Identification of the critical therapeutic entity in secreted Hsp90α that promotes wound healing in newly re-standardized healthy and diabetic pig models

Discovery of Cell Number-Interstitial Fluid Volume (CIF) Ratio Reveals Secretory Autophagy Pathway to Supply eHsp90α for Wound Healing

Cell secretion repairs tissue damage and restores homeostasis throughout adult life. The extracellular heat shock protein-90alpha (eHsp90α) has been reported as an exosome cargo and a potential driver of wound healing. However, neither the mechanism of secretion nor the genetic evidence for eHsp90α in wound healing has been substantiated. Herein, we show that tissue injury causes massive deposition of eHsp90α in tissues and secretion of eHsp90α by cells. Sequential centrifugations of conditioned medium from relevant cell lines revealed the relative distributions of eHsp90α in microvesicle, exosome and trypsin-sensitive supernatant fractions to be approximately <2%, <4% and >95%, respectively. Establishing the cell-number-to-interstitial-fluid-volume (CIF) ratio for the microenvironment of human tissues as 1 × 109 cells: 1 mL interstitial fluid enabled us to predict the corresponding tissue concentrations of eHsp90α in these fractions as 3.74 μg/mL, 5.61 μg/mL and 178 μg/mL. Remarkably, the 178 μg/mL eHsp90α matches the previously reported 100-300 μg/mL of recombinant eHsp90α whose topical application promotes maximum wound healing in animal models. More importantly, we demonstrate that two parallel secretory autophagy-regulating gene families, the autophagy-regulating (AR) genes and the Golgi reassembly-stacking protein (GRASP) genes work together to mediate the secretion of the physiological concentration of eHsp90α to promote wound healing. Thus, utilization of the CIF ratio-based extrapolation method may enable investigators to rapidly predict biomarker targets from cell-conditioned-medium data.

The effect of anatomic location on porcine models of burn injury and wound healing

Porcine models are frequently used for burn healing studies; however, factors including anatomic location and lack of standardised wound methods can impact the interpretation of wound data. The objectives of this study are to examine the influence of anatomical locations on the uniformity of burn creation and healing in porcine burn models. To optimise burn parameters on dorsal and ventral surfaces, ex vivo and in situ euthanized animals were first used to examine the location-dependence of the burn depth and contact time relationship. The location-dependent healing in vivo was then examined using burn and excisional wounds at dorsal, ventral, caudal and cranial locations. Lactate dehydrogenase (LDH) and H&E were used to assess burn depth and wound re-epithelialization. We found that burn depth on the ventral skin was significantly deeper than that of the dorsal skin at identical thermal conditions. Compared with burns created ex vivo, burns created in situ immediately post-mortem were significantly deeper in the ventral location. In live animals, 2 out of 12 burn wounds were fully re-epithelialized after 14 days in contrast to complete re-epithelialization of all excisional wounds. Among the burn wounds, those at the cranial-dorsal site exhibited faster healing than at the caudal-dorsal site. This study showed that anatomical location is an important consideration for the consistency of burn depth creation and healing. These data support symmetric localization of treatment and control for comparative assessment of burn healing in porcine models to prevent misinterpretation of results and increase the translatability of findings to humans.

Assessing Animal Models to Study Impaired and Chronic Wounds

Impaired healing wounds do not proceed through the normal healing processes in a timely and orderly manner, and while they do eventually heal, their healing is not optimal. Chronic wounds, on the other hand, remain unhealed for weeks or months. In the US alone, chronic wounds impact ~8.5 million people and cost ~USD 28-90 billion per year, not accounting for the psychological and physical pain and emotional suffering that patients endure. These numbers are only expected to rise in the future as the elderly populations and the incidence of comorbidities such as diabetes, hypertension, and obesity increase. Over the last few decades, scientists have used a variety of approaches to treat chronic wounds, but unfortunately, to date, there is no effective treatment. Indeed, while there are thousands of drugs to combat cancer, there is only one single drug approved for the treatment of chronic wounds. This is in part because wound healing is a very complex process involving many phases that must occur sequentially and in a timely manner. Furthermore, models that fully mimic human chronic wounds have not been developed. In this review, we assess various models currently being used to study the biology of impaired healing and chronic non-healing wounds. Among them, this paper also highlights one model which shows significant promise; this model uses aged and obese db/db-/- mice and the chronic wounds that develop show characteristics of human chronic wounds that include increased oxidative stress, chronic inflammation, damaged microvasculature, abnormal collagen matrix deposition, a lack of re-epithelialization, and the spontaneous development of multi-bacterial biofilm. We also discuss how important it is that we continue to develop chronic wound models that more closely mimic those of humans and that can be used to test potential treatments to heal chronic wounds.

Sex differences in radiation research

PURPOSE

The Sex Differences in Radiation Research workshop addressed the role of sex as a confounder in radiation research and its implication in real-world radiological and nuclear applications.

