Impaired cutaneous wound healing in granulocyte/macrophage colony-stimulating factor knockout mice

Effects of Recombinant Human Granulocyte/Macrophage Colony-Stimulating Factor on Diabetic Lower Extremity Ulcers: Case Series of Nine Patients

Background

Diabetic lower extremity ulcer, including diabetic foot ulcer (DFU) and leg ulcer, is one of the refractory complications of diabetes, the treatment of which is challenging, expensive, and lengthy. Recombinant Human Granulocyte/Macrophage Colony-stimulating Factor (rhGM-CSF) is an immunomodulatory cytokine that has been mainly applied in the treatment of hematological diseases. Clinical evidence regarding GM-CSF in the treatment of diabetic lower extremity ulcers is limited. This study is the first case series that investigates the repurpose effects of rhGM-CSF on diabetic ulcer healing in real clinical practice.

Methods

Nine patients diagnosed with diabetes and refractory lower extremity ulcer (ulcer duration ≥2 weeks) were included from September 2021 to February 2023 in the Division of Endocrinology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology. Patients with Wagner grade ≥4 and SINDAD ≥5 were excluded. The included subjects were treated with rhGM-CSF plus standard of care (SOC) including glycemic control, foot care education, debridement of necrotic tissues, topical wound dressings, offloading, and infection control when necessary. The observation endpoint was complete epithelialization. Their clinical manifestations, laboratory tests, and therapeutic effects were extracted and analyzed.

Results

The case series included 9 cases aged from 29 to 80 years and all the patients were male. Seven of 9 patients presented neuropathic ulcer. Only one case showed non-infected ulcer from tissue samples and one case presented ankle brachial index (ABI) <0.9. It was observed that the ulcer areas among these 9 patients gradually declined throughout the whole treatment period with the average healing velocity 0.32 ± 013 cm2/day and the mean time to complete healing 16.0 ± 3.7 days. The relative area (percentage of initial ulcer area) decreased to 66.7 ± 13.0% on average after the first treatment. Ulcers in all the 9 patients achieved complete epithelialization after 4-8 times treatments.

Conclusion

The case series suggests rhGM-CSF as a promising therapeutic strategy for the treatment of diabetic ulceration. More robust data from randomized controlled trials are required to further evaluate its clinical efficacy.

CD64 plays a key role in diabetic wound healing

Introduction

Wound healing poses a clinical challenge in diabetes mellitus (DM) due to compromised host immunity. CD64, an IgG-binding Fcgr1 receptor, acts as a pro-inflammatory mediator. While its presence has been identified in various inflammatory diseases, its specific role in wound healing, especially in DM, remains unclear.

Objectives

We aimed to investigate the involvement of CD64 in diabetic wound healing using a DM animal model with CD64 KO mice.

Methods

First, we compared CD64 expression in chronic skin ulcers from human DM and non-DM skin. Then, we monitored wound healing in a DM mouse model over 10 days, with or without CD64 KO, using macroscopic and microscopic observations, as well as immunohistochemistry.

Results

CD64 expression was significantly upregulated (1.25-fold) in chronic ulcerative skin from DM patients compared to non-DM individuals. Clinical observations were consistent with animal model findings, showing a significant delay in wound healing, particularly by day 7, in CD64 KO mice compared to WT mice. Additionally, infiltrating CD163+ M2 macrophages in the wounds of DM mice decreased significantly compared to non-DM mice over time. Delayed wound healing in DM CD64 KO mice correlated with the presence of inflammatory mediators.

Conclusion

CD64 seems to play a crucial role in wound healing, especially in DM conditions, where it is associated with CD163+ M2 macrophage infiltration. These data suggest that CD64 relies on host immunity during the wound healing process. Such data may provide useful information for both basic scientists and clinicians to deal with diabetic chronic wound healing.

Chitosan-Based Dressing as a Sustained Delivery System for Bioactive Cytokines

Wounds represent a common occurrence in human life. Consequently, scientific investigations are underway to advance wound healing methodologies, with a notable focus on dressings imbued with biologically active compounds capable of orchestrating the wound microenvironment through meticulously regulated release mechanisms. Among these bioactive agents are cytokines, which, when administered to the wound milieu without appropriate protection, undergo rapid loss of their functional attributes. Within the context of this research, we present a method for fabricating dressings enriched with G-CSF (granulocyte colony-stimulating factor) or GM-CSF (granulocyte-macrophage colony-stimulating factor), showcasing both biological activity and protracted release dynamics. Based on Ligasano, a commercial polyurethane foam dressing, and chitosan crosslinked with TPP (sodium tripolyphosphate), these dressings are noncytotoxic and enable cytokine incorporation. The recovery of cytokines from dressings varied based on the dressing preparation and storage techniques (without modification, drying, freeze-drying followed by storage at 4 °C or freeze-drying followed by storage at 24 °C) and cytokine type. Generally, drying reduced cytokine levels and their bioactivity, especially with G-CSF. The recovery of G-CSF from unmodified dressings was lower compared to GM-CSF (60% vs. 80%). In summary, our freeze-drying approach enables the storage of G-CSF or GM-CSF enriched dressings at 24 °C with minimal cytokine loss, preserving their biological activity and thus enhancing future clinical availability.

Granulocyte-macrophage colony-stimulating factor promotes endometrial repair after injury by regulating macrophages in mice

Intrauterine adhesion (IUA) caused by endometrial injury is a common cause of female infertility and is challenging to treat. Macrophages play a critical role in tissue repair and cyclical endometrial regeneration. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has significant reparative and anti-fibrotic effects in various tissues. However, there is limited research on the role of GM-CSF in the repair of endometrial injury and the involvement of macrophages in GM-CSF-mediated endometrial repair. In this study, using a mouse model of endometrial scratching injury, we found that GM-CSF treatment accelerated the repair of endometrial injury and improved fertility. At the molecular level, we observed that GM-CSF can downregulate the transcript levels of tumor necrosis factor (TNF) in mouse bone marrow-derived macrophages (BMDMs) stimulated by lipopolysaccharide (LPS) and upregulate the expression of Arginase-1 (Arg-1) and mannose receptor C-type 1 (MRC1). Importantly, during the early and middle stages of injury, GM-CSF increased the proportion of M1-like, M2-like, and M1/M2 mixed macrophages, while in the late stage of injury, GM-CSF facilitated a decline in the number of M2-like macrophages. These findings suggest that GM-CSF may promote endometrial repair by recruiting macrophages and modulating the LPS-induced M1-like macrophages into a less inflammatory phenotype. These insights have the potential to contribute to the development of novel therapeutic approaches for the treatment of intrauterine adhesion and related infertility.

