Alpha 6 beta 4 integrin heterodimer is a component of hemidesmosomes

Artificial keloid skin models: understanding the pathophysiological mechanisms and application in therapeutic studies

Keloid is a type of scar formed by the overexpression of extracellular matrix substances from fibroblasts following inflammation after trauma. The existing keloid treatment methods include drug injection, surgical intervention, light exposure, cryotherapy, etc. However, these methods have limitations such as recurrence, low treatment efficacy, and side effects. Consequently, studies are being conducted on the treatment of keloids from the perspective of inflammatory mechanisms. In this study, keloid models are created to understand inflammatory mechanisms and explore treatment methods to address them. While previous studies have used animal models with gene mutations, chemical treatments, and keloid tissue transplantation, there are limitations in fully reproducing the characteristics of keloids unique to humans, and ethical issues related to animal welfare pose additional challenges. Consequently, studies are underway to create in vitro artificial skin models to simulate keloid disease and apply them to the development of treatments for skin diseases. In particular, herein, scaffold technologies that implement three-dimensional (3D) full-thickness keloid models are introduced to enhance mechanical properties as well as biological properties of tissues, such as cell proliferation, differentiation, and cellular interactions. It is anticipated that applying these technologies to the production of artificial skin for keloid simulation could contribute to the development of inflammatory keloid treatment techniques in the future.

Integrin Beta 4E Promotes Endothelial Phenotypic Changes and Attenuates Lung Endothelial Cell Inflammatory Responses

We previously reported integrin beta 4 (ITGB4) is an important mediator of lung vascular protection by simvastatin, a 3-hydroxy-3-methylglutaryl-coenzyme A-reductase inhibitor. In this study, we report increased endothelial cell (EC) expression specifically of ITGB4E, an ITGB4 mRNA splice variant, by simvastatin with effects on EC protein expression and inflammatory responses. In initial experiments, human pulmonary artery ECs were treated using simvastatin (5 μM, 24 h) prior to immunoprecipitation of integrin alpha 6 (ITGA6), which associates with ITGB4, and Western blotting for full-length ITGB4 and ITGB4E, uniquely characterized by a truncated 114 amino acid cytoplasmic domain. These experiments confirmed a significant increase in both full-length ITGB4 and ITGB4E. To investigate the effects of increased ITGB4E expression alone, ECs were transfected with ITGB4E or control vector, and cells were seeded in wells containing Matrigel to assess effects on angiogenesis or used for scratch assay to assess migration. Decreased angiogenesis and migration were observed in ITGB4E transfected ECs compared with controls. In separate experiments, PCR and Western blots from transfected cells demonstrated significant changes in EC protein expression associated with increased ITGB4E, including marked decreases in platelet endothelial cell adhesion molecule-1 (PECAM-1) and vascular endothelial-cadherin (VE-cadherin) as well as increased expression of E-cadherin and N-cadherin along with increased expression of the Slug and Snail transcription factors that promote endothelial-to-mesenchymal transition (EndMT). We, then, investigated the functional effects of ITGB4E overexpression on EC inflammatory responses and observed a significant attenuation of lipopolysaccharide (LPS)-induced mitogen-activated protein kinase (MAPK) activation, including decreased phosphorylation of both extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), as well as reduced inflammatory cytokines (IL-6 and IL-8), expressed in the media of EC after either LPS or excessive cyclic stretch (CS). Finally, EC expression-increased ITGB4E demonstrated decreased barrier disruption induced by thrombin as measured by transendothelial electrical resistance. Our data support distinct EC phenotypic changes induced by ITGB4E that are also associated with an attenuation of cellular inflammatory responses. These findings implicate ITGB4E upregulation as an important mediator of lung EC protection by statins and may lead to novel therapeutic strategies for patients with or at risk for acute lung injury (ALI).

Syndecans and Their Synstatins: Targeting an Organizer of Receptor Tyrosine Kinase Signaling at the Cell-Matrix Interface

Receptor tyrosine kinases (RTKs) and integrin matrix receptors have well-established roles in tumor cell proliferation, invasion and survival, often functioning in a coordinated fashion at sites of cell-matrix adhesion. Central to this coordination are syndecans, another class of matrix receptor, that organize RTKs and integrins into functional units, relying on docking motifs in the syndecan extracellular domains to capture and localize RTKs (e.g., EGFR, IGF-1R, VEGFR2, HER2) and integrins (e.g., αvβ3, αvβ5, α4β1, α3β1, α6β4) to sites of adhesion. Peptide mimetics of the docking motifs in the syndecans, called “synstatins”, prevent assembly of these receptor complexes, block their signaling activities and are highly effective against tumor cell invasion and survival and angiogenesis. This review describes our current understanding of these four syndecan-coupled mechanisms and their inhibitory synstatins (SSTN_IGF1R, SSTN_VEGFR2, SSTN_VLA-4, SSTN_EGFR and SSTN_HER2).

Conditional Deletion of AP-2β in the Periocular Mesenchyme of Mice Alters Corneal Epithelial Cell Fate and Stratification

The cornea is an anterior eye structure specialized for vision. The corneal endothelium and stroma are derived from the periocular mesenchyme (POM), which originates from neural crest cells (NCCs), while the stratified corneal epithelium develops from the surface ectoderm. Activating protein-2β (AP-2β) is highly expressed in the POM and important for anterior segment development. Using a mouse model in which AP-2β is conditionally deleted in the NCCs (AP-2β NCC KO), we investigated resulting corneal epithelial abnormalities. Through PAS and IHC staining, we observed structural and phenotypic changes to the epithelium associated with AP-2β deletion. In addition to failure of the mutant epithelium to stratify, we also observed that Keratin-12, a marker of the differentiated epithelium, was absent, and Keratin-15, a limbal and conjunctival marker, was expanded across the central epithelium. Transcription factors PAX6 and P63 were not observed to be differentially expressed between WT and mutant. However, growth factor BMP4 was suppressed in the mutant epithelium. Given the non-NCC origin of the epithelium, we hypothesize that the abnormalities in the AP-2β NCC KO mouse result from changes to regulatory signaling from the POM-derived stroma. Our findings suggest that stromal pathways such as Wnt/β-Catenin signaling may regulate BMP4 expression, which influences cell fate and stratification.

Skin-on-a-chip models: General overview and future perspectives

Over the last few years, several advances have been made toward the development and production of in vitro human skin models for the analysis and testing of cosmetic and pharmaceutical products. However, these skin models are cultured under static conditions that make them unable to accurately represent normal human physiology. Recent interest has focused on the generation of in vitro 3D vascularized skin models with dynamic perfusion and microfluidic devices known as skin-on-a-chip. These platforms have been widely described in the literature as good candidates for tissue modeling, as they enable a more physiological transport of nutrients and permit a high-throughput and less expensive evaluation of drug candidates in terms of toxicity, efficacy, and delivery. In this Perspective, recent advances in these novel platforms for the generation of human skin models under dynamic conditions for in vitro testing are reported. Advances in vascularized human skin equivalents (HSEs), transferred skin-on-a-chip (introduction of a skin biopsy or a HSE in the chip), and in situ skin-on-a-chip (generation of the skin model directly in the chip) are critically reviewed, and currently used methods for the introduction of skin cells in the microfluidic chips are discussed. An outlook on current applications and future directions in this field of research are also presented.