METHODS

In April 2022, HHS-wide partners from the Radiation and Nuclear Countermeasures Program, the Office of Research on Women's Health National Institutes of Health Office of Women's Health, U.S. Food and Drug Administration, and the Radiological and Nuclear Countermeasures Branch at the Biomedical Advanced Research and Development Authority conducted a workshop to address the scientific implication and knowledge gaps in understanding sex in basic and translational research. The goals of this workshop were to examine sex differences in 1. Radiation animal models and understand how these may affect radiation medical countermeasure development; 2. Biodosimetry and/or biomarkers used to assess acute radiation syndrome, delayed effects of acute radiation exposure, and/or predict major organ morbidities; 3. medical research that lacks representation from both sexes. In addition, regulatory policies that influence inclusion of women in research, and the gaps that exist in drug development and device clearance were discussed. Finally, real-world sex differences in human health scenarios were also considered.

RESULTS

This report provides an overview of the two-day workshop, and open discussion among academic investigators, industry researchers, and U.S. government representatives.

CONCLUSIONS

This meeting highlighted that current study designs lack the power to determine statistical significance based on sex, and much is unknown about the underlying factors that contribute to these differences. Investigators should accommodate both sexes in all stages of research to ensure that the outcome is robust, reproducible, and accurate, and will benefit public health.

Methodologies to Evaluate the Hair Follicle-Targeted Drug Delivery Provided by Nanoparticles

Nanotechnology has been investigated for treatments of hair follicle disorders mainly because of the natural accumulation of solid nanoparticles in the follicular openings following a topical application, which provides a drug "targeting effect". Despite the promising results regarding the therapeutic efficacy of topically applied nanoparticles, the literature has often presented controversial results regarding the targeting of hair follicle potential of nanoformulations. A closer look at the published works shows that study parameters such as the type of skin model, skin sections analyzed, employed controls, or even the extraction methodologies differ to a great extent among the studies, producing either unreliable results or precluding comparisons altogether. Hence, the present study proposes to review different skin models and methods for quantitative and qualitative analysis of follicular penetration of nano-entrapped drugs and their influence on the obtained results, as a way of providing more coherent study protocols for the intended application.

LSD1 interacting with HSP90 promotes skin wound healing by inducing metabolic reprogramming of hair follicle stem cells through the c-MYC/LDHA axis

It has been demonstrated that hair follicle stem cells (HFSCs) can contribute to wound closure and repair. However, the specific mechanism remains unclear due to the complexity of the wound repair process. Lysine-specific demethylase 1 (LSD1), an important gene for the regulation of stem cell differentiation, has been reported to participate in wound healing regulation. Heat shock protein 90 (HSP90), a chaperone protein, is recently discovered to be a driver gene for wound healing. This study explored the molecular mechanisms by which the binding between LSD1 and HSP90 affects the role of HFSCs during skin wound healing. Following bioinformatics analysis, the key genes acting on HFSCs were identified. The expression of LSD1, HSP90, and c-MYC was found to be upregulated in differentiated HFSCs. Analysis of their binding affinity revealed that LSD1 interacted with HSP90 to enhance the stability of the transcription factor c-MYC. Lactate dehydrogenase A (LDHA) has been documented to be essential for HFSC activation. Therefore, we speculate that LDHA may induce the differentiation of HFSCs through glucose metabolism reprogramming. The results showed that c-MYC activated LDHA activity to promote glycolytic metabolism, proliferation, and differentiation of HFSCs. Finally, in vivo animal experiments further confirmed that LSD1 induced skin wound healing in mice via the HSP90/c-MYC/LDHA axis. From our data, we conclude that LSD1 interacting with HSP90 accelerates skin wound healing by inducing HFSC glycolytic metabolism, proliferation, and differentiation via c-MYC/LDHA axis.

Conductive Polymer-Coated 3D Printed Microneedles: Biocompatible Platforms for Minimally Invasive Biosensing Interfaces

Conductive polymeric microneedle (MN) arrays as biointerface materials show promise for the minimally invasive monitoring of analytes in biodevices and wearables. There is increasing interest in microneedles as electrodes for biosensing, but efforts have been limited to metallic substrates, which lack biological stability and are associated with high manufacturing costs and laborious fabrication methods, which create translational barriers. In this work, additive manufacturing, which provides the user with design flexibility and upscale manufacturing, is employed to fabricate acrylic-based microneedle devices. These microneedle devices are used as platforms to produce intrinsically-conductive, polymer-based surfaces based on polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). These entirely polymer-based solid microneedle arrays act as dry conductive electrodes while omitting the requirement of a metallic seed layer. Two distinct coating methods of 3D-printed solid microneedles, in situ polymerization and drop casting, enable conductive functionality. The microneedle arrays penetrate ex vivo porcine skin grafts without compromising conductivity or microneedle morphology and demonstrate coating durability over multiple penetration cycles. The non-cytotoxic nature of the conductive microneedles is evaluated using human fibroblast cells. The proposed fabrication strategy offers a compelling approach to manufacturing polymer-based conductive microneedle surfaces that can be further exploited as platforms for biosensing.

