Single-cell epigenomic dysregulation of Systemic Sclerosis fibroblasts via CREB1/EGR1 axis in self-assembled human skin equivalents.

Systemic sclerosis (SSc) is an autoimmune disease characterized by skin fibrosis, internal organ involvement and vascular dropout. We previously developed and phenotypically characterized an in vitro 3D skin-like tissue model of SSc, and now analyze the transcriptomic (scRNA-seq) and epigenetic (scATAC-seq) characteristics of this model at single-cell resolution. SSc 3D skin-like tissues were fabricated using autologous fibroblasts, macrophages, and plasma from SSc patients or healthy control (HC) donors. SSc tissues displayed increased dermal thickness and contractility, as well as increased α-SMA staining. Single-cell transcriptomic and epigenomic analyses identified keratinocytes, macrophages, and five populations of fibroblasts (labeled FB1 - 5). Notably, FB1 APOE-expressing fibroblasts were 12-fold enriched in SSc tissues and were characterized by high EGR1 motif accessibility. Pseudotime analysis suggests that FB1 fibroblasts differentiate from a TGF-ß1-responsive fibroblast population and ligand-receptor analysis indicates that the FB1 fibroblasts are active in macrophage crosstalk via soluble ligands including FGF2 and APP. These findings provide characterization of the 3D skin-like model at single cell resolution and establish that it recapitulates subsets of fibroblasts and macrophage phenotypes observed in skin biopsies.

CC chemokine ligand 20 (CCL20) positively regulates collagen type I production in 3D skin equivalent tissues.

Chemokines are a group of small proteins that induce chemoattraction and inflammation and contribute to the differentiation and homeostasis of various cell types. Here we explored the role of chemokines, extracellular matrix production, and myofibroblast differentiation in self-assembled skin equivalents (SASE), a three-dimensional (3D) skin-equivalent tissue model. We found that the expression of three chemokines, C-C motif chemokine ligand (CCL) 20, C-X-C motif chemokine ligand (CXCL) 5, and CXCL8, increased with differentiation to myofibroblasts. Addition of recombinant CCL20 to human skin fibroblast induced collagen Type I alpha 2 gene expression, but did not affect the expression of alpha smooth muscle actin expression. Conversely, siRNA gene knockdown of CCL20 effectively inhibited the expression of collagen Type I gene and protein. Furthermore, when the CCL20 gene in fibroblasts was knocked down in SASE, collagen Type I synthesis and stromal thickness were decreased. Taken together, these results have indicated the utility of SASE in understanding how cytokines such as CCL20 positively regulate extracellular matrix proteins such as collagen Type I production during myofibroblast differentiation in 3D tissues that mimic human skin.

Human dermal fibroblast-derived exosomes induce macrophage activation in systemic sclerosis.

OBJECTIVES: Prior work demonstrates that co-cultured macrophages and fibroblasts from patients with SSc engage in reciprocal activation. However, the mechanism by which these cell types communicate and contribute to fibrosis and inflammation in SSc is unknown. METHODS: Fibroblasts were isolated from skin biopsies obtained from 7 SSc patients or 6 healthy age and gender-matched control subjects following written informed consent. Human donor-derived macrophages were cultured with exosomes isolated from control or SSc fibroblasts for an additional 48 h. Macrophages were immunophenotyped using flow cytometry, qRT-PCR and multiplex. For mutual activation studies, exosome-activated macrophages were co-cultured with SSc or healthy fibroblasts using Transwells. RESULTS: Macrophages activated with dermal fibroblast-derived exosomes from SSc patients upregulated surface expression of CD163, CD206, MHC Class II and CD16 and secreted increased levels of IL-6, IL-10, IL-12p40 and TNF compared with macrophages incubated with healthy control fibroblasts (n = 7, P < 0.05). Exosome-stimulated macrophages and SSc fibroblasts engaged in reciprocal activation, as production of collagen and fibronectin was significantly increased in SSc fibroblasts receiving signals from SSc exosome-stimulated macrophages (n = 7, P < 0.05). CONCLUSION: In this work, we demonstrate for the first time that human SSc dermal fibroblasts mediate macrophage activation through exosomes. Our findings suggest that macrophages and fibroblasts engage in cross-talk in SSc skin, resulting in mutual activation, inflammation, and extracellular matrix (ECM) deposition. Collectively, these studies implicate macrophages and fibroblasts as cooperative mediators of fibrosis in SSc and suggest therapeutic targeting of both cell types may provide maximal benefit in ameliorating disease in SSc patients.