Integrin α2β1 regulates collagen I tethering to modulate hyperresponsiveness in reactive airway disease models

Severe asthma remains challenging to manage and has limited treatment options. We have previously shown that targeting smooth muscle integrin α5β1 interaction with fibronectin can mitigate the effects of airway hyperresponsiveness by impairing force transmission. In this study, we show that another member of the integrin superfamily, integrin α2β1, is present in airway smooth muscle and capable of regulating force transmission via cellular tethering to the matrix protein collagen I and, to a lesser degree, laminin-111. The addition of an inhibitor of integrin α2β1 impaired IL-13-enhanced contraction in mouse tracheal rings and human bronchial rings and abrogated the exaggerated bronchoconstriction induced by allergen sensitization and challenge. We confirmed that this effect was not due to alterations in classic intracellular myosin light chain phosphorylation regulating muscle shortening. Although IL-13 did not affect surface expression of α2β1, it did increase α2β1-mediated adhesion and the level of expression of an activation-specific epitope on the β1 subunit. We developed a method to simultaneously quantify airway narrowing and muscle shortening using 2-photon microscopy and demonstrated that inhibition of α2β1 mitigated IL-13-enhanced airway narrowing without altering muscle shortening by impairing the tethering of muscle to the surrounding matrix. Our data identified cell matrix tethering as an attractive therapeutic target to mitigate the severity of airway contraction in asthma.

Single-keratinocyte transcriptomic analyses identify different clonal types and proliferative potential mediated by FOXM1 in human epidermal stem cells

Autologous epidermal cultures restore a functional epidermis on burned patients. Transgenic epidermal grafts do so also in genetic skin diseases such as Junctional Epidermolysis Bullosa. Clinical success strictly requires an adequate number of epidermal stem cells, detected as holoclone-forming cells, which can be only partially distinguished from the other clonogenic keratinocytes and cannot be prospectively isolated. Here we report that single-cell transcriptome analysis of primary human epidermal cultures identifies categories of genes clearly distinguishing the different keratinocyte clonal types, which are hierarchically organized along a continuous, mainly linear trajectory showing that stem cells sequentially generate progenitors producing terminally differentiated cells. Holoclone-forming cells display stem cell hallmarks as genes regulating DNA repair, chromosome segregation, spindle organization and telomerase activity. Finally, we identify FOXM1 as a YAP-dependent key regulator of epidermal stem cells. These findings improve criteria for measuring stem cells in epidermal cultures, which is an essential feature of the graft.

Steroid hormones and human choriogonadotropin influence the distribution of alpha6-integrin and desmoplakin 1 in gland-like endometrial epithelial spheroids

In human glandular endometrial epithelial cells, desmosomal and adherens junction proteins have been shown to extend from a subapically restricted lateral position to the entire lateral membrane during the implantation window of the menstrual cycle. Similarly, a menstrual cycle stage-dependent redistribution of the extracellular matrix adhesion protein α6-integrin has been reported. These changes are believed to be important for endometrial receptiveness and successful embryo implantation. To prove the hypothesis that steroid hormones and human choriogonadotropin can induce the redistribution of these adhesion molecules, we used the human endometrial cell line Ishikawa in a 3D culture system. Gland-like spheroids were grown in reconstituted basement membrane (Matrigel™). The lumen-bearing spheroids were treated for 2 or 4 days with ovarian steroids or human choriogonadotropin and then assessed by immunofluorescence microscopy. In addition, human endometrial biopsies were obtained from patients, who were in therapy for assisted reproductive technology, and were examined in parallel. Lateral redistribution of the desmosomal plaque protein desmoplakin 1 was observed in the spheroids treated either with progesterone, medroxyprogesterone acetate or human choriogonadotropin. Furthermore, the extracellular matrix adhesion protein α6-integrin showed an increased lateral membrane localization upon gestagen stimulation in the 3D culture system. The results of this study demonstrate that the 3D endometrial Ishikawa cell culture might be suited as an experimental model system to prove the effect of hormonal changes like those occurring during the window of implantation.

Corneal Epithelial "Neuromas": A Case of Mistaken Identity?

Laser scanning in vivo confocal microscopy is a useful clinical tool to assess the corneal nerves in human and laboratory animals. With this new technology, the use of terms such as “neuromas” and “microneuromas” is becoming popular to describe nerve structures seen in humans. Here, we point out that the sites where stromal nerves enter the corneal epithelium are often hyperreflective and can appear dysmorphic when imaged using in vivo confocal microscopy. Furthermore, we clarify what is known anatomically about how the nerves enter the corneal epithelium from the stroma, and we urge colleagues to differentiate between hyperreflective foci at the corneal stromal–epithelial nerve penetration sites and alterations in nerve morphology secondary to injury or disease.

Protein tyrosine phosphatases in cell adhesion

Adhesive structures between cells and with the surrounding matrix are essential for the development of multicellular organisms. In addition to providing mechanical integrity, they are key signalling centres providing feedback on the extracellular environment to the cell interior, and vice versa. During development, mitosis and repair, cell adhesions must undergo extensive remodelling. Post-translational modifications of proteins within these complexes serve as switches for activity. Tyrosine phosphorylation is an important modification in cell adhesion that is dynamically regulated by the protein tyrosine phosphatases (PTPs) and protein tyrosine kinases. Several PTPs are implicated in the assembly and maintenance of cell adhesions, however, their signalling functions remain poorly defined. The PTPs can act by directly dephosphorylating adhesive complex components or function as scaffolds. In this review, we will focus on human PTPs and discuss their individual roles in major adhesion complexes, as well as Hippo signalling. We have collated PTP interactome and cell adhesome datasets, which reveal extensive connections between PTPs and cell adhesions that are relatively unexplored. Finally, we reflect on the dysregulation of PTPs and cell adhesions in disease.

Ultraviolet Light Treatment of Titanium Enhances Attachment, Adhesion, and Retention of Human Oral Epithelial Cells via Decarbonization

Early establishment of soft-tissue adhesion and seal at the transmucosal and transcutaneous surface of implants is crucial to prevent infection and ensure the long-term stability and function of implants. Herein, we tested the hypothesis that treatment of titanium with ultraviolet (UV) light would enhance its interaction with epithelial cells. X-ray spectroscopy showed that UV treatment significantly reduced the atomic percentage of surface carbon on titanium from 46.1% to 28.6%. Peak fitting analysis revealed that, among the known adventitious carbon contaminants, C-C and C=O groups were significantly reduced after UV treatment, while other groups were increased or unchanged in percentage. UV-treated titanium attracted higher numbers of human epithelial cells than untreated titanium and allowed more rapid cell spread. Hemi-desmosome-related molecules, integrin β4 and laminin-5, were upregulated at the gene and protein levels in the cells on UV-treated surfaces. The result of the detachment test revealed twice as many cells remaining adherent on UV-treated than untreated titanium. The enhanced cellular affinity of UV-treated titanium was equivalent to laminin-5 coating of titanium. These data indicated that UV treatment of titanium enhanced the attachment, adhesion, and retention of human epithelial cells associated with disproportional removal of adventitious carbon contamination, providing a new strategy to improve soft-tissue integration with implant devices.

Localization of Integrin Beta-4 Subunit at Soft Tissue-Titanium or Zirconia Interface

Currently, along with titanium (Ti), zirconia is widely used as an abutment material for dental implants because it makes it possible to avoid gingival discoloration; however, the epithelial sealing capability of zirconia remains unknown. The purpose of the present study is to elucidate the localization of integrin β4 subunit (Inβ4), one of the main proteins in the attachment structure between gingival junctional epithelial (JE) cells and substrata. Maxillary first molars were extracted from rats, and implants were placed with Ti or zirconia transgingival parts; then, the localization of Inβ4 was observed. Morphological and functional changes in rat oral epithelial cells (OECs) cultured on a culture dish (Dish) and Ti and zirconia plates were also evaluated with Inβ4 immunofluorescence histochemistry and Western blotting. After four weeks of implant placement, the morphology of the peri-implant epithelium (PIE) and the localization of Inβ4 around the Ti and zirconia transgingival parts were similar. However, both exhibited markedly shorter Inβ4-positive bands in the PIE than in the JE around natural teeth. Decreased expression levels of Inβ4 were observed in OECs cultured on Ti and zirconia plates compared with those cultured on Dish. In conclusion, although inferior to natural teeth, zirconia implants are thought to have epithelial sealing properties comparable to those of titanium.