Characterization and modeling of the in-plane collagen fiber distribution in the porcine dermis

The structural arrangement of collagen fibers in the plane of the dermis layer plays a critical role in accurately predicting the mechanical behavior of skin tissues. This paper combines a histological analysis with statistical modeling to characterize and model the in-plane collagen fiber distribution in the porcine dermis. The histology data reveals that the fiber distribution in the plane of the porcine dermis is non-symmetric. The histology data forms the basis of our model, which employs a combination of two π-periodic von-Mises distribution density functions to create a non-symmetric distribution. We demonstrate that a non-symmetric in-plane fiber distribution is a significant improvement over a symmetric distribution.

Rab37 Promotes Endothelial Differentiation and Accelerates ADSC-Mediated Diabetic Wound Healing through Regulating Secretion of Hsp90α and TIMP1

Accumulating evidence indicates that adipose tissue-derived mesenchymal stem cells (ADSCs) are an effective treatment for diabetic refractory wounds. However, the application of ADSCs to diabetic wounds is still limited, indicating that we still lack sufficient knowledge regarding regulators/mediators of ADSCs during wound healing. Rab37, a member of RabGTPase, may function as regulator of vesicle trafficking, which is a crucial event for the secretion of cytokines by ADSCs. Our previous study indicated that Rab37 promotes the adiopogenic differentiation of ADSCs. In this study, we explored the role of Rab37 in ADSC-mediated diabetic wound healing. An in vivo study in db/db diabetic mice showed that Rab37-expressing ADSCs shortened the wound closure time, improved re-epithelialization and collagen deposition, and promoted angiogenesis during wound healing. An in vitro study showed that Rab37 promoted the proliferation, migration and endothelial differentiation of ADSCs. LC-MS/MS analysis identified Hsp90α and TIMP1 as up-regulated cytokines in conditioned media of Rab37-ADSCs. The up-regulation of Rab37 enhanced the secretion of Hsp90α and TIMP1 during endothelial differentiation and under high-glucose exposure. Interestingly, Rab37 promoted the expression of TIMP1, but not Hsp90α, during endothelial differentiation. PLA showed that Rab37 can directly bind to Hsp90α orTIMP1 in ADSCs. Moreover, Hsp90α and TIMP1 knockdown compromised the promoting effects of Rab37 on the proliferation, migration and endothelial differentiation of ADSCs. In conclusion, Rab37 promotes the proliferation, migration and endothelial differentiation of ADSCs and accelerates ADSC-mediated diabetic wound healing through regulating the secretion of Hsp90α and TIMP1.

Key factors to establish the ovalbumin-induced atopic dermatitis minipig model: age and body weight

Background

Given its similar structure and immune response to the human skin, porcine is a good model for dermal studies. Here, we sensitized ovalbumin (Ova) on minipig back skin for 2–4 weeks to induce chronic atopic dermatitis (AD).

Results

Gross observation, serum cytokine level, epidermal thickness, and epidermal integrity did not change after 4 weeks of Ova induction compared with the control, indicating AD modeling failure. Only the neutrophils in the blood and macrophages in bronchoalveolar lavage fluid changed slightly until 3 or 2 weeks after Ova sensitization, respectively. The successful and failed Ova-induced AD minipig models only differ in age and body weight of the minipigs. The minipigs, 12 months old with a 30-kg median weight, had a two-fold thicker dermis than minipigs 8–10 months old, with an 18.97-kg median weight, resulting in impaired Ova permeability and immune response.

Conclusion

Age and body weight are key factors that should be considered when developing an Ova-induced AD minipig model.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42826-022-00141-4.

Extracellular Heat Shock Protein-90 (eHsp90): Everything You Need to Know

“Extracellular” Heat Shock Protein-90 (Hsp90) was initially reported in the 1970s but was not formally recognized until 2008 at the 4th International Conference on The Hsp90 Chaperone Machine (Monastery Seeon, Germany). Studies presented under the topic of “extracellular Hsp90 (eHsp90)” at the conference provided direct evidence for eHsp90’s involvement in cancer invasion and skin wound healing. Over the past 15 years, studies have focused on the secretion, action, biological function, therapeutic targeting, preclinical evaluations, and clinical utility of eHsp90 using wound healing, tissue fibrosis, and tumour models both in vitro and in vivo. eHsp90 has emerged as a critical stress-responding molecule targeting each of the pathophysiological conditions. Despite the studies, our current understanding of several fundamental questions remains little beyond speculation. Does eHsp90 indeed originate from purposeful live cell secretion or rather from accidental dead cell leakage? Why did evolution create an intracellular chaperone that also functions as a secreted factor with reported extracellular duties that might be (easily) fulfilled by conventional secreted molecules? Is eHsp90 a safer and more optimal drug target than intracellular Hsp90 chaperone? In this review, we summarize how much we have learned about eHsp90, provide our conceptual views of the findings, and make recommendations on the future studies of eHsp90 for clinical relevance.

