Wound closure and metabolic parameter variability in a db/db mouse model for diabetic ulcers

Characterization of heterogeneous skin constructs for full thickness skin regeneration in murine wound models

An autologous heterogeneous skin construct (AHSC) has been developed and used clinically as an alternative to traditional skin grafting techniques for treatment of cutaneous defects. AHSC is manufactured from a small piece of healthy skin in a manner that preserves endogenous regenerative cellular populations. To date however, specific cellular and non-cellular contributions of AHSC to the epidermal and dermal layers of closed wounds have not been well characterized given limited clinical opportunity for graft biopsy following wound closure. To address this limitation, a three-part mouse full-thickness excisional wound model was developed for histologic and macroscopic graft tracing. First, fluorescent mouse-derived AHSC (mHSC) was allografted onto non-fluorescent recipient mice to enable macroscopic and histologic time course evaluation of wound closure. Next, mHSC-derived from haired pigmented mice was allografted onto gender- and major histocompatibility complex (MHC)-mismatched athymic nude mouse recipients. Resulting grafts were distinguished from recipient murine skin via immunohistochemistry. Finally, human-derived AHSC (hHSC) was xenografted onto athymic nude mice to evaluate engraftment and hHSC contribution to wound closure. Experiments demonstrated that mHSC and hHSC facilitated wound closure through production of viable, proliferative cellular material and promoted full-thickness skin regeneration, including hair follicles and glands in dermal compartments. This combined macroscopic and histologic approach to tracing AHSC-treated wounds from engraftment to closure enabled robust profiling of regenerated architecture and further understanding of processes underlying AHSC mechanism of action. These models may be applied to a variety of wound care investigations, including those requiring longitudinal assessments of healing and targeted identification of donor and recipient tissue contributions.

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.

Amnion membranes support wound granulation in a delayed murine excisional wound model

Chronic or delayed healing wounds constitute an ever-increasing burden on healthcare providers and patients alike. Thus, therapeutic modalities that are tailored to particular deficiencies in the delayed wound healing response are of critical importance to improve clinical outcomes. Human amnion-derived viable and devitalized allografts have demonstrated clinical efficacy in promoting the closure of delayed healing wounds, but the mechanisms responsible for this efficacy and the specific wound healing processes modulated by these tissues are not fully understood. Here, we utilized a diabetic murine excisional wound model in which healing is driven by granulation and re-epithelialization, and we applied viable (vHAMA) or devitalized (dHAMA) amnion-derived allografts to the wound bed in order to determine their effects on wound healing processes. Compared to control wounds that were allowed to heal in the absence of treatment, wounds to which vHAMA or dHAMA were applied demonstrated enhanced deposition of granulation tissue accompanied by increased cellular proliferation and increased de novo angiogenesis, while vHAMA-treated wounds also demonstrated accelerated re-epithelialization. Taken together, these data suggest that both vHAMA and dHAMA facilitate wound healing through promoting processes critical to granulation tissue formation. Further understanding of the cellular and tissue mechanisms underlying the effects of tissue-derived matrices on wound healing will enable tailored prescription of their use in order to maximize clinical benefit.

Topical Administration of a Marine Oil Rich in Pro-Resolving Lipid Mediators Accelerates Wound Healing in Diabetic db/db Mice through Angiogenesis and Macrophage Polarization

Impaired wound healing in patients with type 2 diabetes (DM2) is characterized by chronic inflammation, which delays wound closure. Specialized pro-resolving lipid mediators (SPMs) are bioactive molecules produced from essential polyunsaturated fatty acids (PUFAs), principally omega-3 docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). SPMs are potent regulators of inflammation and have been used to suppress chronic inflammation in peripheral artery disease, non-alcoholic fatty liver disease, and central nervous system syndromes. LIPINOVA^® is a commercially available safe-grade nutritional supplement made from a fractionated marine lipid concentrate derived from anchovy and sardine oil that is rich in SPMs and EPA, as well as DHA precursors. Here, we assessed the effect of LIPINOVA^® in wound dressing applications. LIPINOVA^® showed biocompatibility with keratinocytes and fibroblasts, reduced the abundance of pro-inflammatory macrophages (Mφ1), and promoted in vitro wound closure. Daily application of the marine oil to open wounds made by punch biopsy in db/db mice promoted wound closure by accelerating the resolution of inflammation, inducing neoangiogenesis and Mφ1/Mφ2 macrophage polarization. In conclusion, LIPINOVA^® displays pro-resolutive properties and could be exploited as a therapeutic agent for the treatment of diabetic ulcers.