Topically-applied collagen-binding serum albumin-fused interleukin-4 modulates wound microenvironment in non-healing wounds

Non-healing wounds have a negative impact on quality of life and account for many cases of amputation and even early death among patients. Diabetic patients are the predominate population affected by these non-healing wounds. Despite the significant clinical demand, treatment with biologics has not broadly impacted clinical care. Interleukin-4 (IL-4) is a potent modulator of the immune system, capable of skewing macrophages towards a pro-regeneration phenotype (M2) and promoting angiogenesis, but can be toxic after frequent administration and is limited by its short half-life and low bioavailability. Here, we demonstrate the design and characterization of an engineered recombinant interleukin-4 construct. We utilize this collagen-binding, serum albumin-fused IL-4 variant (CBD-SA-IL-4) delivered in a hyaluronic acid (HA)-based gel for localized application of IL-4 to dermal wounds in a type 2 diabetic mouse model known for poor healing as proof-of-concept for improved tissue repair. Our studies indicate that CBD-SA-IL-4 is retained within the wound and can modulate the wound microenvironment through induction of M2 macrophages and angiogenesis. CBD-SA-IL-4 treatment significantly accelerated wound healing compared to native IL-4 and HA vehicle treatment without inducing systemic side effects. This CBD-SA-IL-4 construct can address the underlying immune dysfunction present in the non-healing wound, leading to more effective tissue healing in the clinic.

Eicosapentaenoic acid-rich oil supplementation activates PPAR-γ and delays skin wound healing in type 1 diabetic mice

Delayed wound healing is a devastating complication of diabetes and supplementation with fish oil, a source of anti-inflammatory omega-3 (ω-3) fatty acids including eicosapentaenoic acid (EPA), seems an appealing treatment strategy. However, some studies have shown that ω-3 fatty acids may have a deleterious effect on skin repair and the effects of oral administration of EPA on wound healing in diabetes are unclear. We used streptozotocin-induced diabetes as a mouse model to investigate the effects of oral administration of an EPA-rich oil on wound closure and quality of new tissue formed. Gas chromatography analysis of serum and skin showed that EPA-rich oil increased the incorporation of ω-3 and decreased ω-6 fatty acids, resulting in reduction of the ω-6/ω-3 ratio. On the tenth day after wounding, EPA increased production of IL-10 by neutrophils in the wound, reduced collagen deposition, and ultimately delayed wound closure and impaired quality of the healed tissue. This effect was PPAR-γ-dependent. EPA and IL-10 reduced collagen production by fibroblasts in vitro. In vivo, topical PPAR-γ-blockade reversed the deleterious effects of EPA on wound closure and on collagen organization in diabetic mice. We also observed a reduction in IL-10 production by neutrophils in diabetic mice treated topically with the PPAR-γ blocker. These results show that oral supplementation with EPA-rich oil impairs skin wound healing in diabetes, acting on inflammatory and non-inflammatory cells.

[Low-dose topical recombinant human granulocyte-macrophage colony-stimulating factor (rhu GM-CSF) therapy for chronic venous leg ulcers, 10-year follow-up]

BACKGROUND

The treatment of leg ulcers is an enormous problem worldwide. Chronic venous ulceration affects 1% of the population and often has a protracted course. Recurrence rate is high, ranging up to 69% in the first year after healing.

OBJECTIVES

To determine whether topical application of low-dose topical recombinant human granulocyte-macrophage colony-stimulating factor (rhu GM-CSF) is safe in venous leg ulcer treatment, and whether it accelerates healing rates and reduces recurrence rates.

MATERIALS AND METHODS

Consecutive patients with chronic venous leg ulcers received topical treatment with low-dose rhu GM-CSF (10 µg/mL 0.9% sodium chloride solution; 1.0-2.3 µg rhu GM-CSF/cm²) in combination with treatment of venous insufficiency. All patients were previously treated with other topical wound remedies for several weeks (median 8 weeks) without success.

RESULTS

In 119 of 130 patients, the wounds healed completely (91.5%). No local or systemic adverse reactions were observed. The mean time to healing was 24 weeks (median 14 weeks). Median follow-up of the 119 patients with healed ulcers was 84 months. The recurrence rates were 5.2% after 1 year, 18.9% after 4 years and 32.0% after 10 years.

CONCLUSIONS

Topical low-dose rhu GM-CSF proved to be safe and highly effective. Healing rates were comparable to those reported in the ESCHAR study (Effects of Surgery and Compression on Healing And Recurrence in venous ulceration) and recurrence rates were the lowest reported in the literature. Topical therapy with rhu GM-CSF can be applied in an outpatient setting and does not require hospitalization.

Cytokines and Venous Leg Ulcer Healing-A Systematic Review

Venous leg ulcers (VLUs) are the most common type of leg ulcers with a significant socioeconomic burden due to slow healing. Cytokines may be involved in the pathogenesis of VLUs. In this systematic review, our objective was to investigate the association between cytokine levels, including growth factors, with the healing of VLUs. PubMed, Embase, Web of Science and Cochrane Library were searched from their inception to August 2021. We retrieved 28 articles investigating 38 different cytokines in 790 patients. Cytokines were most commonly investigated in wound fluid and less frequently in biopsies and serum. The studies were judged as having a moderate to high risk of bias, and the results were often inconsistent and sometimes conflicting. A meta-analysis was not performed due to clinical and methodological heterogeneities. We found weak evidence for elevated IL-1α, IL-6, IL-8, TNF-α and VEGF levels in non-healing VLUs, an elevation that declined with healing. TGF-β1 levels tended to increase with VLU healing. Other cytokines warranting further investigations include EGF, FGF-2, GM-CSF, IL-1β, IL-1Ra and PDGF-AA/PDGF-BB. We conclude that non-healing VLUs may be associated with an elevation of a palette of pro-inflammatory cytokines, possibly reflecting activated innate immunity in these wounds. There is a paucity of reliable longitudinal studies monitoring the dynamic changes in cytokine levels during wound healing.

Growth Factors, Reactive Oxygen Species, and Metformin-Promoters of the Wound Healing Process in Burns?

Burns can be caused by various factors and have an increased risk of infection that can seriously delay the wound healing process. Chronic wounds caused by burns represent a major health problem. Wound healing is a complex process, orchestrated by cytokines, growth factors, prostaglandins, free radicals, clotting factors, and nitric oxide. Growth factors released during this process are involved in cell growth, proliferation, migration, and differentiation. Reactive oxygen species are released in acute and chronic burn injuries and play key roles in healing and regeneration. The main aim of this review is to present the roles of growth factors, reactive oxygen species, and metformin in the healing process of burn injuries.

The senescence-associated secretory phenotype: Fueling a wound that never heals

Wound healing is impaired with advanced age and certain chronic conditions, such as diabetes and obesity. Moreover, common cancer treatments, including chemotherapy and radiation, can cause unintended tissue damage and impair wound healing. Available wound care treatments are not always effective, as some wounds fail to heal or recur after treatment. Hence, a more thorough understanding of the pathophysiology of chronic, nonhealing wounds may offer new ideas for the development of effective wound care treatments. Cancers are sometimes referred to as wounds that never heal, sharing mechanisms similar to wound healing. We describe in this review how cellular senescence and the senescence-associated secretory phenotype (SASP) contribute to chronic wounds versus cancer.

