Adhesive anti-fibrotic interfaces on diverse organs.

Implanted biomaterials and devices face compromised functionality and efficacy in the long term owing to foreign body reactions and subsequent formation of fibrous capsules at the implant-tissue interfaces1-4. Here we demonstrate that an adhesive implant-tissue interface can mitigate fibrous capsule formation in diverse animal models, including rats, mice, humanized mice and pigs, by reducing the level of infiltration of inflammatory cells into the adhesive implant-tissue interface compared to the non-adhesive implant-tissue interface. Histological analysis shows that the adhesive implant-tissue interface does not form observable fibrous capsules on diverse organs, including the abdominal wall, colon, stomach, lung and heart, over 12 weeks in vivo. In vitro protein adsorption, multiplex Luminex assays, quantitative PCR, immunofluorescence analysis and RNA sequencing are additionally carried out to validate the hypothesis. We further demonstrate long-term bidirectional electrical communication enabled by implantable electrodes with an adhesive interface over 12 weeks in a rat model in vivo. These findings may offer a promising strategy for long-term anti-fibrotic implant-tissue interfaces.

Spatial transcriptomics in human skin research.

Spatial transcriptomics is a revolutionary technique that enables researchers to characterise tissue architecture and localisation of gene expression. A plethora of technologies that map gene expression are currently being developed, aiming to facilitate spatially resolved, high-dimensional assessment of gene transcription in the context of human skin research. Knowing which gene is expressed by which cell and in which location within skin, facilitates understanding of skin function and dysfunction in both health and disease. In this review, we summarise the available spatial transcriptomic methods and we describe their application to a broad spectrum of dermatological diseases.

Single-cell transcriptomics in human skin research: available technologies, technical considerations and disease applications.

Single-cell technologies have revolutionized research in the last decade, including for skin biology. Single-cell RNA sequencing has emerged as a powerful tool allowing the dissection of human disease pathophysiology at unprecedented resolution by assessing cell-to-cell variation, facilitating identification of rare cell populations and elucidating cellular heterogeneity. In dermatology, this technology has been widely applied to inflammatory skin disorders, fibrotic skin diseases, wound healing complications and cutaneous neoplasms. Here, we discuss the available technologies and technical considerations of single-cell RNA sequencing and describe its applications to a broad spectrum of dermatological diseases.

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.

Minor collagens of the skin with not so minor functions.

The structure and function of the skin relies on the complex expression pattern and organisation of extracellular matrix macromolecules, of which collagens are a principal component. The fibrillar collagens, types I and III, constitute over 90% of the collagen content within the skin and are the major determinants of the strength and stiffness of the tissue. However, the minor collagens also play a crucial regulatory role in a variety of processes, including cell anchorage, matrix assembly, and growth factor signalling. In this article, we review the expression patterns, key functions and involvement in disease pathogenesis of the minor collagens found in the skin. While it is clear that the minor collagens are important mediators of normal tissue function, homeostasis and repair, further insight into the molecular level structure and activity of these proteins is required for translation into clinical therapies.

Use of Serum Protein Measurements as Biomarkers that Can Predict the Outcome of Diabetic Foot Ulceration.

Objectives: To identify proteins that are prognostic for diabetic foot ulcer (DFU) healing and may serve as biomarkers for its management, serum samples were analyzed from diabetic mellitus (DM) patients. Approach: The serum specimens that were evaluated in this study were obtained from DM patients with DFU who participated in a prospective study and were seen biweekly until they healed their ulcer or the exit visit at 12 weeks. The group was divided into Healers (who healed their DFU during the study) and Non-Healers. Results: Interleukin (IL)-10, IL-4, IL-5, IL-6, and IL-13 and interferon-gamma were higher in the Healers while Fractalkine, IL-8, and TNFα were higher in the Non-Healers. The trajectory of IL-10 levels remained stable over time within and across groups, resulting in a strong prognostic ability for the prospective DFU healing course. Classification and Regression Tree analysis created an 11-node decision tree with healing status as the categorical response. Innovation: Consecutive measurements of proteins associated with wound healing can identify biomarkers that can predict DFU healing over a 12-week period. IL-10 was the strongest candidate for prediction. Conclusion: Measurement of serum proteins can serve as a successful strategy in guiding clinical management of DFU. The data also indicate likely superior performance of building a multiprotein biomarker score instead of relying on single biomarkers.

Use of Therapeutic RNAs to Accelerate Wound Healing in Diabetic Rabbit Wounds.