Personalized Scaffolds for Diabetic Foot Ulcer Healing Using Extracellular Matrix from Induced Pluripotent Stem-Reprogrammed Patient Cells.

Diabetic foot ulcers (DFU) are chronic wounds sustained by pathological fibroblasts and aberrant extracellular matrix (ECM). Porous collagen-based scaffolds (CS) have shown clinical promise for treating DFUs but may benefit from functional enhancements. Our previous work showed fibroblasts differentiated from induced pluripotent stem cells are an effective source of new ECM mimicking fetal matrix, which notably promotes scar-free healing. Likewise, functionalizing CS with this rejuvenated ECM showed potential for DFU healing. Here, we demonstrate for the first time an approach to DFU healing using biopsied cells from DFU patients, reprogramming those cells, and functionalizing CS with patient-specific ECM as a personalized acellular tissue engineered scaffold. We took a two-pronged approach: 1) direct ECM blending into scaffold fabrication; and 2) seeding scaffolds with reprogrammed fibroblasts for ECM deposition followed by decellularization. The decellularization approach reduced cell number requirements and maintained naturally deposited ECM proteins. Both approaches showed enhanced ECM deposition from DFU fibroblasts. Decellularized scaffolds additionally enhanced glycosaminoglycan deposition and subsequent vascularization. Finally, reprogrammed ECM scaffolds from patient-matched DFU fibroblasts outperformed those from healthy fibroblasts in several metrics, suggesting ECM is in fact able to redirect resident pathological fibroblasts in DFUs towards healing, and a patient-specific ECM signature may be beneficial.

Soluble triggering receptor expressed on myeloid cells 2 (sTREM2) positively regulates lipopolysaccharide-induced expression of CXC chemokine ligand 10 and 11 in mouse macrophages.

TREM2 (Triggering receptor expressed on myeloid cells 2) is the causative gene for Nasu-Hakola disease, which is characterized by multiple bone cysts and leukoencephalopathy. In addition, mutations in this gene have been found to be correlated with the onset of Alzheimer's disease. TREM2 is an immunoreceptor expressed on dendritic cells, microglia, osteoclasts, and macrophages. TREM2 on the cell membrane is shed by some proteases and released as soluble TREM2 (sTREM2). Meanwhile, several TREM2 ligands have been reported, and lipopolysaccharide (LPS) is one of the candidates. Using RNA interference to examine TREM2-mediated LPS response in macrophages, we identified five chemokines whose expression was induced via TREM2. Furthermore, we showed that LPS-induced expression of CXC-motif chemokine ligand (Cxcl10) and Cxcl11 among the five chemokines was mediated in part through sTREM2. These results suggest that sTREM2 has cytokine-like functions in macrophages.

Self-Assembled Human Skin Equivalents Model Macrophage Activation of Cutaneous Fibrogenesis in Systemic Sclerosis.