Integrin: Basement membrane adhesion by corneal epithelial and endothelial cells

Integrins mediate adhesion of cells to substrates and maintain tissue integrity by facilitating mechanotransduction between cells, the extracellular matrix, and gene expression in the nucleus. Changes in integrin expression in corneal epithelial cells and corneal endothelial cells impacts their adhesion to the epithelial basement membrane (EpBM) and Descemet's membrane, respectively. Integrins also play roles in assembly of basement membranes by both activating TGFβ1 and other growth factors. Over the past two decades, this knowledge has been translated into methods to grow corneal epithelial and endothelial cells in vitro for transplantation in the clinic thereby transforming clinical practice and quality of life for patients. Current knowledge on the expression and function of the integrins that mediate adhesion to the basement membrane expressed by corneal epithelial and endothelial cells in health and disease is summarized. This is the first review to discuss similarities and differences in the integrins expressed by both cell types.

Axonal debris accumulates in corneal epithelial cells after intraepithelial corneal nerves are damaged: A focused Ion Beam Scanning Electron Microscopy (FIB-SEM) study

The intraepithelial corneal nerves (ICNs) that innervate the corneal epithelium are maintained through interactions with corneal epithelial cells and the extracellular matrix they produce. One to several axons bundle together within the basal cell layer and extend parallel to the ocular surface or branch and extend apically. Here we use 3-dimentional (3D) ultrastructural reconstructions of control and trephine injured mouse corneal epithelium and stroma produced using Focused Ion Beam Scanning Electron Microscope (FIB-SEM) to determine whether corneal epithelial or immune cells resident in the epithelium remove axonal debris and degrade it in their lysosomes after trephine injury to the cornea. We demonstrate that axonal fragments are internalized in the corneal epithelium and accumulate within electron dense structures consistent with lysosomes 3 h after trephine injury in both epithelial and immune cells located among the basal cells of the trephine injured cornea. Confocal imaging showed fewer CD45⁺ immune cells within the corneal epithelium after trephine injury compared to controls. The resolution obtained using FIB-SEM also allowed us to show that the presence of sensory axons at the basal aspect of the epithelial basal cells close to the anterior aspect of the epithelial basement membrane (EBM) is associated with a focal reduction in EBM thickness. In addition, we show using FIB-SEM and confocal imaging that superficial trephine injuries that do not penetrate the stroma, damage the integrity of anterior stromal nerves. These studies are the first to look at the mouse cornea following nerve injury using FIB-SEM.

Influence of Vitamin D on Corneal Epithelial Cell Desmosomes and Hemidesmosomes

Purpose

We have observed noticably weak epithelial attachment in vitamin D receptor knockout mice (VDR KO) undergoing epithelial debridement. We hypothesized that VDR KO negatively affects corneal epithelial cell desmosomes and/or hemidesmosomes.

Methods

Transcript levels of desmosome and hemidesmosome proteins in VDR KO corneas were assessed by qPCR. Western blotting and immunochemistry were used to detect proteins in cultured cells exposed to 1,25(OH)₂D3 and 24R,25(OH)₂D3.

Results

VDR KO resulted in decreased corneal desmosomal desmoglein 1 (DSG1) and desmocollin 2 (DSC2) mRNA, and hemidesmosomal plectin mRNA. DSG1 and plectin protein expression were reduced in VDR KO corneas. DSG1 protein expression increased in VDR wild types (VDR WT) and VDR KO mouse primary epithelial cells (MPCEC) treated with 1,25(OH)₂D3 and 24R,25(OH)₂D3. 24R,25(OH)₂D3 treatment resulted in increased plectin and integrin β4 levels in VDR WT MPCEC, and decreased levels in VDR KO MPCEC. Treatment of human corneal epithelial cells (HCEC) with 1,25(OH)₂D3 and 24R,25(OH)₂D3 resulted in increased DSC2 and DSG1 protein expression. Plectin and integrin β4 were only increased in 24R,25(OH)₂D3 treated HCEC.

Conclusions

VDR KO results in reduced desmosomal and hemidesmosomal mRNA and protein levels. 1,25(OH)₂D3 and 24R,25(OH)₂D3 increased DSG1 protein in all cells tested. For hemidesmosome proteins, 24R,25(OH)₂D3 increased plectin and integrin β4 protein expression in VDR WT and HCEC, with decreased expression in VDR KO MPCEC. Thus, vitamin D3 is involved in desmosome and hemidesmosome junction formation/regulation, and their decreased expression likely contributes to the loosely adherent corneal epithelium in VDR KO mice. Our data indicate the presence of a VDR-independent pathway.

Alveolar progenitor cells in the mammary gland are dependent on the β4 integrin

Understanding how progenitor cell function is regulated in the mammary gland is an important developmental problem that has significant implications for breast cancer. Although it had been assumed that the expression the α6β4 integrin (β4) is restricted to the basal lineage, we report that alveolar progenitor cells in the mouse mammary gland also express this integrin based on analysis of single cell RNA-Seq data. Subsequent experiments using a mouse mammary epithelial cell line (NMuMG) confirmed this finding and revealed that β4 is essential for maintaining progenitor function as assessed by serial passage mammosphere assays. These data were substantiated by analyzing the alveolar progenitor population isolated from nulliparous mouse mammary glands. Based on the finding that the alveolar progenitor cells express Whey Acidic Protein (WAP), WAP-Cre mice were crossed with itgβ4^flox/flox mice to generate conditional knock-out of β4 in alveolar progenitor cells. These itgβ4^flox/floxWAP-Cre⁺ mice exhibited significant defects in alveologenesis and milk production during pregnancy compared to itgβ4^flox/floxWAP-Cre^- mice, establishing a novel role for the β4 integrin in alveolar progenitor function and alveologenesis.

Living with Keratinocytes

A feature distinguishing human hematopoietic and epithelial stem cells from other equally fascinating stem cells is perhaps their easier translation into a clinical setting. We have devoted nearly our entire scientific career in trying to turn our understanding of epithelial stem cell biology into something that could help people suffering from virtually untreatable diseases of squamous epithelia. We have done that as a team, together with our numerous students, postdocs, technicians and valuable collaborators, clinicians, regulators, and, lately, industrial partners. We had rewarding successes and burning failures, but we always did our best. This award, given by friends and colleagues deserving it more than us, has been the most important recognition of our work. Below, we summarize our story.

Stem cell therapy for chronic skin wounds in the era of personalized medicine: From bench to bedside

With the significant financial burden of chronic cutaneous wounds on the healthcare system, not to the personal burden mention on those individuals afflicted, it has become increasingly essential to improve our clinical treatments. This requires the translation of the most recent benchtop approaches to clinical wound repair as our current treatment modalities have proven insufficient. The most promising potential treatment options rely on stem cell-based therapies. Stem cell proliferation and signaling play crucial roles in every phase of the wound healing process and chronic wounds are often associated with impaired stem cell function. Clinical approaches involving stem cells could thus be utilized in some cases to improve a body's inhibited healing capacity. We aim to present the laboratory research behind the mechanisms and effects of this technology as well as current clinical trials which showcase their therapeutic potential. Given the current problems and complications presented by chronic wounds, we hope to show that developing the clinical applications of stem cell therapies is the rational next step in improving wound care.

Laminin 332-Dependent YAP Dysregulation Depletes Epidermal Stem Cells in Junctional Epidermolysis Bullosa

Laminin 332-deficient junctional epidermolysis bullosa (JEB) is a severe genetic skin disease. JEB is marked by epidermal stem cell depletion, the origin of which is unknown. We show that dysregulation of the YAP and TAZ pathway underpins such stem cell depletion. Laminin 332-mediated YAP activity sustains human epidermal stem cells, detected as holoclones. Ablation of YAP selectively depletes holoclones, while enforced YAP blocks conversion of stem cells into progenitors and indefinitely extends the keratinocyte lifespan. YAP is dramatically decreased in JEB keratinocytes, which contain only phosphorylated, inactive YAP. In normal keratinocytes, laminin 332 and α6β4 ablation abolish YAP activity and recapitulate the JEB phenotype. In JEB keratinocytes, laminin 332-gene therapy rescues YAP activity and epidermal stem cells in vitro and in vivo. In JEB cells, enforced YAP recapitulates laminin 332-gene therapy, thus uncoupling adhesion from proliferation in epidermal stem cells. This work has important clinical implication for ex vivo gene therapy of JEB.

