Heparan sulfate glycosaminoglycan mimetic improves pressure ulcer healing in a rat model of cutaneous ischemia-reperfusion injury

First-Intention Incisional Wound Healing in Dogs and Cats: A Controlled Trial of Dermapliq and Manuka Honey

This study aimed to compare incisional wound healing in cats and dogs after the topical application of Μanuka honey and a new medical device, Dermapliq. Comparisons were made between each treatment and control, between the two treatments, and between dogs and cats. Twelve cats and twelve dogs were included in this study, and the impact of the two substances was examined through cosmetic, clinical, ultrasonographical, and histological evaluation. The use of Dermapliq in first-intention wound healing achieved a significantly better cosmetic evaluation score and better total clinical score at days 20-41, compared to the control, in both dogs and cats. The ultrasonographically estimated wound area was smaller with Dermapliq compared to the control. Wounds treated with Dermapliq showed histologically less inflammation compared to the control. The use of Manuka honey did not show a significantly better cosmetic score compared to the control. Skin thickening was significantly higher after using Manuka honey compared to the control and so was the total clinical score. However, the median wound area, as was evaluated ultrasonographically, was significantly smaller when wounds were treated with Manuka honey, the difference being more apparent in dogs. Dermapliq was proven to be a better choice in achieving favorable wound healing than Manuka honey in dogs and cats in first-intention healing. In our study, cats had a statistically better cosmetic score and less skin thickening and scar width compared to dogs. Histologically, cats showed significantly less edema, higher inflammation and angiogenesis scores, and lower fibroblast and epidermis thickening scores when compared to dogs.

The healing effect of topical tea tree oil on pressure ulcers in a rat model

Objective: The effects of topical tea tree oil (TTO) on the healing of pressure ulcers (PUs) in an animal model was evaluated. Method: To induce PUs, ischaemia-reperfusion cycles were performed by the external application of magnetic plates, with an ischaemic period of eight hours and a reperfusion period of 16 hours. Male and female Wistar rats were divided into three equally sized groups (n=20): one group received topical glycerin twice daily, another group received topical 10% (volume/volume (v/v)) TTO in glycerin twice daily; and the remaining group was untreated. The animals were assessed after one, four, seven and 14 cycles of ischaemia-reperfusion by thermal camera imaging, and then euthanised and sampled to investigate the degree of inflammation, collagen synthesis and apoptosis in the PUs. Results: Although topical glycerin alone suppressed local inflammation and apoptosis, this suppressive effect was accentuated at all timepoints by the application of topical TTO + glycerin. Similarly, an increase in collagen synthesis was observed in the glycerin group and this was accentuated by TTO at all timepoints. Parallel to the histological findings, the local temperature had decreased significantly on days 4 and 7 for both treatment groups (glycerin and TTO+glycerin). Conclusion: In this study, treatment with 10% (v/v) TTO in glycerin effectively suppressed skin inflammation and apoptosis, while it increased collagen synthesis during PU formation.

The healing effect of topical tea tree oil on pressure ulcers in a rat model

Objective: The effects of topical tea tree oil (TTO) on the healing of pressure ulcers (PUs) in an animal model was evaluated. Method: To induce PUs, ischaemia-reperfusion cycles were performed by the external application of magnetic plates, with an ischaemic period of eight hours and a reperfusion period of 16 hours. Male and female Wistar rats were divided into three equally sized groups (n=20): one group received topical glycerin twice daily, another group received topical 10% (volume/volume (v/v)) TTO in glycerin twice daily; and the remaining group was untreated. The animals were assessed after one, four, seven and 14 cycles of ischaemia-reperfusion by thermal camera imaging, and then euthanised and sampled to investigate the degree of inflammation, collagen synthesis and apoptosis in the PUs. Results: Although topical glycerin alone suppressed local inflammation and apoptosis, this suppressive effect was accentuated at all timepoints by the application of topical TTO + glycerin. Similarly, an increase in collagen synthesis was observed in the glycerin group and this was accentuated by TTO at all timepoints. Parallel to the histological findings, the local temperature had decreased significantly on days 4 and 7 for both treatment groups (glycerin and TTO+glycerin). Conclusion: In this study, treatment with 10% (v/v) TTO in glycerin effectively suppressed skin inflammation and apoptosis, while it increased collagen synthesis during PU formation.

