Experimental ischemic wounds: correlation of cell proliferation and insulin-like growth factor I expression and its modification by different local IGF-I release systems

IL-1β/NF-κB signaling inhibits IGF-1 production via let-7f-5p in dendritic epidermal T cells

Dendritic epidermal T cells (DETCs) are the main source of insulin-like growth factor-1 (IGF-1) in epidermal tissue, which promote re-epithelialization and wound healing. In refractory wounds, IL-1β has been shown to activate NF-κB and suppress IGF-1 expression in DETCs. Nevertheless, the underlying mechanisms remain unclear. In this study, chromatin immunoprecipitation analysis revealed that IL-1β did not inhibit NF-κB binding to IGF-1 promoter, indicating that IL-1β/NF-κB may suppress IGF-1 expression by alternative mechanisms. MiRNAs negatively regulate gene expression predominantly by base pairing to the 3' untranslation region (UTR) of target mRNAs. Let-7f-5p, miR-1a-3p, and miR-98-5p have been identified as IGF-1-specific miRNAs that can bind directly to the 3'UTR of IGF-1 mRNA and dysregulate IGF-1 mRNA and protein levels. In IL-1β-treated epidermis around wounds or DETCs in vitro, NF-κB promoted the expression of let-7f-5p, and IGF-1 expression was impeded via NF-κB/let-7f-5p pathway. As pre-let-7f-5p, let-7f-1 is located in the 3'UTR of LOC118568094, and let-7f-2 is located in the intron of HUWE1. We discovered that NF-κB p65 bound to the promoters of LOC118568094 and HUWE1 to accelerate let-7f-5p expression, but NF-κB p65 did not affect the methylation levels of LOC118568094 and HUWE1 CpG islands. Injections of Let-7f-5p antagomir into IL-1β-treated and ischemic wound margins restored IGF-1 secretion in DETCs and promoted wound healing. In conclusion, we demonstrated that NF-κB signaling pathway activated by IL-1β could increase let-7f-5p expression to inhibit IGF-1 production in DETCs and delay wound healing. And let-7f-5p antagomir utilized in wound margin could effectively promote refractory wound healing.

Biomimetic Hydrogels to Promote Wound Healing

Wound healing is a common physiological process which consists of a sequence of molecular and cellular events that occur following the onset of a tissue lesion in order to reconstitute barrier between body and external environment. The inherent properties of hydrogels allow the damaged tissue to heal by supporting a hydrated environment which has long been explored in wound management to aid in autolytic debridement. However, chronic non-healing wounds require added therapeutic features that can be achieved by incorporation of biomolecules and supporting cells to promote faster and better healing outcomes. In recent decades, numerous hydrogels have been developed and modified to match the time scale for distinct stages of wound healing. This review will discuss the effects of various types of hydrogels on wound pathophysiology, as well as the ideal characteristics of hydrogels for wound healing, crosslinking mechanism, fabrication techniques and design considerations of hydrogel engineering. Finally, several challenges related to adopting hydrogels to promote wound healing and future perspectives are discussed.

Topical administration of hydroethanolic extract of Lawsonia inermis (henna) accelerates excisional wound healing process by reducing tissue inflammation and amplifying glucose uptake

Several studies have reported the beneficial effects of Lawsonia inermis on wound healing, but the mechanism of action is still unknown. This study aimed to investigate the effectiveness of a new ointment formulation of hydroethanolic extract leaves of L. inermis on wound healing by gene expression of glucose transporter-1 (Glut-1) and insulin-like growth factor I (Igf-1) in Wistar rats. The animals were topically treated with different doses of L. inermis. An experimentally induced circular excisional wound model of 314 mm² surface area was surgically created. The percentage of wound contraction and histopathological changes was assessed at different time points following wound induction. The expression of Glut-1 and Igf-1 was evaluated by reverse-transcription PCR. Topical administration of L. inermis, dose dependently, shortened inflammatory phase, accelerated cellular proliferation, and enhanced wound contraction ratio. It also improved revascularization, collagen deposition, and re-epithelialization rate and promoted intracytoplasmic carbohydrate storage (P < 0.05). Moreover, the mRNA levels of Igf-1 and Glut-1 were significantly higher in the L. inermis-treated groups than the control group (P < 0.05). Topical administration of L. inermis promoted the healing process by reducing tissue inflammation and increasing glucose uptake, which was mediated by up-regulating the expression of Igf-1 and Glut-1.