Fibrosis: Shared Lessons From the Lens and Cornea

Regenerative repair in response to wounding involves cell proliferation and migration. This is followed by the reestablishment of cell structure and organization and a dynamic process of remodeling and restoration of the injured cells' extracellular matrix microenvironment and the integration of the newly synthesized matrix into the surrounding tissue. Fibrosis in the lungs, liver, and heart can lead to loss of life and in the eye to loss of vision. Learning to control fibrosis and restore normal tissue function after injury repair remains a goal of research in this area. Here we use knowledge gained using the lens and the cornea to provide insight into how fibrosis develops and clues to how it can be controlled. The lens and cornea are less complex than other tissues that develop life‐threatening fibrosis, but they are well characterized and research using them as model systems to study fibrosis is leading toward an improved understanding of fibrosis. Here we summarize the current state of the literature and how it is leading to promising new treatments. Anat Rec, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Integrin α6 as an invasiveness marker for hepatitis B viral X-driven hepatocellular carcinoma

BACKGROUND

Hepatitis B virus (HBV) accounts for more than 60% of hepatocellular carcinoma (HCC) cases. However, there is limited information about the features of HBV-driven HCC that differentiate it from other types of HCC.

OBJECTIVE

The aim of this study is to find a gene specific to HBV-driven HCC and understand its role during tumorigenesis.

METHODS

The differences in gene expression patterns were analyzed among patients with hepatitis virus-unrelated liver cirrhosis, and hepatitis C virus- and HBV-driven HCC. Genes expressed only in HBV patients were compared to genes of transgenic mice expressing hepatitis B viral X gene.

RESULTS

Integrin α6 was commonly overexpressed in both HBV-driven HCC patients and transgenic mice expressing viral X. This gene's activation induced overexpression of integrin α6, as well as formation of integrins α6β1 and α6β4, without changing the expression of non-integrin laminin receptors. Suppression of integrin α6 caused significant inhibition of tumor migration in vitro.

CONCLUSIONS

This study found a significant association between HBV and integrin α6, which may be responsible for early migration and invasion of HCC. Thus, integrin α6 is a predictive marker for tumor recurrence and invasiveness of HBV-driven HCC.

EphA2/Ephrin-A1 Mediate Corneal Epithelial Cell Compartmentalization via ADAM10 Regulation of EGFR Signaling

Purpose

Progenitor cells of the limbal epithelium reside in a discrete area peripheral to the more differentiated corneal epithelium and maintain tissue homeostasis. What regulates the limbal-corneal epithelial boundary is a major unanswered question. Ephrin-A1 ligand is enriched in the limbal epithelium, whereas EphA2 receptor is concentrated in the corneal epithelium. This reciprocal pattern led us to assess the role of ephrin-A1 and EphA2 in limbal-corneal epithelial boundary organization.

Methods

EphA2-expressing corneal epithelial cells engineered to express ephrin-A1 were used to study boundary formation in vitro in a manner that mimicked the relative abundance of these juxtamembrane signaling proteins in the limbal and corneal epithelium in vivo. Interaction of these two distinct cell populations following initial seeding into discrete culture compartments was assessed by live cell imaging. Immunofluoresence and immunoblotting was used to evaluate the contribution of downstream growth factor signaling and cell-cell adhesion systems to boundary formation at sites of heterotypic contact between ephrin-A1 and EphA2 expressing cells.

Results

Ephrin-A1-expressing cells impeded and reversed the migration of EphA2-expressing corneal epithelial cells upon heterotypic contact formation leading to coordinated migration of the two cell populations in the direction of an ephrin-A1-expressing leading front. Genetic silencing and pharmacologic inhibitor studies demonstrated that the ability of ephrin-A1 to direct migration of EphA2-expressing cells depended on an a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) and epidermal growth factor receptor (EGFR) signaling pathway that limited E-cadherin-mediated adhesion at heterotypic boundaries.

Conclusions

Ephrin-A1/EphA2 signaling complexes play a key role in limbal-corneal epithelial compartmentalization and the response of these tissues to injury.

α6-Integrin alternative splicing: distinct cytoplasmic variants in stem cell fate specification and niche interaction

α6-Integrin subunit (also known as CD49f) is a stemness signature that has been found on the plasma membrane of more than 30 stem cell populations. A growing body of studies have focused on the critical role of α6-containing integrins (α6β1 and α6β4) in the regulation of stem cell properties, lineage-specific differentiation, and niche interaction. α6-Integrin subunit can be alternatively spliced at the post-transcriptional level, giving rise to divergent isoforms which differ in the cytoplasmic and/or extracellular domains. The cytoplasmic domain of integrins is an important functional part of integrin-mediated signals. Structural changes in the cytoplasmic domain of α6 provide an efficient means for the regulation of stem cell responses to biochemical stimuli and/or biophysical cues in the stem cell niche, thus impacting stem cell fate determination. In this review, we summarize the current knowledge on the structural variants of the α6-integrin subunit and spatiotemporal expression of α6 cytoplasmic variants in embryonic and adult stem/progenitor cells. We highlight the roles of α6 cytoplasmic variants in stem cell fate decision and niche interaction, and discuss the potential mechanisms involved. Understanding of the distinct functions of α6 splicing variants in stem cell biology may inform the rational design of novel stem cell-based therapies for a range of human diseases.

The influence of systemically or locally administered mesenchymal stem cells on tissue repair in a rat oral implantation model

BACKGROUND

Multipotent mesenchymal stem cells (MSCs) are used clinically in regenerative medicine. Our previous report showed systemically injected MSCs improved peri-implant sealing and accelerated tissue healing. However, the risks of systemic MSC administration, including lung embolism, must be considered; therefore, their local application must be assessed for clinical safety and efficacy. We investigated differences in treatment effect between local and systemic MSC application using a rat oral implantation model.

METHODS

Rat bone marrow-derived MSCs were isolated and culture-expanded. The rat's right maxillary first molars were extracted and replaced with experimental titanium implants. After 24 h, MSCs (1 × 106/ml) were systemically or locally injected into recipient rats via the tail vein (systemic group) or buccal subcutaneous tissue (local group), respectively. Rats treated in the absence of MSCs were included as a control (control group). The maxillary epithelium was assessed histologically after 4 weeks to evaluate laminin-332 (Ln-332) distribution and horseradish peroxidase invasion, as indicators of peri-implant epithelium (PIE) formation and PIE sealing to the implant surface, respectively. The effect of MSCs on rat oral epithelial cell (OEC) morphology was determined by coculture.

RESULTS

Systemic group MSCs accumulated early at the peri-implant mucosa, while local group MSCs were observed in various organs prior to later accumulation around the implant surface. PIE formation and Ln-332-positive staining at the implant interface were enhanced in the systemic group compared with the local and control groups. Furthermore, OEC adherence on implants was reduced in high-density compared with low-density MSC cocultures.

CONCLUSIONS

Local MSC injection was more ineffective than systemic MSC injection at enhancing PIE sealing around titanium implants. Thus, although local MSC administration has a wide range of applications, further investigations are needed to understand the exact cellular and molecular mechanisms of this approach prior to clinical use.