The pig as a model system for investigating the recruitment and contribution of myofibroblasts in skin healing

In the skin-healing field, porcine models are regarded as a useful analogue for human skin due to their numerous anatomical and physiological similarities. Despite the widespread use of porcine models in skin healing studies, the initial origin, recruitment and transition of fibroblasts to matrix-secreting contractile myofibroblasts are not well defined for this model. In this review, we discuss the merit of the pig as an animal for studying myofibroblast origin, as well as the challenges associated with assessing their contributions to skin healing. Although a variety of wound types (incisional, partial thickness, full thickness, burns) have been investigated in pigs in attempts to mimic diverse injuries in humans, direct comparison of human healing profiles with regards to myofibroblasts shows evident differences. Following injury in porcine models, which often employ juvenile animals, myofibroblasts are described in the developing granulation tissue at 4 days, peaking at Days 7-14, and persisting at 60 days post-wounding, although variations are evident depending on the specific pig breed. In human wounds, the presence of myofibroblasts is variable and does not correlate with the age of the wound or clinical contraction. Our comparison of porcine myofibroblast-mediated healing processes with those in humans suggests that further validation of the pig model is essential. Moreover, we identify several limitations evident in experimental design that need to be better controlled, and standardisation of methodologies would be beneficial for the comparison and interpretation of results. In particular, we discuss anatomical location of the wounds, their size and depth, as well as the healing microenvironment (wet vs. moist vs. dry) in pigs and how this could influence myofibroblast recruitment. In summary, although a widespread model used in the skin healing field, further research is required to validate pigs as a useful analogue for human healing with regards to myofibroblasts.

Wound Healing Driver Gene and Therapeutic Development: Political and Scientific Hurdles

Significance: Since the last Food and Drug Administration (FDA) approval of a wound healing therapeutic in 1997, no new therapeutic candidate (excluding physical therapies, devices, dressings, and antimicrobial agents) has advanced to clinical applications. During this period, the FDA drug approvals for tumors, which have been referred to as "wounds that do not heal," have reached a total of 284 (by end of 2018). Both political and scientific factors may explain this large discrepancy in drug approvals for the two seemingly related and equally complex pathophysiological conditions. Recent Advances: Using the current research funding ratio of 1:150 for wound healing to cancer and the 5% FDA drug approval rate for oncology, we reach a crude estimate of a 0.03% success rate for wound healing therapeutics. Unless a drastic improvement of the current situation, we express a pessimistic outlook toward new and effective wound healing drugs. Critical Issues: We argue that successful development of wound healing therapeutics will rely on identification of wound healing driver genes (WDGs), and the focus should be on WDGs for the wound closure phase of wound healing. Therefore, WDGs must be both necessary and sufficient for wound closure; the absence of a WDG disrupts wound closure, while its supplementation alone is sufficient to restore full wound closure. Successful translation of a WDG into therapeutics requires availability of well-defined animal models with a high degree of relevance to humans. This review discusses the main hurdles faced by the wound healing research community behind the development of so-called "rescuing drugs" for wound healing. Future Directions: Given the lack of new wound healing drugs for the past 23 years, there is a need for a wide range of fresh, innovative, and thorough debates on wound healing drug development, including an organized movement to raise public support for wound healing research.

A review of animal models from 2015 to 2020 for preclinical chronic wounds relevant to human health

SIGNIFICANCE

Chronic wounds fail to heal in a timely manner and exhibit sustained inflammation with slow tissue repair and remodelling. They decrease mobility and quality of life, and remain a major clinical challenge in the long-term care of many patients, affecting 6.5 million individuals annually in the U.S., decreasing mobility and quality of life. Treatment costs are a major burden on the U.S. healthcare system, totalling between $25 and $100 billion annually. Chronic wound severity depends upon several factors such as comorbidities, severity of tissue damage, infection and presence of necrosis and vary greatly in their healing mechanisms. In vivo animal models are critical for studying healing pathways of chronic wounds and seek to replicate clinical factors for trials of topical, systemic, and device-based therapeutics. This comprehensive review discusses murine, rat, lapine, canine, feline and porcine models of chronic wounds.

RECENT ADVANCES

Foundational chronic wound models for several species are discussed together with refinements and advances in the time period between 2015 and 2020 which have the potential for broad utility in investigating biological and device-based wound treatment therapies for human health.

CRITICAL ISSUES

Chronic wounds fail to heal in a timely manner and have differing aetiologies, rendering no single in vivo animal model universally applicable.