Introduction: Diabetes mellitus (DM) affects over 422 million people globally. Patients with DM are subject to a myriad of complications, of which diabetic foot ulcers (DFUs) are the most common with ∼25% chance of developing these wounds throughout their lifetime. Innovation: Currently there are no therapeutic RNAs approved for use in DFUs. Use of dressings containing novel layer-by-layer (LbL)-formulated therapeutic RNAs that inhibit PHD2 and miR-210 can significantly improve diabetic wound healing. These dressings provide sustained release of therapeutic RNAs to the wounds locally without systemic side effects. Clinical Problem Addressed: Diabetic foot wounds are difficult to heal and often result in significant patient morbidity and mortality. Materials and Methods: We used the diabetic neuroischemic rabbit model of impaired wound healing. Diabetes was induced in the rabbits with alloxan, and neuroischemia was induced by ligating the central neurovascular bundle of each ear. Four 6-mm full-thickness wounds were created on each ear. A LbL technique was used to conformally coat the wound dressings with chemically modified RNAs, including an antisense oligonucleotide (antimiR) targeting microRNA-210 (miR-210), an short synthetic hairpin RNA (sshRNA) targeting PHD2, or both. Results: Wound healing was improved by the antimiR-210 but not the PHD2-sshRNA. Specific knockdown of miR-210 in tissue as measured by RT-qPCR was ∼8 Ct greater than nonspecific controls, and this apparent level of knockdown (>99%) suggests that delivery to the tissue is highly efficient at the administered dose. Discussion: Healing of ischemic/neuropathic wounds in diabetic rabbits was accelerated upon inhibition of miR-210 by LbL delivery to the wound bed. miR-210 inhibition was achieved using a chemically modified antisense RNA.

Protocol for xenotransplantation of human skin and streptozotocin diabetes induction in immunodeficient mice to study impaired wound healing.

Here, we present a protocol for the integration of human skin onto the backs of diabetic immunodeficient mice, providing a versatile in vivo model for mimicking and studying mechanisms involved in impaired cutaneous wound healing. This protocol includes instructions for the grafting of human skin, induction of diabetes using streptozotocin and wounding/post-wounding care of immunodeficient mice, as well as suggested downstream tissue analyses. This preclinical mouse model can be used to validate the efficacy of newly developed wound dressings. For complete details on the use and execution of this protocol, please refer to Theocharidis et al. (2022).1.

Experimental treatments in clinical trials for diabetic foot ulcers: wound healers in the pipeline.

INTRODUCTION: Diabetes affects 400 million people globally and patients and causes nephropathy, neuropathy, and vascular disease. Amongst these complications, diabetic foot ulcers remain a substantial problem for patients and clinicians. Aggressive wound care and antibiotics remain important for the healing of these chronic wounds, but even when treated these chronic ulcers can lead to infection and amputations. AREAS COVERED: This paper reviews the pathophysiology of diabetic foot ulcers and the current management strategies. Then, it discusses novel therapeutics such as topical oxygen therapy as well as autologous patches and macrophage creams. EXPERT OPINION: Diabetic foot ulcers are a substantial problem for patients and clinicians. Early identification, aggressive wound care, and normoglycemia remain the standard of care, however when these fail it is important to adapt. Since each patient and wound vary drastically we believe they should be treated as such. For patient with intact perfusion, topical ON101 and sucrose octasulfate creams can help. While patient with peripheral arterial disease should consider topical oxygen therapy as an adjunct. However, as scientists gain a better understanding of the pathophysiology behind DFUs, the hope is that this new wave of therapeutics will emerge.

Future Directions in Research in Transcriptomics in the Healing of Diabetic Foot Ulcers.

Diabetic foot ulcers are a health crisis that affect millions of individuals worldwide. Current standard of care involves diligent wound care with adjunctive antibiotics and surgical debridement. However, despite this, the majority will still become infected and fail to heal. Recent efforts using bioengineered skin initially appeared promising, but randomized clinical trials have disappointed. Scientists have now begun to understand that the normal wound healing physiology does not apply to diabetic foot ulcers as they maintain a chronic state of inflammation and fail to progress in a linear pathway. Using transcriptomics, research over the past decade has started identifying master genes and protein pathways that are dysregulated in patients with diabetes. This review paper discusses those genes involved and how novel advancements are using this information to create new biologically based compounds to accelerate wound healing in patients with diabetic foot ulcers.

Exosomes Derived from Epidermal Stem Cells Improve Diabetic Wound Healing.