Wound Healing Impairment in Type 2 Diabetes Model of Leptin-Deficient Mice—A Mechanistic Systematic Review

Type II diabetes mellitus (T2DM) is one of the most prevalent diseases in the world, associated with diabetic foot ulcers and impaired wound healing. There is an ongoing need for interventions effective in treating these two problems. Pre-clinical studies in this field rely on adequate animal models. However, producing such a model is near-impossible given the complex and multifactorial pathogenesis of T2DM. A leptin-deficient murine model was developed in 1959 and relies on either dysfunctional leptin (ob/ob) or a leptin receptor (db/db). Though monogenic, this model has been used in hundreds of studies, including diabetic wound healing research. In this study, we systematically summarize data from over one hundred studies, which described the mechanisms underlying wound healing impairment in this model. We briefly review the wound healing dynamics, growth factors’ dysregulation, angiogenesis, inflammation, the function of leptin and insulin, the role of advanced glycation end-products, extracellular matrix abnormalities, stem cells’ dysregulation, and the role of non-coding RNAs. Some studies investigated novel chronic diabetes wound models, based on a leptin-deficient murine model, which was also described. We also discussed the interventions studied in vivo, which passed into human clinical trials. It is our hope that this review will help plan future research.

The Antimicrobial Effects of Bacterial Cellulose Produced by Komagataeibacter intermedius in Promoting Wound Healing in Diabetic Mice

As a conventional medical dressing, medical gauze does not adequately protect complex and hard-to-heal diabetic wounds and is likely to permit bacterial entry and infections. Therefore, it is necessary to develop novel dressings to promote wound healing in diabetic patients. Komagataeibacter intermedius was used to produce unmodified bacterial cellulose, which is rarely applied directly to diabetic wounds. The produced cellulose was evaluated for wound recovery rate, level of inflammation, epidermal histopathology, and antimicrobial activities in treated wounds. Diabetic mices' wounds treated with bacterial cellulose healed 1.63 times faster than those treated with gauze; the values for the skin indicators in bacterial cellulose treated wounds were more significant than those treated with gauze. Bacterial cellulose was more effective than gauze in promoting tissue proliferation with more complete epidermal layers and the formation of compact collagen in the histological examination. Moreover, wounds treated with bacterial cellulose alone had less water and glucose content than those treated with gauze; this led to an increase of 6.82 times in antimicrobial protection, lower levels of TNF-α and IL-6 (39.6% and 83.2%), and higher levels of IL-10 (2.07 times) than in mice wounds treated with gauze. The results show that bacterial cellulose produced using K. intermedius beneficially affects diabetic wound healing and creates a hygienic microenvironment by preventing inflammation. We suggest that bacterial cellulose can replace medical gauze as a wound dressing for diabetic patients.

Systematic review and meta-analysis of mouse models of diabetes-associated ulcers

Mouse models are frequently used to study diabetes-associated ulcers, however, whether these models accurately simulate impaired wound healing has not been thoroughly investigated. This systematic review aimed to determine whether wound healing is impaired in mouse models of diabetes and assess the quality of the past research. A systematic literature search was performed of publicly available databases to identify original articles examining wound healing in mouse models of diabetes. A meta-analysis was performed to examine the effect of diabetes on wound healing rate using random effect models. A meta-regression was performed to examine the effect of diabetes duration on wound healing impairment. The quality of the included studies was also assessed using two newly developed tools. 77 studies using eight different models of diabetes within 678 non-diabetic and 720 diabetic mice were included. Meta-analysis showed that wound healing was impaired in all eight models. Meta-regression suggested that longer duration of diabetes prior to wound induction was correlated with greater degree of wound healing impairment. Pairwise comparisons suggested that non-obese diabetic mice exhibited more severe wound healing impairment compared with db/db mice, streptozotocin-induced diabetic mice or high-fat fed mice at an intermediate stage of wound healing (p<0.01). Quality assessment suggested that the prior research frequently lacked incorporation of key clinically relevant characteristics. This systematic review suggested that impaired wound healing can be simulated in many different mouse models of diabetes but these require further refinement to become more clinically relevant.

Topical small molecule granzyme B inhibitor improves remodeling in a murine model of impaired burn wound healing

Granzyme B (GzmB) is a serine protease that has long been thought to function exclusively in lymphocyte-mediated apoptosis. In recent years, this paradigm has been revisited due to the recognition that GzmB accumulates in the extracellular milieu in many autoimmune and chronic inflammatory disorders, and contributes to impaired tissue remodeling due to the cleavage of extracellular matrix proteins. Knockout studies suggest that GzmB-mediated cleavage of decorin (DCN) contributes to impaired collagen fibrillogenesis and remodeling. As DCN is anti-fibrotic and contributes to reduced hypertrophic scarring, GzmB-induced DCN cleavage could play a role in wound healing following burn injury. In the present study, a novel, gel-formulated, first-in-class small-molecule inhibitor of GzmB, VTI-1002, was assessed in a murine model of impaired, diabetic burn wound healing. VTI-1002 exhibited high specificity, potency, and target selectivity. Gel-formulated VTI-1002 was able to penetrate the stratum corneum and was retained in the skin with minimal systemic absorption. Daily topical administration of VTI-1002 gel for 30 days following thermal injury showed significantly accelerated wound closure, increased DCN protein levels, and collagen organization that was translated into significantly increased wound tensile strength compared to controls. Overall, VTI-1002 gel was well-tolerated in vivo and no adverse events were observed. Topical application of VTI-1002 represents a novel therapeutic approach for the treatment of cutaneous burn wounds.