FUTURE DIRECTIONS

Further studies are required to develop clinically relevant chronic wound animal model which reflect the clinical reality of the various influences of age, disease, comorbidities and gender on delayed healing and enhance understanding of the biological processes of human wound healing.

A Novel Approach to Negative Pressure Wound Therapy: Use of High Suction Capillary Device to Improve Wound Healing

INTRODUCTION

Negative Pressure Wound Therapy (NPWT) is a procedure used for nonhealing wounds. In NPWT, a special sealed dressing of large cell foam (>400 µm) or gauze is connected to a pump. Most commonly, negative pressures between -10 and -125 millimeters of mercury (mm Hg) are used. The mechanism of healing is unknown but maybe attributable to removal of the exudate and bacteria, and the stimulation of tissue repair through microdeformation. Reticulated foams with micron-size open cells, Capillary Suction Devices (CSD; 100 to 5 µm) exert capillary suction between 10 and 70 mm of Hg with a multilayered foam dressing.

MATERIALS AND METHODS

Yorkshire pigs received 5 surgical excision wounds, 3 cm2, on each side of the back. The wounds were covered with a NPWT dressing (110 mm Hg negative pressure by a pump), CSD with capillary suctions of 30 mm Hg (CSD-30) and 70 mm Hg (CSD-70), and a conventional gauze dressing. The wounds were measured on day 2, and then every 4-5 days thereafter; the total fluid collected by the various dressing over time.

RESULTS

By post-wound day 20, the wounds treated with CSD-70 and NPWT were 100% closed while the wounds treated with CSD-30 and gauze were 65% and 45%, respectively. This indicated comparable wound closure efficacies for CSD-70 and NPWT. The average total fluid uptake measured in grams dry weight were similar for CSD-70 and NPWT, 36 and 38 g, respectively, while the values were 24 g for CSD-30 and 12 g for gauze. However, the maximum fluid uptake observed at day 2 indicated that CSD-70 and CSD 30, 24 and 14 g, respectively, were superior to NPWT and gauze 12 and 7 g, respectively.

CONCLUSION

This data indicate comparable wound closure efficacies for CSD-70 and NPWT. It is felt that CSD is an effective, safe, and lower cost alternative to vacuum-assisted NPWT.

A murine model of Staphylococcus aureus infected chronic diabetic wound: A new tool to develop alternative therapeutics

Diabetic wound infection is a frequent complication that may result in limb amputation. To develop new treatment strategies in response to increasing bacterial resistance, animal models are needed. We created a diabetic mouse model with chronically infected wounds. Diabetes was induced using streptozotocin, and wounds were performed using a biopsy punch, and then infected with a clinical strain of Staphylococcus aureus. Chronification was reached by delaying healing thanks to chemical products (aminotriazole and mercaptosuccinic acid). Overall survival, as well as clinical, bacteriological and immunological data in skin, blood and spleens were collected at days 1, 7, and 14 after wounding. After a transient bacteremia proved by bacteria presence in spleen and kidneys in the first days after wounding, infected mice showed a chronic infection, with a bioburden impairing the healing process, and bacteria persistence compared to control mice. Infected mice showed gradual increasing skin levels of IL-17A compared to control mice that resulted in an IL-17/IFN-γ inbalance, pointing out a localized Th17 polarization of the immune response. Whether infected or not, the skin level of IL-10 decreased dramatically at days 1 and 7 after wounding, with an increase observed only in the control mice at day 14. After a decrease at day 1 in both groups, spleen IL-10 showed a rather steady level at days 7 and 14 in the control group compared with the decrease observed in the infected group. The spleen IL-10/IFN-γ ratio showed a systemic inflammatory response with Th1 polarization. Therefore, this model provides useful data to study wound healing. It is easy to reproduce, affordable and offers clinical and biological tools to evaluate new therapeutics.

Melanoma-Bearing Libechov Minipig (MeLiM): The Unique Swine Model of Hereditary Metastatic Melanoma

National cancer databases document that melanoma is the most aggressive and deadly cutaneous malignancy with worldwide increasing incidence in the Caucasian population. Around 10% of melanomas occur in families. Several germline mutations were identified that might help to indicate individuals at risk for preventive interventions and early disease detection. More than 50% of sporadic melanomas carry mutations in Ras/Raf/mitogen-activated protein kinase (MAPK/MEK) pathway, which may represent aims of novel targeted therapies. Despite advances in targeted therapies and immunotherapies, the outcomes in metastatic tumor are still unsatisfactory. Here, we review animal models that help our understanding of melanoma development and treatment, including non-vertebrate, mouse, swine, and other mammal models, with an emphasis on those with spontaneously developing melanoma. Special attention is paid to the melanoma-bearing Libechov minipig (MeLiM). This original swine model of hereditary metastatic melanoma enables studying biological processes underlying melanoma progression, as well as spontaneous regression. Current histological, immunohistochemical, biochemical, genetic, hematological, immunological, and skin microbiome findings in the MeLiM model are summarized, together with development of new therapeutic approaches based on tumor devitalization. The ongoing study of molecular and immunological base of spontaneous regression in MeLiM model has potential to bring new knowledge of clinical importance.