Maintenance of Barrier Tissue Integrity by Unconventional Lymphocytes

Mucosal surfaces, as a first barrier with the environment are especially susceptible to damage from both pathogens and physical trauma. Thus, these sites require tightly regulated repair programs to maintain barrier function in the face of such insults. Barrier sites are also enriched for unconventional lymphocytes, which lack rearranged antigen receptors or express only a limited range of such receptors, such as ILCs (Innate Lymphoid Cells), γδ T Cells and MAIT (Mucosal-Associated Invariant T Cells). Recent studies have uncovered critical roles for unconventional lymphocytes in regulating mucosal barrier function, and, in particular, have highlighted their important involvement in barrier repair. The production of growth factors such as amphiregulin by ILC2, and fibroblast growth factors by γδ T cells have been shown to promote tissue repair at multiple barrier sites. Additionally, MAIT cells have been shown to exhibit pro-repair phenotypes and demonstrate microbiota-dependent promotion of murine skin healing. In this review we will discuss how immune responses at mucosal sites are controlled by unconventional lymphocytes and the ways in which these cells promote tissue repair to maintain barrier integrity in the skin, gut and lungs.

In vitro and clinical evaluation of umbilical cord-derived mesenchymal stromal cell-conditioned media for hair regeneration

BACKGROUND

The field of regenerative medicine may present a non-drug, non-steroid, and non-invasive alternative toward addressing male and female pattern hair loss, a global concern.

OBJECTIVE

The aim was to carry out the in vitro and in vivo safety and efficacy evaluation of human umbilical cord-derived mesenchymal stromal cell-conditioned media (MSC-CM) for hair regeneration.

METHODS

Various in vitro parameters were used to estimate the consistency across various batches of MSC-CM. Total protein content was measured by the Biuret method and antioxidant activity by the 2,2-diphenyl-1-picryl hydrazyl (DPPH) assay. Fourier transform infrared spectroscopy (FTIR) analysis was used to determine spectral signatures and biocompatibility was carried out by the Neutral Red Uptake (NRU) and Sulforhodamine B (SRB) assays. In vivo safety and efficacy was evaluated in an experimental pilot study on 15 volunteers.

RESULTS

The in vitro results confirmed stability in the protein content (7 mg/ml), antioxidant activity (49.50%), and FTIR fingerprints of the MSC-CM. In the biocompatibility experiments by both SRB and NRU methods, no IC₅₀ value could be derived at 100% concentration indicating safety at the cellular level. The in vivo results indicated safety with no side effects or adverse reactions, while 86.6% of the subjects experienced a positive effect of hair regeneration.

CONCLUSION

MSC-CM comprises a rich cocktail of physiologically balanced growth factors, cytokines, and beneficial proteins which may explain the bioactivity and mechanism of action in hair regrowth. This may indicate a biocompatible, gentle, and safe regenerative approach to address hair loss.

Mobilization of endothelial progenitor cells promotes angiogenesis after full thickness excision by AMD3100 combined with G-CSF in diabetic mice by SDF-1/CXCR4 axis

AIM

The aim of the present study was to investigate the effect of the mobilization of EPCs by AMD3100 combined with G-CSF on wound healing in diabetic mice.

METHODS

The full-thickness excisional wounds model of diabetic mice (db/db) was examined by hematoxylin and eosin staining, immunohistochemical staining, and western blotting to compare the wound healing and neovascularization among the combination, AMD3100 alone, G-CSF alone, and control groups.

RESULTS

The wounds reached the complete closure in the combination, AMD3100 alone, G-CSF alone, and control groups on days 17, 20, 21, 21 after surgery, respectively. In addition, the combination group promoted the inflammatory cell recruitment and glandular formation. On day 10 from injury, the protein expression of CD31 in the combination group was significantly higher compared with the other three groups (p < 0.001). The level of SDF-1 protein remained high in the combined group until on day 10 after surgery (p < 0.001).

CONCLUSION

The mobilization of endogenous EPCs by AMD3100 combine with G-CSF is able to enhance the complete healing of full-thickness wounds and neovascularization in db/db mice may by SDF-1/CXCR4 axis. These findings provided a novel method and indication of duration of mobilization on diabetic wound healing and tissue regeneration.

What Is the Impact of Depletion of Immunoregulatory Genes on Wound Healing? A Systematic Review of Preclinical Evidence

Cytokines and growth factors are known to play an important role in the skin wound closure process; however, in knockout organisms, the levels of these molecules can undergo changes that result in the delay or acceleration of this process. Therefore, we systematically reviewed evidence from preclinical studies about the main immunoregulatory molecules involved in skin repair through the analysis of the main mechanisms involved in the depletion of immunoregulatory genes, and we carried out a critical analysis of the methodological quality of these studies. We searched biomedical databases, and only original studies were analyzed according to the PRISMA guidelines. The included studies were limited to those which used knockout animals and excision or incision wound models without intervention. A total of 27 studies were selected; data for animal models, gene depletion, wound characteristics, and immunoregulatory molecules were evaluated and compared whenever possible. Methodological quality assessments were examined using the ARRIVE and SYRCLE's bias of risk tool. In our review, the extracellular molecules act more negatively in the wound healing process when silenced and the metabolic pathway most affected involved in these processes was TGF-β/Smad, and emphasis was given to the importance of the participation of macrophages in TGF-β signaling. Besides that, proinflammatory molecules were more evaluated than anti-inflammatory ones, and the main molecules evaluated were, respectively, TGF-β1, followed by VEGF, IL-6, TNF-α, and IL-1β. Overall, most gene depletions delayed wound healing, negatively influenced the concentrations of proinflammatory cytokines, and consequently promoted a decrease of inflammatory cell infiltration, angiogenesis, and collagen deposition, compromising the formation of granulation tissue. The studies presented heterogeneous data and exhibited methodological limitations; therefore, mechanistic and highly controlled studies are required to improve the quality of the evidence.

The Immune Functions of Keratinocytes in Skin Wound Healing

As the most dominant cell type in the skin, keratinocytes play critical roles in wound repair not only as structural cells but also exerting important immune functions. This review focuses on the communications between keratinocytes and immune cells in wound healing, which are mediated by various cytokines, chemokines, and extracellular vesicles. Keratinocytes can also directly interact with T cells via antigen presentation. Moreover, keratinocytes produce antimicrobial peptides that can directly kill the invading pathogens and contribute to wound repair in many aspects. We also reviewed the epigenetic mechanisms known to regulate keratinocyte immune functions, including histone modifications, non-protein-coding RNAs (e.g., microRNAs, and long noncoding RNAs), and chromatin dynamics. Lastly, we summarized the current evidence on the dysregulated immune functions of keratinocytes in chronic nonhealing wounds. Based on their crucial immune functions in skin wound healing, we propose that keratinocytes significantly contribute to the pathogenesis of chronic wound inflammation. We hope this review will trigger an interest in investigating the immune roles of keratinocytes in chronic wound pathology, which may open up new avenues for developing innovative wound treatments.

