. Despite leader cells have been identified in in vitro wound healing assays, little is known about their regulation and function on collective cell migration. First, I investigated the role of leader cells in endothelial cell collective migration. I found that the leader cell density is positively related with the cell monolayer migration rates. Second, we used this knowledge to study the effects of arsenic treatment on skin regeneration via in vitro wound healing assay. We found that low concentration of arsenic treatment can accelerate the keratinocyte monolayer migration. We further found that arsenic affected cell migration by modulating leader cell density through Nrf2 signaling pathway. As a conclusion of these studies, we evaluated the function of leader cells in collective cell migration, and elucidated the mechanism of arsenic treatment on skin regeneration.

Η επούλωση των πληγών είναι μια ουσιώδους σημασίας φυσιολογική διεργασία για τη διατήρηση της ομοιόστασης ενός ιστού, και ειδικά όσον αφορά το δέρμα έχει απασχολήσει πληθώρα μελετητών τα τελευταία 100 χρόνια. Αυτό συμβαίνει σε μεγάλο βαθμό διότι το δέρμα είναι ένας ιδιαίτερα σύνθετος ιστός που οι τραυματισμοί του επηρρεάζουν μια πληθώρα δομών, κυτταρικών στιβάδων και κυτταρικών σειρών. Το τραύμα προκαλεί επίσης βλάβη ακόμα και σε επίπεδο ανεξάρτητων κυττάρων. Η ποικιλία των κυτταρικών τύπων που συμμετέχουν στην επούλωση, η πολυπλοκότητα των μηχανισμών, και ο ιδιαίτερος ρόλος που διαδραματίζουν τα stem κύτταρα σε αυτή τη διαδικασία αναμένεται να αποτελέσει αυξημένου ενδιαφέροντος πεδίο έρευνας και για τα χρόνια που θα επακολουθήσουν. Η παρούσα μελέτη αποτελεί βιβλιογραφική ανασκόπηση η οποία επικεντρώνεται τόσο στους μηχανισμοί αναγέννησης και επούλωσης που λαμβάνουν χώρα στο δέρμα, όσο και στον ρόλο τον οποίο διαδραματίζουν τα stem κύτταρα στην άρτια επιτέλεση αυτών των βιολογικών φαινομένων / Wound healing is a fundamental natural process for maintaining the homeostasis of a tissue. Especially when it comes to skin, wound healing is an especially complex process, and its trauma affects a wide diversity of structures. This study focuses on the cellular and molecular mechanisms of healing and regeneration that take place in skin, as well as the role of stem cells in this procedure.

no / We organized the first International Symposium on Skin Epigenetics at the Centre for Skin Sciences at the University of Bradford (West Yorkshire, UK) on 2nd and 3rd April 2012. The goal of the Symposium was to bring together two research communities—skin and chromatin biologists—and discuss the most important aspects of epigenetic regulatory mechanisms that control skin development and regeneration. The symposium was attended by more than 80 participants from countries across Europe, Australia, Japan, Singapore, and USA, and representing academic institutions and industry. Epigenetic regulation of gene expression programs in the skin is a novel trend in research in cutaneous biology, and several landmark papers arising in the field were published recently (reviewed in Botchkarev et al., 2012; Botchkareva, 2012; Frye and Benitah, 2012; Yi and Fuchs, 2012; Zhang et al., 2012). The Symposium program included six Keynote lectures, the inaugural John M. Wood Memorial Lecture, and six sessions that covered major levels of epigenetic regulation.

No / Skin development, postnatal growth and regeneration are governed by complex and well-balanced programs of gene activation and silencing. The crosstalk between small non-coding microRNAs (miRNAs) and mRNAs is highly important for steadiness of signal transduction and transcriptional activities as well as for maintenance of homeostasis in many organs, including the skin. Recent data demonstrated that the expression of many genes, including cell type-specific master transcription regulators implicated in the control of skin development and homeostasis, is regulated by miRNAs. In addition, individual miRNAs could mediate the effects of these signaling pathways through being their downstream components. In turn, the expression of a major constituent of the miRNA processing machinery, Dicer, can be controlled by cell type-specific transcription factors, which form negative feedback loop mechanisms essential for the proper execution of cell differentiation- associated gene expression programs and cell-cell communications during normal skin development and regeneration. This review summarizes the available data on how miRNA/mRNA regulatory networks are involved in the control of skin development, epidermal homeostasis, hair cycle-associated tissue remodeling and pigmentation. Understanding of the fundamental mechanisms that govern skin development and regeneration will contribute to the development of new therapeutic approaches for many pathological skin conditions by using miRNA-based interventions.