Biopolymer Molecular Weight Can Modulate the Wound Healing Efficacy of Multivalent Sonic Hedgehog-Hyaluronic Acid Conjugates

There is a clinical need for new therapeutics to improve healing of chronic impaired wounds. Thus, we investigated how biopolymer conjugation could be used to improve the wound healing performance of a key growth factor for tissue regeneration: Sonic hedgehog (Shh). We generated two multivalent Shh conjugates (mvShh) using hyaluronic acid with two different MWs, which exhibited equivalent potency and proteolytic protection in vitro. Using db/db diabetic mice, we showed that mvShh made with smaller HyA MW resulted in more rapid and robust neovascularization compared to mvShh made with larger MW HyA. Further, smaller mvShh conjugates resulted in faster wound resolution compared to the unconjugated Shh. This study is the first to show how the wound healing efficacy of multivalent protein-polymer conjugates is sensitive to the polymer MW, and our findings suggest that this parameter could be used to enhance the efficacy of growth factor conjugates.

A Novel Skin Splint for Accurately Mapping Dermal Remodeling and Epithelialization During Wound Healing

The mouse excisional dorsal full-thickness wound model with a silicon splint fixed on the skin has been widely used to mimic human wound healing. However, the method cannot accurately quantify dermal remodeling, since the initial point of epithelialization on the wound surface is unclear. To overcome this limitation, we have developed a novel mouse excisional wound model to assess the degree of epithelial extension and regeneration, using a plastic ring-shaped splint fixed beneath the surrounding epidermal tissue. At the end of the experiment, tissue samples were fixed in formalin, the splint was excised, and paraffin sections were prepared. Splint holes, corresponding to the prior location of the splint, were evident on the tissue cross-sections, and the epidermis above the holes was considered the initial excision site. The epidermal contraction and epithelial regeneration, as independent essential tissue alterations in wound healing, could be distinguishable and quantified. Compared with previous splint models, this method provides an accurate evaluation of epidermal processes in wound healing, and can be a platform to assess the effects of various wound healing factors. J. Cell. Physiol. 232: 1225-1232, 2017. © 2016 Wiley Periodicals, Inc.

Multivalent Conjugates of Sonic Hedgehog Accelerate Diabetic Wound Healing

Despite their preclinical promise, few recombinant growth factors have been fully developed into effective therapies, in part, due to the short interval of therapeutic activity after administration. To address this problem, we developed nanoscale polymer conjugates for multivalent presentation of therapeutic proteins that enhance the activation of targeted cellular responses. As an example of this technology, we conjugated multiple Sonic hedgehog (Shh) proteins onto individual hyaluronic acid biopolymers to generate multivalent protein clusters at defined ratios (i.e., valencies) that yield enhanced Shh pathway activation at equivalent concentrations relative to unconjugated Shh. In this study, we investigated whether these multivalent conjugates (mvShh) could be used to improve the therapeutic function of Shh. We found that a single treatment with mvShh significantly accelerated the closure of full-thickness wounds in diabetic (db/db) mice compared to either an equivalent dose of unconjugated Shh or the vehicle control. Furthermore, we identified specific indicators of wound healing in fibroblasts and endothelial cells (i.e., transcriptional activation and cell migration) that were activated by mvShh in vitro and at concentrations approximately an order of magnitude lower than the unconjugated Shh. Taken together, our findings suggest that mvShh conjugates exhibit greater potency to activate the Shh pathway, and this multivalency advantage improves its therapeutic effect to accelerate wound closure in a diabetic animal model. Our strategy of multivalent protein presentation using nanoscale polymer conjugates has the potential to make a significant impact on the development of protein-based therapies by improving their in vivo performance.

LL37 loaded nanostructured lipid carriers (NLC): A new strategy for the topical treatment of chronic wounds

The LL37 is a human antimicrobial peptide which not only has a broad spectrum of antimicrobial activity, but it has also been proved to modulate wound healing by participating in angiogenesis, epithelial cell migration and proliferation, and immune response. In this work, LL37 has been encapsulated in nanostructured lipid carriers (NLCs), produced by the melt-emulsification method, in order to improve its effectiveness. The characterisation of the NLC-LL37 showed a mean size of 270nm, a zeta potential of -26mV and an encapsulation efficiency of 96.4%. The cytotoxicity assay performed in Human Foreskin Fibroblasts demonstrated that the NLC-LL37 did not affect cell viability. Moreover, the in vitro bioactivityassay evidenced that the peptide remained active after the encapsulation, since the NLC-LL37 reversed the activation of the macrophages induced by LPS in the same way as the LL37 in solution. In addition, the in vitro antimicrobial assay revealed the NLC-LL37 activity against Escherichia coli. The effectiveness of the nanoparticles was assessed in a full thickness wound model indb/dbmice. The data demonstrated that NLC-LL37 significantly improved healing compared to the same concentration of the LL37 solution in terms of wound closure, reepithelisation grade and restoration of the inflammatory process. Overall, these findings suggest a promising potential of the NLC-LL37 formulation for chronic wound healing.