OBJECTIVE: The development of precision therapeutics for systemic sclerosis (SSc) has been hindered by the lack of models that accurately mimic the disease in vitro. This study was undertaken to design and test a self-assembled skin equivalent (saSE) system that recapitulates the cross-talk between macrophages and fibroblasts in cutaneous fibrosis. METHODS: SSc-derived dermal fibroblasts (SScDFs) and normal dermal fibroblasts (NDFs) were cultured with CD14+ monocytes from SSc patients or healthy controls to allow de novo stroma formation. Monocyte donor-matched plasma was introduced at week 3 prior to seeding keratinocytes to produce saSE with a stratified epithelium. Tissue was characterized by immunohistochemical staining, atomic force microscopy, enzyme-linked immunosorbent assay, and quantitative reverse transcriptase-polymerase chain reaction. RESULTS: Stroma synthesized de novo from NDFs and SScDFs supported a fully stratified epithelium to form saSE. A thicker and stiffer dermis was generated by saSE with SScDFs, and more interleukin-6 and transforming growth factor ß (TGFß) was secreted by saSE with SScDFs compared to saSE with NDFs, regardless of the inclusion of monocytes. Tissue with SSc monocytes and plasma had amplified dermal thickness and stiffness relative to control tissue. Viable CD163+ macrophages were found within the stroma of saSE 5 weeks after seeding. Additionally, SSc saSE contained greater numbers of CD163+ and CD206+ macrophages compared to control saSE. TGFß blockade inhibited stromal stiffness to a greater extent in SSc saSE compared to control saSE. CONCLUSION: These data suggest reciprocal activation between macrophages and fibroblasts that increases tissue thickness and stiffness, which is dependent in part on TGFß activation. The saSE system may serve as a platform for preclinical therapeutic testing and for molecular characterization of SSc skin pathology through recapitulation of the interactions between macrophages and fibroblasts.

The Development of Tissue Engineering Scaffolds Using Matrix from iPS-Reprogrammed Fibroblasts.

Tissue engineering solutions have been widely explored for enhanced healing of skin wounds. Diabetic foot ulcers (DFU) are particularly challenging wounds to heal for a variety of reasons, including aberrant ECM, dysregulation of vascularization, and persistent inflammation. Tissue engineering approaches, such as porous collagen-based scaffolds, have shown promise in replacing the current treatments of surgical debridement and topical treatments. Collagen-glycosaminoglycan scaffolds, which are FDA approved for diabetic foot ulcers, can benefit from further functionalization by incorporation of additional signaling factors or extracellular matrix molecules. One option for this is to incorporate matrix from a rejuvenated cell source, as wounds in younger patients heal more quickly. Induced pluripotent stem cells (iPS) are generated from somatic cells and share many functional similarities with embryonic stem cells (ES), while avoiding the ethical concerns. Fibroblasts differentiated from iPS cells have been shown to enrich their ECM with glycosaminoglycan (GAGs), collagen Type III and fibronectin, to have an increased ECM production, and to be pro-angiogenic. Here we describe a technique to grow matrix from post-iPS fibroblasts, and to develop a scaffold from this matrix, in combination with collagen, with the goal of enhancing wound healing. By activating scaffolds with extracellular matrix (ECM) from fibroblasts derived from an iPS source (post-iPSF), the scaffolds are enriched with beneficial elements like GAGs, collagen type III, fibronectin, and VEGF. We believe these scaffolds can enhance skin regeneration and that the techniques can be modified for other tissue engineering applications.

Constitutive Hedgehog/GLI2 signaling drives extracutaneous basaloid squamous cell carcinoma development and bone remodeling.