HA (Hyaluronan, hyaluronic acid) is a predominant component of the extracellular matrix and plays diverse roles in the process of wound healing. The major significance of the biological functions of HA in wound healing arise from early studies showing that rich and prolonged existence of HA is associated with the fetal scarless wound healing. It has been hypothesized that adult wound healing can be modulated by the application of exogenous HA to make the process of wound repair more like regeneration. / In this thesis, the effects of molecular weight and concentration of HA on the biological behavior of human fibroblasts and keratinocytes have been investigated in both monolayer and 3D culture models. In addition, the mechanism for the HA-induced biological effects has also been investigated. Previous laboratory studies have primarily focused on individual cell type, but in wound healing in vivo there is considerable interaction between the keratinocytes and fibroblasts. The role of HA in keratinocyte-fibroblast interactions is not clear, so an organotypical culture model was used to investigate the keratinocyte differentiation and stratification and basement membrane formation with and without fibroblasts to explore the effect of HA on keratinocyte-fibroblast interactions. / The experimental data suggest that exogenous application of HA modulates the process of wound healing so that it becomes more like regeneration by regulating the biological functions of human keratinocytes and fibroblasts, including their interaction. By further understanding the HA-induced cell biological phenomena and involved mechanisms new approaches for wound care may be revealed. / The skin is the largest organ in the body. It consists of an outer layer, the epidermis supported by a connective tissue matrix, the dermis. The keratinocyte and fibroblast are the major cell types in the epidermis and dermis respectively. When the skin is damaged, the body will active a cascade of mechanisms to restore the tissue integrity. If the damaged tissue is limited to the epidermis, it will be restored by the process of regeneration. Regeneration involves the replacement of injured tissue by new tissue which has both form and function identical to the original tissue. If the defect involves the dermis, healing is achieved by repair which results in permanent scar formation. Wound healing is an extremely complex biological process which involves several overlapping steps; inflammation, granulation tissue formation and remodeling which are coordinated by various cell types, growth factors, cytokines and extracellular matrix components including hyaluronan. / Whilst there have been many studies looking at the effect of HA on different cell types using varying molecular parameters, concentrations and sources of HA, the result are often contradictory. Even the endogenous or exogenous application of HA have been reported to have opposite effects on cell behavior. / Gu, Hua. / Adviser: Andrew Bard. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0216. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 116-135). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