Myocutaneous revascularization following graded ischemia in lean and obese mice

BACKGROUND

Murine models of diabetes and obesity have provided insight into the pathogenesis of impaired epithelialization of excisional skin wounds. However, knowledge of postischemic myocutaneous revascularization in these models is limited.

MATERIALS AND METHODS

A myocutaneous flap was created on the dorsum of wild type (C57BL/6), genetically obese and diabetic (ob/ob, db/db), complementary heterozygous (ob⁺/ob^-, db⁺/db^-), and diet-induced obese (DIO) mice (n=48 total; five operative mice per strain and three unoperated mice per strain as controls). Flap perfusion was documented by laser speckle contrast imaging. Local gene expression in control and postoperative flap tissue specimens was determined by quantitative reverse transcription polymerase chain reaction (RT-PCR). Image analysis of immunochemically stained histologic sections confirmed microvascular density and macrophage presence.

RESULTS

Day 10 planimetric analysis revealed mean flap surface area necrosis values of 10.8%, 12.9%, 9.9%, 0.4%, 1.4%, and 23.0% for wild type, db⁺/db^-, ob⁺/ob^-, db/db, ob/ob, and DIO flaps, respectively. Over 10 days, laser speckle imaging documented increased perfusion at all time points with revascularization to supranormal perfusion in db/db and ob/ob flaps. In contrast, wild type, heterozygous, and DIO flaps displayed expected graded ischemia with failure of perfusion to return to baseline values. RT-PCR demonstrated statistically significant differences in angiogenic gene expression between lean and obese mice at baseline (unoperated) and at day 10.

CONCLUSION

Unexpected increased baseline skin perfusion and augmented myocutaneous revascularization accompanied by a control proangiogenic transcriptional signature in genetically obese mice compared to DIO and lean mice are reported. In future research, laser speckle imaging has been planned to be utilized in order to correlate spatiotemporal wound reperfusion with changes in cell recruitment and gene expression to better understand the differences in wound microvascular biology in lean and obese states.

Application of Electron Paramagnetic Resonance (EPR) Oximetry to Monitor Oxygen in Wounds in Diabetic Models

A lack of oxygen is classically described as a major cause of impaired wound healing in diabetic patients. Even if the role of oxygen in the wound healing process is well recognized, measurement of oxygen levels in a wound remains challenging. The purpose of the present study was to assess the value of electron paramagnetic resonance (EPR) oximetry to monitor pO2 in wounds during the healing process in diabetic mouse models. Kinetics of wound closure were carried out in streptozotocin (STZ)-treated and db/db mice. The pO2 was followed repeatedly during the healing process by 1 GHz EPR spectroscopy with lithium phthalocyanine (LiPc) crystals used as oxygen sensor in two different wound models: a full-thickness excisional skin wound and a pedicled skin flap. Wound closure kinetics were dramatically slower in 12-week-old db/db compared to control (db/+) mice, whereas kinetics were not statistically different in STZ-treated compared to control mice. At the center of excisional wounds, measurements were highly influenced by atmospheric oxygen early in the healing process. In pedicled flaps, hypoxia was observed early after wounding. While reoxygenation occurred over time in db/+ mice, hypoxia was prolonged in the diabetic db/db model. This observation was consistent with impaired healing and microangiopathies observed using intravital microscopy. In conclusion, EPR oximetry using LiPc crystals as the oxygen sensor is an appropriate technique to follow wound oxygenation in acute and chronic wounds, in normal and diabetic animals. Nevertheless, the technique is limited for measurements in pedicled skin flaps and cannot be applied to excisional wounds in which diffusion of atmospheric oxygen significantly affects the measurements.

Decelerated vascularization in tissue-engineered constructs in association with diabetes mellitus in vivo

AIMS

Rapid blood vessel ingrowth in transplanted tissue engineering constructs is the key factor for successful incorporation, but many potential patients who may use engineered tissues suffer from widespread diseases that limit the capacity of neovascularization (e.g. diabetes). Thus, in vivo vascularization analyses of tissue-engineered constructs in angiogenically affected organisms are required.

METHODS

We therefore investigated the in vivo incorporation of collagen-coated and cell-seeded poly-L-lactide-co-glycolide scaffolds in diabetic B6.BKS(D)-Lepr(db)/J mice using repetitive intravital fluorescence microscopy over a time period of two weeks. For this purpose, scaffolds were seeded with osteoblast-like or bone marrow mesenchymal stem cells and implanted into the dorsal skinfold chambers of diabetic and non-diabetic (C57BL/6) mice.

RESULTS

Apart from slightly increased inflammatory parameters, diabetic mice showed significantly reduced capillary densities compared with non-diabetic animals from day 6 onward. In line with previous studies, more densely meshed microvascular networks were demonstrated in cell-seeded than in collagen-coated scaffolds from day 6 onward within the single groups (diabetic and control).

CONCLUSIONS

A large number of patients who suffer from systemic diseases that affect angiogenesis would profit from tissue engineering. Therefore, the challenge for the clinical introduction of tissue-engineered constructs will be to overcome the decreased angiogenesis in diabetic organisms.

Coacervate delivery of HB-EGF accelerates healing of type 2 diabetic wounds

Chronic wounds such as diabetic ulcers pose a significant challenge as a number of underlying deficiencies prevent natural healing. In pursuit of a regenerative wound therapy, we developed a heparin-based coacervate delivery system that provides controlled release of heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) within the wound bed. In this study, we used a polygenic type 2 diabetic mouse model to evaluate the capacity of HB-EGF coacervate to overcome the deficiencies of diabetic wound healing. In full-thickness excisional wounds on NONcNZO10 diabetic mice, HB-EGF coacervate enhanced the proliferation and migration of epidermal keratinocytes, leading to accelerated epithelialization. Furthermore, increased collagen deposition within the wound bed led to faster wound contraction and greater wound vascularization. Additionally, in vitro assays demonstrated that HB-EGF released from the coacervate successfully increased migration of diabetic human keratinocytes. The multifunctional role of HB-EGF in the healing process and its enhanced efficacy when delivered by the coacervate make it a promising therapy for diabetic wounds.

The role of mast cells in cutaneous wound healing in streptozotocin-induced diabetic mice

Mast cells (MCs) reside in cutaneous tissue, and an increment of MCs is suggested to induce vascular regression in the process of wound healing. To clarify participation of MCs in diabetic cutaneous wound healing, we created an excisional wound on diabetic mice 4 weeks after streptozotocin injections and subsequently investigated the healing processes for 49 days, comparing them with control mice. The rate of wound closure was not markedly different between the diabetic and control mice. In the proliferative phase at days 7 and 14, neovascularization in the wound was weaker in diabetic mice than in control mice. In the remodeling phase at day 21 and afterward, rapid vascular regression occurred in control mice; however, neovascularization was still observed in diabetic mice where the number of vessels in granulation tissues was relatively higher than in control mice. In the remodeling phase of the control mice, MCs within the wound began to increase rapidly and resulted in considerable accumulation, whereas the increment of MCs was delayed in diabetic mice. In addition, the number of fibroblast growth factor (FGF)- or vascular endothelial growth factor (VEGF)-immunopositive hypertrophic fibroblast-like spindle cells and c-Kit-positive/VEGFR2-positive/FcεRIα-negative endothelial progenitor cells (EPCs) were higher in diabetic wounds. In conclusion, neovascularization in the proliferative phase and vascular regression in the remodeling phase were impaired in diabetic mice. The delayed increment of MCs and sustained angiogenic stimuli by fibroblast-like spindle cells and EPCs may inhibit vascular regression in the remodeling phase and impair the wound-healing process in diabetic mice.

Cell-based regenerative strategies for treatment of diabetic skin wounds, a comparative study between human umbilical cord blood-mononuclear cells and calves' blood haemodialysate

BACKGROUND

Diabetes-related foot problems are bound to increase. However, medical therapies for wound care are limited; therefore, the need for development of new treatment modalities to improve wound healing in diabetic patients is essential and constitutes an emerging field of investigation.

METHODS

Animals were randomly divided into 8 groups (I-VIII) (32 rats/group), all were streptozotocin (STZ)-induced diabetics except groups III and VIII were non-diabetic controls. The study comprised two experiments; the first included 3 groups. Group I injected with mononuclear cells (MNCs) derived from human umbilical cord blood (HUCB), group II a diabetic control group (PBS i.v). The second experiment included 5 groups, groups IV, V, and VI received topical HUCB-haemodialysate (HD), calves' blood HD, and solcoseryl, respectively. Group VII was the diabetic control group (topical saline). Standard circular wounds were created on the back of rats. A sample of each type of HD was analyzed using the high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) system. Wound area measurement and photography were carried out every 4 days. Plasma glucose, catalase (CAT), malondialdehyde (MDA), nitric oxide (NO) and platelets count were assessed. Wound samples were excised for hydroxyproline (HP) and histopathological study.

RESULTS

Treatment with HUCB MNCs or HUCB-HD resulted in wound contraction, increased CAT, NO, platelets count, body weights, and HP content, and decreased MDA and glucose.

CONCLUSION

Systemic administration of HUCB MNCs and topical application of the newly prepared HUCB-HD or calves' blood HD significantly accelerated the rate of diabetic wound healing and would open the possibility of their future use in regenerative medicine.

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.

No Association between Glycemia and Wound Healing in an Experimental db/db Mouse Model

Impaired wound healing is a frequent problem in diabetes. Hyperglycemia may be an operative mechanism, but a link between glycemic control and wound healing has never been established. Wounds in db/db mice have been extensively studied. This study was undertaken to see if plasma glucose was a predictor of wound healing. An excisional wound was made (149 db/db mice). Wound closure was studied versus metabolic variables. The animals were 11.8 ± 0.2 weeks (mean ± standard error of the mean), obese (38.1 ± 0.5 g), and hyperglycemic (fasting plasma glucose 21.0 ± 0.7 mmol/L). Wound closure at day 13 was 30.1 ± 1.6%. In linear mixed model analyses neither fasting plasma glucose nor its change from start to end of experiment was a significant predictor of wound closure (β = 0.15, P = 0.07, 95% CI: −0.01 to 0.31 and β = 0.06, P = 0.5, 95% CI: −0.11 to 0.23, resp.). However, increase in body weight significantly and independently predicted wound closure (for weight change, β = 0.22, P = 0.008, 95% CI: 0.06 to 0.38). This study strongly suggests that wound healing in db/db mice is independent of prevailing glycemia but dependent on anabolic changes such as weight gain over time.

Safety, efficacy and pitfalls of fibrocyte application in the treatment of diabetic foot ulcer

Fibrocytes are unique bone marrow-derived cells with great potential in wound healing. Hence, the aim of this study was to determine the safety and efficacy of the applied circulating fibrocytes in the treatment of non healing diabetic foot ulcers. Peripheral blood mononuclear cells were isolated by centrifugation through Ficoll-Paque method. After 3 days, the non adherent cells were removed by a single, gentle aspiration. Adherent cells were cultured in the same medium for 10 days. The cells were characterised using mouse anti-human-CD45-fluorescein isothiocyanate (FITC) and mouse anti-human-collagen I, and also characterised by immunofluorescence microscopy using the above mentioned antibodies. Sterility measures were applied for clinical evaluation. Based on the literature review, cell transplantation generally requires at least 3 × 10(6) cells regarding efficacy measures. As fibrocytes are non proliferating cells, 350 ml patient's blood is required to prepare patient-specific serum before cell isolation and culture, and 85 ml patient's blood is needed for cell isolation and differentiation on cell transplantation applications. In our survey, no diabetic patient was inclined to be donor of such blood volume, mainly because of their pre-assumption that they are anaemic. It is concluded that fibrocytes do not seem to be candidate cells for cell therapy in the treatment of diabetic foot ulcers because of the rarity of this cell population in circulation.

Alternatives for animal wound model systems

In this chapter a review of animal model systems already being utilized to study normal and pathologic wound healing is provided. We also go into details on alternatives for animal wound model systems. The case is made for limitations in the various approaches. We also discuss the benefits/limitations of in vitro/ex vivo systems bringing everything up to date with our current work on developing a cell-based reporter system for diabetic wound healing.

PED/PEA-15 controls fibroblast motility and wound closure by ERK1/2-dependent mechanisms

Cell migration is dependent on the control of signaling events that play significant roles in creating contractile force and in contributing to wound closure. We evaluated wound closure in fibroblasts from mice overexpressing (TgPED) or lacking ped/pea-15 (KO), a gene overexpressed in patients with type 2 diabetes. Cultured skin fibroblasts isolated from TgPED mice showed a significant reduction in the ability to recolonize wounded area during scratch assay, compared to control fibroblasts. This difference was observed both in the absence and in the presence of mytomicin C, an inhibitor of mitosis. In time-lapse experiments, TgPED fibroblasts displayed about twofold lower velocity and diffusion coefficient, as compared to controls. These changes were accompanied by reduced spreading and decreased formation of stress fibers and focal adhesion plaques. At the molecular level, TgPED fibroblasts displayed decreased RhoA activation and increased abundance of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2). Inhibition of ERK1/2 activity by PD98059 restored RhoA activation, cytoskeleton organization and cell motility, and almost completely rescued wound closure of TgPED fibroblasts. Interestingly, skin fibroblasts isolated from KO mice displayed an increased wound closure ability. In vivo, healing of dorsal wounds was delayed in TgPED and accelerated in KO mice. Thus, PED/PEA-15 may affect fibroblast motility by a mechanism, at least in part, mediated by ERK1/2. J. Cell. Physiol. 227: 2106–2116, 2012. © 2011 Wiley Periodicals, Inc.

Impaired therapeutic capacity of autologous stem cells in a model of type 2 diabetes

Endogenous stem cells in the bone marrow respond to environmental cues and contribute to tissue maintenance and repair. In type 2 diabetes, a multifaceted metabolic disease characterized by insulin resistance and hyperglycemia, major complications are seen in multiple organ systems. To evaluate the effects of this disease on the endogenous stem cell population, we used a type 2 diabetic mouse model (db/db), which recapitulates these diabetic phenotypes. Bone marrow-derived mesenchymal stem cells (MSCs) from db/db mice were characterized in vitro using flow cytometric cell population analysis, differentiation, gene expression, and proliferation assays. Diabetic MSCs were evaluated for their therapeutic potential in vivo using an excisional splint wound model in both nondiabetic wild-type and diabetic mice. Diabetic animals possessed fewer MSCs, which were proliferation and survival impaired in vitro. Examination of the recruitment response of stem and progenitor cells after wounding revealed that significantly fewer endogenous MSCs homed to the site of injury in diabetic subjects. Although direct engraftment of healthy MSCs accelerated wound closure in both healthy and diabetic subjects, diabetic MSC engraftment produced limited improvement in the diabetic subjects and could not produce the same therapeutic outcomes as in their nondiabetic counterparts in vivo. Our data reveal stem cell impairment as a major complication of type 2 diabetes in mice and suggest that the disease may stably alter endogenous MSCs. These results have implications for the efficiency of autologous therapies in diabetic patients and identify endogenous MSCs as a potential therapeutic target.

Pressure ulcers: description of a new model and use of mesenchymal stem cells for repair

BACKGROUND

Pressure ulcers (PUs) still represent a heavy burden on many patients and nursing institutions. Our understanding of the pathophysiology and development of new treatments are hampered by the scarcity of suitable animal models.

OBJECTIVE

Evaluation of the translational value of an easily accessible mouse model.

METHODS

PUs were induced by application of magnetic devices on the dorsal skin of mice, which causes localized ischemia. The extent of the lesions and healing rate were quantified. Variations in ischemic exposure time were compared in hairless and normal mice. A detailed histological analysis of regeneration is presented. The influence of streptozotocin-induced diabetes, skin X-irradiation and treatment of the ulcers with human mesenchymal stem cells (MSCs) was investigated using immunodeficient NOD/SCID mice.

RESULTS

Ulcers induced by this form of ischemia have many features in common with decubitus ulcers in humans. No difference between hairy and hairless mice was observed in the rate of healing of the PUs. Unexpectedly, healing was not delayed in diabetic mice, but skin X-irradiation prior to ischemia resulted in a doubling of the time to complete closure of the PUs, and delayed repair of the dermis and panniculus carnosus muscle. Intradermal transplantation of human MSCs did not accelerate healing. The grafted MSCs were short-lived and only marginally participated in regeneration by differentiating into tissue-specific cells.

CONCLUSION

The results emphasize the difference in the characteristics of PUs as compared to surgical wounds. This experimental model is recommended for preclinical research on decubitus ulcers because of its mechanistic similarity with clinical PUs and its simplicity.

Limitations of the db/db mouse in translational wound healing research: Is the NONcNZO10 polygenic mouse model superior?

Murine models have provided valuable insights into the pathogenesis of both diabetes and chronic wounds. However, only a few published reports to date have investigated wound healing differences among the differing diabetic mouse models. The goal of the present study was to further define the wound healing deficiency phenotypes of streptozotocin-induced (STZ-induced), Akita, and db/db diabetic mice in comparison with a promising new polygenic strain of Type 2 diabetes (NONcNZO10) by using three specific wound models that targeted different critical processes in the pathogenesis of chronic wounds. Incisional, excisional, and ischemia/reperfusion wound models were established on mice of each strain. Wound healing parameters including tensile strength, epithelial gap, and wound necrosis were evaluated. In contrast to the other diabetic mice, the NONcNZO10 strain was found to have significant wound healing impairments in all wound healing models. Not only do the NONcNZO10 mice appear to better model human Type 2 diabetes, these provocative findings suggest that the mice may show more clinically relevant wound healing deficiencies than previous diabetic mouse models.

Acceleration of diabetic wound healing by collagen-binding vascular endothelial growth factor in diabetic rat model

AIMS

Vascular endothelial growth factor (VEGF) is an important active protein for the induction of angiogenesis and plays an important role in the tissue regeneration of diabetic wounds. In this study, we used collagen-binding VEGF in a diabetic rat model to investigate the effects of this new method.

METHODS

We produced a fusion protein (CBD-VEGF) consisting of VEGF and a collagen-binding domain (CBD), which allowed VEGF to bind to collagen. The diabetic rat models were made by injected streptozocin (STZ) peritoneally and removed full thickness skin on the back. All the rats were randomly divided into 3 groups: PBS group (n=24), NAT-VEGF group (n=24), and CBD-VEGF group (n=24). After model establishment, the dissolved drugs were evenly given on the wounds using syringe. The healing rates were calculated and compared among the groups and the tissues of the wound were taken and evaluated for histological analysis.

RESULTS

The CBD-VEGF group showed better result in wound healing rate, better vascularization and higher amount of VEGF in the wound granulation tissue compared with NAT-VEGF group and control.

CONCLUSIONS

Topical application of CBD-VEGF can promote diabetic wound healing in rat model, which could potentially provide a better therapeutic option for diabetic wounds.

Use of sugar on the healing of diabetic ulcers: a review

With the advent of several innovative wound care management tools, the choice of products and treatment modalities available to clinicians continues to expand. High costs associated with wound care, especially diabetic foot wounds, make it important for clinician scientists to research alternative therapies and optimally incorporate them into wound care protocols appropriately. This article reviews using sugar as a treatment option in diabetic foot care and provides a guide to its appropriate use in healing foot ulcers. In addition to a clinical case study, the physiological significance and advantages of sugar are discussed.

Human adipose-derived stromal cells accelerate diabetic wound healing: impact of cell formulation and delivery

Human adipose-derived stromal cells (ASCs) have been shown to possess therapeutic potential in a variety of settings, including cutaneous wound healing; however, it is unknown whether the regenerative properties of this cell type can be applied to diabetic ulcers. ASCs collected from elective surgical procedures were used to treat full-thickness dermal wounds in leptin receptor-deficient (db/db) mice. Cells were delivered either as multicellular aggregates or as cell suspensions to determine the impact of cell formulation and delivery methods on biological activity and in vivo therapeutic effect. After treatment with ASCs that were formulated as multicellular aggregates, diabetic wounds experienced a significant increase in the rate of wound closure compared to wounds treated with an equal number of ASCs delivered in suspension. Analysis of culture supernatant and gene arrays indicated that ASCs formulated as three-dimensional aggregates produce significantly more extracellular matrix proteins (e.g., tenascin C, collagen VI alpha3, and fibronectin) and secreted soluble factors (e.g., hepatocyte growth factor, matrix metalloproteinase-2, and matrix metalloproteinase-14) compared to monolayer culture. From these results, it is clear that cell culture, formulation, and delivery method have a large impact on the in vitro and in vivo biology of ASCs.

Macrophage dysfunction impairs resolution of inflammation in the wounds of diabetic mice

BACKGROUND

Chronic inflammation is a characteristic feature of diabetic cutaneous wounds. We sought to delineate novel mechanisms involved in the impairment of resolution of inflammation in diabetic cutaneous wounds. At the wound-site, efficient dead cell clearance (efferocytosis) is a pre-requisite for the timely resolution of inflammation and successful healing.

METHODOLOGY/PRINCIPAL FINDINGS

Macrophages isolated from wounds of diabetic mice showed significant impairment in efferocytosis. Impaired efferocytosis was associated with significantly higher burden of apoptotic cells in wound tissue as well as higher expression of pro-inflammatory and lower expression of anti-inflammatory cytokines. Observations related to apoptotic cell load at the wound site in mice were validated in the wound tissue of diabetic and non-diabetic patients. Forced Fas ligand driven elevation of apoptotic cell burden at the wound site augmented pro-inflammatory and attenuated anti-inflammatory cytokine response. Furthermore, successful efferocytosis switched wound macrophages from pro-inflammatory to an anti-inflammatory mode.

CONCLUSIONS/SIGNIFICANCE

Taken together, this study presents first evidence demonstrating that diabetic wounds suffer from dysfunctional macrophage efferocytosis resulting in increased apoptotic cell burden at the wound site. This burden, in turn, prolongs the inflammatory phase and complicates wound healing.

Topical atorvastatin in the treatment of diabetic wounds

BACKGROUND

Currently, it is reported that statins may be useful in the treatment of diabetes mellitus foot ulceration. The aim of this study was to evaluate treatment of the wounds in streptozotocin-induced diabetic rats with local atorvastatin.

METHODS

Two 15 x 15 mm-sized wounds were created in 28 streptozotocin-induced rats. A total of 56 diabetic wounds were studied in 8 groups (n = 7). No treatment was administered in the first and second groups, which lasted for 7 and 14 days, respectively. Third and fourth groups consisted of diabetic rats that were administered 1:1 mixture of lanolin and vaseline therapy for 7 and 14 days, respectively. One percent statin plus 1:1 mixture of lanolin and vaseline was used in the fifth and sixth groups for 7 and 14 days, respectively; and in seventh and eighth groups, 5% statin plus 1:1 mixture of lanolin and vaseline therapy was used for 7 and 14 days, respectively. On the 7th and 14th days, state of the wound healing was observed, and the percent of wound healing was determined by measuring its size and by performing a histopathologic study. The statistical analyses were performed by Mann-Whitney U test, using SPSS 14.0 software.

RESULTS

On the 14th day, the rates of wound healing in the first, second, third, and fourth groups were 14%, 40%, 96.59%, and 96.51%, respectively. This ratio was calculated by the formula healing ratio (%) = 100 x (1-wound area/initial wound area). Accordingly, in the multiple comparisons, the rates of wound healing were found to be significantly higher in the diabetic rat groups administered 1% and 5% atorvastatin compared with those administered a mixture of lanolin-vaseline and the untreated group (for comparison each one P < 0.001).

CONCLUSIONS

Local atorvastatin therapy may be useful for healing the wounds in diabetic rats. Further clinical and experimental studies are needed to confirm these results.