Diffusible factors released by fibroblasts support epidermal morphogenesis and deposition of basement membrane components

Angiogenesis and full thickness wound repair in a cell sheet-based vascularized skin substitute

Skin tissue engineering is undergoing tremendous expansion as a result from clinical needs, mandatory replacement of animal models and development of new technologies. Many approaches have been used to produce vascularized skin substitutes for grafting purposes showing the presence of capillary-like structures but with limited analysis of their in vitro maturation and plasticity. Such knowledge is however important for the development of tissue substitutes with improved implantation success as well as for validation of vascularization in vitro models, including as a readout in pharmacological analyses. For optimal interactions of cells with microenvironment and vasculature, we here used a cell sheet approach consisting in the sole production of matrix by the cells. In this context, we limited the density of endothelial cells seeded for self-assembly and rather relied on the stimulation of angiogenesis for the development of an extensive connected microvascular-like network. After detailed characterization of this network, we challenged its plasticity both during and after establishment of the skin substitute. We show that fine tuning of VEGF concentration and time of application differentially affects formation of capillary-like structures and their perivascular coverage. Furthermore, we performed a deep wound assay that displayed tissue repair and angiogenesis with unique characteristics of the physiological process. These studies demonstrate the importance of cell-derived microenvironment for the establishment of mature yet dynamic vascularized skin models allowing a wide range of pharmacological and basic investigations. STATEMENT OF SIGNIFICANCE: The significant advancements in organ-on-chips and tissue engineering call for more relevant models including microvascularization with remodeling potential. While vascularized skin substitutes have been developed for years, focus has primarily been on the impact of microvascularization on implantation rather than on its in vitro characterization. We here developed a cell sheet-based vascularized skin substitute relying on angiogenesis, i.e. growth of vessel-like structures within the 3D model, rather than solely on endothelial cell self-assembly. We then characterized :1/ vascularization after modulation of angiogenic factor VEGF during the substitute construction; -2/ angiogenesis associated to tissue repair after deep mechanical wounding. These studies establish a solid physiologically relevant model for further investigation of skin cell interactions and in vitro wound healing.

Current Status of Biomedical Products for Gene and Cell Therapy of Recessive Dystrophic Epidermolysis Bullosa

This detailed review describes innovative strategies and current products for gene and cell therapy at different stages of research and development to treat recessive dystrophic epidermolysis bullosa (RDEB) which is associated with the functional deficiency of collagen type VII alpha 1 (C7) caused by defects in the COL7A1 gene. The use of allogenic mesenchymal stem/stromal cells, which can be injected intradermally and intravenously, appears to be the most promising approach in the field of RDEB cell therapy. Injections of genetically modified autologous dermal fibroblasts are also worth mentioning under this framework. The most common methods of RDEB gene therapy are gene replacement using viral vectors and gene editing using programmable nucleases. Ex vivo epidermal transplants (ETs) based on autologous keratinocytes (Ks) have been developed using gene therapy methods; one such ET successively passed phase III clinical trials. Products based on the use of two-layer transplants have also been developed with both types of skin cells producing C7. Gene products have also been developed for local use. To date, significant progress has been achieved in the development of efficient biomedical products to treat RDEB, one of the most severe hereditary diseases.

A novel recombinant human collagen hydrogel as minced split-thickness skin graft overlay to promote full-thickness skin defect reconstruction

To overcome limited donor-site availability in patients with extensive burns, split-thickness skin grafts (STSGs) are sometimes minced into micrografts (MGs) to improve the expansion ratio of the grafts, but this may reduce wound healing. We aimed to produce a novel hydrogel as an overlay of minced STSGs to improve wound healing. The new hydrogel was produced using recombinant human collagen type III powder as a raw material. Morphological and physical characteristics (degradation and swelling rate), cytotoxicity, and cell viability of the hydrogel were evaluated in vitro. A full-thickness in vivo skin defect model was constructed with male Sprague-Dawley rats. The animals were randomly assigned to experimental and control groups in which the new hydrogel and Vaseline gauze, respectively, were overlaid on minced STSGs to repair and regenerate skin wound. The healing rates and recovery status were compared between the two groups. The hydrogels exhibited good water retention properties and a suitable degradation rate, which can promote the proliferation and migration of wound healing-related cells in vitro. Further, using the hydrogel as an overlay accelerated wound closure and angiogenesis, increased dermal tissue and basement membrane formation, enhanced collagen synthesis and wound healing-related growth factor expression, while reducing scar formation compared to the Vaseline gauze group. In conclusion, the novel, low-cost recombinant human collagen hydrogel can accelerate wound closure and improve wound healing when used as an overlay of minced STSGs. The new hydrogel could become a new treatment option for traumatic skin wounds caused by burns or injuries.

Extracellular matrix stiffness-The central cue for skin fibrosis

Skin fibrosis is a physiopathological process featuring the excessive deposition of extracellular matrix (ECM), which is the main architecture that provides structural support and constitutes the microenvironment for various cellular behaviors. Recently, increasing interest has been drawn to the relationship between the mechanical properties of the ECM and the initiation and modulation of skin fibrosis, with the engagement of a complex network of signaling pathways, the activation of mechanosensitive proteins, and changes in immunoregulation and metabolism. Simultaneous with the progression of skin fibrosis, the stiffness of ECM increases, which in turn perturbs mechanical and humoral homeostasis to drive cell fate toward an outcome that maintains and enhances the fibrosis process, thus forming a pro-fibrotic "positive feedback loop". In this review, we highlighted the central role of the ECM and its dynamic changes at both the molecular and cellular levels in skin fibrosis. We paid special attention to signaling pathways regulated by mechanical cues in ECM remodeling. We also systematically summarized antifibrotic interventions targeting the ECM, hopefully enlightening new strategies for fibrotic diseases.

GC-TOF/MS-Based Metabolomics for Comparison of Volar and Non-Volar Skin Types

Skin has heterogenous identities on different body sites despite similar cellular compositions. There are two types of skin, volar (palmoplantar) and non-volar (dorsal), which are characterized by epidermal thickness, pigmentation, and presence of hair follicles. However, the mechanisms underlying the development of these different skin types remain unclear. To investigate these, we profiled the cellular metabolites of volar and non-volar skin in mice using gas chromatography-time-of-flight/mass spectrometry (GC-TOF/MS), and further assessed the metabolic differences between them. In total, 96 metabolites from both volar and non-volar skin of mice were identified using the BinBase database system. Metabolomics analysis revealed important differences associated with amino acid metabolism (phenylalanine, tyrosine, and tryptophan biosynthesis; aspartate and glutamate metabolism), sugar metabolism (pentose phosphate pathway), and nucleotide metabolism (pyrimidine metabolism) in volar skin. Fifty metabolites were identified as potential biomarkers differentiating the physiological characteristics of these skin types. Of these, nine were highly increased whereas 41 were significantly decreased in volar skin compared with those in non-volar skin. Overall, these results provide valuable information for understanding the metabolic differences between volar and non-volar skin.