Hydrogel-Based Strategies to Advance Therapies for Chronic Skin Wounds

Chronic skin wounds are the leading cause of nontraumatic foot amputations worldwide and present a significant risk of morbidity and mortality due to the lack of efficient therapies. The intrinsic characteristics of hydrogels allow them to benefit cutaneous healing essentially by supporting a moist environment. This property has long been explored in wound management to aid in autolytic debridement. However, chronic wounds require additional therapeutic features that can be provided by a combination of hydrogels with biochemical mediators or cells, promoting faster and better healing. We survey hydrogel-based approaches with potential to improve the healing of chronic wounds by reviewing their effects as observed in preclinical models. Topics covered include strategies to ablate infection and resolve inflammation, the delivery of bioactive agents to accelerate healing, and tissue engineering approaches for skin regeneration. The article concludes by considering the relevance of treating chronic skin wounds using hydrogel-based strategies.

Endothelial Cell Metabolism

Endothelial cells (ECs) are more than inert blood vessel lining material. Instead, they are active players in the formation of new blood vessels (angiogenesis) both in health and (life-threatening) diseases. Recently, a new concept arose by which EC metabolism drives angiogenesis in parallel to well-established angiogenic growth factors (e.g., vascular endothelial growth factor). 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3-driven glycolysis generates energy to sustain competitive behavior of the ECs at the tip of a growing vessel sprout, whereas carnitine palmitoyltransferase 1a-controlled fatty acid oxidation regulates nucleotide synthesis and proliferation of ECs in the stalk of the sprout. To maintain vascular homeostasis, ECs rely on an intricate metabolic wiring characterized by intracellular compartmentalization, use metabolites for epigenetic regulation of EC subtype differentiation, crosstalk through metabolite release with other cell types, and exhibit EC subtype-specific metabolic traits. Importantly, maladaptation of EC metabolism contributes to vascular disorders, through EC dysfunction or excess angiogenesis, and presents new opportunities for anti-angiogenic strategies. Here we provide a comprehensive overview of established as well as newly uncovered aspects of EC metabolism.

Growth hormone abolishes the negative effects of everolimus on intestinal wound healing

AIM: To investigate whether the simultaneous treatment with human growth hormone (hGH) abolishes the negative effects of everolimus on anastomotic healing.

METHODS: Forty-eight male Sprague-Dawley-rats were randomized to three groups of 16 animals each (I: vehicle; II: everolimus 3 mg/kg po; III: everolimus 3 mg/kg po + hGH 2.5 mg/kg sc). Animals were pre-treated with hGH and/or everolimus daily for seven days. Then a standard anastomosis was created in the descending colon and treatment was continued for another seven days. The anastomosis was resected in toto and the bursting pressure was assessed as a mechanical parameter of intestinal healing. Moreover, biochemical (Hydroxyproline, PCNA, MPO, MMP-2 and MMP-9) and histological (cell density, angiogenesis, amount of granulation tissue) parameters of intestinal healing were assessed.