Depletion of langerin+ cells enhances cutaneous wound healing

Langerin is a C-type lectin receptor that is expressed on Langerhans cells and langerin-positive dermal dendritic cells in the skin. Little is known about the function of langerin⁺ cells in wound healing. In this study, the effects of ablation of langerin⁺ cells on healing of a full-thickness excision wound were investigated using the langerin-DTR depletable mouse. Strikingly, depletion of langerin⁺ cells resulted in more rapid reduction in wound area. Accelerated wound healing in the langerin⁺ -cell-depleted group was characterized by enhanced neo-epidermis and granulation tissue formation, and increased cellular proliferation within the newly formed tissues. Accelerated healing in the absence of langerin⁺ cells was associated with increased levels of granulocyte-macrophage colony-stimulating factor, F4/80⁺ cells and blood vessels within the granulation tissue. These data support an inhibitory role for langerin⁺ cells during wound healing. Therapies that suppress langerin⁺ cells or their function may therefore have utility in progressing the healing of wounds in humans.

The origins and non-canonical functions of macrophages in development and regeneration

The discovery of new non-canonical (i.e. non-innate immune) functions of macrophages has been a recurring theme over the past 20 years. Indeed, it has emerged that macrophages can influence the development, homeostasis, maintenance and regeneration of many tissues and organs, including skeletal muscle, cardiac muscle, the brain and the liver, in part by acting directly on tissue-resident stem cells. In addition, macrophages play crucial roles in diseases such as obesity-associated diabetes or cancers. Increased knowledge of their regulatory roles within each tissue will therefore help us to better understand the full extent of their functions and could highlight new mechanisms modulating disease pathogenesis. In this Review, we discuss recent studies that have elucidated the developmental origins of various macrophage populations and summarize our knowledge of the non-canonical functions of macrophages in development, regeneration and tissue repair.

The Dynamics of the Skin's Immune System

The skin is a complex organ that has devised numerous strategies, such as physical, chemical, and microbiological barriers, to protect the host from external insults. In addition, the skin contains an intricate network of immune cells resident to the tissue, crucial for host defense as well as tissue homeostasis. In the event of an insult, the skin-resident immune cells are crucial not only for prevention of infection but also for tissue reconstruction. Deregulation of immune responses often leads to impaired healing and poor tissue restoration and function. In this review, we will discuss the defensive components of the skin and focus on the function of skin-resident immune cells in homeostasis and their role in wound healing.

CCL2/MCP-1 signaling drives extracellular matrix turnover by diverse macrophage subsets

Macrophage plasticity, cellular origin, and phenotypic heterogeneity are perpetual challenges for studies addressing the biology of this pivotal immune cell in development, homeostasis, and tissue remodeling/repair. Consequently, a myriad of macrophage subtypes has been described in these contexts. To facilitate the identification of functional macrophage subtypes in vivo, here we used a flow cytometry-based assay that allows for detailed phenotyping of macrophages engaged in extracellular matrix (ECM) degradation. Of the five macrophage subtypes identified in the remodeling dermis by using this assay, collagen degradation was primarily executed by Ly6C⁻CCR2⁺ and Ly6C⁻CCR2^low macrophages via mannose receptor-dependent collagen endocytosis, while Ly6C⁺CCR2⁺ macrophages were the dominant fibrin-endocytosing cells. Unexpectedly, the CCL2/MCP1-CCR2 signaling axis was critical for both collagen and fibrin degradation, while collagen degradation was independent of IL-4Ra signaling. Furthermore, the cytokine GM-CSF selectively enhanced collagen degradation by Ly6C⁺CCR2⁺ macrophages. This study reveals distinct subsets of macrophages engaged in ECM turnover and identifies novel wound healing-associated functions for CCL2 and GM-CSF inflammatory cytokines.

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Phenotypically diverse subsets of dermal macrophages undertake the degradation of extracellular matrix

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C-C motif chemokine Ligand 2 (CCL2) signaling is critical for macrophage-mediated endocytosis of collagen and fibrin.

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Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) and Interleukin (IL)-13 stimulate collagen endocytosis.

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The wound healing-associated IL4-IL4 Receptor a (IL4Ra) signaling is dispensable for collagen endocytosis by macrophages.

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The mannose receptor is the principal endocytic collagen receptor utilized by resident dermal macrophages.

Nanocrystalline cellulose-hyaluronic acid composite enriched with GM-CSF loaded chitosan nanoparticles for enhanced wound healing

In recent years, applications of biopolymers such as hyaluronic acid (HA) for wound dressing have attracted more attention. However, the poor mechanical properties of HA-based wound dressings limit their clinical applications. Incorporation of reinforcing agents such as nanocrystalline cellulose (CNC) in HA-based wound dressings can improve their mechanical properties. In addition, controlled delivery of growth factors to the wound site using nanoparticles can significantly improve the healing process. In this study, we focus on development and characterization of a novel CNC reinforced HA-based composite containing chitosan nanoparticles loaded with GM-CSF (CNC-HA/GM-CSF-Chi-NPs composite) as an effective wound dressing. CNC-HA/GM-CSF-Chi-NPs composite showed some physicochemical characteristics such as appropriate mechanical properties, high swelling capacity (swelling ratio: 2622.1% ± 35.2%) and controlled release of GM-CSF up to 48 h which make it an excellent candidate for wound dressing. In vivo investigation showed that, after 13 d, the wounds covered with CNC-HA/GM-CSF-Chi-NPs composite could reach to nearly full wound closure and complete re-epithelialization compared to the normal saline treated wounds which exhibited nearly 70% of wound size reduction. Furthermore, the CNC-HA/GM-CSF-Chi-NPs composite treated wounds exhibited significantly lower inflammatory reaction, enhanced re-epithelialization and improved granulation tissue formation compared with CNC-HA/Chi-NPs composite treated wound; it might be due to positive effects of GM-CSF on the wound healing process. Our results suggest that CNC-HA/GM-CSF-Chi-NPs composite can be potentially applied in clinical practice for wound treatment.

Carnosol suppresses interleukin-6 production in mouse lungs injured by ischemia–reperfusion operation and in RAW264.7 macrophages treated with lipopolysaccharide

Carnosol is a naturally occurring herbal compound, known for its antioxidative properties. We previously found that carnosol protected mouse lungs from ischemia–reperfusion injury in ex vivo cultures. To elucidate the molecular mechanisms underpinning carnosol-mediated lung protection, we analyzed modes of interleukin-6 (IL-6) gene expression, which is associated with lung ischemia–reperfusion injury. Microarray analysis of mouse lungs suggested that IL-6 mRNA levels were elevated in the mouse lungs subjected to clamp-reperfusion, which was associated with elevated levels of other inflammatory modulators, such as activating transcription factor 3 (ATF3). Carnosol pretreatment lowered the IL-6 protein levels in mouse lung homogenates prepared after the clamp-reperfusion. On the other hand, the ATF3 gene expression was negatively correlated with that of IL-6 in RAW264.7 cells. IL-6 mRNA levels and gene promoter activities were suppressed by carnosol in RAW264.7 cells, but rescued by ATF3 knockdown. When RAW264.7 cells were subjected to hypoxia–reoxygenation, carnosol treatment lowered oxygen consumption after reoxygenation, which was coupled with a correlation with a transient production of mitochondrial reactive oxygen species and following ATF3 gene expression. These results suggest that carnosol treatment could be a new strategy for protecting lungs from ischemia–reperfusion injury by modulating the ATF3–IL-6 axis.

Cellular and Molecular Interaction of Human Dermal Fibroblasts with Bacterial Nanocellulose Composite Hydrogel for Tissue Regeneration

The evaluation of the interaction of cells with biomaterials is fundamental to establish the suitability of the biomaterial for a specific application. In this study, the properties of bacterial nanocellulose/acrylic acid (BNC/AA) hydrogels fabricated with varying BNC to AA ratios and electron-beam irradiation doses were determined. The manner these hydrogel properties influence the behavior of human dermal fibroblasts (HDFs) at the cellular and molecular levels was also investigated, relating it to its application both as a cell carrier and wound dressing material. Swelling, hardness, adhesive force (wet), porosity, and hydrophilicity (dry) of the hydrogels were dependent on the degree of cross-linking and the amount of AA incorporated in the hydrogels. However, water vapor transmission rate, pore size, hydrophilicity (semidry), and topography were similar between all formulations, leading to a similar cell attachment and proliferation profile. At the cellular level, the hydrogel demonstrated rapid cell adhesion, maintained HDFs viability and morphology, restricted cellular migration, and facilitated fast transfer of cells. At the molecular level, the hydrogel affected nine wound-healing genes (IL6, IL10, MMP2, CTSK, FGF7, GM-CSF, TGFB1, COX2, and F3). The findings indicate that the BNC/AA hydrogel is a potential biomaterial that can be employed as a wound-dressing material to incorporate HDFs for the acceleration of wound healing.

Dectin-2-Mediated Signaling Leads to Delayed Skin Wound Healing through Enhanced Neutrophilic Inflammatory Response and Neutrophil Extracellular Trap Formation

Dendritic cell-associated C-type lectin-2 (i.e., dectin-2) recognizes fungal polysaccharides, including α-mannan. Dectin-2-mediated recognition of fungi, such as Candida albicans, leads to NF-κB activation, which induces production of inflammatory cytokines. However, the role of dectin-2 in skin wound healing remains unclear. In this study, we sought to determine how dectin-2 deficiency and the administration of α-mannan affected the wound healing process. Full-thickness wounds were created on the backs of wild type C57BL/6 and dectin-2-deficient mice. We analyzed wound closure, histological findings, and re-epithelialization. We also examined the neutrophilic inflammatory responses and neutrophil extracellular trap (NET)-osis at the wound sites after administration of α-mannan. The percent wound closure and re-epithelialization was significantly accelerated in dectin-2-knockout mice compared with wild-type mice on days 3 and 5 after wounding. In contrast, administration of α-mannan delayed wound closure in wild-type mice, and these responses were canceled in dectin-2-knockout mice. Furthermore, mice administered α-mannan, neutrophil infiltration was prolonged, and the expression of citrullinated histone, an indicator of NETosis, at the wound sites was accelerated. Administration of a neutrophil elastase inhibitor significantly improved the delayed wound healing caused by α-mannan. These results suggest that dectin-2 may have a deep impact on the skin wound healing process through regulation of neutrophilic responses.

Challenges in the local delivery of peptides and proteins for oral mucositis management

Oral mucositis, a common inflammatory side effect of oncological treatments, is a disorder of the oral mucosa that can cause painful ulcerations, local motor disabilities, and an increased risk of infections. Due to the discomfort it produces and the associated health risks, it can lead to cancer treatment restrains, such as the need for dose reduction, cycle delays or abandonment. Current mucositis management has low efficiency in prevention and treatment. A topical drug application for a local action can be a more effective approach than systemic routes when addressing oral cavity pathologies. Local delivery of growth factors, antibodies, and anti-inflammatory cytokines have shown promising results. However, due to the peptide and protein nature of these novel agents, and the several anatomic, physiological and environmental challenges of the oral cavity, their local action might be limited when using traditional delivering systems. This review is an awareness of the issues and strategies in the local delivery of macromolecules for the management of oral mucositis.

Drug delivery and tissue engineering to promote wound healing in the immunocompromised host: Current challenges and future directions

As regenerative medicine matures as a field, more promising technologies are being translated from the benchtop to the clinic. However, many of these strategies are designed with otherwise healthy hosts in mind and validated in animal models without other co-morbidities. In reality, many of the patient populations benefiting from drug delivery and tissue engineering-based devices to enhance wound healing also have significant underlying immunodeficiency. Specifically, patients suffering from diabetes, malignancy, human immunodeficiency virus, post-organ transplantation, and other compromised states have significant pleotropic immune defects that affect wound healing. In this work, we review the role of different immune cells in the regenerative process, highlight the effect of several common immunocompromised states on wound healing, and discuss different drug delivery strategies for overcoming immunodeficiencies.

GM-CSF ameliorates microvascular barrier integrity via pericyte-derived Ang-1 in wound healing

Skin wound healing involves complex coordinated interactions of cells, tissues, and mediators. Maintaining microvascular barrier integrity is one of the key events for endothelial homeostasis during wound healing. Vasodilation is observed after vasoconstriction, which causes blood vessels to become porous, facilitates leukocyte infiltration and aids angiogenesis at the wound-area, postinjury. Eventually, vessel integrity has to be reestablished for vascular maturation. Numerous studies have found that granulocyte macrophage colony-stimulating factor (GM-CSF) accelerates wound healing by inducing recruitment of repair cells into the injury area and releases of cytokines. However, whether GM-CSF is involving in the maintaining of microvascular barrier integrity and the underlying mechanism remain still unclear. Aim of this study was to investigate the effects of GM-CSF on modulation of microvascular permeability in wound healing and underlying mechanisms. Wound closure and microvascular leakage was investigated using a full-thickness skin wound mouse model after GM-CSF intervention. The endothelial permeability was measured by Evans blue assay in vivo and in vitro endothelium/pericyte co-culture system using a FITC-Dextran permeability assay. To identify the source of angiopoietin-1 (Ang-1), double staining is used in vivo and ELISA and qPCR are used in vitro. To determine the specific effect of Ang-1 on GM-CSF maintaining microvascular stabilization, Ang-1 siRNA was applied to inhibit Ang-1 production in vivo and in vitro. Wound closure was significantly accelerated and microvascular leakage was ameliorated after GM-CSF treatment in mouse wound sites. GM-CSF decreased endothelial permeability through tightening endothelial junctions and increased Ang-1 protein level that was derived by perictye. Furthermore, applications of siRNAAng-1 inhibited GM-CSF mediated protection of microvascular barrier integrity both in vivo and in vitro. Our data indicate that GM-CSF ameliorates microvascular barrier integrity via pericyte-derived Ang-1 during wound healing.