Uncontrolled activation of the Hedgehog (Hh) signaling pathway, operating through GLI transcription factors, plays a central role in the pathogenesis of cutaneous basal cell carcinoma and contributes to the development of several malignancies arising in extracutaneous sites. We now report that K5-tTA;tetO-Gli2 bitransgenic mice develop distinctive epithelial tumors within their jaws. These tumors consist of large masses of highly proliferative, monomorphous, basaloid cells with scattered foci of keratinization and central necrosis, mimicking human basaloid squamous cell carcinoma (BSCC), an aggressive upper aerodigestive tract tumor. Like human BSCC, these tumors express epidermal basal keratins and differentiation-specific keratins within squamous foci. Mouse BSCCs express high levels of Gli2 and Hh target genes, including Gli1 and Ptch1, which we show are also upregulated in a subset of human BSCCs. Mouse BSCCs appear to arise from distinct epithelial sites, including the gingival junctional epithelium and epithelial rests of Malassez, a proposed stem cell compartment. Although Gli2 transgene expression is restricted to epithelial cells, we also detect striking alterations in bone adjacent to BSCCs, with activated osteoblasts, osteoclasts and osteal macrophages, indicative of active bone remodeling. Gli2 transgene inactivation resulted in rapid BSCC regression and reversal of the bone remodeling phenotype. This first-reported mouse model of BSCC supports the concept that uncontrolled Hh signaling plays a central role in the pathogenesis of a subset of human BSCCs, points to Hh/GLI2 signaling as a potential therapeutic target and provides a powerful new tool for probing the mechanistic underpinnings of tumor-associated bone remodeling.

Cellular reprogramming of diabetic foot ulcer fibroblasts triggers pro-healing miRNA-mediated epigenetic signature.

Diabetic foot ulcers (DFUs), a prevalent complication of diabetes, constitute a major medical challenge with a critical need for development of cell-based therapies. We previously generated induced pluripotent stem cells (iPSCs) from dermal fibroblasts derived from the DFU patients, location-matched skin of diabetic patients and normal healthy donors and re-differentiated them into fibroblasts. To assess the epigenetic microRNA (miR) regulated changes triggered by cellular reprogramming, we performed miRs expression profiling. We found let-7c, miR-26b-5p, -29c-3p, -148a-3p, -196a-5p, -199b-5p and -374a-5p suppressed in iPSC-derived fibroblasts in vitro and in 3D dermis-like self-assembly tissue, whereas their corresponding targets involved in cellular migration were upregulated. Moreover, targets involved in organization of extracellular matrix were induced after fibroblast reprogramming. PLAT gene, the crucial fibrinolysis factor, was upregulated in iPSC-derived fibroblasts and was confirmed as a direct target of miR-196a-5p. miR-197-3p and miR-331-3p were found upregulated specifically in iPSC-derived diabetic fibroblasts, while their targets CAV1 and CDKN3 were suppressed. CAV1, an important negative regulator of wound healing, was confirmed as a direct miR-197-3p target. Together, our findings demonstrate that iPSC reprogramming is an effective approach for erasing the diabetic non-healing miR-mediated epigenetic signature and promoting a pro-healing cellular phenotype.

Virus-mediated inactivation of anti-apoptotic Bcl-2 family members promotes Gasdermin-E-dependent pyroptosis in barrier epithelial cells.

Two sets of innate immune proteins detect pathogens. Pattern recognition receptors (PRRs) bind microbial products, whereas guard proteins detect virulence factor activities by the surveillance of homeostatic processes within cells. While PRRs are well known for their roles in many types of infections, the role of guard proteins in most infectious contexts remains less understood. Here, we demonstrated that inhibition of protein synthesis during viral infection is sensed as a virulence strategy and initiates pyroptosis in human keratinocytes. We identified the BCL-2 family members MCL-1 and BCL-xL as sensors of translation shutdown. Virus- or chemical-induced translation inhibition resulted in MCL-1 depletion and inactivation of BCL-xL, leading to mitochondrial damage, caspase-3-dependent cleavage of gasdermin E, and release of interleukin-1α (IL-1α). Blocking this pathway enhanced virus replication in an organoid model of human skin. Thus, MCL-1 and BCL-xL can act as guard proteins within barrier epithelia and contribute to antiviral defense.

Optimization of extracellular matrix production from human induced pluripotent stem cell-derived fibroblasts for scaffold fabrication for application in wound healing.