RESULTS: Anastomotic bursting pressure was significantly reduced by everolimus and a simultaneous treatment with hGH resulted in considerably higher values (I: 134 ± 19 mmHg, II: 85 ± 25 mmHg, III: 114 ± 25 mmHg; P < 0.05, I vs II; P = 0.09, I vs III and II vs III) Hydroxyproline concentration was significantly increased by hGH compared to everolimus alone (I: 14.9 ± 2.5 μg/mg, II: 8.9 ± 3.6 μg/mg, III: 11.9 ± 2.8 μg/mg; P < 0.05, I vs II/III and II vs III). The number of MPO-positive cells was reduced significantly by hGH compared to everolimus alone (I: 10 ± 1 n/mm², II: 15 ± 3 n/mm², III: 9 ± 2 n/mm²; P < 0.05, I vs II and II vs III), while the number of PCNA-positive cells were increased by hGH (I: 28 ± 3 /mm², II: 12 ± 3 /mm², III: 26 ± 12 /mm²; P < 0.05, I vs II and II vs III). Corresponding to these biochemical findings, HE-histology revealed significantly increased amount of granulation tissue in hGH-treated animals.

CONCLUSION: Inhibition of intestinal wound healing by everolimus is partially neutralized by simultaeous treatment with hGH. Both inflammation as well as collagen deposition is influenced by hGH.

Intermediates of Metabolism: From Bystanders to Signalling Molecules

The integration of biochemistry into immune cell biology has contributed immensely to our understanding of immune cell function and the associated pathologies. So far, most studies have focused on the regulation of metabolic pathways during an immune response and their contribution to its success. More recently, novel signalling functions of metabolic intermediates are being discovered that might play important roles in the regulation of immunity. Here we describe the three long-known small metabolites lactate, acetyl-CoA, and succinate in the context of immunometabolic signalling. Functions of these ubiquitous molecules are largely dependent on their intra- and extracellular concentrations as well as their subcompartmental localisation. Importantly, the signalling functions of these metabolic intermediates extend beyond self-regulatory roles and include cell-to-cell communication and sensing of microenvironmental conditions to elicit stress responses and cellular adaptation.

Aspp2 negatively regulates body growth but not developmental timing by modulating IRS signaling in zebrafish embryos

The growth and developmental rate of developing embryos and fetus are tightly controlled and coordinated to maintain proper body shape and size. The insulin receptor substrate (IRS) proteins, key intracellular transducers of insulin and insulin-like growth factor signaling, play essential roles in the regulation of growth and development. A short isoform of apoptosis-stimulating protein of p53 2 (ASPP2) was recently identified as a binding partner of IRS-1 and IRS-2 in mammalian cells in vitro. However, it is unclear whether ASPP2 plays any role in vertebrate embryonic growth and development. Here, we show that zebrafish Aspp2a and Aspp2b negatively regulate embryonic growth without affecting developmental rate. Human ASPP2 had similar effects on body growth in zebrafish embryos. Aspp2a and 2b inhibit Akt signaling. This inhibition was reversed by coinjection of myr-Akt1, a constitutively active form of Akt1. Zebrafish Aspp2a and Aspp2b physically bound with Irs-1, and the growth inhibitory effects of ASPP2/Aspp2 depend on the presence of their ankyrin repeats and SH3 domains. These findings uncover a novel role of Aspp2 in regulating vertebrate embryonic growth.

Insulin-like growth factor-1 promotes wound healing in estrogen-deprived mice: new insights into cutaneous IGF-1R/ERα cross talk

Although it is understood that endogenous IGF-1 is involved in the wound repair process, the effects of exogenous IGF-1 administration on wound repair remain largely unclear. In addition, the signaling links between IGF-1 receptor (IGF-1R) and estrogen receptors (ERs), which have been elucidated in other systems, have yet to be explored in the context of skin repair. In this study, we show that locally administered IGF-1 promotes wound repair in an estrogen-deprived animal model, the ovariectomized (Ovx) mouse, principally by dampening the local inflammatory response and promoting re-epithelialization. Using specific IGF-1R and ER antagonists in vivo, we reveal that IGF-1-mediated effects on re-epithelialization are directly mediated by IGF-1R. By contrast, the anti-inflammatory effects of IGF-1 are predominantly via the ERs, in particular ERα. Crucially, in ERα-null mice, IGF-1 fails to promote healing, and local inflammation is increased. Our findings illustrate the complex interactions between IGF-1 and estrogen in skin. The fact that IGF-1 may compensate for estrogen deficiency in wound repair, and potentially other contexts, is an important consideration for the treatment of postmenopausal pathology.