The molecules in the corneal basement membrane zone affected by mustard exposure suggest potential therapies

Mustard exposures result in epithelial-stromal separations in the cornea and epidermal-dermal separations in the skin. Large blisters often manifest in skin, while the cornea develops microblisters, and, when enough form, the epithelium sloughs. If the exposure is severe, healing can be imperfect and can result in long-term adverse consequences. For the cornea, this could manifest as recurrent corneal erosions. Since the corneal epithelial-stromal separations are in the region identified by electron microscopy as the lamina lucida, the same region affected by the blistering disease junctional epidermolysis bullosa (JEB), we postulated that the molecules that are defective in JEB would be the same ones cleaved by mustard compounds. These molecules are α6β4 integrin and collagen XVII, which can be cleaved by matrix metalloproteinase-9 (MMP-9) and ADAM17, respectively. Therefore, our laboratory has tested MMP-9 and ADAM17 inhibitors as potential therapies to attenuate corneal mustard injury. Our results demonstrated that inhibiting MMP-9 and ADAM17 resulted in less epithelial-stromal separation in the corneas at 24 h postexposure, as compared with using only medium as a therapy.

The Integrins Involved in Soybean Agglutinin-Induced Cell Cycle Alterations in IPEC-J2

Soybean agglutinin (SBA) is an anti-nutritional factor of soybean, affecting cell proliferation and inducing cytotoxicity. Integrins are transmembrane receptors, mediating a variety of cell biological processes. This research aims to study the effects of SBA on cell proliferation and cell cycle progression of the intestinal epithelial cell line from piglets (IPEC-J2), to identify the integrin subunits especially expressed in IPEC-J2s, and to analyze the functions of these integrins on IPEC-J2 cell cycle progression and SBA-induced IPEC-J2 cell cycle alteration. The results showed that SBA lowered cell proliferation rate as the cell cycle progression from G0/G1 to S phase (P < 0.05) was inhibited. Moreover, SBA lowered mRNA expression of cell cycle-related gene CDK4, Cyclin E and Cyclin D1 (P < 0.05). We successfully identified integrins α2, α3, α6, β1, and β4 in IPEC-J2s. These five subunits were crucial to maintain normal cell proliferation and cell cycle progression in IPEC-J2s. Restrain of either these five subunits by their inhibitors, lowered cell proliferation rate, and arrested the cells at G0/G1 phase of cell cycle (P < 0.05). Further analysis indicated that integrin α2, α6, and β1 were involved in the blocking of G0/G1 phase induced by SBA. In conclusion, these results suggested that SBA lowered the IPEC-J2 cell proliferation rate through the perturbation of cell cycle progression. Furthermore, integrins were important for IPEC-J2 cell cycle progression, and they were involved in the process of SBA-induced cell cycle progression alteration, which provide a basis for further revealing SBA anti-proliferation and anti-nutritional mechanism.

Corneal epithelial cells function as surrogate Schwann cells for their sensory nerves

The eye is innervated by neurons derived from both the central nervous system and peripheral nervous system (PNS). While much is known about retinal neurobiology and phototransduction, less attention has been paid to the innervation of the eye by the PNS and the roles it plays in maintaining a functioning visual system. The ophthalmic branch of the trigeminal ganglion contains somas of neurons that innervate the cornea. These nerves provide sensory functions for the cornea and are referred to as intraepithelial corneal nerves (ICNs) consisting of subbasal nerves and their associated intraepithelial nerve terminals. ICNs project for several millimeters within the corneal epithelium without Schwann cell support. Here, we present evidence for the hypothesis that corneal epithelial cells function as glial cells to support the ICNs. Much of the data supporting this hypothesis is derived from studies of corneal development and the reinnervation of the ICNs in the rodent and rabbit cornea after superficial wounds. Corneal epithelial cells activate in response to injury via mechanisms similar to those induced in Schwann cells during Wallerian Degeneration. Corneal epithelial cells phagocytize distal axon fragments within hours of ICN crush wounds. During aging, the proteins, lipids, and mitochondria within the ICNs become damaged in a process exacerbated by UV light. We propose that ICNs shed their aged and damaged termini and continuously elongate to maintain their density. Available evidence points to new unexpected roles for corneal epithelial cells functioning as surrogate Schwann cells for the ICNs during homeostasis and in response to injury. GLIA 2017;65:851-863.

Heparanase Inhibitors Facilitate the Assembly of the Basement Membrane in Artificial Skin

Recent research suggests that the basement membrane at the dermal-epidermal junction of the skin plays an important role in maintaining a healthy epidermis and dermis, and repeated damage to the skin can destabilize the skin and accelerate the aging process. Skin-equivalent models are suitable for studying the reconstruction of the basement membrane and its contribution to epidermal homeostasis because they lack the basement membrane and show abnormal expression of epidermal differentiation markers. By using these models, it has been shown that reconstruction of the basement membrane is enhanced not only by supplying basement membrane components, but also by inhibiting proteinases such as urokinase and matrix metalloproteinase. Although matrix metalloproteinase inhibitors assist in the reconstruction of the basement membrane structure, their action is not sufficient to promote its functional recovery. However, heparanase inhibitors stabilize the heparan sulfate chains of perlecan (a heparan sulfate proteoglycan) and promote the regulation of heparan sulfate binding growth factors in the basement membrane. Heparan sulfate promotes effective protein-protein interactions, thereby facilitating the assembly of type VII collagen anchoring fibrils and elastin-associated microfibrils. Using both matrix metalloproteinase inhibitors and heparanase inhibitors, the basement membrane in a skin-equivalent model comes close to recapitulating the structure and function of an in vivo basement membrane. Therefore, by using an appropriate dermis model and suitable protease inhibitors, it may be possible to produce skin-equivalent models that are more similar to natural skin

Elevated integrin α6β4 expression is associated with venous invasion and decreased overall survival in non-small cell lung cancer

Lung cancer carries a poor prognosis and is the most common cause of cancer-related death worldwide. The integrin α6β4, a laminin receptor, promotes carcinoma progression in part by cooperating with various growth factor receptors to facilitate invasion and metastasis. In carcinoma cells with mutant TP53, the integrin α6β4 promotes cell survival. TP53 mutations and integrin α6β4 overexpression co-occur in many aggressive malignancies. Because of the high frequency of TP53 mutations in lung squamous cell carcinoma (SCC), we sought to investigate the association of integrin β4 expression with clinicopathologic features and survival in non-small cell lung cancer (NSCLC). We constructed a lung cancer tissue microarray and stained sections for integrin β4 subunit expression using immunohistochemistry. We found that integrin β4 expression is elevated in SCC compared with adenocarcinoma (P<.0001), which was confirmed in external gene expression data sets (P<.0001). We also determined that integrin β4 overexpression associates with the presence of venous invasion (P=.0048) and with reduced overall patient survival (hazard ratio, 1.46; 95% confidence interval, 1.01-2.09; P=.0422). Elevated integrin β4 expression was also shown to associate with reduced overall survival in lung cancer gene expression data sets (hazard ratio, 1.49; 95% confidence interval, 1.31-1.69; P<.0001). Using cBioPortal, we generated a network map demonstrating the 50 most highly altered genes neighboring ITGB4 in SCC, which included laminins, collagens, CD151, genes in the EGFR and PI3K pathways, and other known signaling partners. In conclusion, we demonstrate that integrin β4 is overexpressed in NSCLC where it is an adverse prognostic marker.

Biocompatibility of a fish scale-derived artificial cornea: Cytotoxicity, cellular adhesion and phenotype, and in vivo immunogenicity

PURPOSE

To determine whether a fish scale-derived collagen matrix (FSCM) meets the basic criteria to serve as an artificial cornea, as determined with in vitro and in vivo tests.

METHODS

Primary corneal epithelial and stromal cells were obtained from human donor corneas and used to examine the (in)direct cytotoxicity effects of the scaffold. Cytotoxicity was assessed by an MTT assay, while cellular proliferation, corneal cell phenotype and adhesion markers were assessed using an EdU-assay and immunofluorescence. For in vivo-testing, FSCMs were implanted subcutaneously in rats. Ologen(®) Collagen Matrices were used as controls. A second implant was implanted as an immunological challenge. The FSCM was implanted in a corneal pocket of seven New Zealand White rabbits, and compared to sham surgery.