Extracellular matrix is a key component of all tissues, including skin and it plays a crucial role in the complex events of wound healing. These events are impaired in chronic wounds, with chronic inflammation and infection often present in these non-healing wounds. Many tissue engineering approaches for wound healing provide a scaffold to mimic the native matrix. Fibroblasts derived from iPS cells (iPSF) represent a novel source of matrix rich in pro-regenerative components, which can be used for scaffold fabrication to improve wound healing. However, in vitro production of matrix by cells for scaffold fabrication requires long cell culturing times which increases cost. The aim of this work is to optimize the iPSF matrix production by boosting matrix deposition, without affecting its composition. A good candidate technique to achieve this goal is macromolecular crowding, which is known to promote conversion of procollagen into mature collagen and its accumulation. We tested two molecular crowders, Ficoll and Carrageenan-in combination with ascorbic acid-over a prolonged period of time. Ficoll in combination with ascorbic acid notably increased collagen deposition and matrix dry weight compared to ascorbic acid alone, and did not affect matrix composition as measured by RT-PCR. Interestingly, Carrageenan did not affect collagen quantity, but it significantly increased glycosaminoglycan deposition. Finally, we successfully fabricated scaffolds from harvested matrix and confirmed their ability for cell growth and viability. This work lays the foundation for development of a time and cost effective protocol for novel iPSF ECM production for tissue engineering scaffolds.

A Novel Three-Dimensional Skin Disease Model to Assess Macrophage Function in Diabetes.

A major challenge in the management of patients suffering from diabetes is the risk of developing nonhealing foot ulcers. Most in vitro methods to screen drugs for wound healing therapies rely on conventional 2D cell cultures that do not closely mimic the complexity of the diabetic wound environment. In addition, while three-dimensional (3D) skin tissue models of human skin exist, they have not previously been adapted to incorporate patient-derived macrophages to model inflammation from these wounds. In this study, we present a 3D human skin equivalent (HSE) model incorporating blood-derived monocytes and primary fibroblasts isolated from patients with diabetic foot ulcers (DFUs). We demonstrate that the monocytes differentiate into macrophages when incorporated into HSEs and secrete a cytokine profile indicative of the proinflammatory M1 phenotype seen in DFUs. We also show how the interaction between fibroblasts and macrophages in the HSE can guide macrophage polarization. Our findings take us a step closer to creating a human, 3D skin-like tissue model that can be applied to evaluate the response of candidate compounds needed for potential new foot ulcer therapies in a more complex tissue environment that contributes to diabetic wounds. Impact statement This study is the first to incorporate disease-specific, diabetic macrophages into a three-dimensional (3D) model of human skin. We show how to fabricate skin that incorporates macrophages with disease-specific fibroblasts to guide macrophage polarization. We also show that monocytes from diabetic patients can differentiate into macrophages directly in this skin disease model, and that they secrete a cytokine profile mimicking the proinflammatory M1 phenotype seen in diabetic foot ulcers. The data presented here indicate that this 3D skin disease model can be used to study macrophage-related inflammation in diabetes and as a drug testing tool to evaluate new treatments for the disease.

The lubricating effect of iPS-reprogrammed fibroblasts on collagen-GAG scaffolds for cartilage repair applications.