Engineered insulin-like growth factor-1 for improved smooth muscle regeneration

Insulin-like growth factor-1 (IGF-1) has been shown to induce potent mitogenic responses in various cell types, yet its sustained local delivery is still an underdeveloped domain in the clinic. We report here an engineered IGF-1 that facilitates extended local delivery to a site through its immobilization capacity within fibrin. Through recombinant fusion with a substrate sequence tag derived from α(2)-plasmin inhibitor (α(2)PI(1-8)), the resulting variant, α(2)PI(1-8)-IGF-1, was covalently incorporated into fibrin matrices during normal thrombin/factor XIIIa-mediated polymerization. Bioactivity of the variant was confirmed to be equivalent to wild type (WT) IGF-1 via IGF-1 receptor phosphorylation and cell proliferation studies in urinary tract-derived cells in 2-D. Assessment of functional retention within 3-D fibrin matrices demonstrated that incorporation of α(2)PI(1-8)-IGF-1 induced a 1.3- and 1.5-fold more robust proliferative response in smooth muscle cells (SMCs) than WT IGF-1 and negative control matrices, respectively, when release was not contained. Sustained α(2)PI(1-8)-IGF-1 availability at bladder lesion sites in vivo evoked a considerable increase in SMC proliferation and a favorable host tissue response after 28 days in rats. We conclude that the sustained local IGF-1 availability from fibrin provided by our variant protein enhances smooth muscle regeneration better than the WT form of the protein.

Effects of isoniazid and niacin on experimental wound-healing

BACKGROUND

There is a need for effective treatments of ischemic wounds. Our aim was to test the hypothesis that systemic administration of isoniazid or niacin can enhance wound healing in ischemic as well as nonischemic tissues.

METHODS

One 8-mm, full-thickness wound was made in a standardized, ischemic skin flap and 1 in adjacent nonischemic skin on the back of male Sprague-Dawley rats. Starting just after wounding, twice-daily intraperitoneal isoniazid (10 mg/kg b.i.d.), xanthinol nicotinate (30 mg/kg), or saline (control) were given for 14 days. Wound-healing was monitored by planimetry and oxygen tension in periphery of the wound using a microcatheter probe. Cellular proliferation in granulation tissue was assessed by immunohistochemical detection of proliferating cell nuclear antigen. The angiogenic activity of isoniazid and niacin was assessed using in vitro and ex vivo models.

RESULTS

Although wound ischemia was evident by decreased oxygen tension (26 +/- 10 mmHg; n = 9) compared with the adjacent nonischemic wounds (51 +/- 8 mmHg; n = 8), neither compound significantly influenced intracutaneous oxygen tension. Isoniazid (P < .0001), but not niacin, promoted ischemic wound-healing even though both compounds increased proliferation measured on day 14 (P < .01). In normal wounds, the cumulative change in relative wound area over 14 days was increased by niacin (P = .002), but not by isoniazid, although both niacin (P = .011) and isoniazid (P = .036) increased cellular proliferation. Neither isoniazid nor niacin showed activity in either an endothelial tube formation assay or organotypic angiogenic assay under normoxic conditions.

CONCLUSION

Isoniazid was capable of stimulating wound-healing in ischemic tissue to the level of nonischemic wounds and might offer a novel treatment option for wounds associated with arterial insufficiency. Although active in normal wounds, niacin did not promote ischemic wound-healing.

Everolimus interferes with the inflammatory phase of healing in experimental colonic anastomoses

BACKGROUND

Delayed wound healing is a serious side effect of mTOR inhibitor-based immunosuppression after solid organ transplantation. The aim of this study was to test the hypothesis that the mTOR inhibitor everolimus interferes with the inflammatory phase of healing in experimental colonic anastomoses.

MATERIALS AND METHODS

Thirty male Sprague-Dawley rats received a colonic anastomosis. Then, animals were randomized to three groups of daily treatment with either vehicle or everolimus in two different dosages (1.0mg/kg or 3.0mg/kg). After 7 d, rats were sacrificed, and mechanical, histologic, and biochemical parameters of intestinal healing were assessed.

RESULTS

Anastomotic bursting pressure was significantly decreased by everolimus in both dosages, whereas hydroxyproline content was reduced only by the high everolimus dosage. Everolimus diminished cellular proliferation and new vessel growth. Furthermore, both quantity as well as quality of newly synthesized collagen fibers in the anastomotic granulation tissue was reduced. On the other hand, myeloperoxidase-positive (MPO) cells and interleukin-6 (IL-6) concentrations were increased, as was the activity of matrix-metalloproteinases MMP-2 and MMP-9.

CONCLUSION

Everolimus interferes with the inflammatory phase of healing. However, it remains unclear whether this phenomenon is involved in everolimus impairment of experimental anastomotic repair.

A female survivor of childhood medulloblastoma presenting with growth-hormone-induced edema and inflammatory lesions: a case report

INTRODUCTION

The improved survival of children with brain tumors has increased concerns about treatment-related sequelae. Growth hormone deficiency is frequently observed after craniospinal irradiation for medulloblastoma. It has been widely reported that growth hormone replacement therapy does not increase the risk of second tumors, but there are reports in the literature of growth hormone, and its downstream mediator insulin-like Growth Factor 1, having an important proinflammatory action. There are few reports, however, on the "in-vivo" induction of edema and symptomatic inflammatory lesions during replacement therapy.

CASE PRESENTATION

We report the case of a 7-year-old girl treated for metastatic medulloblastoma who developed growth hormone deficiency 2 years after oncological treatment.Three months after replacement therapy, magnetic resonance imaging showed exacerbation of her brain edema, which was already present after oncological treatment. We consequently suspended the growth hormone until a new magnetic resonance image obtained 3 months later documented a reduction of the inflammatory areas. We then re-introduced somatotropin at lower doses with no further increase in brain edema in subsequent radiological controls.

CONCLUSION

This case and its iconography suggest a strong association between growth hormone administration and the exacerbation of inflammatory reactions within the tumor bed. Replacement therapy should be carefully monitored in this particular subset of patients.

Effects of decreased insulin-like growth factor-1 stimulation on hypoxia inducible factor 1-alpha protein synthesis and function during cutaneous repair in diabetic mice

Insulin-like growth factor-1 (Igf-1), a critical mediator of tissue repair, is significantly decreased in diabetic wounds. Furthermore, decreased levels of hypoxia-inducible factor 1-alpha (Hif-1alpha) and its target genes are also associated with impaired wound healing in diabetic mice. The aim of our study was to examine whether the reduced levels of Igf-1 are responsible for the reduction in Hif-1alpha protein synthesis and activity in diabetic wounds. We provide evidence that Igf-1 regulates Hif-1alpha protein synthesis and activity during wound repair. In addition, Igf-1 stimulated phosphytidylinositol 3-kinase activity in diabetic fibroblasts, which, in turn, increased activation of the translational regulatory protein, p70 S6 kinase. Moreover, improved healing of diabetic wounds by addition of recombinant IGF-1 protein was associated with an increase in Hif-1alpha protein synthesis and function in vivo.

Stromal progenitor cell therapy corrects the wound-healing defect in the ischemic rabbit ear model of chronic wound repair

Chronic wounds create a formidable clinical problem resulting in considerable morbidity and healthcare expenditure. The etiology for wound healing impairment appears to be multifactorial; however, ischemia is a common factor in most types of chronic wounds. Ideal therapy for such wounds would be to correct deficiencies in growth factors and matrix components and provide cellular precursors required for timely wound closure. We hypothesized that stromal progenitor cell (SPC) therapy could correct the ischemic wound-healing defect through both direct and indirect mechanisms. To test this hypothesis, we used the ischemic rabbit ear model of chronic wound healing. We found that treatment of the wounds with SPCs was able to reverse the ischemic wound-healing impairment, with improved granulation tissue formation and reepithelialization compared with vehicle or bone marrow mononuclear cell controls. In vitro, SPCs were found to produce factors involved in angiogenesis and reepithelialization, and extracellular matrix components, providing evidence for both direct and indirect mechanisms for the observed correction of the healing impairment in these wounds. Treatment of ischemic wounds with SPCs can dramatically improve wound healing and provides a rationale for further studies focused on SPCs as a potential cellular therapy in impaired wound healing.