Delivery of monocyte lineage cells in a biomimetic scaffold enhances tissue repair

The monocyte lineage is essential to normal wound healing. Macrophage inhibition or knockout in mice results in impaired wound healing through reduced neovascularization, granulation tissue formation, and reepithelialization. Numerous studies have either depleted macrophages or reduced their activity in the context of wound healing. Here, we demonstrate that by increasing the number of macrophages or monocytes in the wound site above physiologic levels via pullulan-collagen composite dermal hydrogel scaffold delivery, the rate of wound healing can be significantly accelerated in both wild-type and diabetic mice, with no adverse effect on the quality of repair. Macrophages transplanted onto wounds differentiate into M1 and M2 phenotypes of different proportions at various time points, ultimately increasing angiogenesis. Given that monocytes can be readily isolated from peripheral blood without in vitro manipulation, these findings hold promise for translational medicine aimed at accelerating wound healing across a broad spectrum of diseases.

Role of plasma-derived fibrin on keratinocyte and fibroblast wound healing

Fibrin has excellent biocompatibility and biological properties to support tissue regeneration and promote wound healing. However, the role of diluted fibrin in wound healing has yet to be elucidated as it is commonly used in high concentration. This study was aimed to examine the effects of diluted plasma-derived fibrin (PDF) on keratinocyte and fibroblast wound healing in term of cell proliferation, migration, extracellular matrix (ECM) production and soluble factor secretion. Two PDF concentrations, 10 and 20% (v/v) were tested on keratinocytes and fibroblasts indirectly co-cultured in the transwell system. The control group was cultured with 5% FBS. Results showed that PDF reduced the keratinocyte growth rate and fibroblast migration, and increased the fibroblast ECM gene expression whereby significant differences were found between the 20% PDF group and the 5% FBS group. Similar trend was seen for the 10% PDF group but the differences were not significant. Comparison of the soluble factors between the PDF groups demonstrated that the level of growth-related oncogene alpha, interleukin-8 and epithelial neutrophil-activating peptide-78 were significantly higher in the 10% PDF group, whilst interleukin-1 alpha and granulocyte-macrophage colony stimulating factor were significantly more concentrated in the 20% PDF group. Our results suggested that PDF selectively elevated the expression of collagen type 1 and collagen type 3 in fibroblasts but slowed down the migration in concentration-dependent manner. These novel findings provide new insight into the role of PDF in wound healing and may have important implications for the use of fibrin in skin tissue engineering.

Local injection of granulocyte-colony stimulating factor accelerates wound healing in a rat excisional wound model

A systemic treatment of granulocyte-colony stimulating factor (G-CSF) is known to improve healings of damaged tissues. However, recent studies suggested local actions of G-CSF on the healing processes of damaged tissues. We investigated the treatment effect of locally injected G-CSF and compared to that of systemically injected G-CSF in a rat model. A wound was created on the rat dorsum and treated either by local injection or by systemic injection of G-CSF. Wound healing rate, deposition of collagen, and gene expression were evaluated. G-CSF receptor (G-CSFR) protein was detected by Western blotting. The wound healing rate in the local injection group was significantly higher than that in the systemic injection group at days 9 and 15; it was also significantly higher than that in the control group at days 3, 9, and 15. The expression of G-CSFR protein in wound tissues was higher than in normal skin tissues. The local injection of G-CSF is more effective than systemic injection of G-CSF in promoting wound healing, which may implicate the local action of G-CSF treatment in wound healing processes.

Effects of Granulocyte-Macrophage Colony-Stimulating (GM-CSF) Factor on Corneal Epithelial Cells in Corneal Wound Healing Model

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic cytokine that activates granulocyte and macrophage cell lineages. It is also known to have an important function in wound healing. This study investigated the effect of GM-CSF in wound healing of human corneal epithelial cells (HCECs). We used human GM-CSF derived from rice cells (rice cell-derived recombinant human GM-CSF; rhGM-CSF). An in vitro migration assay was performed to investigate the migration rate of HCECs treated with various concentrations of rhGM-CSF (0.1, 1.0, and 10.0 μg/ml). MTT assay and flow cytometric analysis were used to evaluate the proliferative effect of rhGM-CSF. The protein level of p38MAPK was analyzed by western blotting. For in vivo analysis, 100 golden Syrian hamsters were divided into four groups, and their corneas were de-epithelialized with alcohol and a blade. The experimental groups were treated with 10, 20, or 50 μg/ml rhGM-CSF four times daily, and the control group was treated with phosphate-buffered saline. The corneal wound-healing rate was evaluated by fluorescein staining at the initial wounding and 12, 24, 36, and 48 hours after epithelial debridement. rhGM-CSF accelerated corneal epithelial wound healing both in vitro and in vivo. MTT assay and flow cytometric analysis revealed that rhGM-CSF treatment had no effects on HCEC proliferation. Western blot analysis demonstrated that the expression level of phosphorylated p38MAPK increased with rhGM-CSF treatment. These findings indicate that rhGM-CSF enhances corneal wound healing by accelerating cell migration.

The Roles of Growth Factors in Keratinocyte Migration

Significance: The re-epithelialization of wounded skin requires the rapid and coordinated migration of keratinocytes (KC) into the wound bed. Almost immediately after wounding, cells present at or attracted to the wound site begin to secrete a complex milieu of growth factors. These growth factors exert mitogenic and motogenic effects on KCs, inducing the rapid proliferation and migration of KCs at the wound edge. Recent Advances: New roles for growth factors in KC biology are currently being discovered and investigated. This review will highlight the growth factors, particularly transforming growth factor-α (TGF-α), heparin-binding epidermal growth factor (HB-EGF), insulin-like growth factor 1 (IGF-1), fibroblast growth factor 7 (FGF-7), FGF-10, and hepatocyte growth factor (HGF), which have conclusively been shown to be the most motogenic for KCs. Critical Issues: The cellular and molecular heterogeneity of wounded tissue makes establishing direct relationships between specific growth factors and KC migration difficult in situ. The absence of this complexity in simplified in vitro experimental models of migration makes the clinical relevance of the results obtained from these in vitro studies ambiguous. Future Directions: Deciphering the relationship between growth factors and KC migration is critical for understanding the process of wound healing in normal and disease states. Insights into the basic science of the effects of growth factors on KC migration will hopefully lead to the development of new therapies to treat acute and chronic wounds.