A robust strategy for proteomic identification of biomarkers of invasive phenotype complexed with extracellular heat shock proteins

As an extension of their orchestration of intracellular pathways, secretion of extracellular heat shock proteins (HSPs) is an emerging paradigm of homeostasis imperative to multicellular organization. Extracellular HSP is axiomatic to the survival of cells during tumorigenesis; proportional representation of specific HSP family members is indicative of invasive potential and prognosis. Further significance has been added by the knowledge that all cancer-derived exosomes have surface-exposed HSPs that reflect the membrane topology of cells that secrete them. Extracellular HSPs are also characteristic of chronic inflammation and sepsis. Accordingly, interrogation of extracellular HSPs secreted from cell culture models may represent a facile means of identifying translational biomarker signatures for targeting in situ. In the current study, we evaluated a simple peptide-based multivalent HSP affinity approach using the Vn96 peptide for low speed pelleting of HSP complexes from bioreactor cultures of cell lines with varying invasive phenotype in xenotransplant models: U87 (glioblastoma multiforme; invasive); HELA (choriocarcinoma; minimally invasive); HEK293T (virally transformed immortalized; embryonic). Proteomic profiling by bottom-up mass spectrometry revealed a comprehensive range of candidate biomarkers including primary HSP ligands. HSP complexes were associated with additional chaperones of prognostic significance such as protein disulfide isomerases, as well as pleiotropic metabolic enzymes, established as proportionally reflective of invasive phenotype. Biomarkers of inflammatory and mechanotransductive phenotype were restricted to the most invasive cell model U87, including chitinase CHI3L1, lamin C, amyloid derivatives, and histone isoforms.

Heat shock proteins in the physiology and pathophysiology of epidermal keratinocytes

Heat shock proteins (HSPs), a large group of highly evolutionary conserved proteins, are considered to be main elements of the cellular proteoprotection system. HSPs are encoded by genes activated during the exposure of cells to proteotoxic factors, as well as by genes that are expressed constitutively under physiological conditions. HSPs, having properties of molecular chaperones, are involved in controlling/modulation of multiple cellular and physiological processes. In the presented review, we summarize the current knowledge on HSPs in the biology of epidermis, the outer skin layer composed of stratified squamous epithelium. This tissue has a vital barrier function preventing from dehydratation due to passive diffusion of water out of the skin, and protecting from infection and other environmental insults. We focused on HSPB1 (HSP27), HSPA1 (HSP70), HSPA2, and HSPC (HSP90), because only these HSPs have been studied in the context of physiology and pathophysiology of the epidermis. The analysis of literature data shows that HSPB1 plays a role in the regulation of final steps of keratinization; HSPA1 is involved in the cytoprotection, HSPA2 contributes to the early steps of keratinocyte differentiation, while HSPC is essential in the re-epithelialization process. Since HSPs have diverse functions in various types of somatic tissues, in spite of multiple investigations, open questions still remain about detailed roles of a particular HSP isoform in the biology of epidermal keratinocytes.

Light-emitting diode irradiation using 660 nm promotes human fibroblast HSP90 expression and changes cellular activity and morphology

We evaluated changes in cell viability and morphology in response to low-level light irradiation and underlying variations in the levels of heat shock proteins (HSPs). Human fibroblasts were irradiated with a light-emitting diode (LED) array at 660 nm (50 mW for 15, 30, and 60 minutes). Cell viability and morphological changes were evaluated via epifluorescence analysis; we also assessed cell viability and length changes. The expression levels of adenosine triphosphate (ATP) and various HSPs (HSP27, 60, 70, and 90) were analyzed by immunohistochemical staining, Western blotting and microarray analysis. After LED irradiation, cellular viability and morphology changed. Of the several HSPs analyzed, the HSP90 level increased significantly, suggesting that this protein played roles in the morphological and cellular changes. Thus, low-level irradiation triggered cellular changes mediated by increased HSP90 expression; this may explain why skin irradiation enhances wound-healing.

After Conventional Wisdom Has Failed, What Drives Wound Healing?