Tissue engineering products, like collagen-glycosaminoglycan scaffolds, have been successfully applied to chondrogenic defects. Inducible Pluripotent Stem cell (iPS) technology allows reprograming of somatic cells into an embryonic-like state, allowing for redifferentiation. We postulated that a fibroblast cell line (BJ cells - 'pre-iPSF') cycled through iPS reprogramming and redifferentiated into fibroblasts (post-iPSF) could lubricate collagen-glycosaminoglycan scaffolds; fibroblasts are known to produce lubricating molecules (e.g., lubricin) in the synovium. Herein, we quantified the coefficient of friction (CoF) of collagen-glycosaminoglycan scaffolds seeded with post-iPSF; tested whether cell-free scaffolds made of post-iPSF derived extracellular matrix had reduced friction vs. pre-iPSF; and assessed lubricin quantity as a possible protein responsible for lubrication. Post-iPSF seeded CG had 6- to 10-fold lower CoF versus pre-iPSF. Scaffolds consisting of a collagen and pre-/post-iPSF extracellular matrix blend outperformed these cell-seeded scaffolds (~5-fold lower CoF), yielding excellent CoF values close to synovial fluid. Staining revealed an increased presence of lubricin within post-iPSF scaffolds (confirmed by western blotting) and on the surface of iPSF-seeded collagen-glycosaminoglycan scaffolds. Interestingly, when primary cells from patient biopsy-derived fibroblasts were used, iPS reprogramming did not further reduce the already low CoF of these cells and no lubricin expression was found. We conclude that iPS reprogramming activates lubricating properties in iPS-derived cells in a source cell-specific manner. Additionally, lubricin appears to play a lubricating role, yet other proteins also contribute to lubrication. This work constitutes an important step for understanding post-iPSF lubrication of scaffolds and its potential for cartilage tissue engineering.

Facilitating stakeholder engagement in early stage translational research.

INTRODUCTION: Stakeholder engagement can play an important role in increasing public trust and the understanding of scientific research and its impact. Frameworks for stakeholder identification exist, but these frameworks may not apply well to basic science and early stage translational research. METHODS: Four Clinical and Translational Science Award (CTSA) hubs led six focus groups and two semi-structured interviews using a semi-structured discussion guide to learn from basic science researchers about stakeholder engagement in their work. The 24 participants represented fourteen clinical and academic disciplines. RESULTS: Early stage translational researchers reported engagement with a broad array of stakeholders. Those whose research has a clinical focus reported working with a more diverse range of stakeholders than those whose work did not. Common barriers to stakeholder engagement were grouped into three major themes: a poor definition of concepts, absence of guidance, and limited resources. DISCUSSION: The National Center for Advancing Translational Sciences (NCATS), the consortium of CTSAs, and the individual CTSA "hubs" are three actors that can help early stage translational researchers develop shared terms of reference, build the necessary skills, and assemble the appropriate resources for engaging stakeholders in Clinical and Translational Research. Getting this right will involve a coordinated push by all three entities.

De novo production of human extracellular matrix supports increased throughput and cellular complexity in 3D skin equivalent model.

Three-dimensional (3D) tissue models of human skin are being developed to better understand disease phenotypes and to screen new drugs for potential therapies. Several factors will increase the value of these in vitro 3D skin tissues for these purposes. These include the need for human-derived extracellular matrix (ECM), higher throughput tissue formats, and greater cellular complexity. Here, we present an approach for the fabrication of 3D skin-like tissues as a platform that addresses these three considerations. We demonstrate that human adult and neonatal fibroblasts deposit an endogenous ECM de novo that serves as an effective stroma for full epithelial tissue development and differentiation. We have miniaturized these tissues to a 24-well format to adapt them for eventual higher throughput drug screening. We have shown that monocytes from the peripheral blood can be incorporated into this model as macrophages to increase tissue complexity. This humanized skin-like tissue decreases dependency on animal-derived ECM while increasing cellular complexity that can enable screening inflammatory responses in tissue models of human skin.

Scaffolds Functionalized with Matrix from Induced Pluripotent Stem Cell Fibroblasts for Diabetic Wound Healing.