Clinical application of growth factors and cytokines in wound healing

Wound healing is a complex and dynamic biological process that involves the coordinated efforts of multiple cell types and is executed and regulated by numerous growth factors and cytokines. There has been a drive in the past two decades to study the therapeutic effects of various growth factors in the clinical management of nonhealing wounds (e.g., pressure ulcers, chronic venous ulcers, diabetic foot ulcers). For this review, we conducted an online search of Medline/PubMed and critically analyzed the literature regarding the role of growth factors and cytokines in the management of these wounds. We focused on currently approved therapies, emerging therapies, and future research possibilities. In this review, we discuss four growth factors and cytokines currently being used on and off label for the healing of wounds. These include granulocyte-macrophage colony-stimulating factor, platelet-derived growth factor, vascular endothelial growth factor, and basic fibroblast growth factor. While the clinical results of using growth factors and cytokines are encouraging, many studies involved a small sample size and are disparate in measured endpoints. Therefore, further research is required to provide definitive evidence of efficacy.

Granulocyte/macrophage colony-stimulating factor influences angiogenesis by regulating the coordinated expression of VEGF and the Ang/Tie system

Granulocyte/macrophage colony-stimulating factor (GM-CSF) can accelerate wound healing by promoting angiogenesis. The biological effects of GM-CSF in angiogenesis and the corresponding underlying molecular mechanisms, including in the early stages of primitive endothelial tubule formation and the later stages of new vessel maturation, have only been partially clarified. This study aimed to investigate the effects of GM-CSF on angiogenesis and its regulatory mechanisms. Employing a self-controlled model (Sprague-Dawley rats with deep partial-thickness burn wounds), we determined that GM-CSF can increase VEGF expression and decrease the expression ratio of Ang-1/Ang-2 and the phosphorylation of Tie-2 in the early stages of the wound healing process, which promotes the degradation of the basement membrane and the proliferation of endothelial cells. At later stages of wound healing, GM-CSF can increase the expression ratio of Ang-1/Ang-2 and the phosphorylation of Tie-2 and maintain a high VEGF expression level. Consequently, pericyte coverages were higher, and the basement membrane became more integrated in new blood vessels, which enhanced the barrier function of blood vessels. In summary, we report here that increased angiogenesis is associated with GM-CSF treatment, and we indicate that VEGF and the Ang/Tie system may act as angiogenic mediators of the healing effect of GM-CSF on burn wounds.

Exercise, Obesity, and Cutaneous Wound Healing: Evidence from Rodent and Human Studies

Significance: Impaired cutaneous wound healing is a major health concern. Obesity has been shown in a number of studies to impair wound healing, and chronic nonhealing wounds in obesity and diabetes are a major cause of limb amputations in the United States. Recent Advances: Recent evidence indicates that aberrant wound site inflammation may be an underlying cause for delayed healing. Obesity, diabetes, and other conditions such as stress and aging can result in a chronic low-level inflammatory state, thereby potentially affecting wound healing negatively. Critical Issues: Interventions which can speed the healing rate in individuals with slowly healing or nonhealing wounds are of critical importance. Recently, physical exercise training has been shown to speed healing in both aged and obese mice and in older adults. Exercise is a relatively low-cost intervention strategy which may be able to be used clinically to prevent or treat impairments in the wound-healing process. Future Directions: Little is known about the mechanisms by which exercise speeds healing. Future translational studies should address potential mechanisms for these exercise effects. Additionally, clinical studies in obese humans are necessary to determine if findings in obese rodent models translate to the human population.

Engineering the regenerative microenvironment with biomaterials

Modern synthetic biomaterials are being designed to integrate bioactive ligands within hydrogel scaffolds for cells to respond and assimilate within the matrix. These advanced biomaterials are only beginning to be used to simulate the complex spatio-temporal control of the natural healing microenvironment. With increasing understanding of the role of growth factors and cytokines and their interactions with components of the extracellular matrix, novel biomaterials are being developed that more closely mimic the natural healing environments of tissues, resulting in increased efficacy in applications of tissue repair and regeneration. Herein, the important aspects of the healing microenvironment, and how these features can be incorporated within innovative hydrogel scaffolds, are presented.

Tissue-protective cytokines: structure and evolution

Cytokines are important mediators of host defense and immunity, and were first identified for their role in immunity to infections. It was then found that some of them are pathogenic mediators in inflammatory diseases and much of the emphasis is now on pro-inflammatory cytokines, also in consideration of the fact that TNF inhibitors became effective drugs in chronic inflammatory diseases. The recent studies on the tissue-protective activities of erythropoietin (EPO) led to the term "tissue-protective cytokine." We discuss here how tissue-protective actions might be common to other cytokines, particularly those of the 4-alpha helical structural superfamily.

Hypoxia and hypoxia signaling in tissue repair and fibrosis

Following injury, vascular damage results in the loss of perfusion and consequent low oxygen tension (hypoxia) which may be exacerbated by a rapid influx of inflammatory and mesenchymal cells with high metabolic demands for oxygen. Changes in systemic and cellular oxygen concentrations induce tightly regulated response pathways that attempt to restore oxygen supply to cells and modulate cell function in hypoxic conditions. Most of these responses occur through the induction of the transcription factor hypoxia-inducible factor-1 (HIF-1) which regulates many processes needed for tissue repair during ischemia in the damaged tissue. HIF-1 transcriptionally upregulates expression of metabolic proteins (GLUT-1), adhesion proteins (integrins), soluble growth factors (TGF-β and VEGF), and extracellular matrix components (type I collagen and fibronectin), which enhance the repair process. For these reasons, HIF-1 is viewed as a positive regulator of wound healing and a potential regulator of organ repair and tissue fibrosis. Understanding the complex role of hypoxia in the loss of function in scarring tissues and biology of chronic wound, and organ repair will aid in the development of pharmaceutical agents that can redress the detrimental outcomes often seen in repair and scarring.

Hematological abnormalities and the use of granulocyte-colony-stimulating factor in patients with Stevens-Johnson syndrome and toxic epidermal necrolysis

BACKGROUND

Derangements in blood cell counts have been described in patients with Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) but are not well characterized. We aim to describe the relationship between our patients' hematological results and the evolution of disease and hypothesize on the possible roles of granulocyte-colony-stimulating factor (G-CSF) in the management of these conditions.

MATERIALS AND METHODS

Clinical records of our patients with SJS and TEN from January 2005 to 2010 were analyzed.

RESULTS

Anemia and lymphopenia were most commonly seen, while thrombocytopenia was uncommon. Leukopenia and neutropenia were seen in patients with more severe disease, and the trend of leukopenia and neutropenia followed the evolution of disease. Two patients received G-CSF for febrile neutropenia and had a rapid recovery of their neutrophil counts as well as a shorter time to re-epithelialization.