Diabetic foot ulceration is a major diabetic complication with unmet needs. We investigated the efficacy of epidermal stem cells and epidermal stem cells-derived exosomes (ESCs-Exo) in improving impaired diabetic wound healing and their mechanisms of action. In vitro experiments showed that ESCs-Exo enhanced the proliferation and migration of diabetic fibroblasts and macrophages and promoted alternative or M2 macrophage polarization. In wounds of db/db mice, treatment with both epidermal stem cells and ESCs-Exo, when compared with fibroblast exosomes and PBS control, accelerated wound healing by decreasing inflammation, augmenting wound cell proliferation, stimulating angiogenesis, and inducing M2 macrophage polarization. Multiplex protein quantification of wound lysates revealed TGFß signaling influenced by ESCs-Exo. High-throughput sequencing of small RNAs contained in the ESCs-Exo showed higher proportions of microRNAs than those contained in fibroblast exosomes. In silico functional analysis showed that the ESCs-Exo microRNAs‒target genes were primarily involved in homeostatic processes and cell differentiation and highlighted regulatory control of phosphatidylinositol-3 kinase/protein kinase B and TGFß signaling pathways. This was also validated in vitro. Collectively, our results indicate that epidermal stem cells and ESCs-Exo are equally effective in promoting impaired diabetic wound healing and that ESCs-Exo treatment may be a promising and technically advantageous alternative to stem cell therapies.

Murine macrophages or their secretome delivered in alginate dressings enhance impaired wound healing in diabetic mice.

Diabetic foot ulceration is a devastating diabetic complication with unmet needs. We explored the efficacy of calcium-crosslinked alginate dressings in topically delivering primary macrophages and their secretome to diabetic wounds. The alginate bandages had a microporous structure that enabled even cell loading with prolonged cell survival and egress following wound placement. In vitro experiments showed that we could successfully differentiate and polarize primary murine bone marrow derived monocytes into M0, M1, M2a and M2c defined states with distinct gene expression, surface protein and secretome profiles. The primary macrophages were delivered in the bandages, migrated within the wounds and were still present for as long as 16 days post-injury. In wounds of db/db mice, treatment with all macrophage subtypes and their secretome, when compared to control, accelerated wound healing. Bulk RNA sequencing analysis and multiplex protein quantification of wound lysates revealed that M2c macrophages conditioned media had the most impact in wound healing affecting processes like neurogenesis, while M1 conditioned media promoted keratinization and epidermal differentiation. Collectively, our results indicate that alginate dressings can serve as a delivery platform for topical treatment of diabetic wounds and that conditioned media from distinctly polarized macrophages is equally or more effective than their parental cells in advancing wound healing and could therefore be a promising and technically advantageous alternative to cell therapy.

A strain-programmed patch for the healing of diabetic wounds.

Diabetic foot ulcers and other chronic wounds with impaired healing can be treated with bioengineered skin or with growth factors. However, most patients do not benefit from these treatments. Here we report the development and preclinical therapeutic performance of a strain-programmed patch that rapidly and robustly adheres to diabetic wounds, and promotes wound closure and re-epithelialization. The patch consists of a dried adhesive layer of crosslinked polymer networks bound to a pre-stretched hydrophilic elastomer backing, and implements a hydration-based shape-memory mechanism to mechanically contract diabetic wounds in a programmable manner on the basis of analytical and finite-element modelling. In mouse and human skin, and in mini-pigs and humanized mice, the patch enhanced the healing of diabetic wounds by promoting faster re-epithelialization and angiogenesis, and the enrichment of fibroblast populations with a pro-regenerative phenotype. Strain-programmed patches might also be effective for the treatment of other forms of acute and chronic wounds.

Single cell transcriptomic landscape of diabetic foot ulcers.

Diabetic foot ulceration (DFU) is a devastating complication of diabetes whose pathogenesis remains incompletely understood. Here, we profile 174,962 single cells from the foot, forearm, and peripheral blood mononuclear cells using single-cell RNA sequencing. Our analysis shows enrichment of a unique population of fibroblasts overexpressing MMP1, MMP3, MMP11, HIF1A, CHI3L1, and TNFAIP6 and increased M1 macrophage polarization in the DFU patients with healing wounds. Further, analysis of spatially separated samples from the same patient and spatial transcriptomics reveal preferential localization of these healing associated fibroblasts toward the wound bed as compared to the wound edge or unwounded skin. Spatial transcriptomics also validates our findings of higher abundance of M1 macrophages in healers and M2 macrophages in non-healers. Our analysis provides deep insights into the wound healing microenvironment, identifying cell types that could be critical in promoting DFU healing, and may inform novel therapeutic approaches for DFU treatment.

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.

Autonomic nerve dysfunction and impaired diabetic wound healing: The role of neuropeptides.