Diabetic foot ulcers (DFUs) are chronic wounds, with 20% of cases resulting in amputation, despite intervention. A recently approved tissue engineering product-a cell-free collagen-glycosaminoglycan (GAG) scaffold-demonstrates 50% success, motivating its functionalization with extracellular matrix (ECM). Induced pluripotent stem cell (iPSC) technology reprograms somatic cells into an embryonic-like state. Recent findings describe how iPSCs-derived fibroblasts ("post-iPSF") are proangiogenic, produce more ECM than their somatic precursors ("pre-iPSF"), and their ECM has characteristics of foetal ECM (a wound regeneration advantage, as fetuses heal scar-free). ECM production is 45% higher from post-iPSF and has favorable components (e.g., Collagen I and III, and fibronectin). Herein, a freeze-dried scaffold using ECM grown by post-iPSF cells (Post-iPSF Coll) is developed and tested vs precursors ECM-activated scaffolds (Pre-iPSF Coll). When seeded with healthy or DFU fibroblasts, both ECM-derived scaffolds have more diverse ECM and more robust immune responses to cues. Post-iPSF-Coll had higher GAG, higher cell content, higher Vascular Endothelial Growth Factor (VEGF) in DFUs, and higher Interleukin-1-receptor antagonist (IL-1ra) vs. pre-iPSF Coll. This work constitutes the first step in exploiting ECM from iPSF for tissue engineering scaffolds.

Systemic Sclerosis Dermal Fibroblasts Induce Cutaneous Fibrosis Through Lysyl Oxidase-like 4: New Evidence From Three-Dimensional Skin-like Tissues.

OBJECTIVE: Systemic sclerosis (SSc) is a clinically heterogeneous disease characterized by increased collagen accumulation and skin stiffness. Our previous work has demonstrated that transforming growth factor ß (TGFß) induces extracellular matrix (ECM) modifications through lysyl oxidase-like 4 (LOXL-4), a collagen crosslinking enzyme, in bioengineered human skin equivalents (HSEs) and self-assembled stromal tissues (SAS). We undertook this study to investigate cutaneous fibrosis and the role of LOXL-4 in SSc pathogenesis using HSEs and SAS. METHODS: SSc-derived dermal fibroblasts (SScDFs; n = 8) and normal dermal fibroblasts (NDFs; n = 6) were incorporated into HSEs and SAS. These 3-dimensional skin-like microenvironments were used to study the effects of dysregulated LOXL-4 on ECM remodeling, fibroblast activation, and response to TGFß stimulation. RESULTS: SScDF-containing SAS showed increased stromal thickness, collagen deposition, and interleukin-6 secretion compared to NDF-containing SAS (P < 0.05). In HSE, SScDFs altered collagen as seen by a more mature and aligned fibrillar structure (P < 0.05). With SScDFs, enhanced stromal rigidity with increased collagen crosslinking (P < 0.05), up-regulation of LOXL4 expression (P < 0.01), and innate immune signaling genes were observed in both tissue models. Conversely, knockdown of LOXL4 suppressed rigidity, contraction, and α-smooth muscle actin expression in SScDFs in HSE, and TGFß-induced ECM aggregation and collagen crosslinking in SAS. CONCLUSION: A limitation to the development of effective therapeutics in SSc is the lack of in vitro human model systems that replicate human skin. Our findings demonstrate that SAS and HSE can serve as complementary in vitro skin-like models for investigation of the mechanisms and mediators that drive fibrosis in SSc and implicate a pivotal role for LOXL-4 in SSc pathogenesis.

Differentiation of diabetic foot ulcer-derived induced pluripotent stem cells reveals distinct cellular and tissue phenotypes.