Wounds: an overview of the role of oxygen

We sought to review the role of oxygen in wound healing, with an emphasis on the role tissue oximetry has played in clinical advances in the care of patients with wounds. Oxygen is required for wound healing. Hypoxia sufficient to impair healing is common in wounds, frequently resulting from sympathetically induced vasoconstriction. Correction or prevention of vasoconstriction, as well as provision of increased inspired oxygen in well-perfused patients, has been shown in randomized, controlled clinical trials to improve wound outcomes. Our understanding of the role of oxygen in wound healing has been fueled by tissue oximetry. Advances in technology will lead to further advances in the management of patients with wounds.

Stimulation of steroid-suppressed cutaneous healing by repeated topical application of IGF-I: different mechanisms of action based upon the mode of IGF-I delivery

BACKGROUND

Insulin-like growth factor-I (IGF-I) is accepted as a potent stimulus of wound healing when applied in combination with its binding proteins. However, there is only one study published that has investigated the effect of repeated topical application of unbound IGF-I on ischemic wound healing. The aim of this study was to show the effect of daily topical IGF-I therapy on cutaneous ulcer healing in a steroid-suppressed wound model.

MATERIALS AND METHODS

Full-thickness wounds were created on the back of 40 male Sprague-Dawley rats. Before surgery, animals received depot-steroids subcutaneously. Wounds were treated daily with either a standard hydrogel dressing (control), topical IGF-I dissolved in 0.2% methylcellulose gel (IGF-I gel), or a hydrogel dressing containing IGF-I (IGF-I dressing). After 7 days of treatment, wounds were excised and measured by photoplanimetry. SMA- and PCNA-expression as well as the formation of granulation tissue were assessed in tissue sections. Results are given as median(min-max). Differences between groups were calculated by the Mann-Whitney U test.

RESULTS

Subcutaneous injection of depot-steroids induced a significant delay in healing, as shown by an enlarged wound size [44(33-65) versus 25(20-35)] mm(2); P = 0.001). In steroid-treated rats, both IGF-I gel and IGF-I dressing enhanced excisional healing, as shown by a significant reduction in wound size (P = 0.0001), with IGF-I released from the dressing being even more effective than IGF-I gel (P = 0.03). However, in these animals only IGF-I released from the hydrogel dressing stimulated SMA- (P = 0.03) as well as PCNA-expression (P = 0.001) and increased granulation tissue formation (P = 0.018).

CONCLUSIONS

Our data indicate that a repeated application of topical IGF-I enhances cutaneous ulcer healing. In addition, only the controlled release of IGF-I from the hydrogel dressing is capable of reversing the steroid-induced delay of healing, suggesting different mechanisms of action with respect to the mode of IGF-I delivery.

Using Physiology to Improve Surgical Wound Outcomes

Despite major advances in surgical management and approaches, including aseptic techniques, prophylactic antibiotics, and laparoscopic surgery, surgical wound infection and wound failure remain common complications of surgery. In a review of the literature, the authors found that a growing body of literature supports the concept that patient factors are a major determinant of wound outcome after surgery. In particular, wounds are exquisitely sensitive to hypoxia, which is both common and preventable. Perioperative management can be adapted to promote postoperative wound healing and resistance to infection. The most important factors are fluid management, temperature management, pain control, increased arterial oxygen tension, and, as has been long recognized, appropriate sterile techniques and administration of prophylactic antibiotics. This article reviews how knowledge of and attention to physiology can improve quality of care in both acute and chronic wounds.