Engineering a 3D In Vitro Model of Human Gingival Tissue Equivalent with Genipin/Cytochalasin D

Although three-dimensional (3D) co-culture of gingival keratinocytes and fibroblasts-populated collagen gel can mimic 3D structure of in vivo tissue, the uncontrolled contraction of collagen gel restricts its application in clinical and experimental practices. We here established a stable 3D gingival tissue equivalent (GTE) using hTERT-immortalized gingival fibroblasts (hGFBs)-populated collagen gel directly crosslinked with genipin/cytochalasin D and seeding hTERT-immortalized gingival keratinocytes (TIGKs) on the upper surface for a 2-week air–liquid interface co-culture. MTT assay was used to measure the cell viability of GTEs. GTE size was monitored following culture period, and the contraction was analyzed. Immunohistochemical assay was used to analyze GTE structure. qRT-PCR was conducted to examine the mRNA expression of keratinocyte-specific genes. Fifty µM genipin (G50) or combination (G + C) of G50 and 100 nM cytochalasin D significantly inhibited GTE contraction. Additionally, a higher cell viability appeared in GTEs crosslinked with G50 or G + C. GTEs crosslinked with genipin/cytochalasin D showed a distinct multilayered stratified epithelium that expressed keratinocyte-specific genes similar to native gingiva. Collagen directly crosslinked with G50 or G + C significantly reduced GTE contraction without damaging the epithelium. In summary, the TIGKs and hGFBs can successfully form organotypic multilayered cultures, which can be a valuable tool in the research regarding periodontal disease as well as oral mucosa disease. We conclude that genipin is a promising crosslinker with the ability to reduce collagen contraction while maintaining normal cell function in collagen-based oral tissue engineering.

Granulocyte macrophage-colony stimulating factor and keratinocyte growth factor control of early stages of differentiation of oral epithelium

Oral epithelial differentiation is known to be directed by underlying fibroblasts, but the responsible factor(s) have not been identified. We aimed here to identify fibroblast‐derived factors responsible for oral epithelial differentiation. Primary normal human oral keratinocytes and fibroblasts were isolated from healthy volunteers after informed consent (n = 5) and 3D‐organotypic (3D‐OT) cultures were constructed. Various growth factors were added at a range of 0.1‐100 ng/ml. 3D‐OTs were harvested after ten days and assessed histologically, by immunohistochemistry and the TUNEL method. Epithelium developed in 3D‐OT without fibroblasts showed an undifferentiated phenotype. Addition of granulocyte macrophage‐colony stimulating factor (GM‐CSF) induced expression of cytokeratin 13 in suprabasal cell layers. Admixture of GM‐CSF and keratinocyte growth factor (KGF) induced, in addition, polarization of epidermal growth factor (EGF) receptor and β1‐integrin to basal cell layer and collagen IV deposition. Terminal differentiation with polarization of TUNEL‐positive cells to superficial layers occurred only in the presence of fibroblasts in collagen gels either in direct contact or at distance from normal oral keratinocytes. Taken together, these results show that major aspects of oral epithelial differentiation are regulated by the synergic combination of GM‐CSF and KGF. However, the terminal stage seems to be controlled by other yet unidentified fibroblast‐derived diffusible factor(s).

The bright side of fibroblasts: molecular signature and regenerative cues in major organs

Fibrosis is a pathologic process characterized by the replacement of parenchymal tissue by large amounts of extracellular matrix, which may lead to organ dysfunction and even death. Fibroblasts are classically associated to fibrosis and tissue repair, and seldom to regeneration. However, accumulating evidence supports a pro-regenerative role of fibroblasts in different organs. While some organs rely on fibroblasts for maintaining stem cell niches, others depend on fibroblast activity, particularly on secreted molecules that promote cell adhesion, migration, and proliferation, to guide the regenerative process. Herein we provide an up-to-date overview of fibroblast-derived regenerative signaling across different organs and discuss how this capacity may become compromised with aging. We further introduce a new paradigm for regenerative therapies based on reverting adult fibroblasts to a fetal/neonatal-like phenotype.

Novel leukocyte-depleted platelet-rich plasma-based skin equivalent as an in vitro model of chronic wounds: a preliminary study

BACKGROUND

Chronic leg ulcerations are associated with Haemoglobin disorders, Type2 Diabetes Mellitus, and long-term venous insufficiency, where poor perfusion and altered metabolism develop into a chronic inflammation that impairs wound closure. Skin equivalent organotypic cultures can be engineered in vitro to study skin biology and wound closure by modelling the specific cellular components of the skin. This study aimed to develop a novel bioactive platelet-rich plasma (PRP) leukocyte depleted scaffold to facilitate the study of common clinical skin wounds in patients with poor chronic skin perfusion and low leukocyte infiltration. A scratch assay was performed on the skin model to mimic two skin wound conditions, an untreated condition and a condition treated with recombinant tumour necrotic factor (rTNF) to imitate the stimulation of an inflammatory state. Gene expression of IL8 and TGFA was analysed in both conditions. Statistical analysis was done through ANOVA and paired student t-test. P < 0.05 was considered significant.

RESULTS

A skin model that consisted of a leukocyte-depleted, platelet-rich plasma scaffold was setup with embedded fibroblasts as dermal equivalents and seeded keratinocytes as multi-layered epidermis. Gene expression levels of IL8 and TGFA were significantly different between the control and scratched conditions (p < 0.001 and p < 0.01 respectively), as well as between the control and treated conditions (p < 0.01 and p < 0.001 respectively). The scratch assay induced IL8 upregulation after 3 h (p < 0.05) which continued to increase up to day 1 (p < 0.05). On the other hand, the administration of TNF led to the downregulation of IL8 (p < 0.01), followed by an upregulation on day 2. IL8 gene expression decreased in the scratched condition after day 1 as the natural healing process took place and was lower than in the treated condition on day 8 (p < 0.05). Both untreated and treated conditions showed a downregulation of TGFA 3 h after scratch when compared with the control condition (p < 0.01). Administration of rTNF showed significant downregulation of TGFA after 24 h when compared with the control (p < 0.01) and treated conditions (p < 0.05).

CONCLUSION

This study suggests that a leukocyte-depleted PRP-based skin equivalent can be a useful model for the in vitro study of chronic skin wounds related to poor skin perfusion.

Differential Wound Healing Capacity of Mesenchymal Stem Cell-Derived Exosomes Originated From Bone Marrow, Adipose Tissue and Umbilical Cord Under Serum- and Xeno-Free Condition

Exosomes are nano-scale and closed membrane vesicles which are promising for therapeutic applications due to exosome-enclosed therapeutic molecules such as DNA, small RNAs, proteins and lipids. Recently, it has been demonstrated that mesenchymal stem cell (MSC)-derived exosomes have capacity to regulate many biological events associated with wound healing process, such as cell proliferation, cell migration and blood vessel formation. This study investigated the regenerative potentials for cutaneous tissue, in regard to growth factors associated with wound healing and skin cell proliferation and migration, by exosomes released from primary MSCs originated from bone marrow (BM), adipose tissue (AD), and umbilical cord (UC) under serum- and xeno-free condition. We found crucial wound healing-mediated growth factors, such as vascular endothelial growth factor A (VEGF-A), fibroblast growth factor 2 (FGF-2), hepatocyte growth factor (HGF), and platelet-derived growth factor BB (PDGF-BB) in exosomes derived from all three MSC sources. However, expression levels of these growth factors in exosomes were influenced by MSC origins, especially transforming growth factor beta (TGF-β) was only detected in UCMSC-derived exosomes. All exosomes released by three MSCs sources induced keratinocyte and fibroblast proliferation and migration; and, the induction of cell migration is a dependent manner with the higher dose of exosomes was used (20 μg), the faster migration rate was observed. Additionally, the influences of exosomes on cell proliferation and migration was associated with exosome origins and also target cells of exosomes that the greatest induction of primary dermal fibroblasts belongs to BMMSC-derived exosomes and keratinocytes belongs to UCMSC-derived exosomes. Data from this study indicated that BMMSCs and UCMSCs under clinical condition secreted exosomes are promising to develop into therapeutic products for wound healing treatment.

Interplay Between Keratinocytes and Fibroblasts: A Systematic Review Providing a New Angle for Understanding Skin Fibrotic Disorders

Background/Objective: Skin fibrosis is the result of aberrant processes leading to abnormal deposition of extracellular matrix (ECM) in the dermis. In healthy skin, keratinocytes participate to maintain skin homeostasis by actively crosstalking with fibroblasts. Within the wide spectrum of fibrotic skin disorders, relatively little attention has been devoted to the role of keratinocytes for their capacity to participate to skin fibrosis. This systematic review aims at summarizing the available knowledge on the reciprocal interplay of keratinocytes with fibroblasts and their soluble mediators in physiological states, mostly wound healing, and conditions associated with skin fibrosis.