Lower extremity ulcerations represent a major complication in diabetes mellitus and involve multiple physiological factors that lead to impairment of wound healing. Neuropeptides are neuromodulators implicated in various processes including diabetic wound healing. Diabetes causes autonomic and small sensory nerve fibers neuropathy as well as inflammatory dysregulation, which manifest with decreased neuropeptide expression and a disproportion in pro- and anti- inflammatory cytokine response. Therefore to fully understand the contribution of autonomic nerve dysfunction in diabetic wound healing it is crucial to explore the implication of neuropeptides. Here, we will discuss recent studies elucidating the role of specific neuropeptides in wound healing.

Integrated Skin Transcriptomics and Serum Multiplex Assays Reveal Novel Mechanisms of Wound Healing in Diabetic Foot Ulcers.

Nonhealing diabetic foot ulcers (DFUs) are characterized by low-grade chronic inflammation, both locally and systemically. We prospectively followed a group of patients who either healed or developed nonhealing chronic DFUs. Serum and forearm skin analysis, both at the protein expression and the transcriptomic level, indicated that increased expression of factors such as interferon-γ (IFN-γ), vascular endothelial growth factor, and soluble vascular cell adhesion molecule-1 were associated with DFU healing. Furthermore, foot skin single-cell RNA sequencing analysis showed multiple fibroblast cell clusters and increased inflammation in the dorsal skin of patients with diabetes mellitus (DM) and DFU specimens compared with control subjects. In addition, in myeloid cell DM and DFU upstream regulator analysis, we observed inhibition of interleukin-13 and IFN-γ and dysregulation of biological processes that included cell movement of monocytes, migration of dendritic cells, and chemotaxis of antigen-presenting cells pointing to an impaired migratory profile of immune cells in DM skin. The SLCO2A1 and CYP1A1 genes, which were upregulated at the forearm of nonhealers, were mainly expressed by the vascular endothelial cell cluster almost exclusively in DFU, indicating a potential important role in wound healing. These results from integrated protein and transcriptome analyses identified individual genes and pathways that can potentially be targeted for enhancing DFU healing.

Topical Application of a Mast Cell Stabilizer Improves Impaired Diabetic Wound Healing.

Impaired wound healing in the diabetic foot is a major problem often leading to amputation. Mast cells have been shown to regulate wound healing in diabetes. We developed an indole-carboxamide type mast cell stabilizer, MCS-01, which proved to be an effective mast cell degranulation inhibitor in vitro and can be delivered topically for prolonged periods through controlled release by specifically designed alginate bandages. In diabetic mice, both pre- and post-wounding, topical MCS-01 application accelerated wound healing comparable to that achieved with systemic mast cell stabilization. Moreover, MCS-01 altered the macrophage phenotype, promoting classically activated polarization. Bulk transcriptome analysis from wounds treated with MCS-01 or placebo showed that MCS-01 significantly modulated the mRNA and microRNA profile of diabetic wounds, stimulated upregulation of pathways linked to acute inflammation and immune cell migration, and activated the NF-κB complex along with other master regulators of inflammation. Single-cell RNA sequencing analysis of 6,154 cells from wounded and unwounded mouse skin revealed that MCS-01 primarily altered the gene expression of mast cells, monocytes, and keratinocytes. Taken together, these findings offer insights into the process of diabetic wound healing and suggest topical mast cell stabilization as a potentially successful treatment for diabetic foot ulceration.

Type VI Collagen Regulates Dermal Matrix Assembly and Fibroblast Motility.

Type VI collagen is a nonfibrillar collagen expressed in many connective tissues and implicated in extracellular matrix (ECM) organization. We hypothesized that type VI collagen regulates matrix assembly and cell function within the dermis of the skin. In the present study we examined the expression pattern of type VI collagen in normal and wounded skin and investigated its specific function in new matrix deposition by human dermal fibroblasts. Type VI collagen was expressed throughout the dermis of intact human skin, at the expanding margins of human keloid samples, and in the granulation tissue of newly deposited ECM in a mouse model of wound healing. Generation of cell-derived matrices (CDMs) by human dermal fibroblasts with stable knockdown of COL6A1 revealed that type VI collagen-deficient matrices were significantly thinner and contained more aligned, thicker, and widely spaced fibers than CDMs produced by normal fibroblasts. In addition, there was significantly less total collagen and sulfated proteoglycans present in the type VI collagen-depleted matrices. Normal fibroblasts cultured on de-cellularized CDMs lacking type VI collagen displayed increased cell spreading, migration speed, and persistence. Taken together, these findings indicate that type VI collagen is a key regulator of dermal matrix assembly, composition, and fibroblast behavior and may play an important role in wound healing and tissue regeneration.