The use of marrow-derived stem cells to accelerate healing in chronic wounds

The Efficacy of Stem Cells in Wound Healing: A Systematic Review

Wound healing is an intricate process involving coordinated interactions among inflammatory cells, skin fibroblasts, keratinocytes, and endothelial cells. Successful tissue repair hinges on controlled inflammation, angiogenesis, and remodeling facilitated by the exchange of cytokines and growth factors. Comorbid conditions can disrupt this process, leading to significant morbidity and mortality. Stem cell therapy has emerged as a promising strategy for enhancing wound healing, utilizing cells from diverse sources such as endothelial progenitor cells, bone marrow, adipose tissue, dermal, and inducible pluripotent stem cells. In this systematic review, we comprehensively investigated stem cell therapies in chronic wounds, summarizing the clinical, translational, and primary literature. A systematic search across PubMed, Embase, Web of Science, Google Scholar, and Cochrane Library yielded 22,454 articles, reduced to 44 studies after rigorous screening. Notably, adipose tissue-derived mesenchymal stem cells (AD-MSCs) emerged as an optimal choice due to their abundant supply, easy isolation, ex vivo proliferative capacities, and pro-angiogenic factor secretion. AD-MSCs have shown efficacy in various conditions, including peripheral arterial disease, diabetic wounds, hypertensive ulcers, bullous diabeticorum, venous ulcers, and post-Mohs micrographic surgery wounds. Delivery methods varied, encompassing topical application, scaffold incorporation, combination with plasma-rich proteins, and atelocollagen administration. Integration with local wound care practices resulted in reduced pain, shorter healing times, and improved cosmesis. Stem cell transplantation represents a potential therapeutic avenue, as transplanted stem cells not only differentiate into diverse skin cell types but also release essential cytokines and growth factors, fostering increased angiogenesis. This approach holds promise for intractable wounds, particularly chronic lower-leg wounds, and as a post-Mohs micrographic surgery intervention for healing defects through secondary intention. The potential reduction in healthcare costs and enhancement of patient quality of life further underscore the attractiveness of stem cell applications in wound care. This systematic review explores the clinical utilization of stem cells and stem cell products, providing valuable insights into their role as ancillary methods in treating chronic wounds.

Bone marrow-derived mesenchymal stem cells: A promising therapeutic option for the treatment of diabetic foot ulcers

Chronic wounds fail to heal through the three normal stages of healing (inflammatory, proliferative, and remodelling), resulting in a chronic tissue injury that is not repaired within the average time limit. Patients suffering from type 1 and type 2 diabetes are prone to develop diabetic foot ulcers (DFUs), which commonly develop into chronic wounds that are non treatable with conventional therapies. DFU develops due to various risk factors, such as peripheral neuropathy, peripheral vascular disease, arterial insufficiency, foot deformities, trauma and impaired resistance to infection. DFUs have gradually become a major problem in the health care system worldwide. In this review, we not only focus on the pathogenesis of DFU but also comprehensively summarize the outcomes of preclinical and clinical studies thus far and the potential therapeutic mechanism of bone marrow-derived mesenchymal stem cells (BMSCs) for the treatment of DFU. Based on the published results, BMSC transplantation can contribute to wound healing through growth factor secretion, anti-inflammation, differentiation into tissue-specific cells, neovascularization, re-epithelialization and angiogenesis in DFUs. Moreover, clinical trials showed that BMSC treatment in patients with diabetic ulcers improved ulcer healing and the ankle-brachial index, ameliorated pain scores, and enhanced claudication walking distances with no reported complications. In conclusion, although BMSC transplantation exhibits promising therapeutic potential in DFU treatment, additional studies should be performed to confirm their efficacy and long-term safety in DFU patients.

Role of stem cell therapies in treating chronic wounds: A systematic review

BACKGROUND

The impairment of cutaneous wound healing results in chronic, non-healing wounds that are caused by altered wound environment oxygenation, tissue injury, and permissive microbial growth. Current modalities for the treatment of these wounds inadequately address the complex changes involved in chronic wound pathogenesis. Consequently, stem cell therapies have emerged as a potential therapeutic modality to promote cutaneous regeneration through trophic and paracrine activity.