RESULTS

The FSCM was used as a scaffold to grow corneal epithelial and stromal cells, and displayed no cytotoxicity to these cells. Corneal epithelial cells displayed their normal phenotypical markers (CK3/12 and E-cadherin), as well as cell-matrix adhesion molecules: integrin-α6 and β4, laminin 332, and hemi-desmosomes. Corneal stromal cells similarly expressed adhesion molecules (integrin-α6 and β1). A subcutaneous implant of the FSCM in rats did not induce inflammation or sensitization; the response was comparable to the response against the Ologen(®) Collagen Matrix. Implantation of the FSCM in a corneal stromal pocket in rabbits led to a transparent cornea, healthy epithelium, and, on histology, hardly any infiltrating immune cells.

CONCLUSION

The FSCM allows excellent cell growth, is not immunogenic and is well-tolerated in the cornea, and thus meets the basic criteria to serve as a scaffold to reconstitute the cornea.

Partial denervation of sub-basal axons persists following debridement wounds to the mouse cornea

Although sensory reinnervation occurs after injury in the peripheral nervous system, poor reinnervation in the elderly and those with diabetes often leads to pathology. Here we quantify sub-basal axon density in the central and peripheral mouse cornea over time after three different types of injury. The mouse cornea is highly innervated with a dense array of sub-basal nerves that form a spiral called the vortex at the corneal center or apex; these nerves are readily detected within flat mounted corneas. After anesthesia, corneal epithelial cells were removed using either a dulled blade or a rotating burr within an area demarcated centrally with a 1.5 mm trephine. A third wound type, superficial trephination, involved demarcating the area with the 1.5 mm trephine but not removing cells. By 7 days after superficial trephination, sub-basal axon density returns to control levels; by 28 days the vortex reforms. Although axon density is similar to control 14 days after dulled blade and rotating burr wounding, defects in axon morphology at the corneal apex remain. After 14 days, axons retract from the center leaving the sub-basal axon density reduced by 37.2 and 36.8% at 28 days after dulled blade and rotating burr wounding, respectively, compared with control. Assessment of inflammation using flow cytometry shows that persistent inflammation is not a factor in the incomplete reinnervation. Expression of mRNAs encoding 22 regeneration-associated genes involved in axon targeting assessed by QPCR reveals that netrin-1 and ephrin signaling are altered after wounding. Subpopulations of corneal epithelial basal cells at the corneal apex stop expressing ki67 as early as 7 days after injury and by 14 and 28 days after wounding, many of these basal cells undergo apoptosis and die. Although sub-basal axons are restored to their normal density and morphology after superficial trephination, sub-basal axon recovery is partial after debridement wounds. The increase in corneal epithelial basal cell apoptosis at the apex observed at 14 days after corneal debridement may destabilize newly reinnervated sub-basal axons and lead to their retraction toward the periphery.

Cell Adhesion Molecules and Stem Cell-Niche-Interactions in the Limbal Stem Cell Niche

Interactions between stem cells and their microenvironment are critical for regulation and maintenance of stem cell function. To elucidate the molecular interactions within the human limbal epithelial stem/progenitor cell (LEPC) niche, which is essential for maintaining corneal transparency and vision, we performed a comprehensive expression analysis of cell adhesion molecules (CAMs) using custom-made quantitative real-time polymerase chain reaction (qRT-PCR) arrays and laser capture-microdissected LEPC clusters, comprising LEPCs, melanocytes, mesenchymal cells, and transmigrating immune cells. We show that LEPCs are anchored to their supporting basement membrane by the laminin receptors α3β1 and α6β4 integrin and the dystroglycan complex, while intercellular contacts between LEPCs and melanocytes are mediated by N-, P-, and E-cadherin together with L1-CAM, a member of the immunoglobulin superfamily (Ig)CAMs. In addition to the LEPC-associated heparan sulfate proteoglycans syndecan-2, glypican-3, and glypican-4, the IgCAM members ICAM-1 and VCAM-1 were found to be variably expressed on LEPCs and associated niche cells and to be dynamically regulated in response to chemokines such as interferon-γ to enhance interactions with immune cells. Moreover, junctional adhesion molecule JAM-C accumulating in the subepithelial limbal matrix, appeared to be involved in recruitment of immune cells, while mesenchymal stromal cells appeared to use the nephronectin receptor integrin α8 for approaching the limbal basement membrane. In summary, we identified a novel combination of cell surface receptors that may regulate both stable and dynamic cell-matrix and cell-cell interactions within the limbal niche. The findings provide a solid foundation for further functional studies and for advancement of our current therapeutic strategies for ocular surface reconstruction.

Corneal Epithelial Wound Healing

The cornea is important for a clear vision by refracting light onto the lens, which in turn focusing on the retina. To maintain a smooth optical surface, corneal epithelium has to continuously renew itself to function as a barrier so that it protects the eye from various environmental insults. The adult corneal epithelium is maintained homeostatically by an integrated process of cell proliferation, migration, differentiation, stratification, and desquamation/apoptosis. Impairment of this process results in persistent corneal defect, leading to the blindness. Researches throughout the years revealed that appropriate integration and coordination of cell signaling events are responsible for corneal epithelial renewal and wound healing. In this chapter, we will review works done on cell culture, animal models, and human trials to focus on the signaling network during corneal wound healing process which will have potential for the discovery of novel drug to improve corneal wound healing.

Combining GWAS and RNA-Seq Approaches for Detection of the Causal Mutation for Hereditary Junctional Epidermolysis Bullosa in Sheep

In this study, we demonstrate the use of a genome-wide association mapping together with RNA-seq in a reduced number of samples, as an efficient approach to detect the causal mutation for a Mendelian disease. Junctional epidermolysis bullosa is a recessive genodermatosis that manifests with neonatal mechanical fragility of the skin, blistering confined to the lamina lucida of the basement membrane and severe alteration of the hemidesmosomal junctions. In Spanish Churra sheep, junctional epidermolysis bullosa (JEB) has been detected in two commercial flocks. The JEB locus was mapped to Ovis aries chromosome 11 by GWAS and subsequently fine-mapped to an 868-kb homozygous segment using the identical-by-descent method. The ITGB4, which is located within this region, was identified as the best positional and functional candidate gene. The RNA-seq variant analysis enabled us to discover a 4-bp deletion within exon 33 of the ITGB4 gene (c.4412_4415del). The c.4412_4415del mutation causes a frameshift resulting in a premature stop codon at position 1472 of the integrin β4 protein. A functional analysis of this deletion revealed decreased levels of mRNA in JEB skin samples and the absence of integrin β4 labeling in immunohistochemical assays. Genotyping of c.4412_4415del showed perfect concordance with the recessive mode of the disease phenotype. Selection against this causal mutation will now be used to solve the problem of JEB in flocks of Churra sheep. Furthermore, the identification of the ITGB4 mutation means that affected sheep can be used as a large mammal animal model for the human form of epidermolysis bullosa with aplasia cutis. Our approach evidences that RNA-seq offers cost-effective alternative to identify variants in the species in which high resolution exome-sequencing is not straightforward.