Simultaneous production of N-acetylheparosan and recombinant chondroitin using gene-engineered Escherichia coli K5

N-Acetylheparosan and chondroitin are increasingly needed as alternative sources of animal-derived sulfated glycosaminoglycans (GAGs) and as inert substances in medical devices and pharmaceuticals. The N-acetylheparosan productivity of E. coli K5 has achieved levels of industrial applications, whereas E.coli K4 produces a relatively lower amount of fructosylated chondroitin. In this study, the K5 strain was gene-engineered to co-express K4-derived, chondroitin-synthetic genes, namely kfoA and kfoC. The productivities of total GAG and chondroitin in batch culture were 1.2 g/L and 1.0 g/L respectively, which were comparable to the productivity of N-acetylheparosan in the wild K5 strain (0.6-1.2 g/L). The total GAG of the recombinant K5 was partially purified by DEAE-cellulose chromatography and was subjected to degradation tests with specific GAG-degrading enzymes combined with HPLC and 1H NMR analyses. The results indicated that the recombinant K5 simultaneously produced both 100-kDa chondroitin and 45-kDa N-acetylheparosan at a weight ratio of approximately 4:1. The content of chondroitin in total GAG partially purified was 73.2%. The molecular weight of recombinant chondroitin (100 kDa) was 5-10 times higher than that of commercially available chondroitin sulfate. These results indicated that the recombinant K5 strain acquired the chondroitin-producing ability without altering the total GAG productivity of the host.

A Retrospective Self-Controlled Study Evaluating the Prophylactic Effects of CACIPLIQ20 on Postsurgical Scars

Background

CACIPLIQ20 (OTR3, Paris, France) is a medical device used for the treatment of chronic skin ulcers. It contains a heparan sulfate mimetic that accelerates tissue healing by stabilizing matrix proteins and protecting heparin-binding growth factors. In humans, an open self-controlled study suggested that the topical application of CACIPLIQ20 optimizes skin healing following surgery.

Objectives

To expand previous findings using a different CACIPLIQ20 administration regimen.

Methods

Twenty-four females were referred for breast-reduction surgery. Each patient had their own control with 1 CACIPLIQ20-treated and 1 saline-treated control breast. The treated side (right or left) was randomly assigned by the operating surgeon. Scar appearance was assessed by 6 independent raters using a global visual scar comparison scale based on scar photographs. All raters were blinded toward the CACIPLIQ20-treated side.

Results

The follow-up period following surgery ranged from 1 to 12 months with a median follow-up of 6 months. Overall, there was a mean improvement of 15.2% (SD = 26.7) in favor of CACIPLIQ20 (P = .016). On the CACIPLIQ20-treated side, the mean score per patient was above 20% in 11 patients and above 30% improvement in 8 cases. In contrast, only 3 patients were considered improved by at least 20% on the control side and only 1 above 30%. A comparison of different application regimens suggested that the best trend was obtained with a single administration of CACIPLIQ20 at Day 0.

Conclusions

In conclusion, CACIPLIQ20 could represent an interesting scar prophylactic therapy, based on a single administration at the time of surgery, and without any known adverse effects.

Level of Evidence 3

Challenges faced in developing an ideal chronic wound model

INTRODUCTION

Chronic wounds are a major drain on healthcare resources and can lead to substantial reductions in quality of life for those affected. Moreover, they often precede serious events such as limb amputations and premature death. In the long run, this burden is likely to escalate with an ageing population and lifestyle diseases such as obesity. Thus far, the identification of beneficial therapeutics against chronic wounds have been hindered by the lack of an ideal chronic wound animal model. Although animal models of delayed healing have been developed, none of these models fully recapitulate the complexity of the human chronic wound condition. Furthermore, most animals do not develop chronic wounds. Only the thoroughbred racehorse develops chronic ulcers.

AREAS COVERED

In this review, the different characteristics of chronic wounds that highlight its complexity are described. In addition, currently available models reflecting different aspects of chronic wound pathology and their relevance to human chronic wounds are discussed. This article concludes by listing relevant features representative of an ideal chronic wound model. Additionally, alternative approaches for the development of chronic wound models are discussed.

EXPERT OPINION

Delayed models of healing, including the streptozotocin diabetic model, skin flap model and magnet-induced IR models have emerged. While these models have been widely adopted for preclinical therapeutic testing, their relevance towards human chronic wounds remains debatable. In particular, current delayed healing models often fail to fully incorporate the key characteristics of chronic ulcers. Ultimately, more representative models are required to expedite the advancement of novel therapeutics to the clinic.

Pyroptosis and inflammasomes in diabetic wound healing

Diabetic wound is one of the complications of diabetes and is not easy to heal. It often evolves into chronic ulcers, and severe patients will face amputation. Compared with normal wounds, diabetic wounds have an increased proportion of pro-inflammatory cytokines that are detrimental to the normal healing response. The burden of this disease on patients and healthcare providers is overwhelming, and practical solutions for managing and treating diabetic wounds are urgently needed. Pyroptosis, an inflammatory type of programmed cell death, is usually triggered by the inflammasome. The pyroptosis-driven cell death process is primarily mediated by the traditional signaling pathway caused by caspase -1 and the non-classical signaling pathways induced by caspase -4/5/11. Growing evidence that pyroptosis promotes diabetic complications, including diabetic wounds. In addition, inflammation is thought to be detrimental to wound healing. It is worth noting that the activation of the NLRP3 inflammasome plays a crucial role in the recovery of diabetic wounds. This review has described the mechanisms of pyroptosis-related signaling pathways and their impact on diabetic wounds. It has discussed new theories and approaches to promote diabetic wound healing, as well as some potential compounds targeting pyroptosis and inflammasome signaling pathways that could be new approaches to treating diabetic wounds.

ReGeneraTing Agents (rgta®) technology combined with antibiotics improves outcomes for infections in the upper limb

A matrix therapy agent marketed as CACIPLIQ20® showed marked improvement in the healing rate of hand infections, including functional recovery. It can be used at both earlier and later stages to promote faster healing and prevent an adverse outcome.

Wound healing activity of Pimpinella anisum methanolic extract in streptozotocin-induced diabetic rats

OBJECTIVE

To assess the wound healing potential of Pimpinella anisum on cutaneous wounds in diabetic rats.

METHOD

Full-thickness excisional wounds were made on the back of male, Sprague-Dawley rats with diabetes. The rats were randomly allocated into four treatment groups: 1ml basal cream; tetracycline (3%); Pimpinella anisum 10% for 14 days; and a control group. At days seven, 14 and 21 post-injury, five animals of each group were euthanised, and wounds were assessed through gross, histopathological and oxidant/antioxidant evaluations. Additionally, the dry matter and hydroxyproline contents of the skin samples were measured.

RESULTS

A total of 60 rats were used in the study. A significant decrease in the wound size was observed in treated animals with Pimpinella anisum compared with other groups during the experiment. Additionally, treatment with Pimpinella anisum decreased the number of lymphocytes and improved the number of fibroblasts at the earlier stages and increased a number of fibrocytes at the later stages of wound healing. Other parameters such as re-epithelialisation, tissue alignment, greater maturity of collagen fibres and large capillary-sized blood vessels revealed significant changes when compared with the control. Pimpinella anisum significantly reverted oxidative changes of total antioxidant capacity, malondialdehyde and glutathione peroxidase induced by diabetic wounds (p<0.05). Furthermore, it significantly increased the dry matter and hydroxyproline contents at various stages of wound healing (p<0.05).

CONCLUSION

The present study showed that application of Pimpinella anisum extract promotes wound healing activity in diabetic rats. The wound-healing property of Pimpinella anisum can be attributed to the phytoconstituents present in the plant.

Matrix therapy is a cost-effective solution to reduce amputation risk and improve quality of life: pilot and case studies

Introduction: Chronic, non-healing ulcers remain one of the most challenging clinical situations for health care practitioners. Often, conventional treatments fail and lead to amputation, further decreasing the patient's quality of life and resulting in enormous medical expenditures for healthcare systems. Here we evaluated the use of and cost-effectiveness of the RGTA (ReGeneraTing Agents) medical device CACIPLIQ20 (OTR4120) for chronic lower-extremity ulcers in patients with Leriche and Fontaine Stage IV peripheral arterial disease who were not eligible for revascularization. Methods: This uncontrolled pilot study included 14 chronic lower extremity ulcers in 12 patients in one hospital. The pilot study included 12 patients with TcPO₂ < 20 mm Hg and ABPI < 0.5 who had either a minimum of one chronic lower extremity ulcer or a chronic ulcer related to amputation. OTR4120 was applied twice a week or until complete healing, for up to 12 weeks. Ulcer surface area reduction (%)after 2, 4, 8 and 12 weeks, appearance after 4 weeks, and healing after 12 weeks were measured and recorded. Results: A 35% reduction in ulcer size was achieved after 4 weeks. 7 (50%) out of 14 ulcers completely healed within 1 to 3 months of treatment. Discussion: OTR4120 is an effective therapeutic option for patients with chronic lower extremity ulcers, can provide major improvement of quality of life and has the added benefit of being a significant cost-effective solution for healthcare systems.

ReGeneraTing Agents (RGTA®): A new option for healing and improving treatment outcomes for traumatic and burn injuries of the hand

CACIPLIQ20® significantly improved the outcomes of severe burn injuries of the hand. Healing was accelerated, with little or no scarring, allowing for greater mobility over the joints and maintained suppleness. Functional recovery was achieved in all cases.

ReGeneraTing Agents (RGTA®) are a new option to improve amputation outcomes in the recovery of severe hand injuries

CACIPLIQ20® was used to accelerate the healing process and stimulate the viability of flaps and skin grafts, thereby improving amputation outcomes. An excellent range of motion was achieved with hardly any contracture or scarring. Pain relief and reduced sensitivity was noted, while healing of bone and tendon also improved, resulting in functional recovery.

Heparan sulfate inhibits inflammation and improves wound healing by downregulating the NLR family pyrin domain containing 3 (NLRP3) inflammasome in diabetic rats

BACKGROUND

Heparan sulfate (HS) attenuates the inflammatory response and improves diabetic wound healing in rats. However, the specific mechanisms by which HS suppresses inflammation are not clear. Given that NLR family pyrin domain containing 3 (NLRP3) is a major receptor involved in innate immune regulation, the aim of the present study was to elucidate the effects of HS on NLRP3 and proinflammatory cytokines in diabetic wounds.

METHODS

Full-thickness wounds were created on the back of diabetic rats. The experimental group received HS treatment (1 mg/kg, i.m., on Days 0 and 7), whereas the control group received vehicle (0.1% dimethylsulfoxide in 0.9% NaCl). Expression of NLRP3 and its downstream effector molecules, namely cleaved interleukin (IL)-1β, IL-18, tumor necrosis factor (TNF)-α, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), proteinase inhibitor 9, and caspase-12, in the wound tissues was examined.

RESULTS

Treatment with HS accelerated wound healing in diabetic rats. Rats treated with HS exhibited decreased activation of cleaved IL-1β, IL-18, and TNF-α, as well as decreased expression of NLRP3 and ASC. In addition, HS increased levels of proteinase inhibitor 9 and caspase-12.

CONCLUSIONS

Heparan sulfate inhibits inflammation and improves wound healing by downregulating the NLRP3 inflammasome and cleaved IL-1β during the wound healing process in diabetic rats.

Caffeic acid phenethyl ester promotes wound healing of mice pressure ulcers affecting NF-κB, NOS2 and NRF2 expression

AIMS

In pressure ulcers, the synthesis of reactive oxygen species induced by ischemia and reperfusion leads to chronic inflammation and tissue damage, which impair the closure of these lesions. Caffeic acid phenethyl ester (CAPE), found in propolis, promotes cutaneous wound healing of acute lesions and severe burns. However, the effects of CAPE on wound healing of pressure ulcers have not been investigated. This study investigated the effects of CAPE administration in a murine model of pressure ulcers.

MAIN METHODS

To induce pressure ulcers, two cycles of ischemia and reperfusion by external application of two magnetic plates were performed in the skin dorsum of mice. After the last cycle, animals were treated daily with CAPE or vehicle until they were euthanized.

KEY FINDINGS

The nitric oxide synthesis, lipid peroxidation, macrophage migration, protein nuclear factor kappa B and nitric-oxide synthase-2 expression were increased 3 days after ulceration but decreased 7 days later, in pressure ulcers of the CAPE group compared to that of the control group. CAPE reduced the protein expression of nuclear factor-erythroid2-related factor 2 in pressure ulcers 3 days after ulceration, but increased 7 days later. Myofibroblast density was increased in the CAPE group 7 days after ulceration, but reduced 12 days later when compared to control group. In addition, CAPE promoted collagen deposition, re-epithelialization and wound closure of mice pressure ulcers 12 days after ulceration.

SIGNIFICANCE

CAPE brings forward inflammatory response and oxidative damage involved in injury by ischemia and reperfusion, promoting dermal reconstruction and closure of pressure ulcers.

Improved recovery from limb ischaemia by delivery of an affinity-isolated heparan sulphate

Peripheral arterial disease is a major cause of limb loss and its prevalence is increasing worldwide. As most standard-of-care therapies yield only unsatisfactory outcomes, more options are needed. Recent cell- and molecular-based therapies that have aimed to modulate vascular endothelial growth factor-165 (VEGF₁₆₅) levels have not yet been approved for clinical use due to their uncertain side effects. We have previously reported a heparan sulphate (termed HS7) tuned to avidly bind VEGF₁₆₅. Here, we investigated the ability of HS7 to promote vascular recovery in a murine hindlimb vascular ischaemia model. HS7 stabilised VEGF₁₆₅ against thermal and enzyme degradation in vitro, and isolated VEGF₁₆₅ from serum via affinity-chromatography. C57BL6 mice subjected to unilateral hindlimb ischaemia injury received daily intramuscular injections of respective treatments (n = 8) and were assessed over 3 weeks by laser Doppler perfusion, magnetic resonance angiography, histology and the regain of function. Mice receiving HS7 showed improved blood reperfusion in the footpad by day 7. In addition, they recovered hindlimb blood volume two- to fourfold faster compared to the saline group; the greatest rate of recovery was observed in the first week. Notably, 17% of HS7-treated animals recovered full hindlimb function by day 7, a number that grew to 58% and 100% by days 14 and 21, respectively. This was in contrast to only 38% in the control animals. These results highlight the potential of purified glycosaminoglycan fractions for clinical use following vascular insult, and confirm the importance of harnessing the activity of endogenous pro-healing factors generated at injury sites.

Hyperbaric oxygen therapy for wound healing in diabetic rats: Varying efficacy after a clinically-based protocol

Hyperbaric oxygen therapy (HBOT) is a clinical treatment in which a patient breathes pure oxygen for a limited period of time at an increased pressure. Although this therapy has been used for decades to assist wound healing, its efficacy for many conditions is unproven and its mechanism of action is not yet fully clarified. This study investigated the effects of HBOT on wound healing using a diabetes-impaired pressure ulcer rat model. Seven weeks after streptozotocin-induced diabetes in rats (n = 55), a pressure ulcer was created on dorsal skin. Subsequently, animals received HBOT during 6 weeks following a standard clinical protocol (HBOT group with varying endpoints up to 42 days post-wounding) versus controls without HBOT. Capillary venous oxygen saturation (SO₂) showed a significant increase in the HBOT group on day 24; however, this increase was significant at this time point only. The quantity of hemoglobin in the micro-blood vessels (rHB) showed a significant decrease in the HBOT group on days 21 and 42, and showed a trend to decrease on day 31. Blood flow in the microcirculation showed a significant increase on days 17, 21 and 31 but a significant decrease on days 24 and 28. Inflammation scoring showed significantly decreased CD68 counts in the HBOT group on day 42, but not in the early stages of wound healing. Animals in the HBOT group showed a trend for an increase in mean wound breaking strength on day 42.

Efficacy of a New Heparan Sulfate Mimetic Dressing in the Healing of Foot and Lower Extremity Ulcerations in Type 2 Diabetes: A Case Series

A novel heparan sulfate glycosaminoglycan mimetic product for local application to promote wound healing (CACIPLIQ) has recently become available. It is a biophysical therapeutic product comprising a polysaccharide as an innovative biomaterial to accomplish mechanical tissue engineering and skin regeneration in the site of ulceration. We present a series of 12 patients with type 2 diabetes (4 men and 8 women; age 53-87 years; diabetes duration 8-25 years) having chronic resistance to therapy for foot and lower extremity ulcerations. CACIPLIQ was locally applied twice per week after careful debridement. Complete ulcer healing was accomplished in all patients after a mean treatment duration of 4.92 months (range = 2-12 months). The product was very well tolerated. In conclusion, these results, although preliminary, are encouraging and suggest adequate efficacy and safety of the new product in difficult-to-heal foot and lower extremity ulcerations in type 2 diabetes.

Pressure ulcers in palliative ward patients: hyponatremia and low blood pressure as indicators of risk

BACKGROUND

Prevention strategies for pressure ulcer formation remain critical in patients with an advanced illness. We analyzed factors associated with the development of pressure ulcers in patients hospitalized in a palliative care ward setting.

PATIENTS AND METHODS

This study was a retrospective analysis of 329 consecutive patients with a mean age (± standard deviation) of 70.4±11.8 years (range: 30-96 years, median 70.0 years; 55.3% women), who were admitted to the Palliative Care Department between July 2012 and May 2014.

RESULTS

Patients were hospitalized for mean of 24.8±31.4 days (1-310 days, median 14 days). A total of 256 patients (77.8%) died in the ward and 73 patients (22.2%) were discharged. Two hundred and six patients (62.6%) did not develop pressure ulcers during their stay in the ward, 84 patients (25.5%) were admitted with pressure ulcers, and 39 patients (11.9%) developed pressure ulcers in the ward. Four factors assessed at admission appear to predict the development of pressure ulcers in the multivariate logistic regression model: Waterlow score (odds ratio [OR] =1.140, 95% confidence interval [CI] =1.057-1.229, P=0.001), transfer from other hospital wards (OR =2.938, 95% CI =1.339-6.448, P=0.007), hemoglobin level (OR =0.814, 95% CI =0.693-0.956, P=0.012), and systolic blood pressure (OR =0.976, 95% CI =0.955-0.997, P=0.023). Five other factors assessed during hospitalization appear to be associated with pressure ulcer development: mean evening body temperature (OR =3.830, 95% CI =1.729-8.486, P=0.001), mean Waterlow score (OR =1.194, 95% CI =1.092-1.306, P<0.001), the lowest recorded sodium concentration (OR =0.880, 95% CI =0.814-0.951, P=0.001), mean systolic blood pressure (OR =0.956, 95% CI =0.929-0.984, P=0.003), and the lowest recorded hemoglobin level (OR =0.803, 95% CI =0.672-0.960, P=0.016).

CONCLUSION

Hyponatremia and low blood pressure may contribute to the formation of pressure ulcers in patients with an advanced illness.

Heparin-Mimicking Polymers: Synthesis and Biological Applications

Heparin is a naturally occurring, highly sulfated polysaccharide that plays a critical role in a range of different biological processes. Therapeutically, it is mostly commonly used as an injectable solution as an anticoagulant for a variety of indications, although it has also been employed in other forms such as coatings on various biomedical devices. Due to the diverse functions of this polysaccharide in the body, including anticoagulation, tissue regeneration, anti-inflammation, and protein stabilization, and drawbacks of its use, analogous heparin-mimicking materials are also widely studied for therapeutic applications. This review focuses on one type of these materials, namely, synthetic heparin-mimicking polymers. Utilization of these polymers provides significant benefits compared to heparin, including enhancing therapeutic efficacy and reducing side effects as a result of fine-tuning heparin-binding motifs and other molecular characteristics. The major types of the various polymers are summarized, as well as their applications. Because development of a broader range of heparin-mimicking materials would further expand the impact of these polymers in the treatment of various diseases, future directions are also discussed.

Inhalation anesthesia of rats: influence of the fraction of inspired oxygen on limb ischemia/reperfusion injury

Inhalation anesthesia with isoflurane is a well-established and safe method used in small laboratory animals. In most cases oxygen is used as a carrier gas for isoflurane, but room air or mixtures of oxygen with air or nitrous oxide are also being used. Anesthesia is therefore administered using different fractions of inspired oxygen (FiO2), and this may have consequences for the outcome of experiments. The aim of the present study was to investigate the influence of FiO2 on rat hind limb ischemia/reperfusion injury and to refine the used inhalation anesthesia. Male Wistar rats were subjected to 3.5 h of ischemia and 2 h of reperfusion, and divided into three groups according to FiO2 in the O2/air/isoflurane anesthesia gas mixture: 40%, 60%, and 100% O2 Normal, healthy rats were used as controls. Muscle edema and creatine kinase MM, a marker for myocyte necrosis, were significantly increased with 40% FiO2 as compared with 100% FiO2 (P < 0.05). Partial pressure of oxygen, oxygen saturation, and oxyhemoglobin were significantly higher in the 100% O2 group as compared with 40% O2 No significant differences were detected for other parameters, such as the oxidative stress markers malondialdehyde and superoxide dismutase. We conclude that a refined inhalation anesthesia setting using 40% FiO2, reflecting more or less the clinical situation, leads to a more severe and more physiologically relevant reperfusion injury than higher FiO2. Oxidative stress did not correlate with FiO2 and seemed to have no influence on reperfusion injury.

Adipose stromal cells repair pressure ulcers in both young and elderly mice: potential role of adipogenesis in skin repair

More than 2.5 million patients in the U.S. require treatment for pressure ulcers annually, and the elderly are at particularly high risk for pressure ulcer development. Current therapy for pressure ulcers consists of conservative medical management for shallow lesions and aggressive debridement and surgery for deeper lesions. The current study uses a murine model to address the hypothesis that adipose-derived stromal/stem cell (ASC) treatment would accelerate and enhance pressure ulcer repair. The dorsal skin of both young (2 months old [mo]) and old (20 mo) C57BL/6J female mice was sandwiched between external magnets for 12 hours over 2 consecutive days to initiate a pressure ulcer. One day following the induction, mice were injected with ASCs isolated from congenic mice transgenic for the green fluorescent protein under a ubiquitous promoter. Relative to phosphate-buffered saline-treated controls, ASC-treated mice displayed a cell concentration-dependent acceleration of wound closure, improved epidermal/dermal architecture, increased adipogenesis, and reduced inflammatory cell infiltration. The ASC-induced improvements occurred in both young and elderly recipients, although the expression profile of angiogenic, immunomodulatory, and reparative mRNAs differed as a function of age. The results are consistent with clinical reports that fat grafting improved skin architecture in thermal injuries; the authors of this published study have invoked ASC-based mechanisms to account for their clinical outcomes. Thus, the current proof-of-principle study sets the stage for clinical translation of autologous and/or allogeneic ASC treatment of pressure ulcers.

SIGNIFICANCE

Adipose-derived stromal/stem cells (ASCs) promote the healing of pressure ulcer wounds in both young and old mice. ASCs enhance wound healing rates through adipogenic differentiation and regeneration of the underlying architecture of the skin.

Hyperbaric oxygen therapy to treat diabetes impaired wound healing in rats

Wound healing in diabetes is frequently impaired and its treatment remains a challenge. Hyperbaric oxygen therapy (HBOT) receives a wide attendance and is often used as a last resort treatment option, however, its effectiveness for many conditions is unproven. We tested the effect of HBOT on healing of diabetic ulcers in an animal experimental setting. Experimental diabetes was induced by intraperitoneal injection of streptozotocin. Four weeks after diabetes induction, rats were ulcerated by clamping a pair of magnet disks on the dorsal skin for 16 h. After magnet removal, the animals received HBOT, daily on weekdays, for 4 weeks. To examine the effect of HBOT on diabetes impaired wound healing, the degree of wound tissue perfusion, inflammation, angiogenesis, and tissue breaking strength were evaluated. HBOT effects on the degree of inflammation and number of blood vessels could not be observed. HBOT improved the tissue breaking strength of the wound, however, this did not reach statistical significance. Twenty hours after ending the HBOT, a significantly improved oxygen saturation of the hemoglobin at the venous end of the capillaries and the quantity of hemoglobin in the micro-blood vessels was measured.

Specific effects of fibrinogen and the γA and γ'-chain fibrinogen variants on angiogenesis and wound healing

In a newly formed wound, the natural fibrin network provides the first temporary matrix for tissue repair. Topical application of fibrin to a new wound may improve wound healing. A matrix of the common natural γ' fibrin variant may further improve wound healing because it is expected to have a different architecture and this will influence angiogenesis, because it possesses increased thrombin and factor XIII binding and decreased platelet binding, when compared with the common γA fibrin matrix. Our objective was to determine the effect of fibrinogen and its γA and γ' variants on angiogenesis and wound healing. We used in vitro angiogenesis models and an in vivo rat full-thickness excisional wound healing model. When comparing γA and γ' fibrin in vitro, more tube-like structures were formed on day 7 in γA fibrin than in γ' fibrin (13.83±6.12 AU vs. 6.1±1.46 AU). Wounds treated with fibrin demonstrated improved healing in vivo with more perfusion (47%±3% vs. 26%±4%, p<0.01 in placebo) and higher CD34 density score (2.0±0.4 vs. 2.8±0.1, p<0.01) on day 21 with fibrin matrices when compared with placebo-treated wounds. Increased perfusion was observed in γA fibrin-treated wounds on day 21 (53%±10% vs. 41%±7% for γ' fibrin). The other parameters showed slightly improved (not significant) wound healing with γA fibrin compared with γ' fibrin matrices. In conclusion, the use of fibrin and fibrin variant matrices offers an interesting methodology to stimulate the wound healing process.

Avocado/soybean unsaponifiables: a novel regulator of cutaneous wound healing, modelling and remodelling

We investigated the effects of avocado/soybean unsaponifiables (ASU) on the healing response of cutaneous wound defect in rats. Sixty male rats were randomly divided into three groups including control, vehicle and treatment (n = 20 in each group). A 2 × 2 cm(2) wound defect was made on the dorsum. The control, vehicle and treatment groups were treated daily with topical application of saline, cream and cream/ASU for 10 days, respectively. The wounds were monitored daily. The animals were euthanised at 10, 20 and 30 days post injury (D). The dry matter, hydroxyproline, collagen, n-acetyl glucosamine (NAGLA) and n-acetyl galactosamine (NAGAA) contents of the skin samples were measured and the histopathological and biomechanical characteristics of the samples were investigated. Statistics of P < 0·05 was considered significant. Treatment significantly increased tissue glycosaminoglycans and collagen contents at various stages of wound healing compared to controls. Treatment modulated inflammation, improved fibroplasia and produced high amounts of scar tissue at short term. At long term, treatment reduced the scar tissue size and increased the quality and rate of wound contraction and reepithelisation compared to controls. The treated lesions were more cosmetically pleasing and had significantly higher biomechanical characteristics than controls. ASU was effective in rat wound healing.

Skin microvascular response to pressure load in obese mice

PURPOSE

The role of obesity in the appearance of skin pressure ulcers remains controversial. The aim of the present study was to evaluate blood perfusion and related lesions after skin compression in obese mice.

METHODS

Sixty C57BL6 male mice were randomly assigned to a control or hypercalorific diet (HCD) for 2, 4 and 12weeks. Skin compression was induced by a magnetic force of 11 kPa overlying a subcutaneous metal plate and applied for 4h. Skin perfusion was examined using laser Doppler imaging before skin compression, immediately after compression release and 24h later. 24h after magnet removal, skin injuries were determined by photography.

RESULTS

A heterogeneous distribution of blood perfusion was observed using the colour-coded map of the skin perfusion on the compressed area. At 24-h post-compression release, 60% to 75% of the compressed area was ischaemic in the 2-week HCD group and in all the control groups compared to 35% in the 4- and 15% in the 12-week HCD groups. The lowest occurrence of skin lesion seen as skin redness or pressure-sores was observed in the 12- week HCD group (4%) compared to about 12% in either the control or the 2- and 4-week HCD groups.

CONCLUSIONS

This study suggests that there was no clear relationship between the extent of ischaemia and skin lesion occurrence after skin compression in short-duration obese mice. In contrast, it appears that long-duration obesity could reduce both ischaemia and skin lesions in response to skin compression through changes in skin structure.

Tissue response to composite hydrogels for vertical bone augmentation in the rat

The objective of the present study was to develop a preclinical animal model for evaluating bone augmentation and to examine the level of bone augmentation induced by hydrogel composites. Design criteria outlined for the development of the animal model included rigid immobilization of bilateral implants apposed to the parietal bone of the rat, while avoiding the calvarial sutures. The animal model was evaluated through the implantation of hydrogel composites of oligo(poly(ethylene glycol) fumarate) (OPF) and gelatin microparticles releasing bone morphogenetic protein-2 (BMP-2). The BMP-2 release profile was varied and compared to the implantation of a material control without BMP-2. Each hydrogel composite was implanted within a polypropylene cassette, which was immobilized to the calvarial bone using screws, and empty cassettes were implanted as a control. The design criteria for the animal model were realized; however, the level of bone augmentation did not vary between any of the groups after 4 weeks. Osteoclastic bone resorption occurred to a higher extent in groups releasing BMP-2, but the cause could not be elucidated. In conclusion, a promising bone augmentation model was established in the rat; however, refinement of the hydrogel composites was suggested to optimize the constructs for bone augmentation applications.

Diabetes-impaired wound healing is improved by matrix therapy with heparan sulfate glycosaminoglycan mimetic OTR4120 in rats

Wound healing in diabetes is frequently impaired, and its treatment remains a challenge. We tested a therapeutic strategy of potentiating intrinsic tissue regeneration by restoring the wound cellular environment using a heparan sulfate glycosaminoglycan mimetic, OTR4120. The effect of OTR4120 on healing of diabetic ulcers was investigated. Experimental diabetes was induced by intraperitoneal injection of streptozotocin. Seven weeks after induction of diabetes, rats were ulcerated by clamping a pair of magnet disks on the dorsal skin for 16 h. After magnet removal, OTR4120 was administered via an intramuscular injection weekly for up to 4 weeks. To examine the effect of OTR4120 treatment on wound heal-ing, the degree of ulceration, inflammation, angiogenesis, and collagen synthesis were evaluated. We found that OTR4120 treatment significantly reduced the degree of ulceration and the time of healing. These effects were associated with reduced neutrophil infiltration and macrophage accumulation and enhanced angiogenesis. OTR4120 treatment also increased the collagen content with an increase of collagen type I biosynthesis and reduction of collagen type III biosynthesis. Moreover, restoration of the ulcer biomechanical strength was significantly enhanced after OTR4120 treatment. This study shows that matrix therapy with OTR4120 improves diabetes-impaired wound healing.