AIM

To investigate current literature regarding use of stem cell therapies for the clinical treatment of chronic, non-healing wounds.

METHODS

PubMed, EMBASE, Cochrane Library, Web of Science, and Scopus were queried with combinations of the search terms “mesenchymal stem cells,” “adult stem cells,” “embryonic stem cells,” “erythroid precursor cells,” “stem cell therapies,” and “chronic wounds” in order to find relevant articles published between the years of 2000 and 2019 to review a 20-year experience. Reference lists from the articles were reviewed to identify additional pertinent articles. Retrieved manuscripts (reviews, case reports/series, retrospective/prospective studies, and clinical trials) were evaluated by the authors for their depiction of clinical stem cell therapy use. Data were extracted from the articles using a standardized collection tool.

RESULTS

A total of 43 articles describing the use of stem cell therapies for the treatment of chronic wounds were included in this review. While stem cell therapies have been explored in in vitro and in vivo applications in the past, recent efforts are geared towards assessing their clinical role. A review of the literature revealed that adipose-derived stem cells, bone marrow-derived stem cells, bone marrow-derived mononuclear cells, epidermally-derived mesenchymal stem cells, fibroblast stem cells, keratinocyte stem cells, placental mesenchymal stem cells, and umbilical cord mesenchymal stem cells have all been employed in the treatment of chronic wounds of various etiologies. Most recently, embryonic stem cells have emerged as a novel stem cell therapy with the capacity for multifaceted germ cell layer differentiation. With the capacity for self-renewal and differentiation, stem cells can enrich existing cell populations in chronic wounds in order to overcome barriers impeding the progression of wound healing. Further, stem cell therapies can be utilized to augment cell engraftment, signaling and activity, and resultant patient outcomes.

CONCLUSION

Assessing observed clinical outcomes, potential for stem cell use, and relevant therapeutic challenges allows wound care stakeholders to make informed decisions regarding optimal treatment approaches for their patients’ chronic wounds.

Autologous bone marrow-derived cells for venous leg ulcers treatment: a pilot study

BACKGROUND

Chronic venous leg ulcers (VLUs) are a common problem in clinical practice and available treatments are not satisfactory. The use of adjuvant therapies in combination with lower limb compression may lead to improved healing rates. Chronic wounds are candidates for new strategies in the emergent field of regenerative medicine. Bone marrow-derived cells (BMDCs) contain cells and secrete cytokines known to participate in wound healing. Thus, BMDC therapy seems a logical strategy for the treatment of chronic wounds. Our objective was to evaluate feasibility, safety and initial clinical outcome of autologous BMDC therapy associated with standard treatment in patients with VLUs.

METHODS

We conducted an open-label, single-arm, prospective pilot clinical trial in four patients with six chronic VLUs. The study protocol was approved by the institutional and national review boards and ethics committees. Bone marrow was harvest, processed and then administered by multiple injections into the ulcers. All patients received standard treatment and non-healing characteristics of the VLUs were confirmed at study entry.

RESULTS

Ulcer size and wound pain evaluated 12 months after BMDC treatment were significantly reduced (P < 0.05). BMDC treatment was safe and well tolerated in long-term follow-up.

DISCUSSION

Despite the low number of patients studied, our results showed that autologous BMDC treatment could be a useful, feasible and safe procedure to enhance ulcer healing. However, randomized controlled trials with more patients are needed to address this question and translate this approach into clinical practice.