Autologous transplantation of oral mucosal epithelial cell sheets cultured on an amniotic membrane substrate for intraoral mucosal defects

The human amniotic membrane (AM) is a thin intrauterine placental membrane that is highly biocompatible and possesses anti-inflammatory and anti-scarring properties. Using AM, we developed a novel method for cultivating oral mucosal epithelial cell sheets. We investigated the autologous transplantation of oral mucosal epithelial cells cultured on AM in patients undergoing oral surgeries. We obtained specimens of AM from women undergoing cesarean sections. This study included five patients without any history of a medical disorder who underwent autologous cultured oral epithelial transplantation following oral surgical procedures. Using oral mucosal biopsy specimens obtained from these patients, we cultured oral epithelial cells on an AM carrier. We transplanted the resultant cell sheets onto the oral mucosal defects. Patients were followed-up for at least 12 months after transplantation. After 2–3 weeks of being cultured on AM, epithelial cells were well differentiated and had stratified into five to seven layers. Immunohistochemistry revealed that the cultured cells expressed highly specific mucosal epithelial cell markers and basement membrane proteins. After the surgical procedures, no infection, bleeding, rejection, or sheet detachment occurred at the reconstructed sites, at which new oral mucous membranes were evident. No recurrence was observed in the long-term follow-up, and the postoperative course was excellent. Our results suggest that AM-cultured oral mucosal epithelial cell sheets represent a useful biomaterial and feasible method for oral mucosal reconstruction. However, our primary clinical study only evaluated their effects on a limited number of small oral mucosal defects.

Galectin-3 as a regulator of the epithelial junction: Implications to wound repair and cancer

Epithelial cells are closely connected to each other and to the extracellular matrix by a set of adhesive contacts that provide tissues with unique barrier properties and play a prominent role in cell morphology, tissue physiology, and cell signaling. This review highlights advances made in understanding the contributions of galectin-3, a carbohydrate-binding protein with affinity toward β-galactosides, as a modulator of epithelial junction assembly and function. The interactions of galectin-3 within adhesive structures are discussed in relation to wound healing and tumor progression.

Integrin α6β4 and TRPV1 channel coordinately regulate directional keratinocyte migration

The directional migration of epithelial cells is crucial for wound healing. Among integrins, a family of cell adhesion receptors, integrin β4 has been assumed to be a promigratory factor, in addition to its role in stable adhesion. In turn, Ca(2+) signaling is also a key coordinator of migration. Keratinocytes reportedly express transient receptor potential vanilloid channels (TRPV1); however, the function of these channels as a regulator of intracellular Ca(2+) level in cell migration has remained uncharacterized. In the present study, we investigated the role of TRPV1 in directional migration related to integrin β4 using a scratch wound assay on a confluent monolayer sheet of murine keratinocytes (Pam212 cells). Double immunofluorescence staining revealed the de novo expression of integrin β4 and TRPV1 in migrating cells at the wound edge in response to scratch wounding, and both expression levels were almost matched. Epidermal growth factor (EGF) not only promoted keratinocyte migration, but also caused the further up-regulation of both integrin β4 and TRPV1. In addition, the knockdown of the integrin β4 or TRPV1 gene significantly impeded wound closure. The TRPV1 agonist capsaicin significantly promoted migration, while a selective TRPV1 antagonist inhibited it. The gene knockdown of TRPV1 inhibited the expression of the integrin β4 gene and that of β4 protein in migrating cells. These findings suggest that TRPV1 may stimulate directional migration directly by eliciting a Ca(2+) signal or indirectly via integrin β4 expression.

Reduced fibulin-2 contributes to loss of basement membrane integrity and skin blistering in mice lacking integrin α3β1 in the epidermis

Deficient epidermal adhesion is a hallmark of blistering skin disorders and chronic wounds, implicating integrins as potential therapeutic targets. Integrin α3β1, a major receptor in the epidermis for adhesion to laminin-332 (LN-332), has critical roles in basement membrane (BM) organization during skin development. In the current study we identify a role for α3β1 in promoting stability of nascent epidermal BMs through induction of fibulin-2, a matrix-associated protein that binds LN-332. We demonstrate that mice lacking α3β1 in the epidermis display ruptured BM beneath neo-epidermis of wounds, characterized by extensive blistering. This junctional blistering phenocopies defects reported in newborn α3-null mice, as well as in human patients with α3 gene mutations, indicating that the developmental role of α3β1 in BM organization is recapitulated during wound healing. Mice lacking epidermal α3β1 also have reduced fibulin-2 expression, and fibulin-2-null mice display perinatal skin blisters similar to those in α3β1-deficient mice. Interestingly, α3-null wound epidermis or keratinocytes also show impaired processing of the LN-332 γ2 chain, although this defect was independent of reduced fibulin-2 and did not appear to cause blistering. Our findings indicate a role for integrin α3β1 in BM stability through fibulin-2 induction, both in neonatal skin and in adult wounds.

Integrin αvβ5 in endothelial cells of rat splenic sinus: an immunohistochemical and ultrastructural study

Localization of integrins β1-8, α1, α2, α3, α5, α6 and αv in sinus endothelial cells of the rat spleen was examined by immunofluorescence microscopy. Labeling for anti-integrin β5 and integrin αv was detected and colocalized in the entire circumference of endothelial cells. Labeling for integrin β5, vinculin and actin filaments demonstrated that they lay close to each other in the basal part of the endothelial cells. Although the other integrin βs, including integrin β1 and integrins α1, α2, α3, α5 and α6 in combination with integrin β1, were localized in leukocytes, slightly large cells, megakaryocytes and/or platelets in the sinus lumen and splenic cords, they were not detected in endothelial cells. Labeling for vitronectin, a component of the extracellular-matrix-binding integrin αvβ5, was strongly stained in the periphery of the wall of sinuses, as was collagen IV and, in addition, was localized in the cytoplasm of endothelial cells. Ultrastructural localization of integrin β5, vitronectin and clathrin was examined by immunogold electron microscopy to elucidate the involvement of integrin αvβ5 in the endocytosis of vitronectin in sinus endothelial cells. Electron microscopy with detergent extraction revealed abundant coated pits and coated vesicles in endothelial cells. Immunogold labeling for vitronectin was present in pits, vesicles and the stacked endoplasmic reticulum. Double-labeling for integrin β5 or integrin αv and clathrin revealed that they were colocalized in some vesicles in close proximity to the apical and lateral plasma membrane of the endothelial cells. The possible functional roles of integrin αvβ5 in endothelial cells of the splenic sinus are discussed.

A central role for vimentin in regulating repair function during healing of the lens epithelium

A unique ex vivo mock cataract surgery model is used to study the role of vimentin in repair cell function during wound healing within a clinically relevant setting. Vimentin is found to be critical for the function of repair cells in directing the collective migration of the epithelium during wound healing.

Mock cataract surgery provides a unique ex vivo model for studying wound repair in a clinically relevant setting. Here wound healing involves a classical collective migration of the lens epithelium, directed at the leading edge by an innate mesenchymal subpopulation of vimentin-rich repair cells. We report that vimentin is essential to the function of repair cells as the directors of the wound-healing process. Vimentin and not actin filaments are the predominant cytoskeletal elements in the lamellipodial extensions of the repair cells at the wound edge. These vimentin filaments link to paxillin-containing focal adhesions at the lamellipodial tips. Microtubules are involved in the extension of vimentin filaments in repair cells, the elaboration of vimentin-rich protrusions, and wound closure. The requirement for vimentin in repair cell function is revealed by both small interfering RNA vimentin knockdown and exposure to the vimentin-targeted drug withaferin A. Perturbation of vimentin impairs repair cell function and wound closure. Coimmunoprecipitation analysis reveals for the first time that myosin IIB is associated with vimentin, linking vimentin function in cell migration to myosin II motor proteins. These studies reveal a critical role for vimentin in repair cell function in regulating the collective movement of the epithelium in response to wounding.

The role of phosphoinositide 3-kinase in adhesion of oral epithelial cells to titanium

BACKGROUND

Oral epithelial cells (OECs) adhesion to titanium may improve the success rate of implant restoration.

PURPOSE

We investigated the mechanism by which OECs adhere to titanium dental implants.

MATERIALS AND METHODS

(1) After culturing rat OECs on titanium plates (Ti) or culture dishes in the presence or absence of a phosphoinositide 3-kinase (PI3K) activator or inhibitors and/or growth factors, and OEC morphology under these conditions were analyzed. (2) Right maxillary first molars were extracted and replaced with experimental implants. The rats were treated with or without growth factors.