Between 2006 and 2015, the U.S. Food and Drug Administration’s (FDA) overall likelihood of approval (LOA) from Phase I clinical trials for all therapeutic candidates was 9.6%, with the highest LOA in haematology (26.1%) and the lowest in oncology (5.1%). Two critical features attributed to the success of advancing trials were i) targeting driver genes responsible for disease, and ii) use of human disease-relevant animal models during preclinical studies. For decades, conventional wisdom has been that growth factors are the drivers of wound healing, but few have either advanced to clinical applications or proven effective. The purpose of this paper is to explore heat shock protein 90-alpha (Hsp90α)’s role as a potential driver of wound healing and as a possible future therapeutic entity through a review of recent literature, including studies with human disease-relevant animal models. Of the approximately 7,000 gene products generated by a given mammalian cell type, the Hsp90 family of proteins (Hsp90α and Hsp90β) accounts for 2–3% of them. Hsp90β fulfils the role of an intracellular chaperone, but Hsp90α’s intracellular function is surprisingly dispensable. Instead, the abundancy of Hsp90α appears to have been prepared for extracellular purposes. When secreted via exosomes by cells under environmental stress, such as injury, Hsp90α protects cells from hypoxia-induced cell death, reduces local inflammation, and subsequently promotes cell migration to repair the injured tissue. Unlike conventional growth factors, secreted Hsp90α stimulates all major cell types involved in wound healing equally, resists microenvironmental inhibitors like TGFβ and hyperglycaemia, and is highly stable. Inhibition of exosome-mediated Hsp90α secretion, neutralisation of Hsp90α’s ATPase-independent extracellular functions, or interruption of Hsp90α-LRP-1 signalling blocks wound closure in vivo. Topical application of Hsp90α’s therapeutic entity, F-5 (a 115-amino acid peptide), has shown great promise for healing acute burn and diabetic wounds in mice and pigs.

Topical Application of Tat-Rac1 Promotes Cutaneous Wound Healing in Normal and Diabetic Mice

The endogenous small GTPase, Rac1, plays a critical role during normal skin wound healing. It remains to be determined whether endogenous Rac1 can be appropriately activated in chronic wounds; if not, whether exogenous Rac1 has therapeutic effects on wound healing. Here we show that Rac1 protein levels were lower in wounds of db/db diabetic mice than wounds in wild type mice during the healing process. To assess the therapeutic potential of exogenous Rac1 in wound healing, we produced a Tat-Rac1 fusion protein that enters into cells through protein transduction. Tat-Rac1 increased proliferation and migration of keratinocytes and dermal fibroblasts in vitro. Topical application of Tat-Rac1 accelerated cutaneous wound closure in vivo in db/db mice as well as wild type mice. Further analyses revealed that Tat-Rac1 had faster re-epithelialization, higher keratinocyte proliferation and migration without an earlier onset of myofibroblast activation than vehicle treated wounds. Tat-Rac1 also reduced inflammation in wounds. Our findings revealed the failure of diabetic wounds to elevate Rac1 expression and suggested a therapeutic strategy utilizing a Rac1-based biologic to compensate for this defect thereby promoting wound healing.

Review: Multimodal bioactive material approaches for wound healing

Wound healing is a highly complex process of tissue repair that relies on the synergistic effect of a number of different cells, cytokines, enzymes, and growth factors. A deregulation in this process can lead to the formation of a non-healing chronic ulcer. Current treatment options, such as collagen wound dressings, are unable to meet the demand set by the wound environment. Therefore, a multifaceted bioactive dressing is needed to elicit a targeted affect. Wound healing strategies seek to develop a targeted effect through the delivery of a bioactive molecule to the wound by a hydrogel or a polymeric scaffold. This review examines current biomaterial and small molecule-based approaches that seek to develop a bioactive material for targeted wound therapy and accepted wound healing models for testing material efficacy.

Extracellular and Non-Chaperone Function of Heat Shock Protein-90α Is Required for Skin Wound Healing

Despite years of effort and investment, there are few topical or systemic medications for skin wounds. Identifying natural drivers of wound healing could facilitate the development of new and effective treatments. When skin is injured, there is a massive increase of heat shock protein (Hsp) 90α inside the wound bed. The precise role for these Hsp90α proteins, however, was unclear. The availability of a unique mouse model that lacked the intracellular ATPase-driven chaperoning, but spared the extracellular fragment-5-supported pro-motility function of Hsp90α allowed us to test specifically the role of the non-chaperone function of Hsp90α in normal wound closure. We found that the chaperone-defective Hsp90α-Δ mutant mice showed similar wound closure rate as the wild-type Hsp90α mice. We generated recombinant proteins from the mouse cDNAs encoding the Hsp90α-Δ and wild-type Hsp90α. Topical application of Hsp90α-Δ mutant protein promoted wound closure as effectively as the full-length wild-type Hsp90α protein. More importantly, selective inhibition of the extracellular Hsp90α-Δ protein function by a monoclonal antibody targeting the fragment-5 region disrupted normal wound closure in both wild-type Hsp90α and Hsp90α-Δ mice. Thus, this study provides direct support for non-chaperone, extracellular Hsp90α as a potential driver for normal wound closure.

The role of secreted heat shock protein-90 (Hsp90) in wound healing - how could it shape future therapeutics?

INTRODUCTION

Defects in tissue repair or wound healing pose a clinical, economic and social problem worldwide. Despite decades of studies, there have been few effective therapeutic treatments. Areas covered: We discuss the possible reasons for why growth factor therapy did not succeed. We point out the lack of human disorder-relevant animal models as another blockade for therapeutic development. We summarize the recent discovery of secreted heat shock protein-90 (Hsp90) as a novel wound healing agent. Expert commentary: Wound healing is a highly complex and multistep process that requires participations of many cell types, extracellular matrices and soluble molecules to work together in a spatial and temporal fashion within the wound microenvironment. The time that wounds remain open directly correlates with the clinical mortality associated with wounds. This time urgency makes the healing process impossible to regenerate back to the unwounded stage, rather forces it to take many shortcuts in order to protect life. Therefore, for therapeutic purpose, it is crucial to identify so-called 'driver genes' for the life-saving phase of wound closure. Keratinocyte-secreted Hsp90α was discovered in 2007 and has shown the promise by overcoming several key hurdles that have blocked the effectiveness of growth factors during wound healing.

Dual therapeutic functions of F-5 fragment in burn wounds: preventing wound progression and promoting wound healing in pigs

Burn injuries are a leading cause of morbidity including prolonged hospitalization, disfigurement, and disability. Currently there is no Food and Drug Administration-approved burn therapeutics. A clinical distinction of burn injuries from other acute wounds is the event of the so-called secondary burn wound progression within the first week of the injury, in which a burn expands horizontally and vertically from its initial boundary to a larger area. Therefore, an effective therapeutics for burns should show dual abilities to prevent the burn wound progression and thereafter promote burn wound healing. Herein we report that topically applied F-5 fragment of heat shock protein-90α is a dual functional agent to promote burn wound healing in pigs. First, F-5 prevents burn wound progression by protecting the surrounding cells from undergoing heat-induced caspase 3 activation and apoptosis with increased Akt activation. Accordingly, F-5-treated burn and excision wounds show a marked decline in inflammation. Thereafter, F-5 accelerates burn wound healing by stimulating the keratinocyte migration-led reepithelialization, leading to wound closure. This study addresses a topical agent that is capable of preventing burn wound progression and accelerating burn wound healing.

Keratinocyte-Secreted Heat Shock Protein-90alpha: Leading Wound Reepithelialization and Closure

Significance: Delayed and nonhealing wounds pose a health, economic, and social problem worldwide. For decades, the conventional wisdom pointed to growth factors as the driving force of wound healing and granted them a center stage for therapeutic development. To date, few have obtained US FDA approvals or shown clinical effectiveness and safety. Critical Issue: Wound closure is the initial and most critical step during wound healing. Closing chronic wounds to shut down continued infection is the primary and likely the only achievable goal at the clinic in the foreseeable future. The critical question here is to identify the factor(s) in wounded tissues that drives the initial wound closure. Recent Advances: We made an unexpected discovery of the secreted form of heat shock protein-90alpha (Hsp90α) for promoting skin cell motility, reepithelialization, and wound closure. Secreted Hsp90α possesses unique properties to remain functional under the hostile wound environment that compromises conventional growth factors' effectiveness. Through the common lipoprotein receptor-related protein-1 cell surface receptor and activation of the Akt signaling pathway, topical application of human recombinant Hsp90α protein greatly accelerates excision, burn, and diabetic skin wound closure in rodent and porcine models. Future Directions: In almost all cells, the 2-3% of their total proteins (∼7,000 per cell) are Hsp90 (α and β), a long unraveled puzzle. Our new finding of Hsp90 secretion in wounded tissues suggests that the stockpile of Hsp90α by all cells is to rapidly supply the need for extracellular Hsp90α to repair damaged tissues. We propose that keratinocytes at the wound edge secrete Hsp90α that leads the reepithelialization process to close the wound.

Hsp90α and Hsp90β together operate a hypoxia and nutrient paucity stress-response mechanism during wound healing

When tissues are injured and blood vessels clot, the local environment becomes ischemic, meaning that there is a lack of adequate supply of oxygen and glucose delivered to the surrounding cells. The heat shock protein-90 (Hsp90) family proteins protect tissues from various environmental insults and participate in the repair of damaged tissue. Here, we report discovery of a new ischemia-responsive mechanism in which the two Hsp90 isoforms Hsp90α and Hsp90β (also known as HSP90AA1 and HSP90AB1, respectively) work together to promote cell motility in wounded skin and accelerate wound closure. We demonstrate that Hsp90α and Hsp90β have distinct and non-exchangeable functions during wound healing. Under hypoxia and when there is a lack of serum factors, Hsp90β binds to the cytoplasmic tail of the LDL receptor-related protein-1 (LRP-1) and stabilizes the receptor at the cell surface. Hsp90α, however, is secreted by the cell into extracellular space where it binds and signals through the LRP-1 receptor to promote cell motility, leading to wound closure. In addition to skin injury, we suggest that this repair mechanism applies broadly to other non-cutaneous injured tissues.