Diabetic foot ulcers (DFUs) are a major complication of diabetes, and there is a critical need to develop novel cell- and tissue-based therapies to treat these chronic wounds. Induced pluripotent stem cells (iPSCs) offer a replenishing source of allogeneic and autologous cell types that may be beneficial to improve DFU wound-healing outcomes. However, the biologic potential of iPSC-derived cells to treat DFUs has not, to our knowledge, been investigated. Toward that goal, we have performed detailed characterization of iPSC-derived fibroblasts from both diabetic and nondiabetic patients. Significantly, gene array and functional analyses reveal that iPSC-derived fibroblasts from both patients with and those without diabetes are more similar to each other than were the primary cells from which they were derived. iPSC-derived fibroblasts showed improved migratory properties in 2-dimensional culture. iPSC-derived fibroblasts from DFUs displayed a unique biochemical composition and morphology when grown as 3-dimensional (3D), self-assembled extracellular matrix tissues, which were distinct from tissues fabricated using the parental DFU fibroblasts from which they were reprogrammed. In vivo transplantation of 3D tissues with iPSC-derived fibroblasts showed they persisted in the wound and facilitated diabetic wound closure compared with primary DFU fibroblasts. Taken together, our findings support the potential application of these iPSC-derived fibroblasts and 3D tissues to improve wound healing.-Kashpur, O., Smith, A., Gerami-Naini, B., Maione, A. G., Calabrese, R., Tellechea, A., Theocharidis, G., Liang, L., Pastar, I., Tomic-Canic, M., Mooney, D., Veves, A., Garlick, J. A. Differentiation of diabetic foot ulcer-derived induced pluripotent stem cells reveals distinct cellular and tissue phenotypes.

Lysyl oxidase enzymes mediate TGF-ß1-induced fibrotic phenotypes in human skin-like tissues.

Cutaneous fibrosis is a common complication seen in mixed connective tissue diseases. It often occurs as a result of TGF-ß-induced deposition of excessive amounts of collagen in the skin. Lysyl oxidases (LOXs), a family of extracellular matrix (ECM)-modifying enzymes responsible for collagen cross-linking, are known to be increased in dermal fibroblasts from patients with fibrotic diseases, denoting a possible role of LOXs in fibrosis. To directly study this, we have developed two bioengineered, in vitro skin-like models: human skin equivalents (hSEs), and self-assembled stromal tissues (SASs) that contain either normal or systemic sclerosis (SSc; scleroderma) patient-derived fibroblasts. These tissues provide an organ-level structure that could be combined with non-invasive, label-free, multiphoton microscopy (SHG/TPEF) to reveal alterations in the organization and cross-linking levels of collagen fibers during the development of cutaneous fibrosis, which demonstrated increased stromal rigidity and activation of dermal fibroblasts in response to TGF-ß1. Specifically, inhibition of specific LOXs isoforms, LOX and LOXL4, in foreskin fibroblasts (HFFs) resulted in antagonistic effects on TGF-ß1-induced fibrogenic hallmarks in both hSEs and SASs. In addition, a translational relevance of these models was seen as similar antifibrogenic phenotypes were achieved upon knocking down LOXL4 in tissues containing SSc patient-derived-dermal fibroblasts (SScDFs). These findings point to a pivotal role of LOXs in TGF-ß1-induced cutaneous fibrosis through impaired ECM homeostasis in skin-like tissues, and show the value of these tissue platforms in accelerating the discovery of antifibrosis therapeutics.

An Antiviral Branch of the IL-1 Signaling Pathway Restricts Immune-Evasive Virus Replication.

Virulent pathogens often cause the release of host-derived damage-associated molecular patterns (DAMPs) from infected cells. During encounters with immune-evasive viruses that block inflammatory gene expression, preformed DAMPs provide backup inflammatory signals that ensure protective immunity. Whether DAMPs exhibit additional backup defense activities is unknown. Herein, we report that viral infection of barrier epithelia (keratinocytes) elicits the release of preformed interleukin-1 (IL-1) family cytokines, including the DAMP IL-1α. Mechanistic studies revealed that IL-1 acts on skin fibroblasts to induce an interferon (IFN)-like state that restricts viral replication. We identified a branch in the IL-1 signaling pathway that induces IFN-stimulated gene expression in infected cells and found that IL-1 signaling is necessary to restrict viral replication in human skin explants. These activities are most important to control immune-evasive virus replication in fibroblasts and other barrier cell types. These findings highlight IL-1 as an important backup antiviral system to ensure barrier defense.