Efficacy of Cellular Therapy for Diabetic Foot Ulcer: A Meta-Analysis of Randomized Controlled Clinical Trials

Diabetes mellitus is a widely spread chronic disease with growing incidence worldwide, and diabetic foot ulcer is one of the most serious complications of diabetes. Cellular therapy has shown promise in the management of diabetic foot ulcer in many preclinical experiments and clinical researches. Here, we performed a meta-analysis to evaluate the efficacy and safety of cellular therapy in the management of diabetic foot ulcer. We systematically searched PubMed, MEDLINE, EMBASE, and Cochrane Library databases from inception to May 2017 for randomized controlled trials assessing the efficacy of cellular therapy in diabetic foot ulcer, and a meta-analysis was conducted. A total of 6 randomized controlled clinical trials involving 241 individuals were included in this meta-analysis. The results suggested that cellular therapy could help accelerating the healing of diabetic foot ulcer, presented as higher ankle-brachial index (mean difference = 0.17, 95% confidence interval [CI] = 0.11 to 0.23), higher transcutaneous oxygen pressure (standardized mean difference [SMD] = 1.43; 95% CI, 1.09– to 1.78), higher ulcer healing rate (relative risk [RR] = 1.78; 95% CI, 1.41 to 2.25), higher amputation-free survival (RR = 1.25; 95% CI, 1.11 to 1.40), and lower scale of pain (SMD = −1.69; 95% CI, −2.05 to −1.33). Furthermore, cellular therapy seemed to be safe, with no serious complications and low risk of short-term slight complications. Cellular therapy could accelerate the rate of diabetic foot ulcer healing and may be more efficient than standard therapy for diabetic foot treatment.

Treatment of human chronic wounds with autologous extracellular matrix/stromal vascular fraction gel: A STROBE-compliant study

Stem cell therapy is considered as the most promising treatment for chronic wounds. Extracellular matrix/stromal vascular fraction gel (ECM/SVF gel), an adipose-derived stem cell-based cytotherapy, has shown healing potential in experimental wounds in animal models. However, the effects of ECM/SVF gel on human chronic wounds have not been investigated. The aim of the present study is to investigate the therapeutic effect of ECM/SVF gel on human chronic wounds.Autologous ECM/SVF gel was prepared and used to treat patients with chronic wounds in clinics, with negative pressure wound therapy as the positive control. Wound healing rate per week and histological changes were performed.The average wound healing rate per week in the ECM/SVF gel group was 34.55 ± 11.18% compared with 10.16 ± 2.67% in the negative pressure wound therapy group (P < .001). Histological analysis with hematoxylin and eosin, Masson's trichrome staining, and CD31 immunohistochemistry showed less lymphocyte infiltration, more collagen accumulation, and more newly formed vessels in the ECM/SVF gel group treated skins compared to the control.ECM/SVF gel is an effective therapeutic option for chronic wound healing in clinics.

Adjuvant Biological Therapies in Chronic Leg Ulcers

Current biological treatments for non-healing wounds aim to address the common deviations in healing mechanisms, mainly inflammation, inadequate angiogenesis and reduced synthesis of extracellular matrix. In this context, regenerative medicine strategies, i.e., platelet rich plasmas and mesenchymal stromal cell products, may form part of adjuvant interventions in an integral patient management. We synthesized the clinical experience on ulcer management using these two categories of biological adjuvants. The results of ten controlled trials that are included in this systematic review favor the use of mesenchymal stromal cell based-adjuvants for impaired wound healing, but the number and quality of studies is moderate-low and are complicated by the diversity of biological products. Regarding platelet-derived products, 18 controlled studies investigated their efficacy in chronic wounds in the lower limb, but the heterogeneity of products and protocols hinders clinically meaningful quantitative synthesis. Most patients were diabetic, emphasizing an unmet medical need in this condition. Overall, there is not sufficient evidence to inform routine care, and further clinical research is necessary to realize the full potential of adjuvant regenerative medicine strategies in the management of chronic leg ulcers.

Stem Cells and Tissue Engineering: Regeneration of the Skin and Its Contents

In this review, the authors discuss the stages of skin wound healing, the role of stem cells in accelerating skin wound healing, and the mechanism by which these stem cells may reconstitute the skin in the context of tissue engineering.

A Retrospective Look at Integrating a Novel Regenerative Medicine Approach in Plastic Limb Reconstruction

Full-thickness wounds that have rendered patients candidates for amputation may require techniques that may include a combinatorial approach above traditional standard of care. The purpose of this retrospective study was to evaluate the effectiveness of an innovative approach whereby several therapies were combined to avoid amputation. