Effects of insulin on wound healing: A review of animal and human evidences

Elastogenesis in Focus: Navigating Elastic Fibers Synthesis for Advanced Dermal Biomaterial Formulation

Elastin, a fibrous extracellular matrix (ECM) protein, is the main component of elastic fibers that are involved in tissues' elasticity and resilience, enabling them to undergo reversible extensibility and to endure repetitive mechanical stress. After wounding, it is challenging to regenerate elastic fibers and biomaterials developed thus far have struggled to induce its biosynthesis. This review provides a comprehensive summary of elastic fibers synthesis at the cellular level and its implications for biomaterial formulation, with a particular focus on dermal substitutes. The review delves into the intricate process of elastogenesis by cells and investigates potential triggers for elastogenesis encompassing elastin-related compounds, ECM components, and other molecules for their potential role in inducing elastin formation. Understanding of the elastogenic processes is essential for developing biomaterials that trigger not only the synthesis of the elastin protein, but also the formation of a functional and branched elastic fiber network.

Integrated insulin-iron nanoparticles: a multi-modal approach for receptor-specific bioimaging, reactive oxygen species scavenging, and wound healing

Metallic nanoparticles have emerged as a promising option for various biological applications, owing to their distinct characteristics such as small size, optical properties, and ability to exhibit luminescence. In this study, we have successfully employed a one-pot method to synthesize multifunctional insulin-protected iron [Fe(II)] nanoparticles denoted as [IFe(II)NPs]. The formation of IFe(II)NPs is confirmed by the presence of FTIR bonds at 447.47 and 798.28 cm-1, corresponding to Fe-O and Fe-N bonds, respectively. Detailed analysis of the HR-TEM-EDS-SAED data reveals that the particles are spherical in shape, partially amorphous in nature, and have a diameter of 28.6 ± 5.2 nm. Additionally, Metal Ion Binding (MIB) and Protein Data Bank (PDB) analyses affirm the binding of iron ions to the insulin hexamer. Our findings underscore the potential of IFe(II)NPs as a promising new platform for a variety of biomedical applications due to their high signal-to-noise ratio, and minimal background fluorescence. The particles are highly luminescent, biocompatible, and have a significant quantum yield (0.632). Exemplar applications covered in this paper include insulin receptor recognition and protection against reactive oxygen species (ROS), harmful molecules known to inflict damage on cells and DNA. The IFe(II)NPs effectively mitigate ROS-induced inflammation, which is a hinderance to wound recovery, thereby facilitating enhanced wound recovery.

Topical Insulin for Ocular Surface Disease

Background: Insulin and insulin-like growth factor (IGF)-1 receptors are present in ocular tissues such as corneal epithelium, keratocytes, and conjunctival cells. Insulin plays a crucial role in the growth, differentiation, and proliferation of corneal epithelial cells, as well as in wound healing processes in various tissues. Purpose: This review explores the potential role of topical insulin in the treatment of ocular surface diseases. Specifically, it examines its impact on corneal nerve regeneration, sub-basal plexus corneal nerves, and its application in conditions like corneal epithelial defects, dry eye disease, and diabetic keratopathy. Methods: The review analyzes studies conducted over the past decade that have investigated the use of topical insulin in ocular surface diseases. It focuses on indications, drug preparation methods, side effects, efficacy outcomes, and variations in insulin concentrations and dosages used. Results: While off-label use of topical insulin has shown promising results in refractory corneal epithelial defects, its efficacy in dry eye disease is yet to be demonstrated. Variations in concentrations, dilutions, and dosing guidelines have been reported. However, limited data on ocular penetration, ocular toxicity, and systemic side effects pose challenges to its widespread utility. Conclusion: This review synthesizes findings from ocular investigations on topical insulin to assess its potential applicability in treating ocular surface and corneal diseases. By highlighting indications, preparation methods, side effects, and efficacy outcomes, it aims to provide insights into the current status and future prospects of using topical insulin in ophthalmic practice.

In Vitro and In Vivo Evaluation of Chitosan/HPMC/Insulin Hydrogel for Wound Healing Applications

Treatment of chronic wounds is challenging, and the development of different formulations based on insulin has shown efficacy due to their ability to regulate oxidative stress and inflammatory reactions. The formulation of insulin with polysaccharides in biohybrid hydrogel systems has the advantage of synergistically combining the bioactivity of the protein with the biocompatibility and hydrogel properties of polysaccharides. In this study, a hydrogel formulation containing insulin, chitosan, and hydroxypropyl methyl cellulose (Chi/HPMC/Ins) was prepared and characterized by FTIR, thermogravimetric, and gel point analyses. The in vitro cell viability and cell migration potential of the Chi/HPMC/Ins hydrogel were evaluated in human keratinocyte cells (HaCat) by MTT and wound scratch assay. The hydrogel was applied to excisional full-thickness wounds in diabetic mice for twenty days for in vivo studies. Cell viability studies indicated no cytotoxicity of the Chi/HPMC/Ins hydrogel. Moreover, the Chi/HPMC/Ins hydrogel promoted faster gap closure in the scratch assay. In vivo, the wounds treated with the Chi/HPMC/Ins hydrogel resulted in faster wound closure, formation of a more organized granulation tissue, and hair follicle regeneration. These results suggest that Chi/HPMC/Ins hydrogels might promote wound healing in vitro and in vivo and could be a new potential dressing for wound healing.

Protein-modified nanomaterials: emerging trends in skin wound healing

Prolonged inflammation can impede wound healing, which is regulated by several proteins and cytokines, including IL-4, IL-10, IL-13, and TGF-β. Concentration-dependent effects of these molecules at the target site have been investigated by researchers to develop them as wound-healing agents by regulating signaling strength. Nanotechnology has provided a promising approach to achieve tissue-targeted delivery and increased effective concentration by developing protein-functionalized nanoparticles with growth factors (EGF, IGF, FGF, PDGF, TGF-β, TNF-α, and VEGF), antidiabetic wound-healing agents (insulin), and extracellular proteins (keratin, heparin, and silk fibroin). These molecules play critical roles in promoting cell proliferation, migration, ECM production, angiogenesis, and inflammation regulation. Therefore, protein-functionalized nanoparticles have emerged as a potential strategy for improving wound healing in delayed or impaired healing cases. This review summarizes the preparation and applications of these nanoparticles for normal or diabetic wound healing and highlights their potential to enhance wound healing.

Insulin-cobalt core-shell nanoparticles for receptor-targeted bioimaging and diabetic wound healing

Diabetic wounds represent a major issue in medical care and need advanced therapeutic and tissue imaging systems for better management. The utilization of nano-formulations involving proteins like insulin and metal ions plays significant roles in controlling wound outcomes by decreasing inflammation or reducing microbial load. This work reports the easy one-pot synthesis of extremely stable, biocompatible, and highly fluorescent insulin-cobalt core-shell nanoparticles (ICoNPs) with enhanced quantum yield for their highly specific receptor-targeted bioimaging and normal and diabetic wound healing in vitro (HEKa cell line). The particles were characterized using physicochemical properties, biocompatibility, and wound healing applications. FTIR bands at 670.35 cm^-1, 849.79, and 973.73 indicating the Co-O bending, CoO-OH bond, and Co-OH bending, respectively, confirm the protein-metal interactions, which is further supported by the Raman spectra. In silico studies indicate the presence of cobalt binding sites on the insulin chain B at 8 GLY, 9 SER, and 10 HIS positions. The particles exhibit a magnificent loading efficiency of 89.48 ± 0.049% and excellent release properties (86.54 ± 2.15% within 24 h). Further, based on fluorescent properties, the recovery process can be monitored under an appropriate setup, and the binding of ICoNPs to insulin receptors was confirmed by bioimaging. This work helps synthesize effective therapeutics with numerous wound-healing promoting and monitoring applications.

Insulin modified Decellularized Adipose Tissue/Tremella Polysaccharide hydrogel loaded with ADSCs for skin wound healing

Full-thickness skin wounds still represent a challenge for clinical treatment. Adipose-derived stem cells (ADSCs) therapy is a promising approach to achieve efficient healing in skin wounds. The excellent cell scaffold can promote proliferation, differentiation and paracrine of ADSCs in wound microenvironment, and is a key factor in ADSCs application. Herein, we first prepared the composite hydrogel with decellularized adipose tissue (DAT) and tremella polysaccharide (TPS), and loaded insulin (INS) into the DAT/TPS composite hydrogel (DAT/TPS-gel) to fabricate an efficient carrier for ADSCs in treating skin wound. Our study showed that INS modified DAT/TPS-gel (INS-DAT/TPS-gel) can promote the proliferation, differentiation and paracrine of ADSCs. INS-DAT/TPS-gel laden with ADSCs (ADSCs/INS-DAT/TPS-gel) effectively facilitated the skin wound healing in SD rats. These findings indicated that INS-DAT/TPS-gel was an effective scaffold for ADSCs transplantation, and ADSCs/INS-DAT/TPS-gel provides a potential strategy for the treatment of skin wounds.

Bioactive Insulin-Loaded Electrospun Wound Dressings for Localized Drug Delivery and Stimulation of Protein Expression Associated with Wound Healing

Effective therapy of wounds is difficult, especially for chronic, non-healing wounds, and novel therapeutics are urgently needed. This challenge can be addressed with bioactive wound dressings providing a microenvironment and facilitating cell proliferation and migration, ideally incorporating actives, which initiate and/or progress effective healing upon release. In this context, electrospun scaffolds loaded with growth factors emerged as promising wound dressings due to their biocompatibility, similarity to the extracellular matrix, and potential for controlled drug release. In this study, electrospun core-shell fibers were designed composed of a combination of polycaprolactone and polyethylene oxide. Insulin, a proteohormone with growth factor characteristics, was successfully incorporated into the core and was released in a controlled manner. The fibers exhibited favorable mechanical properties and a surface guiding cell migration for wound closure in combination with a high uptake capacity for wound exudate. Biocompatibility and significant wound healing effects were shown in interaction studies with human skin cells. As a new approach, analysis of the wound proteome in treated ex vivo human skin wounds clearly demonstrated a remarkable increase in wound healing biomarkers. Based on these findings, insulin-loaded electrospun wound dressings bear a high potential as effective wound healing therapeutics overcoming current challenges in the clinics.

A poloxamer/hyaluronic acid/chitosan-based thermosensitive hydrogel that releases dihydromyricetin to promote wound healing

Wounds caused by accidents and surgery are inevitable, and inflammation and microbial infection during the healing process are serious clinical challenges, resulting in slow wound healing. In this study, we created a 37 °C-sensitive hydrogel using poloxamer, chitosan and hyaluronic acid, loaded with the active substance dihydromyricetin, and further evaluated its potential for wound healing. The hydrogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis for their micromorphological structure, characteristic functional groups, crystal structure and thermal stability, and in vitro drug release assays showed that the hydrogel could slowly release dihydromyricetin. In addition, the hydrogels were found to exhibit good biocompatibility and significant in vitro antioxidant and anti-inflammatory activity according to hemolysis, in vitro antioxidant and anti-inflammatory tests. Methyl thiazolyl tetrazole cytotoxicity tests verified that the film was non-toxic to human keratinocyte (HaCaT) cells, while in vivo experiments showed that this hydrogel could promote skin repair by promoting skin-associated growth factor expression and inhibiting nuclear factor kappa B-mediated cellular inflammatory factors. These results demonstrated that the temperature-sensitive hydrogels loaded with dihydromyricetin could serve as potential candidates for guided skin repair.

Relation Between Gender and Concomitant Medications With Erythropoietin-Treatment on Wound Healing in Burn Patients. Post Hoc Subgroup-Analysis of the Randomized, Placebo-Controlled Clinical Trial “EPO in Burns”

Burns are leading causes of mortality and morbidity, including prolonged hospitalization, disfigurement, and disability. Erythropoietin (EPO) is a well-known hormone causing erythropoiesis. However, EPO may play a role in healing acute and chronic wounds due to its anti-inflammatory and pro-regenerative effects. Therefore, the large, prospective, placebo-controlled, randomized, double-blind, multi-center clinical trial “EPO in Burns” was initiated to investigate the effects of EPO versus placebo treatment in severely burned patients. The primary endpoint of “EPO in Burns” was defined as the time elapsed until complete re-epithelialization of a defined split skin graft donor site. Additional analyses of post hoc defined subgroups were performed in view of the primary endpoint. The verum (n 45) and control (n 39) groups were compared with regard to the time it took for study wounds (a predefined split skin graft donor site) to reach the three stages of wound healing (re-epithelialization levels). In addition, the effects of gender (females n 18) and concomitant medications insulin (n 36), non-steroidal anti-inflammatory drugs (NSAIDs) (n 41), and vasopressor agents (n 43) were tested. Life tables were used to compare study groups (EPO vs. placebo) within subgroups. The Cox regression model was applied to evaluate interactions between the study drug (EPO) and concomitant medications for each re-epithelialization level. Using our post hoc defined subgroups, we observed a lower chance of wound healing for women compared to men (in terms of hazard ratio: hr^100%: 5.984 [95%-CI: (0.805–44.490), p = 0.080]) in our study population, regardless of the study medication. In addition, results indicated an earlier onset of re-epithelialization in the first days of EPO treatment (EPO: 10% vs. Placebo: 3%). Moreover, the interpretation of the hazard ratio suggested EPO might have a positive, synergistic effect on early stages of re-epithelialization when combined with insulin [hr^50%: 1.307 (p = 0.568); hr^75%: 1,199 (p = 0.715)], as well as a stabilizing effect on critically ill patients [reduced need for vasopressors in the EPO group (EPO: 44% vs. Placebo 59%)]. However, additional high-quality data from clinical trials designed to address these endpoints are required to gain further insight into these effects.

Oral Administration of Bacillus toyonensis Strain SAU-20 Improves Insulin Resistance and Ameliorates Hepatic Steatosis in Type 2 Diabetic Mice

In this study, the ameliorative effects of Bacillus toyonensis-SAU-20 (B. toyo SAU-20), a new probiotic strain isolated and identified by our laboratory from Ageratina adenophora, on the development of insulin resistance and hepatic steatosis in type 2 diabetic (T2DM) mice was investigated. Thirty Specific-pathogen free Kunming (SPFKM) mice were randomly allocated to three groups: control, high fat diet/streptozotocin (HFD/STZ), and HFD/STZ+B. toyo SAU-20 groups with oral administration of B. toyo SAU-20 for 35 days. Biochemistry parameters, glucose tolerance, and insulin resistance were measured in the blood whereas histological analysis, inflammatory cytokines and lipogenic genes in the liver tissues. The results showed that, the levels of serum glucose, lipid profile, mRNA expression of lipogenic related genes and pro-inflammatory cytokines were significantly increased in T2DM mice. However, after B. toyo SAU-20 administration, the elevation of these parameters was significantly suppressed (P<0.05). In addition, the feeding of B. toyo SAU-20 significantly improved the morphological changes of the liver with significant alleviation of dyslipidemia, oxidative stress status and inflammation (P<0.05) indicating the ameliorating effect of B. toyo SAU-20 in hepatic steatosis in T2DM. Therefore, we concluded that, B. toyo SAU-20 alleviated insulin resistance and hepatic steatosis by improving the lipid profiles, antioxidant status and downregulating lipogenic genes as well as pro-inflammation cytokines expression.

Design, preparation and in vitro characterization of biomimetic and bioactive chitosan/polyethylene oxide based nanofibers as wound dressings

Chitosan-based nanofibers (CS-NFs) are excellent artificial extracellular matrices (ECMs) due to the resemblance of CS with the glycosaminoglycans of the natural ECMs. Despite this excellent feature, the poor electrospinnability and mechanical properties of CS are responsible for important limitations in respect to its biomedical applications. To improve the CS's physico-chemical properties, new bioactive and biomimetic CS-NFs were formulated with polyethylene oxide (PEO), having incorporated different active components (ACs) with important beneficial effects for healing. Manuka honey (trophic and antimicrobial effects), propolis (antimicrobial effects), Calendula officinalis infusion (antioxidant effect, reepithelialization stimulating agent), insulin (trophic effect), and L-arginine (angiogenic effect) were selected as ACs. SEM morphology analysis revealed well-alignment, unidirectional arrays, with small diameters, no beads, and smooth surfaces for developed CS_PEO-ACs NFs. The developed NFs showed good biodegradability (NFs mats lost up to 60% of their initial weight in PBS), increased hemocompatibility (hemolytic index less than 4%), and a reduced cytotoxicity degree (cell viability degree more than 90%). In addition, significant antioxidant and antimicrobial effects were noted for the developed NFs which make them suitable for chronic wounds, due to the role of oxidative stress and infection risk in delaying normal wound healing. The most suitable for wound healing applications seems to be CS_PEO@P_C which showed an improved hemolysis index (2.92 ± 0.16%), is non-toxic (cell viability degree more than 97%), and has also significant radical scavenging effect (DPPH inhibition more than 65%). In addition, CS_PEO@P_C presents increased antimicrobial effects, more noticeably for Staphylococcus aureus strain, which is a key feature in preventing wound infection and delaying the healing process. It can be concluded that the developed CS/PEO-ACs NFs are very promising biomaterials for wound care, especially CS_PEO@P_C.

Topical Insulin-Utility and Results in Refractory Neurotrophic Keratopathy in Stages 2 and 3

PURPOSE

The purpose of this study was to evaluate the clinical outcome of patients with refractory neurotrophic keratopathy (NK) in stages 2 and 3 treated with topical insulin.

METHODS

Retrospective analysis of eyes with NK in stages 2 and 3 refractory to standard medical and/or surgical treatment which were treated with topical insulin (1 unit per mL). This treatment was applied 4 times per day and was continued until the persistent epithelial defect (PED) or ulcer resolved. The primary outcome of the study was the complete reepithelialization of the PED or persistent ulcer. "Best-corrected visual acuity" pretreatment and posttreatment, "days until complete reepithelialization" data, and anterior segment photographs were obtained. Outcome measures were compared before and after treatment in both groups using paired and independent samples t tests.

RESULTS

Twenty-one eyes were included in this study, and 90% achieved complete reepithelialization of the PED and/or persistent ulcer within 7 to 45 days of follow-up. The mean number of days until complete reepithelialization was significantly lower in NK stage 2 (18 ± 9 days) when compared with NK stage 3 (29 ± 11 days) (P = 0.025). The best-corrected visual acuity improved significantly in both NK stage 2 (P < 0.001) and NK stage 3 (P = 0.004). No side effects were reported during the follow-up.

CONCLUSIONS

Our results suggest that topical insulin drops may be an effective therapeutic in refractory NK. This therapy may prove extremely useful because of its low cost and high accessibility.

Anti-inflammation biomaterial platforms for chronic wound healing

Nowadays, there has been an increase in the number of people with chronic wounds, which has resulted in serious health problems worldwide. The rate-limiting stage of chronic wound healing has been found to be the inflammation stage, and strategies for shortening the prolonged inflammatory response have proven to be effective for increasing the healing rate. Recently, various anti-inflammatory strategies (such as anti-inflammatory drugs, antioxidant, NO regulation, antibacterial, immune regulation and angiogenesis) have attracted attention as potential therapeutic pathways. Moreover, various biomaterial platforms based on anti-inflammation therapy strategies have also emerged in the spotlight as potential therapies to accelerate the repair of chronic wounds. In this review, we systematically investigated the advances of various biomaterial platforms based on anti-inflammation strategies for chronic wound healing, to provide valuable guidance for future breakthroughs in chronic wound treatment.

New Hyaluronic Acid/Polyethylene Oxide-Based Electrospun Nanofibers: Design, Characterization and In Vitro Biological Evaluation

Natural compounds have been used as wound-healing promoters and are also present in today's clinical proceedings. In this research, different natural active components such as propolis, Manuka honey, insulin, L-arginine, and Calendula officinalis infusion were included into hyaluronic acid/poly(ethylene)oxide-based electrospun nanofiber membranes to design innovative wound-dressing biomaterials. Morphology and average fiber diameter were analyzed by scanning electron microscopy. Chemical composition was proved by Fourier transform infrared spectroscopy, which indicated successful incorporation of the active components. The nanofiber membranes with propolis and Calendula officinalis showed best antioxidant activity, cytocompatibility, and antimicrobial properties against pathogen strains Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa and had an average diameter of 217 ± 19 nm with smooth surface aspect. Water vapor transmission rate was in agreement with the range suitable for preventing infections or wound dehydration (~5000 g/m2 24 h). Therefore, the developed hyaluronic acid/poly(ethylene)oxide nanofibers with additional natural components showed favorable features for clinical use as wound dressings.

Development of a Topical Insulin Polymeric Nanoformulation for Skin Burn Regeneration: An Experimental Approach

Insulin is a peptide hormone with many physiological functions, besides its use in diabetes treatment. An important role of insulin is related to the wound healing process-however, insulin itself is too sensitive to the external environment requiring the protective of a nanocarrier. Polymer-based nanoparticles can protect, deliver, and retain the protein in the target area. This study aims to produce and characterize a topical treatment for wound healing consisting of insulin-loaded poly-DL-lactide/glycolide (PLGA) nanoparticles. Insulin-loaded nanoparticles present a mean size of approximately 500 nm and neutral surface charge. Spherical shaped nanoparticles are observed by scanning electron microscopy and confirmed by atomic force microscopy. SDS-PAGE and circular dichroism analysis demonstrated that insulin preserved its integrity and secondary structure after the encapsulation process. In vitro release studies suggested a controlled release profile. Safety of the formulation was confirmed using cell lines, and cell viability was concentration and time-dependent. Preliminary safety in vivo assays also revealed promising results.

Protection of lead-induced cytotoxicity using paramagnetic nickel–insulin quantum clusters

Pb-toxicity is associated with inflammation which leads to delay in wound healing. Pb²⁺ utilizes calcium ion channels to enter the cell. Therefore, to achieve effective healing in a Pb-poisoned system, capturing Pb²⁺ from the circulatory system would be an effective approach without hampering the activity of the calcium ion channel. In this work insulin–nickel fluorescent quantum clusters (INiQCs) have been synthesized and used for the specific detection of Pb²⁺ ions in vitro and in cell-free systems. INiQCs (0.09 μM) can detect Pb²⁺ concentrations as low as 10 pM effectively in a cell-free system using the fluorescence turn-off method. In vitro INiQCs (0.45 μM) can detect Pb²⁺ concentrations as low as 1 μM. INiQCs also promote wound healing which can easily be monitored using the bright fluorescence of INiQCs. INiQCs also help to overcome the wound recovery inhibitory effect of Pb²⁺in vitro using lead nitrate. This work helps to generate effective biocompatible therapeutics for wound recovery in Pb²⁺ poisoned individuals.

Receptor targeted ferromagnetic Insulin–Nickel Quantum fluorescence Clusters (INiQCs) can specifically detect Pb²⁺ and prevents Pb²⁺ poisoning.

Inhibition of 11β-HSD1 Expression by Insulin in Skin: Impact for Diabetic Wound Healing

Chronic, non-healing wounds impose a great burden on patients, professionals and health care systems worldwide. Diabetes mellitus (DM) and obesity are globally highly prevalent metabolic disorders and increase the risk for developing chronic wounds. Glucocorticoids (GCs) are endogenous stress hormones that exert profound effects on inflammation and repair systems. 11-beta-hydroxysteroid dehydrogenase 1 (11β-HSD1) is the key enzyme which controls local GC availability in target tissues such as skin. Since treatment with GCs has detrimental side effects on skin integrity, causing atrophy and delayed wound healing, we asked whether the dysregulated expression of 11β-HSD1 and consequently local GC levels in skin contribute to delayed wound healing in obese, diabetic db/db mice. We found increased expression of 11β-HSD1 during disturbed wound healing and in the healthy skin of obese, diabetic db/db mice. Cell analysis revealed increased expression of 11β-HSD1 in fibroblasts, myeloid cells and dermal white adipose tissue from db/db mice, while expression in keratinocytes was unaffected. Among diabetes- and obesity-related factors, insulin and insulin-like growth factor 1 down-regulated 11β-HSD1 expression in fibroblasts and myeloid cells, while glucose, fatty acids, TNF-α and IL-1β did not affect it. Insulin exerted its inhibitory effect on 11β-HSD1 expression by activating PI3-kinase/Akt-signalling. Consequently, the inhibitory effect of insulin is attenuated in fibroblasts from insulin-resistant db/db mice. We conclude that insulin resistance in obesity and diabetes prevents the down-regulation of 11β-HSD1, leading to elevated endogenous GC levels in diabetic skin, which could contribute to impaired wound healing in patients with DM.

Therapeutic advances in wound healing

Wound healing is a complex physiological process that occurs in the human body involving the sequential activation of multiple cell types and signaling pathways in a coordinated manner. Chronic wounds and burns clearly decrease quality of life of the patients since they are associated with an increase in physical pain and socio-economical complications. Furthermore, incidence and prevalence of chronic wounds (unlike burns) have been increasing mainly due to population aging resulting in increased costs for national health systems. Thus, the development of new and more cost-effective technologies/therapies is not only of huge interest but also necessary to improve the long-term sustainability of national health systems. This review covers the current knowledge on recent technologies/therapies for skin regeneration, such as: wound dressings; skin substitutes; exogenous growth factor based therapy and systemic therapy; external tissue expanders; negative pressure; oxygen; shock wave, and photobiomodulation wound therapies. Associated benefits and risks as well as the clinical use and availability are all addressed for each therapy. Moreover, future trends in wound care including novel formulations using metallic nanoparticles and topical insulin are herein presented. These novel formulations have shown to be promising therapeutic options in the near future that may change the wound care paradigm.

Effects of Topical Insulin on Wound Healing: A Review of Animal and Human Evidences

Wound healing is a complex biological process that repairs damaged tissues and restores skin integrity. Insulin, a potent factor of wound healing, has been reported for nearly a century to induce rapid recovery of various wounds, as shown by numerous human and animal studies. Although many studies have addressed the healing effect of systemic insulin on burn wound, only few have investigated the efficacy of topical insulin. Thus, this study aimed to review evidence of the effects of topical insulin on wound healing, including on diabetic and non-diabetic wounds. The presented animal and clinical studies support that topical insulin improves wound healing through several mechanisms without causing side effects. Additionally, various wound dressings accelerate the wound healing with controlled and sustained delivery of bioactive insulin. Therefore, topical insulin has been appreciated in field of wound healing, and further studies are needed to improve our understanding of the role of insulin in the healing of various wounds.

Topical application of Cinnamomum hydroethanolic extract improves wound healing by enhancing re-epithelialization and keratin biosynthesis in streptozotocin-induced diabetic mice

Context: Cinnamomum verum J. Presl. (Lauraceae) has a high number of polyphenols with insulin-like activity, increases glucose utilization in animal muscle, and might be beneficial for diabetic patients.Objective: This study evaluated the effectiveness of an ointment prepared from Cinnamomum verum hydroethanolic extract on wound healing in diabetic mice.Materials and methods: A total of 54 male BALB/c mice were divided into three groups: (1) diabetic non-treated group mice that were treated with soft yellow paraffin, (2 and 3) mice that were treated with 5 and 10% C. verum. Two circular full-thickness excisional wounds were created in each mouse, and the trial lasted for 16 d following induction of the wound. Further evaluation was made on the wound contraction ratio, histopathology parameters and mRNA levels of cyclin D1, insulin-like growth factor 1 (IGF-1), glucose transporter-1 (GLUT-1), total antioxidant capacity, and malondialdehyde of granulation tissue contents. HPLC apparatus was utilized to identify the compounds.Results: The HPLC data for cinnamon hydroethanolic extract identified cinnamaldehyde (11.26%) and 2-hydroxyl cinnamaldehyde (6.7%) as the major components. A significant increase was observed in wound contraction ratio, fibroblast proliferation, collagen deposition, re-epithelialization and keratin biosynthesis in the C. verum-treated groups in comparison to the diabetic non-treated group (p < 0.05). The expression level of cyclin D1, IGF1, GLUT 1 and antioxidant capacity increased in the C. verum-treated groups in comparison to the diabetic non-treated group (p < 0.05).Conclusions: Topical administration of C. verum accelerated wound healing and can possibly be employed in treating the wounds of diabetic patients.

Topical Insulin Modulates Inflammatory and Proliferative Phases of Burn-Wound Healing in Diabetes-Induced Rats

The healing time of burn wounds depends on surface area and depth of the burn and associated comorbidities. Diabetes mellitus (DM) causes delays in the healing process by extending the inflammatory phase. Treatment with topical insulin can improve the inflammatory phase, restore metabolic dysregulation, and modulate impaired cellular signaling in burn wounds. The objective of this study was to evaluate markers of the inflammatory and proliferative phases of second-degree burns after topical insulin treatment in diabetic rats. Type I DM was induced with streptozotocin in male Wistar rats. The animals' backs were shaved and subjected to thermal burning. Rats were randomized into two groups: control diabetic (DC) and insulin diabetic (DI). At Days 7 and 14 postburn, rats were euthanized, and wound-tissue sections were evaluated by hematoxylin and eosin, Weigert, and Verhöeff staining, immunohistochemistry-paraffin, and enzyme-linked immunosorbent assay. A significant increase in reepithelialization was seen on Days 7 and 14 in DI versus DC rats. On Day 7, interleukin (IL)-1β, IL-6, monocyte chemotactic protein (MCP)-1, and F4/80 expression were increased in DI versus DC rats. On Day 14, MCP-1 expression was decreased and F4/80 increased in DI versus DC rats. On Days 7 and 14, Ki-67, transforming growth factor-β1, vascular endothelial growth factor expression, and formation of elastic fibers were increased in DI versus DC rats. Topical insulin modulates burn-wound healing in diabetic animals by balancing inflammation and promoting angiogenesis and formation of elastic fibers.

Polydeoxyribonucleotides Improve Diabetic Wound Healing in Mouse Animal Model for Experimental Validation

Background

Wound healing mechanisms is believed to have effects similar to wound healing disorders in diabetic patients, including abnormal inflammatory cells, angiogenesis disorders, and reduced collagen synthesis. Therefore, reestablishment of structural and promoted angiogenesis could be beneficial to promote wound healing process.

Objective

Therefore, we investigated whether the polydeoxyribonucleotide (PDRN) that was self-production in Korea, could be useful as an intradermal injection for promoting wound healing. Also, we validate for wound healing effect of PDRN using healing-impaired (db/db) mice.

Methods

In this study, we confirmed the effects of PDRN by creating wound models in in vitro and in vivo model. Using an in vitro wound healing assay, we observed that PDRN stimulated closure of wounded monolayers of human fibroblast cells. PDRN (8.25 mg/ml) or phosphate-buffered saline (0.9% NaCl) was injected once daily into the dermis adjacent to the wound for 12 days after skin injury.

Results

Time course observations revealed that mice treated with PDRN showed accelerated wound closure and epidermal and dermal regeneration, enhanced angiogenesis. The wound area and depth decreased at 3, 6, 9, and 12 days after skin injury. Histological evaluation showed an increase of vascular endothelial growth factor, CD31, and collagen fibers in the PDRN group compared with the control group, indicating that PDRN was effective in the treatment of delayed wound healing caused by diabetes.

Conclusion

This study suggests that our PDRN has a wound healing effect in transgenic animal models with cells and diabetes through angiogenesis.

Basic concepts, current evidence, and future potential for gene therapy in managing cutaneous wounds

OBJECTIVE

Several studies have investigated the role of gene therapy in the healing process. The aim of this review is to explain the gene delivery systems in wound area.

RESULTS

Ninety-two studies were included and comprehensively overviewed. We described the importance of viral vectors such as adenoviruses, adeno-associated viruses, and retroviruses, and conventional non-viral vectors such as naked DNA injections, liposomes, gene gun, electroporation, and nanoparticles in achieving high-level expression of genes. Application of viral transfection, liposomal vectors, and electroporation were the main gene delivery systems. Genes encoding for growth factors or cytokines have been shown to result in a better wound closure in comparison to application of the synthetic growth factors. In addition, a combination of stem cell and gene therapy has been found an effective approach in regeneration of cutaneous wounds.

CONCLUSIONS

This article gives an overview of the methods and investigations applied on gene therapy in wound healing. However, clinical investigations need to be undertaken to gain a better understanding of gene delivery technologies and their roles in stimulating wound repair.

The Bardet-Biedl syndrome protein complex regulates cell migration and tissue repair through a Cullin-3/RhoA pathway

Cell motility and migration play critical roles in various physiological processes and disease states. Here, we show that the BBBsome, a macromolecule composed of eight Bardet-Biedl syndrome (BBS) proteins including BBS1, is a critical determinant of cell migration and wound healing. Fibroblast cells derived from mice or humans harboring a homozygous missense mutation (BBS1^M390R/M390R) that disrupt the BBSome exhibit defects in migration and wound healing. Furthermore, we demonstrate that BBS1^M390R/M390R mice have significantly delayed wound closure. In line with this, we provide data suggesting that BBS1^M390R/M390R fibroblasts have impaired platelet-derived growth factor-AA (PDGF) receptor-α signaling, a key regulator of directional cell migration acting as a chemoattractant during postnatal migration responses such as wound healing. In addition, we show that BBS1^M390R/M390R fibroblasts have upregulated RhoA expression and activity. The relevance of RhoA upregulation is demonstrated by the ability of RhoA-kinase inhibitor Y27632 to partially rescue the migration defect of BBS1^M390R/M390R fibroblasts cells. We also show that accumulation of RhoA protein in BBS1^M390R/M390R fibroblasts cells is associated with reduction and inactivation of the ubiquitin ligase Cullin-3. Consistent with this, Cullin-3 inhibition with MLN4924 is sufficient to reduce migration of normal fibroblasts. These data implicate the BBSome in cell motility and tissue repair through a mechanism that involves PDGF receptor signaling and Cullin-3-mediated control of RhoA.

Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies

Cutaneous wound healing in adult mammals is a complex multi-step process involving overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodelling. Re-epithelialization describes the resurfacing of a wound with new epithelium. The cellular and molecular processes involved in the initiation, maintenance, and completion of epithelialization are essential for successful wound closure. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here, we focus on cellular mechanisms underlying keratinocyte migration and proliferation during epidermal closure. Inability to re-epithelialize is a clear indicator of chronic non-healing wounds, which fail to proceed through the normal phases of wound healing in an orderly and timely manner. This review summarizes the current knowledge regarding the management and treatment of acute and chronic wounds, with a focus on re-epithelialization, offering some insights into novel future therapies.

Side effects of frequently used oral antidiabetics on wound healing in vitro

Lifestyle diseases such as diabetes and arteriosclerosis are rising in the increasingly aging society, and the number of patients with daily intake of glucose-lowering medication has also increased. Interestingly, knowledge about oral antidiabetics with regard to wound healing is scarce. Therefore, the aim of this study was to identify possible (side) effects of the most frequently prescribed oral antidiabetics on skin cells and wound healing. Four oral antidiabetics of different substance classes (i.e., metformin, glibenclamide, sitagliptin, repaglinide) were investigated with regard to the promotion of cell metabolism and migration of human skin fibroblasts and keratinocytes by XTT and scratch assays. In addition, histological and immunohistochemical analyses were performed in a 3D wound model to address the impact of the antidiabetics on regeneration processes, such as cell migration, fibroblast activity, epidermal thickness, and cell apoptosis. In comparison to systemic application, metformin displayed the most adverse effects in vitro in nearly all analyses, interestingly at serum equivalent concentrations. In contrast, sitagliptin and glibenclamide had a slight but insignificant effect on fibroblasts compared with keratinocytes. Repaglinide tended to have a negative influence on keratinocyte metabolism. Interestingly, antidiabetics generally induced a significantly enhanced rate of apoptosis in fibroblasts, with the exception of repaglinide.Antidiabetics influenced key players in wound healing, namely, keratinocytes and fibroblasts. Particularly, metformin impaired human skin cells. These findings should be kept in mind in further studies because of their putative relevance in patients suffering from chronic wounds that do not respond to various wound therapies.

Update on management of diabetic foot ulcers

Diabetic foot ulcers (DFUs) are a serious complication of diabetes that results in significant morbidity and mortality. Mortality rates associated with the development of a DFU are estimated to be 5% in the first 12 months, and 5-year morality rates have been estimated at 42%. The standard practices in DFU management include surgical debridement, dressings to facilitate a moist wound environment and exudate control, wound off-loading, vascular assessment, and infection and glycemic control. These practices are best coordinated by a multidisciplinary diabetic foot wound clinic. Even with this comprehensive approach, there is still room for improvement in DFU outcomes. Several adjuvant therapies have been studied to reduce DFU healing times and amputation rates. We reviewed the rationale and guidelines for current standard of care practices and reviewed the evidence for the efficacy of adjuvant agents. The adjuvant therapies reviewed include the following categories: nonsurgical debridement agents, dressings and topical agents, oxygen therapies, negative pressure wound therapy, acellular bioproducts, human growth factors, energy-based therapies, and systemic therapies. Many of these agents have been found to be beneficial in improving wound healing rates, although a large proportion of the data are small, randomized controlled trials with high risks of bias.

Dracorhodin Perchlorate Accelerates Cutaneous Wound Healing in Wistar Rats

Dracorhodin perchlorate (DP) is extracted from Dragon's blood, which is widely used in traditional Chinese medicine, especially in wound healing. The aim of this paper is to investigate the influence of DP ointment, which contained DP dissolved in DMSO and mixed with Vaseline, on cutaneous wound healing in Wistar rats. Forty Wistar rats were divided into two groups: control and DP groups. The skin on the back of each rat was punched with two full-thickness wounds and then treated with the corresponding drug. After 3, 7, 10, 14, and 21 days, four rats were sacrificed for immunological, biochemical, and histological analyses. Compared with the control treatment, DP could significantly promote wound closure. Histological and biochemical analyses of the skin biopsies also showed that DP regulated the expression of inflammatory responses by TNF-α and IL-β and by supporting wound tissue growth and collagen deposition. Western blot revealed that DP could also facilitate the expression of EGF and VEGF proteins. In conclusion, DP promotes wound healing.

Hypoxia primed placental mesenchymal stem cells for wound healing

AIMS

To investigate how Placental Mesenchymal Stem Cells (P-MSCs) would adapt themselves and survive under hypoxic conditions which are prevalent in most injury sites.

MAIN METHODS

P-MSCs were isolated from term placenta and characterised under normoxia and hypoxia (2-2.5% O₂). Cells were examined for morphology and surface marker variations by flow cytometry analysis. Glucose stimulated insulin secretion was assayed by Insulin ELISA Kit. Gene expression levels were estimated using Real Time PCR for hypoxia inducible factor1 alpha, Insulin (INS), Glucose transporters (GLUT-1, GLUT-2 and GLUT-3), Adhesion Proteins- Integrins, Fibronectin1 (FN1), E-Cadherin (CDH1), and N-Cadherin (CDH2) and angiogenesis marker VEGFA. Immunofluorescence assay was done to confirm the presence of C-Peptide, GLUT 2, E-Cadherin and ITGB3. Adhesion was confirmed assessed on fibronectin binding.

KEY FINDINGS

We show that insulin secretion is not hampered under hypoxia. We found an upregulation of glucose transporters under hypoxia indicating enhanced glucose uptake needed to cater to metabolic demands of proliferating cells. Up regulation of adhesion molecules was seen under hypoxia indicative of a favoured environment for retention of cells at the injury site. We also found increased level of angiogenesis of P-MSCs under hypoxia.

SIGNIFICANCE

Our present study thus demonstrates for the first time that P-MSCs modulate themselves under hypoxic conditions by secreting insulin, up regulating glucose transporters and adhesion molecules and eventually exhibiting an increased angiogenic potential. We thus infer that priming P-MSCs under hypoxia, could make them more suitable for wound healing applications.