皮膚是人體最大的器官，具有多種功能，其中最重要的功能之一就是作為身體內部和外界環境之間的的保護屏障。完整地修復這一保護屏障是創傷癒合和組織再生領域的一個重要內容。本論文探討了人類臍帶被覆上皮細胞 (cord lining epithelial cells, CLECs)作為一種幹細胞來源，可用于表皮重建的潛能. / 本論文的第二章對CLECs的體外分離和增殖進行了詳細地描述。這一類細胞具有較長的染色體端粒，較高的增殖潛能和傳代能力。同時，它們表達上皮幹細胞和多能性幹細胞的標誌性表面抗原。它們還具有多種分化潛能，包括成脂、成骨和成軟骨。然而當皮下異種移植後，它們並不會形成畸胎瘤。 / 本論文的第三章對CLECs的免疫特性進行了評估。結果顯示CLECs不但具有低免疫原性，還具有免疫調節功能。它們表達典型性的一型主要組織相容性複合體(MHC class I)，即人白細胞ABC抗原(HLA-ABC)，但不表達典型性的二型主要組織相容性複合體(MHC class II)，即人白細胞DR抗原(HLA-DR)。它們同時還表達非典型性的MHC class I, 包括人白細胞G抗原和人白細胞E 抗原(HLA-G和HLA-E), 但不表達共激分子(CD40, CD80和CD86)。此外，體外檢測還發現它們表達適度的促炎/抗炎細胞因子和大量的生長因子. / 本論文的第四章對CLECs在表皮重建應用中的潛能進行了考察。結果顯示無論在體外器官培養還是異種移植動物模型中，CLECs都能形成分層的上皮結構，與用表皮細胞構建的分層上皮結構相類似。而且在CLECs構建的皮膚替代物中證實了有表皮分化標誌性抗原的表達。 / 結論：本論文證明了CLECs具有幹細胞樣特性但無致瘤性，具有低免疫原性和表皮分化的可塑性。研究結果支持CLECs在創傷癒合和皮膚再生領域的臨床應用可行性. / The skin is the largest organ in the body and has multiple functions. One of the most important functions is to serve as a protective barrier between the internal and external environments of the body. Restoration of the integrity of this protective barrier is an essential aspect of wound healing and tissue regeneration. In this thesis, the potential of human umbilical cord lining epithelial cells (CLECs) as a source of stem cells with appropriate differentiation capacity for epidermal reconstitution has been explored. / The isolation and propagation of CLECs from human umbilical cord lining epithelium were described in Chapter II. The cells presented a long telomere length and had high proliferative potential and passaging capability. They were also shown to display both epithelial and pluripotent stem cell markers. They were capable of multipotent differentiation, including adipogenesis, osteogenesis and chondrogenesis. However, they didn’t form teratoma after subcutaneous xenotransplantation until 12 weeks. / The immune properties of CLECs in vitro were assessed in Chapter III. The cells were shown to have low immunogenicity but high immunosuppressive function. They expressed classical major histocompatibility complex (MHC) class I antigens (HLA-ABC), but not MHC class II antigen (HLA-DR). They also expressed non-classical MHC class I antigens (HLA-G and HLA-E), but lacked the expression of the co-stimulatory molecules (CD40, CD80 and CD86). Moreover, they expressed moderate pro/anti-inflammatory cytokines and multiple growth factors both in cell supernatants and cell lysates. / The potential of CLECs for epidermal reconstitution was investigated in Chapter IV. In both organotypic culture and xenotransplantation model, CLECs were capable of generating a stratified epithelial structure, which is similar to that constructed by using keratinocytes. Furthermore, the expression of epidermal differentiation markers was verified in CLEC-constructed skin substitutes. / In conclusion, the stem cell-like properties of CLECs have been demonstrated in the present study. In addition to the lack of tumorigenicity, CLECs also have low immunogenicity and significant plasticity in epidermal differentiation. The findings support the potential clinical application of CLECs in wound healing and skin regeneration. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Cai, Yijun. / "October 2012." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 114-129). / Abstract also in Chinese. / Abstrac --- p.i / Table of Contents --- p.v / Abbreviations --- p.vii / List of Figures --- p.viii / List of Tables --- p.x / Chapter Chapter I --- Introduction --- p.1 / Skin --- p.3 / Wound healing --- p.6 / Wound regeneration and repair --- p.6 / Recent history of wound treatment --- p.9 / Skin substitutes --- p.11 / Stem cells for wound treatment --- p.14 / Stem cells overview --- p.15 / Adult stem cells --- p.16 / Fetal stem cells --- p.18 / Amniotic membrane derived stem cells --- p.19 / Umbilical cord stem cells --- p.22 / Hypothesis and Specific aims --- p.24 / Chapter Chapter II --- The Isolation and Characterization of the Stem Cell-like Properties of Human Umbilical Cord Lining Epithelial Cells --- p.28 / Introduction --- p.28 / Materials and methods --- p.30 / Results --- p.47 / Discussion --- p.62 / Conclusion --- p.67 / Chapter Chapter III --- The assessment of the Immune Properties of Human Umbilical Cord Lining Epithelial Cells --- p.69 / Introduction --- p.69 / Materials and methods --- p.72 / Results --- p.75 / Discussion --- p.83 / Conclusion --- p.88 / Chapter Chapter IV --- The Investigation of the Potential of Human Umbilical Cord Lining Epithelial Cells for the Epidermal Reconstitution --- p.89 / Introduction --- p.89 / Materials and methods --- p.91 / Results --- p.94 / Discussion --- p.101 / Conclusion --- p.104 / Chapter Chapter V --- Summary and Future Plan --- p.105 / Summary --- p.105 / Future plan --- p.108 / Acknowledgements --- p.113 / References --- p.114 / Appendix --- p.130

Large doses of recombinant growth factors formulated in solution form directly injected into the body is usual clinical practice in treating second-degree scald injuries, with promising results, but this approach creates side effects; furthermore, it may not allow appropriate levels of the factor to be sensed by the target injured tissue/organ in the specific time frame, owing to complications arising from regeneration. In this research, two delivery methods (infusion pumping and local topical application) were applied to deliver recombinant human erythropoietin (rHuEPO) for skin regeneration. First, rHuEPO was given in deep second-degree scald injury sites in mice by infusion pump. Vascularization was remarkably higher in the rHuEPO pumping group than in controls. Second, local topical application of rHuEPO gel was given in deep second-degree scald injury sites in rats. Histological analysis showed that epithelialization rate was significantly higher in the rHuEPO gel-treated group than in controls. Immunohistochemical studies showed that the rHuEPO gel-treated group showed remarkably higher expression of skin regeneration makers than the control group. An accurate method for visualization and quantification of blood vessel networks in target areas has still not been developed up to this point, because of technical difficulties in detecting such thin blood vessels. A method which utilizes a series of steps to enhance the image, removes noise from image background, and tracks the vessels edges for vessel segmentation and quantification has been used in this study. Using image analysis methods, we were able to detect the microvascular networks of newly formed blood vessels (less than 500 μm thickness), which participate in the healing process, providing not only nutrition and oxygen to grow tissues but also necessary growth factors to grow tissue cells for complete skin regeneration. The rHuEPO-treated group showed higher expression of stem cell markers (CD 31, CD 90, CD 71, and nestin), which actively contribute to in-wound-healing processes for new hair follicle generation as well as skin regeneration. Collectively, both rHuEPO group pumping into the systemic circulation system, and injection into the local injury area, prompted mice and rats to form new blood vessel networks in scald injury sites, which significantly participate in the scald healing process. These results may lead to the development of novel treatments for scald wounds.