Methods: We performed a systematic literature search on PubMed to identify in vitro and ex vivo human studies investigating the keratinocyte characteristics and their interplay with fibroblasts in physiological conditions and within fibrotic skin disorders including hypertrophic scars, keloids, and systemic sclerosis. Studies were selected according to pre-specified eligibility criteria. Data on study methods, models, stimuli and outcomes were retrieved and summarized according to pre-specified criteria.

Results: Among the 6,271 abstracts retrieved, 73 articles were included, of which 14 were specifically dealing with fibrotic skin pathologies. Fifty-six studies investigated how keratinocyte may affect fibroblast responses in terms of ECM-related genes or protein production, phenotype modification, and cytokine production. Most studies in both physiological conditions and fibrosis demonstrated that keratinocytes stimulate fibroblasts through the production of interleukin 1, inducing keratinocyte growth factor (KGF) and metalloproteinases in the fibroblasts. When the potential of keratinocytes to modulate collagen synthesis by healthy fibroblasts was explored, the results were controversial. Nevertheless, studies investigating keratinocytes from fibrotic skin, including keloids, hypertrophic scar, and scleroderma, suggested their potential involvement in enhancing ECM deposition. Twenty-three papers investigated keratinocyte proliferation differentiation and production of soluble mediators in response to interactions with fibroblasts. Most studies showed that fibroblasts modulate keratinocyte viability, proliferation, and differentiation. The production of KGF by fibroblast was identified as key for these functions.

Conclusions: This review condenses evidence for the active interaction between keratinocytes and fibroblasts in maintaining skin homeostasis and the altered homeostatic interplay between keratinocytes and dermal fibroblasts in scleroderma and scleroderma-like disorders.

Collagen VII Expression Is Required in Both Keratinocytes and Fibroblasts for Anchoring Fibril Formation in Bilayer Engineered Skin Substitutes

The blistering disease recessive dystrophic epidermolysis bullosa (RDEB) is caused by mutations in the gene encoding collagen VII (COL7), which forms anchoring fibrils that attach the epidermis to the dermis. Cutaneous gene therapy to restore COL7 expression in RDEB patient cells has been proposed, and cultured epithelial autograft containing COL7-modified keratinocytes was previously tested in clinical trials. Because COL7 in normal skin is expressed in both fibroblasts and keratinocytes, cutaneous gene therapy using a bilayer skin substitute may enable faster restoration of anchoring fibrils. Hypothetically, COL7 expression in either dermal fibroblasts or epidermal keratinocytes might be sufficient for functional anchoring fibril formation in a bilayer skin substitute. To test this, engineered skin substitutes (ESS) were prepared using four combinations of normal + RDEB cells: (1) RDEB fibroblasts + RDEB keratinocytes; (2) RDEB fibroblasts + normal keratinocytes; (3) normal fibroblasts + RDEB keratinocytes; and (4) normal fibroblasts + normal keratinocytes. ESS were incubated in vitro for 2 weeks prior to grafting to full-thickness wounds in immunodeficient mice. Biopsies were analyzed in vitro and at 1, 2, or 3 weeks after grafting. COL7 was undetectable in ESS prepared using all RDEB cells (group 1), and macroscopic blistering was observed by 2 weeks after grafting in ESS containing RDEB cells. COL7 was expressed, in vitro and in vivo, in ESS prepared using combinations of normal + RDEB cells (groups 2 and 3) or all normal cells (group 4). However, transmission electron microscopy revealed structurally normal anchoring fibrils, in vitro and by week 2 in vivo, only in ESS prepared using all normal cells (group 4). The results suggest that although COL7 protein is produced in engineered skin when cells in only one layer express the COL7 gene, formation of structurally normal anchoring fibrils appears to require expression of COL7 in both dermal fibroblasts and epidermal keratinocytes.

One-step approach for full-thickness skin defect reconstruction in rats using minced split-thickness skin grafts with Pelnac overlay

Background

Split-thickness skin grafting is the current gold standard for the treatment of traumatic skin loss. However, for patients with extensive burns, split-thickness skin grafting is limited by donor skin availability. Grafting split-thickness skin minced into micrografts increases the expansion ratio but may reduce wound repair quality. Dermal substitutes such as Pelnac can enhance the healing of full-thickness skin wounds, but their application currently requires two surgeries. The present study investigated whether it is possible to repair full-thickness skin defects and improve wound healing quality in a single surgery using Pelnac as an overlay of minced split-thickness skin grafts in a rat model.

Methods

A full-thickness skin defect model was established using male Sprague-Dawley rats of 10 weeks old. The animals were randomly divided into control and experimental groups in which Vaseline gauze and Pelnac, respectively, were overlaid on minced split-thickness skin grafts to repair the defects. Wound healing rate and quality were compared between the two groups. For better illustration of the quality of wound healing, some results were compared with those obtained for normal skin of rats.

Results

We found that using Pelnac as an overlay for minced split-thickness skin grafts accelerated wound closure and stimulated cell proliferation and tissue angiogenesis. In addition, this approach enhanced collagen synthesis and increased the formation of basement membrane and dermis as well as the expression of growth factors related to wound healing while reducing scar formation.

Conclusions

Using minced split-thickness skin grafts overlaid with Pelnac enables the reconstruction of full-thickness skin defects in a single step and can increase the healing rate while improving the quality of wound healing.

Beyond proteases: Basement membrane mechanics and cancer invasion

In epithelial cancers, cells must invade through basement membranes (BMs) to metastasize. The BM, a thin layer of extracellular matrix underlying epithelial and endothelial tissues, is primarily composed of laminin and collagen IV and serves as a structural barrier to cancer cell invasion, intravasation, and extravasation. BM invasion has been thought to require protease degradation since cells, which are typically on the order of 10 µm in size, are too large to squeeze through the nanometer-scale pores of the BM. However, recent studies point toward a more complex picture, with physical forces generated by cancer cells facilitating protease-independent BM invasion. Moreover, collective cell interactions, proliferation, cancer-associated fibroblasts, myoepithelial cells, and immune cells are all implicated in regulating BM invasion through physical forces. A comprehensive understanding of BM structure and mechanics and diverse modes of BM invasion may yield new strategies for blocking cancer progression and metastasis.

IL-1 and TGF-β Modulation of Epithelial Basement Membrane Components Perlecan and Nidogen Production by Corneal Stromal Cells

Purpose

To determine whether (1) the in vitro expression of epithelial basement membrane components nidogen-1, nidogen-2, and perlecan by keratocytes, corneal fibroblasts, and myofibroblasts is modulated by cytokines/growth factors, and (2) perlecan protein is produced by stromal cells after photorefractive keratectomy.

Methods

Marker-verified rabbit keratocytes, corneal fibroblasts, myofibroblasts were stimulated with TGF-β1, IL-1α, IL-1β, TGF-β3, platelet-derived growth factor (PDGF)-AA, or PDGF-AB. Real-time quantitative RT-PCR was used to detect expression of nidogen-1, nidogen-2, and perlecan mRNAs. Western blotting evaluated changes in protein expression. Immunohistochemistry was performed on rabbit corneas for perlecan, alpha-smooth muscle actin, keratocan, vimentin, and CD45 at time points from 1 day to 1 month after photorefractive keratectomy (PRK).

Results

IL-1α or -1β significantly upregulated perlecan mRNA expression in keratocytes. TGF-β1 or -β3 markedly downregulated nidogen-1 or -2 mRNA expression in keratocytes. None of these cytokines had significant effects on nidogen-1, -2, or perlecan mRNA expression in corneal fibroblasts or myofibroblasts. IL-1α significantly upregulated, while TGF-β1 significantly downregulated, perlecan protein expression in keratocytes. Perlecan protein expression was upregulated in anterior stromal cells at 1 and 2 days after −4.5 or −9 diopters (D) PRK, but the subepithelial localization of perlecan became disrupted at 7 days and later time points in −9-D PRK corneas when myofibroblasts populated the anterior stroma.

Conclusions

IL-1 and TGF-β1 have opposing effects on perlecan and nidogen expression by keratocytes in vitro. Proximate participation of keratocytes is likely needed to regenerate normal epithelial basement membrane after corneal injury.

In vivo evaluation of an electrospun gelatin nonwoven mat for regeneration of epithelial tissues

One major objective in epithelial tissue engineering is to identify a suitable biomaterial that supports epithelial tissue formation. Therefore, the purpose of this study is to elucidate a novel electrospun gelatin nonwoven mat (NWM) for epithelial tissue engineering purposes in vivo. This NWM was seeded with either human gingival keratinocytes (GK, in coculture with gingival fibroblast) or human skin epithelial keratinocytes (EK, in coculture with skin dermal fibroblasts). These constructs were ex vivo cultured for 4 days before subcutaneous implantation into athymic nude mice. After 7 days, the constructs were explanted and investigated by immunohistology. Our results show that GK form a stratified epithelium on the surface of the NWM, mostly independent of a fibroblastic counterpart. Like native mucosa, the regenerated epithelium showed expression of epidermal growth factor receptor, cytokeratin-14 and -1, and involucrin. Only the expression of the basement membrane constituent laminin 5 was more pronounced in cocultures. Comparing GK and skin EK, we found that skin EK form a less developed epithelial tissue. Furthermore, the NWM allows not only for epithelial tissue formation by GK, but also for infiltration of human fibroblasts and mouse immune cells, thus representing a biomaterial with potential regenerative capacity for oral mucosa tissue engineering applications. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1605-1614, 2019.

Evaluation of Cilia Function in Rat Trachea Reconstructed Using Collagen Sponge Scaffold Seeded with Adipose Tissue-Derived Stem Cells

The tracheal lumen is essential for conducting air to the lung alveoli and for voice production. However, patients with severe tracheal stenosis and malignant tumors invading the trachea often require tracheal resection. Recently, various reported tissue engineering methods for tracheal reconstruction show that regeneration of ciliated epithelium in the reconstructed areas, as well as preservation of the luminal structure is possible. However, only few studies report on the mucociliary transport function in reconstructed tracheae. We investigated mucociliary transport function within rat tracheal epithelium, reorganized after autologous adipose tissue-derived stem cell (ASC) transplantation. Rat ASCs were expanded in culture, and then seeded in a collagen sponge, which was physically supported with a polypropylene framework. The ASC-seeded collagen sponge was transplanted into the rat tracheal defect. We then examined the motility and transport function of cilia generated in the transplanted area using ciliary beat frequency (CBF) and microsphere movement analyses. Our data suggested that autologous ASC transplantation promoted ciliogenesis, consistent with previous reports. The CBF analysis revealed that motility of the cilia generated in the ASC group was comparable to that observed in the normal rat tracheal epithelium. Transport function in the ASC group was higher than that in the control group. These data suggested that autologous ASC transplantation increased ciliated cells in the reconstructed area without significantly disrupting cilia motility, thereby promoting transport function regeneration. Autologous ASC transplantation is expected to be beneficial in morphological and functional regeneration of tracheal epithelium. Anat Rec, 303:471-477, 2020. © 2019 American Association for Anatomy.

Electrospun Nanometer to Micrometer Scale Biomimetic Synthetic Membrane Scaffolds in Drug Delivery and Tissue Engineering: A Review

The scaffold technology research utilizes biomimicry to produce efficient scaffolds that mimic the natural cell growth environment including the basement membrane for tissue engineering. Because the natural basement membrane is composed of fibrillar protein networks of nanoscale diameter, the scaffold produced should efficiently mimic the nanoscale topography at a low production cost. Electrospinning is a technique that can achieve that. This review discusses the physical and chemical characteristics of the basement membrane and its significance on cell growth and overall focuses on nanoscale biomimetic synthetic membrane scaffolds primarily generated using electrospinning and their application in drug delivery and tissue engineering.

Tissue microenvironment initiates an immune response to structural components of Staphylococcus aureus

Cell-to-cell communication in skin participates to the maintenance of homeostatic responses to foreign substances. Certain strains of Staphylococcus (S) aureus are vicious pathogens that cause deleterious effects in host cells and tissues. Both secreted toxins and structural components of S. aureus trigger an immune response, though how S. aureus stimulates host immune responses is poorly understood. We explored here how keratinocytes and fibroblasts initiate the first steps of an immune response by activating dendritic cells (DCs) through recognition of structural components of S. aureus. We treated monocyte-derived Langerhans cells (moLCs) and monocyte-derived DCs (moDCs) with conditioned media from keratinocytes (K-CM) and fibroblasts (F-CM) treated with heat-killed S. aureus (HKSA) respectively, or directly with HKSA. Immune and inflammatory responses from keratinocytes, fibroblasts, moLCs and moDCs were assessed by analysis of cell surface markers and cytokine production using flow cytometry, real-time PCR and ELISA assays. K-CM and F-CM increased the expression of CD86 and HLA-DR on moLCs and moDCs, in association with a specific cytokine profile. K-CM upregulated TNFA, IL-1B and GM-CSF mRNA expression in moLCs, while F-CM upregulated IL-12 and downregulated TNFA and TGFB mRNA expression in moDCs. Additionally, F-CM attenuated the induction of an inflammatory profile in monocytes. The recognition of structural components from S. aureus by cutaneous microenvironment induces the activation and the expression of specific cytokines from LCs and DCs.

Basement membranes in the cornea and other organs that commonly develop fibrosis

Basement membranes are thin connective tissue structures composed of organ-specific assemblages of collagens, laminins, proteoglycan-like perlecan, nidogens, and other components. Traditionally, basement membranes are thought of as structures which primarily function to anchor epithelial, endothelial, or parenchymal cells to underlying connective tissues. While this role is important, other functions such as the modulation of growth factors and cytokines that regulate cell proliferation, migration, differentiation, and fibrosis are equally important. An example of this is the critical role of both the epithelial basement membrane and Descemet's basement membrane in the cornea in modulating myofibroblast development and fibrosis, as well as myofibroblast apoptosis and the resolution of fibrosis. This article compares the ultrastructure and functions of key basement membranes in several organs to illustrate the variability and importance of these structures in organs that commonly develop fibrosis.

Specialized Living Wound Dressing Based on the Self-Assembly Approach of Tissue Engineering

There is a high incidence of failure and recurrence for chronic skin wounds following conventional therapies. To promote healing, the use of skin substitutes containing living cells as wound dressings has been proposed. The aim of this study was to produce a scaffold-free cell-based bilayered tissue-engineered skin substitute (TES) containing living fibroblasts and keratinocytes suitable for use as wound dressing, while considering production time, handling effort during the manufacturing process, and stability of the final product. The self-assembly method, which relies on the ability of mesenchymal cells to secrete and organize connective tissue sheet sustaining keratinocyte growth, was used to produce TESs. Three fibroblast-seeding densities were tested to produce tissue sheets. At day 17, keratinocytes were added onto 1 or 3 (reference method) stacked tissue sheets. Four days later, TESs were subjected either to 4, 10, or 17 days of culture at the air–liquid interface (A/L). All resulting TESs were comparable in terms of their histological aspect, protein expression profile and contractile behavior in vitro. However, signs of extracellular matrix (ECM) digestion that progressed over culture time were noted in TESs produced with only one fibroblast-derived tissue sheet. With lower fibroblast density, the ECM of TESs was almost completely digested after 10 days A/L and lost histological integrity after grafting in athymic mice. Increasing the fibroblast seeding density 5 to 10 times solved this problem. We conclude that the proposed method allows for a 25-day production of a living TES, which retains its histological characteristics in vitro for at least two weeks.

The Corneal Basement Membranes and Stromal Fibrosis

Purpose

The purpose of this review was to provide detailed insights into the pathophysiology of myofibroblast-mediated fibrosis (scarring or late haze) after corneal injury, surgery, or infection.

Method

Literature review.

Results

The epithelium and epithelial basement membrane (EBM) and/or endothelium and Descemet's basement membrane (BM) are commonly disrupted after corneal injuries, surgeries, and infections. Regeneration of these critical regulatory structures relies on the coordinated production of BM components, including laminins, nidogens, perlecan, and collagen type IV by epithelial, endothelial, and keratocyte cells. Whether a cornea, or an area in the cornea, heals with transparency or fibrosis may be determined by whether there is injury to one or both corneal basement membranes (EBM and/or Descemet's BM) and delayed or defective regeneration or replacement of the BM. These opaque myofibroblasts, and the disordered extracellular matrix these cells produce, persist in the stroma until the EBM and/or Descemet's BM is regenerated or replaced.

Conclusions

Corneal stromal fibrosis (also termed "stromal scarring" or "late haze") occurs as a consequence of BM injury and defective regeneration in both the anterior (EBM) and posterior (Descemet's BM) cornea. The resolution of fibrosis and return of stromal transparency depends on reestablished BM structure and function. It is hypothesized that defective regeneration of the EBM or Descemet's BM allows key profibrotic growth factors, including transforming growth factor beta-1 (TGF-β1) and TGF-β2, to penetrate the stroma at sustained levels necessary to drive the development and maintenance of mature opacity-producing myofibroblasts from myofibroblast precursors cells, and studies suggest that perlecan and collagen type IV are the critical components in EBM and Descemet's BM that bind TGF-β1, TGF-β2, platelet-derived growth factor, and possibly other growth factors, and regulate their bioavailability and function during homeostasis and corneal wound healing.

The Benefit of Microskin in Combination With Autologous Keratinocyte Suspension to Treat Full Skin Loss In Vivo

Patients with extensive deep burns often lack enough autologous skin to cover the wounds. This study explores a new method using microskin in combination with autologous keratinocytes in the treatment of extensive deep burn. Wounds in the combination group were treated with automicroskin at an area expansion ratio of 20:1 (wound area to automicroskin area) and autologous keratinocyte suspension, which were compared with the following treatments: no autotransplant, only allografts (control group); autologous keratinocyte suspension only (keratinocyte only group); automicroskin at an area expansion ratio of 20:1 (20:1 group); and automicroskin at an area expansion ratio of 10:1 (10:1 group, positive control). The authors used epithelialization rate (epithelialized area on day 21 divided by original wound area), hematoxylin and eosin staining, laminin, and type IV collagen immunohistochemistry to assess wound healing. The epithelialization rate of combination group (74.2% ± 8.0%) was similar to that of 10: 1 group (84.3% ± 11.9%, P = .085) and significantly (P < .05) higher than that of 20:1 group (59.2% ± 10.8%), keratinocyte only group (53.8% ± 11.5%), and control group (22.7% ± 5.5%). The hematoxylin and eosin staining and immunohistochemistry showed the epithelialization in the combination group was better than that in the keratinocyte only group and control group. Microskin in combination with autologous keratinocyte suspension can promote the reepithelialization of full-thickness wounds and reduce the requirements for automircoskin, and it is a useful option in the treatment of extensive deep burns.

Foxn1 in Skin Development, Homeostasis and Wound Healing

Intensive research effort has focused on cellular and molecular mechanisms that regulate skin biology, including the phenomenon of scar-free skin healing during foetal life. Transcription factors are the key molecules that tune gene expression and either promote or suppress gene transcription. The epidermis is the source of transcription factors that regulate many functions of epidermal cells such as proliferation, differentiation, apoptosis, and migration. Furthermore, the activation of epidermal transcription factors also causes changes in the dermal compartment of the skin. This review focuses on the transcription factor Foxn1 and its role in skin biology. The regulatory function of Foxn1 in the skin relates to physiological (development and homeostasis) and pathological (skin wound healing) conditions. In particular, the pivotal role of Foxn1 in skin development and the acquisition of the adult skin phenotype, which coincides with losing the ability of scar-free healing, is discussed. Thus, genetic manipulations with Foxn1 expression, specifically those introducing conditional Foxn1 silencing in a Foxn1+/+ organism or its knock-in in a Foxn1−/− model, may provide future perspectives for regenerative medicine.

Characterization of In Vitro Reconstructed Human Normotrophic, Hypertrophic, and Keloid Scar Models

To understand scar pathology, develop new drugs, and provide a platform for personalized medicine, physiologically relevant human scar models are required, which are characteristic of different scar pathologies. Hypertrophic scars and keloids are two types of abnormal scar resulting from unknown abnormalities in the wound healing process. While they display different clinical behavior, differentiation between the two can be difficult-which in turn means that it is difficult to develop optimal therapeutic strategies. The aim of this study was to develop in vitro reconstructed human hypertrophic and keloid scar models and compare these to normotrophic scar and normal skin models to identify distinguishing biomarkers. Keratinocytes and fibroblasts from normal skin and scar types (normotrophic, hypertrophic, keloid) were used to reconstruct skin models. All skin models showed a reconstructed differentiated epidermis on a fibroblast populated collagen-elastin matrix. Both abnormal scar types showed increased contraction, dermal thickness, and myofibroblast staining compared to normal skin and normotrophic scar. Notably, the expression of extracellular matrix associated genes showed distinguishing profiles between all scar types and normal skin (hyaluronan synthase-1, matrix-metalloprotease-3), between keloid and normal skin (collagen type IV), between normal scar and keloid (laminin α1), and between keloid and hypertrophic scar (matrix-metalloprotease-1, integrin α5). Also, inflammatory cytokine and growth factor secretion (CCL5, CXCL1, CXCL8, CCL27, IL-6, HGF) showed differential secretion between scar types. Our results strongly suggest that abnormal scars arise from different pathologies rather than simply being on different ends of the scarring spectrum. Furthermore, such normal skin and scar models together with biomarkers, which distinguish the different scar types, would provide an animal free, physiologically relevant scar diagnostic and drug testing platform for the future.

Development of a Full-Thickness Human Gingiva Equivalent Constructed from Immortalized Keratinocytes and Fibroblasts

Organotypic models make it possible to investigate the unique properties of oral mucosa in vitro. For gingiva, the use of human primary keratinocytes (KC) and fibroblasts (Fib) is limited due to the availability and size of donor biopsies. The use of physiologically relevant immortalized cell lines would solve these problems. The aim of this study was to develop fully differentiated human gingiva equivalents (GE) constructed entirely from cell lines, to compare them with the primary cell counterpart (Prim), and to test relevance in an in vitro wound healing assay. Reconstructed gingiva epithelium on a gingiva fibroblast-populated collagen hydrogel was constructed from cell lines (keratinocytes: TERT or HPV immortalized; fibroblasts: TERT immortalized) and compared to GE-Prim and native gingiva. GE were characterized by immunohistochemical staining for proliferation (Ki67), epithelial differentiation (K10, K13), and basement membrane (collagen type IV and laminin 5). To test functionality of GE-TERT, full-thickness wounds were introduced. Reepithelialization, fibroblast repopulation of hydrogel, metabolic activity (MTT assay), and (pro-)inflammatory cytokine release (enzyme-linked immunosorbent assay) were assessed during wound closure over 7 days. Significant differences in basal KC cytokine secretion (IL-1α, IL-18, and CXCL8) were only observed between KC-Prim and KC-HPV. When Fib-Prim and Fib-TERT were stimulated with TNF-α, no differences were observed regarding cytokine secretion (IL-6, CXCL8, and CCL2). GE-TERT histology, keratin, and basement membrane protein expression very closely represented native gingiva and GE-Prim. In contrast, the epithelium of GE made with HPV-immortalized KC was disorganized, showing suprabasal proliferating cells, limited keratinocyte differentiation, and the absence of basement membrane proteins. When a wound was introduced into the more physiologically relevant GE-TERT model, an immediate inflammatory response (IL-6, CCL2, and CXCL8) was observed followed by complete reepithelialization. Seven days after wounding, tissue integrity, metabolic activity, and cytokine levels had returned to the prewounded state. In conclusion, immortalized human gingiva KC and fibroblasts can be used to make physiologically relevant GE, which resemble either the healthy gingiva or a neoplastic disease model. These organotypic models will provide valuable tools to investigate oral mucosa biology and can also be used as an animal alternative for drug targeting, vaccination studies, microbial biofilm studies, and testing new therapeutics.

Human Papillomavirus and the Stroma: Bidirectional Crosstalk during the Virus Life Cycle and Carcinogenesis

Human papillomaviruses (HPVs) are double-stranded DNA (dsDNA) tumor viruses that are causally associated with human cancers of the anogenital tract, skin, and oral cavity. Despite the availability of prophylactic vaccines, HPVs remain a major global health issue due to inadequate vaccine availability and vaccination coverage. The HPV life cycle is established and completed in the terminally differentiating stratified epithelia, and decades of research using in vitro organotypic raft cultures and in vivo genetically engineered mouse models have contributed to our understanding of the interactions between HPVs and the epithelium. More recently, important and emerging roles for the underlying stroma, or microenvironment, during the HPV life cycle and HPV-induced disease have become clear. This review discusses the current understanding of the bidirectional communication and relationship between HPV-infected epithelia and the surrounding microenvironment. As is the case with other human cancers, evidence suggests that the stroma functions as a significant partner in tumorigenesis and helps facilitate the oncogenic potential of HPVs in the stratified epithelium.

Study of Proliferative Activity of Vaginal Epithelium in Women with Stress Urinary Incontinence Treated by Er:YAG Laser

The expression of Ki-67 proliferation marker was studied in vaginal biopsy specimens from women with stress urinary incontinence treated using a Fotona nonablative erbium laser. Cells expressing Ki-67 were located in all cases in the parabasal and basal levels of stratified squamous epithelium, the index of labeled nuclei before Er:YAG laser exposure was 19.05±2.86%. After 1-2 months of laser therapy, the index of labeled nuclei in the epithelium increased significantly and reached 31.79±2.25%. These changes were interpreted as a result of epithelial-stromal interactions. Presumably, the increase in proliferative activity of the vaginal epithelium after exposure to Er:YAG laser was due to the presence of an appreciable level of synthetically active fibroblasts in the subepithelial stroma.

Development of a new model of reconstituted mouse epidermis and characterization of its response to proinflammatory cytokines

The development of three-dimensional models of reconstituted mouse epidermis (RME) has been hampered by the difficulty to maintain murine primary keratinocyte cultures and to achieve a complete epidermal stratification. In this study, a new protocol is proposed for the rapid and convenient generation of RME, which reproduces accurately the architecture of a normal mouse epidermis. During RME morphogenesis, the expression of differentiation markers such as keratins, loricrin, filaggrin, E-cadherin and connexins was followed, showing that RME structure at day 5 was similar to those of a normal mouse epidermis, with the acquisition of the natural barrier function. It was also demonstrated that RME responded to skin-relevant proinflammatory cytokines by increasing the expression of antimicrobial peptides and chemokines, and inhibiting epidermal differentiation markers, as in the human system. This new model of RME is therefore suitable to investigate mouse epidermis physiology further and opens new perspectives to generate reconstituted epidermis from transgenic mice.

The Interaction Between Human Papillomaviruses and the Stromal Microenvironment

Human papillomaviruses (HPVs) are small, double-stranded DNA viruses that replicate in stratified squamous epithelia and cause a variety of malignancies. Current efforts in HPV biology are focused on understanding the virus-host interactions that enable HPV to persist for years or decades in the tissue. The importance of interactions between tumor cells and the stromal microenvironment has become increasingly apparent in recent years, but how stromal interactions impact the normal, benign life cycle of HPVs, or progression of lesions to cancer is less understood. Furthermore, how productively replicating HPV impacts cells in the stromal environment is also unclear. Here we bring together some of the relevant literature on keratinocyte-stromal interactions and their impacts on HPV biology, focusing on stromal fibroblasts, immune cells, and endothelial cells. We discuss how HPV oncogenes in infected cells manipulate other cells in their environment, and, conversely, how neighboring cells may impact the efficiency or course of HPV infection.

Androgen actions in mouse wound healing: Minimal in vivo effects of local antiandrogen delivery

The aims of this work were to define the role of androgens in female wound healing and to develop and characterize a novel wound dressing with antiandrogens. Androgens retard wound healing in males, but their role in female wound healing has not been established. To understand androgen receptor (AR)-mediated androgen actions in male and female wound healing, we utilized the global AR knockout (ARKO) mouse model, with a mutated AR deleting the second zinc finger to disrupt DNA binding and transcriptional activation. AR inactivation enhanced wound healing rate in males by increasing re-epithelialization and collagen deposition even when wound contraction was eliminated. Cell proliferation and migration in ARKO male fibroblasts was significantly increased compared with wild-type (WT) fibroblasts. However, ARKO females showed a similar healing rate compared to WT females. To exploit local antiandrogen effects in wound healing, while minimizing off-target systemic effects, we developed a novel electrospun polycaprolactone (PCL) scaffold wound dressing material for sustained local antiandrogen delivery. Using the antiandrogen hydroxyl flutamide (HF) at 1, 5, and 10 mg/mL in PCL scaffolds, controlled HF delivery over 21 days significantly enhanced in vitro cell proliferation of human dermal fibroblasts and human keratinocytes. HF-PCL scaffolds also promoted in vivo wound healing in mice compared with open wounds but not to PCL scaffolds.

miR-130b-3p Modulates Epithelial-Mesenchymal Crosstalk in Lung Fibrosis by Targeting IGF-1

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and usually lethal fibrotic lung disease with largely unknown etiology and pathogenesis. Evidence suggests microRNAs (miRNA) contribute to pathogenesis of IPF. In this study, we sought to identify miRNA expression signatures and determine the role of miR-130b-3p in lung fibrosis. The miRNA expression profile of the lungs from patients with IPF and normal donors was determined by Affymetrix microarray, and transcriptome with Affymetrix array. The functions and signal pathways as well as miRNA-mRNA networks were established by bioinformatics analysis. Luciferase assays and ELISA were used to confirm the miRNA target gene. The effect of miRNA-transfected epithelium on fibroblast activities was assessed using a co-culture system. The fibroblast activities were determined by qRT-PCR, western blotting, Transwell and BrdU assays. Seven miRNAs were significantly decreased in IPF lungs, with miR-130b-3p being the highest in the miRNA-mRNA network. Insulin-like growth factor (IGF-1) was a target gene of miR-130b-3p in the epithelium. miR-130b-3p inhibition in the epithelium induced collagen I expression and enhanced the proliferation and migration ability of fibroblast in co-culture systems, which mimicked the functions of exogenous IGF-1 on fibroblasts. Neutralizing IGF-1 with an antibody significantly reduced the modulatory effects of miR-130b-3p inhibitor-transfected epithelium on the activation of fibroblasts. Our results show that miR-130b-3p was downregulated in IPF lungs. miR-130b-3p downregulation contributed to the activation of fibroblasts and the dysregulated epithelial-mesenchymal crosstalk by promoting IGF-1 secretion from lung epithelium, suggesting a key regulatory role for this miRNA in preventing lung fibrosis.

Human proximal tubule cells form functional microtissues

The epithelial cells lining the proximal tubules of the kidney mediate complex transport processes and are particularly vulnerable to drug toxicity. Drug toxicity studies are classically based on two-dimensional cultures of immortalized proximal tubular cells. Such immortalized cells are dedifferentiated, and lose transport properties (including saturable endocytic uptake) encountered in vivo. Generating differentiated, organotypic human microtissues would potentially alleviate these limitations and facilitate drug toxicity studies. Here, we describe the generation and characterization of kidney microtissues from immortalized (HK-2) and primary (HRPTEpiC) human renal proximal tubular epithelial cells under well-defined conditions. Microtissue cultures were done in hanging drop GravityPLUS™ culture plates and were characterized for morphology, proliferation and differentiation markers, and by monitoring the endocytic uptake of albumin. Kidney microtissues were successfully obtained by co-culturing HK-2 or HRPTEpiC cells with fibroblasts. The HK-2 microtissues formed highly proliferative, but dedifferentiated microtissues within 10 days of culture, while co-culture with fibroblasts yielded spherical structures already after 2 days. Low passage HRPTEpiC microtissues (mono- and co-culture) were less proliferative and expressed tissue-specific differentiation markers. Electron microscopy evidenced epithelial differentiation markers including microvilli, tight junctions, endosomes, and lysosomes in the co-cultured HRPTEpiC microtissues. The co-cultured HRPTEpiC microtissues showed specific uptake of albumin that could be inhibited by cadmium and gentamycin. In conclusion, we established a reliable hanging drop protocol to obtain functional kidney microtissues with proximal tubular epithelial cell lines. These microtissues could be used for high-throughput drug and toxicology screenings, with endocytosis as a functional readout.

Development of a Full-Thickness Human Skin Equivalent In Vitro Model Derived from TERT-Immortalized Keratinocytes and Fibroblasts

Currently, human skin equivalents (HSEs) used for in vitro assays (e.g., for wound healing) make use of primary human skin cells. Limitations of primary keratinocytes and fibroblasts include availability of donor skin and donor variation. The use of physiologically relevant cell lines could solve these limitations. The aim was to develop a fully differentiated HSE constructed entirely from human skin cell lines, which could be applied for in vitro wound-healing assays. Skin equivalents were constructed from human TERT-immortalized keratinocytes and fibroblasts (TERT-HSE) and compared with native skin and primary HSEs. HSEs were characterized by hematoxylin–eosin and immunohistochemical stainings with markers for epidermal proliferation and differentiation, basement membrane (BM), fibroblasts, and the extracellular matrix (ECM). Ultrastructure was determined with electron microscopy. To test the functionality of the TERT-HSE, burn and cold injuries were applied, followed by immunohistochemical stainings, measurement of reepithelialization, and determination of secreted wound-healing mediators. The TERT-HSE was composed of a fully differentiated epidermis and a fibroblast-populated dermis comparable to native skin and primary HSE. The epidermis consisted of proliferating keratinocytes within the basal layer, followed by multiple spinous layers, a granular layer, and cornified layers. Within the TERT-HSE, the membrane junctions such as corneosomes, desmosomes, and hemidesmosomes were well developed as shown by ultrastructure pictures. Furthermore, the BM consisted of a lamina lucida and lamina densa comparable to native skin. The dermal matrix of the TERT-HSE was more similar to native skin than the primary construct, since collagen III, an ECM marker, was present in TERT-HSEs and absent in primary HSEs. After wounding, the TERT-HSE was able to reepithelialize and secrete inflammatory wound-healing mediators. In conclusion, the novel TERT-HSE, constructed entirely from human cell lines, provides an excellent opportunity to study in vitro skin biology and can also be used for drug targeting and testing new therapeutics, and ultimately, for incorporating into skin-on-a chip in the future.

Standardized 3D Bioprinting of Soft Tissue Models with Human Primary Cells

Cells grown in 3D are more physiologically relevant than cells cultured in 2D. To use 3D models in substance testing and regenerative medicine, reproducibility and standardization are important. Bioprinting offers not only automated standardizable processes but also the production of complex tissue-like structures in an additive manner. We developed an all-in-one bioprinting solution to produce soft tissue models. The holistic approach included (1) a bioprinter in a sterile environment, (2) a light-induced bioink polymerization unit, (3) a user-friendly software, (4) the capability to print in standard labware for high-throughput screening, (5) cell-compatible inkjet-based printheads, (6) a cell-compatible ready-to-use BioInk, and (7) standard operating procedures. In a proof-of-concept study, skin as a reference soft tissue model was printed. To produce dermal equivalents, primary human dermal fibroblasts were printed in alternating layers with BioInk and cultured for up to 7 weeks. During long-term cultures, the models were remodeled and fully populated with viable and spreaded fibroblasts. Primary human dermal keratinocytes were seeded on top of dermal equivalents, and epidermis-like structures were formed as verified with hematoxylin and eosin staining and immunostaining. However, a fully stratified epidermis was not achieved. Nevertheless, this is one of the first reports of an integrative bioprinting strategy for industrial routine application.

Genotoxicity assessment of reactive and disperse textile dyes using human dermal equivalent (3D cell culture system)

Thousands of dyes are marketed daily for different purposes, including textile dyeing. However, there are several studies reporting attributing to dyes deleterious human effects such as DNA damage. Humans may be exposed to toxic dyes through either ingestion of contaminated waters or dermal contact with colored garments. With respect to dermal exposure, human skin equivalents are promising tools to assess in vitro genotoxicity of dermally applied chemicals using a three-dimensional (3D) model to mimic tissue behavior. This study investigated the sensitivity of an in-house human dermal equivalent (DE) for detecting genotoxicity of textile dyes. Two azo (reactive green 19 [RG19] and disperse red 1[DR1]) dyes and one anthraquinone (reactive blue 2 [RB2]) dye were analyzed. RG19 was genotoxic for DE in a dose-responsive manner, whereas RB2 and DR1 were nongenotoxic under the conditions tested. These findings are not in agreement with previous genotoxicological assessment of these dyes carried out using two-dimensional (2D) cell cultures, which showed that DR1 was genotoxic in human hepatoma cells (HepG2) and RG19 was nongenotoxic for normal human dermal fibroblasts (NHDF). These discrepant results probably may be due to differences between metabolic activities of each cell type (organ-specific genotoxicity, HepG2 and fibroblasts) and the test setup systems used in each study (fibroblasts cultured at 2D and three-dimensional [3D] culture systems). Genotoxicological assessment of textile dyes in context of organ-specific genotoxicity and using in vitro models that more closely resemble in vivo tissue architecture and physiology may provide more reliable estimates of genotoxic potential of these chemicals.

Construction of the tissue engineering seed cell (HaCaT-EGF) and analysis of its biological characteristics

OBJECTIVE

To construct the tissue engineering seed cell (HaCaT cell line) with stable expression of the human epidermal growth factor (EGF), and analyze the changes of its biological characteristics.

METHODS

PCDNA3.1-EGF eukaryotic expression vector was transferred into HaCaT cell, and G418 was utilized to select the HaCaT-EGF cell line. Using an inverted microscope, PCR, ELISA method to detect the changes of the cell morphology, the expression of the EGF gene and protein, and the mRNA expression levels of apoptosis related molecule Caspase-3, the cell cycle related protein cyclin D1.