RESULTS

(1) Cell adherence was lower of OECs on Ti than in those on culture dishes, as were the levels of integrin β4 and the continuity of F-actin structures. After PI3K inhibition, markedly reducing adherence to both substrates. In contrast, PI3K activation with activator or insulin-like growth factor restored the OEC adherence and the expression of adhesion molecules on Ti to the levels seen in OECs cultured on dishes. Cell migration was inhibited by PI3K activation. (2) High expression of integrin β4 was observed in the peri-implant epithelia of PI3K-activated rats.

CONCLUSION

These findings suggest that PI3K plays an important role in the adhesion of OECs to Ti.

The corneal epithelial basement membrane: structure, function, and disease

The corneal epithelial basement membrane (BM) is positioned between basal epithelial cells and the stroma. This highly specialized extracellular matrix functions not only to anchor epithelial cells to the stroma and provide scaffolding during embryonic development but also during migration, differentiation, and maintenance of the differentiated epithelial phenotype. Basement membranes are composed of a diverse assemblage of extracellular molecules, some of which are likely specific to the tissue where they function; but in general they are composed of four primary components--collagens, laminins, heparan sulfate proteoglycans, and nidogens--in addition to other components such as thrombospondin-1, matrilin-2, and matrilin-4 and even fibronectin in some BM. Many studies have focused on characterizing BM due to their potential roles in normal tissue function and disease, and these structures have been well characterized in many tissues. Comparatively few studies, however, have focused on the function of the epithelial BM in corneal physiology. Since the normal corneal stroma is avascular and has relatively low keratocyte density, it is expected that the corneal BM would be different from the BM in other tissues. One function that appears critical in homeostasis and wound healing is the barrier function to penetration of cytokines from the epithelium to stroma (such as transforming growth factor β-1), and possibly from stroma to epithelium (such as keratinocyte growth factor). The corneal epithelial BM is also involved in many inherited and acquired corneal diseases. This review examines this structure in detail and discusses the importance of corneal epithelial BM in homeostasis, wound healing, and disease.

Id2 complexes with the SNAG domain of Snai1 inhibiting Snai1-mediated repression of integrin β4

The epithelial-mesenchymal transition (EMT) is a fundamental process that underlies development and cancer. Although the EMT involves alterations in the expression of specific integrins that mediate stable adhesion to the basement membrane, such as α6β4, the mechanisms involved are poorly understood. Here, we report that Snai1 inhibits β4 transcription by increasing repressive histone modification (trimethylation of histone H3 at K27 [H3K27Me3]). Surprisingly, Snai1 is expressed and localized in the nucleus in epithelial cells, but it does not repress β4. We resolved this paradox by discovering that Id2 complexes with the SNAG domain of Snai1 on the β4 promoter and constrains the repressive function of Snai1. Disruption of the complex by depleting Id2 resulted in Snai1-mediated β4 repression with a concomitant increase in H3K27Me3 modification on the β4 promoter. These findings establish a novel function for Id2 in regulating Snai1 that has significant implications for the regulation of epithelial gene expression.

Metallopanstimulin-1 regulates invasion and migration of gastric cancer cells partially through integrin β4

MPS-1 (metallopanstimulin-1), also known as ribosomal protein S27, was overexpressed in gastric cancer cells. However, how MPS-1 contributes to gastric carcinogenesis has not been well characterized. Here, we show that high expression of MPS-1 was observed in gastric cancer tissues and associated with gastric cancer cell metastasis. Alteration of MPS-1 expression regulates invasion and migration of gastric cancer cells both in vitro and in vivo. Furthermore, by using Signal-Net and cluster analyses of microarray data we identified integrin β4 (ITGB4) as a downstream target of MPS-1 that mediates its effects on cell metastasis. Knockdown of MPS-1 expression in gastric cancer cells led to significant reduction of ITGB4 expression at both the RNA and protein levels. Mechanically, we found that overexpression of ITGB4 in MPS-1 knockdown cells largely recovers the ability of invasion and migration. Conversely, knockdown of ITGB4 partially reduced cell invading/migrating ability induced by MPS-1 overexpression. Moreover, MPS-1 and ITGB4 expressions are positively correlated in gastric cancer cell lines and tissues. Finally, the survival analyses show that the expression of MPS-1 and ITGB4 is associated with poor outcomes in gastric cancer patients. Collectively, our findings suggest that MPS-1 regulates cell invasiveness and migration partially through ITGB4 and that MPS-1/ITGB4 signaling axis may serve as therapeutic targets in the treatment of gastric cancer.

Promotive effect of insulin-like growth factor-1 for epithelial sealing to titanium implants

Improvement of oral epithelial adhesion to titanium (Ti) may significantly enhance the efficacy of dental implants. Here, we investigated whether insulin-like growth factor-1 (IGF-1) improved the sealing of the peri-implant epithelium (PIE) around the implant. Right maxillary first molars were extracted from rats and replaced with experimental implants. After 4 weeks of IGF-1 treatment, the implant-PIE interface exhibited a band of immunoreactive laminin-332 (Ln-5), similar to the tooth-junctional epithelium interface, that was partially absent in the untreated group. Immunoelectron microscopy showed a characteristic Ln-5-positive band including hemidesmosomes at both the apical and upper portions of the implant-PIE interface in the IGF-1-treated group. We also investigated the effects of IGF-1/PI3K inhibitors on the dynamics of rat oral epithelial cells (OECs) grown on Ti plates. In OECs cultured with IGF-1, adhesion protein expression increased, cell adherence to Ti plates was higher, and proliferation was faster, whereas migration and apoptosis were induced in the absence of IGF-1 or in the presence of both IGF-1 and a PI3K inhibitor. These data suggest that PI3K mediates the promotive effects of IGF-1, and that IGF-1 is effective at enhancing epithelial integration around Ti implants.

Initial attachment, subsequent cell proliferation/viability and gene expression of epithelial cells related to attachment and wound healing in response to different titanium surfaces

OBJECTIVES

A tight seal between the epithelium and the dental implant surface is required to prevent bacterial inflammation and soft tissue recession and therefore to demonstrate a long-term success. Surface hydrophilicity was recently shown to promote osseointegration. The aim of this study was to investigate the influence of surface hydrophilicity in combination with surface topography of Ti implant surfaces on the behavior and activation/differentiation of epithelial cells using a set of in vitro experiments mimicking the implant-soft tissue contact.

METHODS

Hydrophobic acid-etched (A) and coarse-grit-blasted, acid-etched (SLA) surfaces and hydrophilic acid-etched (modA) and modSLA surfaces were produced. The behavior of an oral squamous cell carcinoma cell line (HSC-2) grown on all surfaces was compared through determination of cell attachment and proliferation/viability (CCK-8 and MTT assay), time-lapse microscopy of fluorescence labeled cells and determination of gene expression by real time polymerase chain reaction.

RESULTS

Within the surfaces with similar wettability cell spreading and cell movements observed by time-lapse microscopy after one day of incubation were most pronounced on smoother (A and modA) surfaces compared to rougher (SLA and modSLA) surfaces. Within the surfaces with similar roughness the hydrophilic surfaces (modA and modSLA) showed more cell spreading and cell activity compared to the hydrophobic surfaces (A and SLA). The relative gene expressions of cytokeratin14, integrin α6, integrin β4, vinculin, transforming growth factor (TGF)-β, TGF-β1, and TGF-β3 were decreased in HSC-2 on all four types of Ti surfaces compared to control surfaces (tissue culture polystyrene; p<0.01) and there was no significant difference of gene expression on the four different implant-surfaces.

SIGNIFICANCE

We have demonstrated that for proliferation and spreading of HSC-2 cells the smoother and hydrophilic surface is optimal (modA). These results suggest that surface hydrophilicity might positively influence the epithelial seal around dental implants. All tested titanium surfaces downregulate cell attachment, cell proliferation, expression of adhesion promoters, and cytokines involved in wound healing in HSC-2 cells compared to control surfaces.