CONCLUSION

Our patients tended to have leukopenia and neutropenia that followed a predictable trend of decline and subsequent improvement depending on the stage of disease. This may be of pathogenic significance, and G-CSF may be used in these cases to manage febrile neutropenia and aid re-epithelialization. Further basic science research is required to prove our hypotheses.

Increased in vitro Cell Proliferation by Chitosan/pGM-CSF Complexes

Granulocyte macrophage colony stimulating factor, a potent hematopoietic cytokine, has been shown to stimulate production of white blood cells following chemotherapy. Therefore, the granulocyte macrophage colony stimulating factor gene is a potential candidate for the treatment of different pathological conditions. The purpose of this study is to investigate the suitability of chitosan as carrier for pORF-hGMCSF plasmid encoding granulocyte macrophage colony stimulating factor gene and also to study the effect of complexes on protein production and cell proliferation. Chitosan/pGM-CSF complexes were prepared using different (+/-) ratios (from 0.01/1 to 5/1). Complex formation was checked with agarose gel electrophoresis. The size and zeta potential values were measured. Enzyme and serum stability of complexes were studied. In vitro transfection properties of complexes were studied in HeLa cells. According to agarose gel electrophoresis, full complexation was obtained at 0.1/1 and higher chitosan/pGM-CSF ratios. Complexes having about 132 nm size and +13.7 mV zeta potential value were obtained. Chitosan complexes protected plasmid against enzymatic and serum effects. The gene expression-dependent cell proliferation after transfection of chitosan/pGM-CSF complexes at 72 h was markedly increased in comparision with the level of control group. These results indicate that the effect of chitosan/pGM-CSF complexes on cell proliferation was changed with N/P ratio and time-dependently. For GM-CSF therapy, chitosan/pGM-CSF complexes may be used as alternative to conventional protein treatments. Chitosan may be a good carrier for pORF-hGMCSF. Further, in vivo study is ongoing.

Promotion of angiogenesis by sustained release of rhGM-CSF from heparinized collagen/chitosan scaffolds

A novel dermal substitute of combining recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) with a porous heparinized collagen/chitosan scaffolds was developed, considering the inadequate angiogenesis during repair of full-thickness skin defects. The physicochemical properties of heparinized collagen/chitosan scaffolds were examined and in vitro release pattern of rhGM-CSF from scaffolds was measured by ELISA. Four groups of composite scaffolds (heparinized or unheparinized scaffolds loaded with or without rhGM-CSF) were fabricated for subcutaneous implantation in young adult male Sprague-Dawley (SD) rats. Tissue specimens were harvested at different time points after implantation for histopathological, immunohistochemical observation, and Western blotting analysis. The heparinized scaffolds (H(1)E) showed slower biodegradation and sustained release of rhGM-CSF in vitro, although no significantly different release pattern was observed between the H(1)E and unheparinized scaffolds (H(0)E). In vivo investigation revealed that the heparinized scaffolds loaded with rhGM-CSF (H(1)E/rhGM-CSF) had the best cellular adhesion and migration, new vessel formation, and highest expression of VEGF and TGF-β1, indicating promoted angiogenesis. This study demonstrated that composite dermal substitute of combining rhGM-CSF with a porous heparinized collagen/chitosan scaffolds could be a potential therapeutic agent for full-thickness skin defects because of its sustained delivery of rhGM-CSF.

Regulation of epidermal keratinocytes by growth factors

Epidermal keratinocytes are the main component cells of the epidermis and their function is regulated by various kinds of growth factors, cytokines, and chemokines. Of these, members of the epidermal growth factor and fibroblast growth factor families, as wells as hepatocyte growth factor and insulin-like growth factor, play central roles in keratinocyte proliferation, while transforming growth factor-beta, vitamin D3, and interferon-gamma are important inhibitors of keratinocyte growth. Keratinocytes are known to produce many of the currently identified growth factors, cytokines and chemokines. Keratinocyte-derived growth factors and cytokines regulate immune and inflammatory responses, and play important roles in pathological skin conditions. This review focuses on the regulation of keratinocytes by growth factors, cytokines, and chemokines.

The functional behavior of a macrophage/fibroblast co-culture model derived from normal and diabetic mice with a marine gelatin-oxidized alginate hydrogel

Tissues/cells-mediated biodegradable material degradation is epitomized by the constantly changing tissues/cell-implant interface, implicating the constant adaptation of the tissues/cells. Macrophages and fibroblasts are multi-functional cells highly involved in the interactions; the two cell types modulates the behaviors of each other, but their combinatorial functional behavior in the presence of interactive bioactive wound dressings has not been adequately examined. The activity is further complicated by the implantation of biodegradable materials, such as hydrogels commonly utilized as wound dressings, in a pathological environment and this is exemplified by the macrophages with a diabetic pathology producing an alternative cytokine profile which is implicated in wound healing delay. In this study, an in situ gelable formable/conformable hydrogel formulated from modified alginate and marine gelatin was used as a model biodegradable interactive wound dressing to elucidate the combinatorial behavior of macrophages/fibroblasts derived from both normal and diabetic hosts. Cell proliferation, migration and distribution were first characterized; this was followed by simultaneous quantitative detection of 40 inflammatory cytokines and chemokines by a protein microarray. The results showed that the macrophages/fibroblasts co-culture promoted fibroblasts proliferation and migration in the presence of the hydrogel; moreover, the expressions of inflammatory cytokines and chemokines were altered when compared with the corresponding fibroblasts or macrophages monocultures. The inflammatory cytokines patterns between the normal and diabetic hosts were considerably different.

MAPKAPK-2 signaling is critical for cutaneous wound healing

Cutaneous wound healing is a complex process, which is heavily dependent on successful inflammatory action. Mitogen-activated protein kinase (MAPK)-activated protein kinase-2 (MAPKAPK-2 or MK2), a major substrate of p38 MAPK, has been shown to be a major player in multiple inflammatory diseases, but its role in cutaneous wound healing has not yet been explored. In this study, by comparing excisional wounds made on the backs of MK2 knockout (KO) and MK2 wild-type (WT) mice, we found that the kinetics of wound healing are significantly affected by the absence of MK2 (P=0.010 to P<0.001). Histological examination showed a higher level of acanthosis of the migrating wound keratinocyte layer as well as a higher level of collagen deposition in the granulation tissue of the wounds from MK2 WT mice compared with those from MK2 KO mice. Interestingly, although MK2 did not influence macrophage and neutrophil infiltration of the wounds, the expression of many cytokines and chemokines was significantly affected at different days post wounding. Furthermore, the delayed healing rate of wounds in MK2 KO mice can be significantly improved by passive transfer of macrophages with intact MK2. Overall, these results show a critical role for MK2 gene expression in macrophages participating in the process of cutaneous wound healing.