RESULTS

The mRNA expression levels of the obtained HaCaT-EGF cell were more than 100 times higher than the level of ordinary HaCaT cell. The colony of the HaCaT-EGF cells was more focused and tight compared to the empty vector transfected HaCaT cells and normal HaCaT cells. The expression levels of apoptotic factor Caspase-3 and cyclin D1 in HaCaT-EGF cell were significantly higher than those in the empty vector HaCaT- pcDNA3.1 cell, and the differences were statistically significant (P<0.01), but there was no significant difference compared to the normal HaCaT cells (P>0.05).

CONCLUSIONS

HaCaT-EGF cell can continuously secrete EGF, and the biological characteristic is stable. It can be used for tissue engineering experiment and is an ideal seed cell for constructing tissue engineered skin.

Abnormally differentiating keratinocytes in the epidermis of systemic sclerosis patients show enhanced secretion of CCN2 and S100A9

Skin involvement with dermal fibrosis is a hallmark of systemic sclerosis (SSc), and keratinocytes may be critical regulators of fibroblast function through secretion of chemo-attracting agents, as well as through growth factors and cytokines influencing the phenotype and proliferation rate of fibroblasts. Epithelial-fibroblast interactions have an important role in fibrosis in general. We have characterized the SSc epidermis and asked whether SSc-injured epidermal cells release factors capable of promoting fibrosis. Our results show that the SSc epidermis is hypertrophic, and has altered expression of terminal differentiation markers involucrin, loricrin, and filaggrin. Multiplex profiling revealed that SSc epidermal explants release increased levels of CCN2 and S100A9. CCN2 induction was found to spread into the upper papillary dermis, whereas S100A9 was shown to induce fibroblast proliferation and to enhance fibroblast CCN2 expression via Toll-like receptor 4. These data suggest that the SSc epidermis provides an important source of pro-fibrotic CCN2 and proinflammatory S100A9 in SSc skin, and therefore contributes to the fibrosis and inflammation seen in the disease.

A comparative analysis of advanced techniques for skin reconstruction with autologous keratinocyte culture in severely burned children: own experience

INTRODUCTION

The local treatment in burns larger than 50% of total body surface area is still the great challenge for surgeons.

AIM

This paper presents a review of different solutions for deep burn wound healing in children and the early outcomes of treatment with combined autologous cell culture technique.

MATERIAL AND METHODS

For this study, 20 children aged between 4 and 12 years with 55-65% of TBSA III grade burn injury were analyzed. A skin sample, 1 cm × 1 cm in size, for keratinocyte cultivation, was taken on the day of the burn. After necrotic tissue excision, the covering of the burned area with an isolated meshed skin graft was carried out between day 4 and 7. After 7 days of keratinocyte cultivation, the mentioned areas were covered with cells from the culture. We divided the burned regions, according to the way of wound closure, into 3 groups each consisting of 15 treated regions of the body. We used meshed split thickness skin grafts (SSG group), cultured autologous keratinocytes (CAC group), and both techniques applied in one stage (SSG + CAC group).

RESULTS

In the SSG group, the mean time for complete closure of wounds was 12.7 days. Wounds treated with CAC only needed a non-significantly longer time to heal - 14.2 days (p = 0.056) when compared to SSG. The shortest time to heal was observed in the group treated with SSG + CAC - 8.5 days, and it was significantly shorter when compared to the SSG and CAC groups (p < 0.001).

CONCLUSIONS

This study suggests that cultured keratinocytes obtained after short-time multiplication, combined with meshed autologous split thickness skin grafts, constitute the optimal wound closure in burned children.

Tissue engineering airway mucosa: a systematic review

OBJECTIVES/HYPOTHESIS

Effective treatments for hollow organ stenosis, scarring, or agenesis are suboptimal or lacking. Tissue-engineered implants may provide a solution, but those performed to date are limited by poor mucosalization after transplantation. We aimed to perform a systematic review of the literature on tissue-engineered airway mucosa. Our objectives were to assess the success of this technology and its potential application to airway regenerative medicine and to determine the direction of future research to maximize its therapeutic and commercial potential.

DATA SOURCES AND REVIEW METHODS

A systematic review of the literature was performed searching Medline (January 1996) and Embase (January 1980) using search terms "tissue engineering" or "tissue" and "engineering" or "tissue engineered" and "mucous membrane" or "mucous" and "membrane" or "mucosa." Original studies utilizing tissue engineering to regenerate airway mucosa within the trachea or the main bronchi in animal models or human studies were included.

RESULTS

A total of 719 papers matched the search criteria, with 17 fulfilling the entry criteria. Of these 17, four investigated mucosal engineering in humans, with the remaining 13 studies investigating mucosal engineering in animal models. The review demonstrated how an intact mucosal layer protects against infection and suggests a role for fibroblasts in facilitating epithelial regeneration in vitro. A range of scaffold materials were used, but no single material was clearly superior to the others.

CONCLUSION

The review highlights gaps in the literature and recommends key directions for future research such as epithelial tracking and the role of the extracellular environment.

Elastin signaling in wound repair

Skin is an important organ to the human body as it functions as an interface between the body and environment. Cutaneous injury elicits a complex wound healing process, which is an orchestration of cells, matrix components, and signaling factors that re-establishes the barrier function of skin. In adults, an unavoidable consequence of wound healing is scar formation. However, in early fetal development, wound healing is scarless. This phenomenon is characterized by an attenuated inflammatory response, differential expression of signaling factors, and regeneration of normal skin architecture. Elastin endows a range of mechanical and cell interactive properties to skin. In adult wound healing, elastin is severely lacking and only a disorganized elastic fiber network is present after scar formation. The inherent properties of elastin make it a desirable inclusion to adult wound healing. Elastin imparts recoil and resistance and induces a range of cell activities, including cell migration and proliferation, matrix synthesis, and protease production. The effects of elastin align with the hallmarks of fetal scarless wound healing. Elastin synthesis is substantial in late stage in utero and drops to a trickle in adults. The physical and cell signaling advantages of elastin in a wound healing context creates a parallel with the innate features of fetal skin that can allow for scarless healing.

Upregulation of IL-6, IL-8 and CXCL-1 production in dermal fibroblasts by normal/malignant epithelial cells in vitro: Immunohistochemical and transcriptomic analyses

BACKGROUND INFORMATION

Considering an analogy between wound healing and tumour progression, we studied chemokine and cytokine transcription and expression in normal fibroblasts by co-culture and in situ.

RESULTS

Whole-genome transcriptome profiling revealed strong upregulation for the interleukin (IL)-6, IL-8 and the chemokine CXCL-1 in in vitro co-cultures of normal fibroblasts with either normal or malignant epithelial cells compared to fibroblast cultures. The same ILs/chemokines were distinctly upregulated in clinical samples of squamous cell carcinoma when compared with paired normal mucosae. Analysis of culture supernatants showed that during the course of co-culture of the fibroblasts with the epithelial cells, IL-6, IL-8 and CXCL-1 were secreted to the culture medium. Experiments with addition of any of the proteins to the culture medium supported the notion that these ILs/chemokines strongly contributed to maintenance of a low-differentiation phenotype of epithelial cells, evaluated by the detection of keratin-8. Simultaneous addition of all factors increased the extent of the effect. These studies were extended by experiments with epithelial cells, either cultured in medium conditioned by preceding use for malignant keratinocytes without and in the presence of normal or cancer-associated fibroblasts or medium containing antibodies against IL-6, IL-8 and CXCL-1.

CONCLUSIONS

Our results indicate an analogy between wound healing and tumour growth, support the importance of epithelial-mesenchymal interaction in this model system and establish a potential bio-inspired anticancer therapy.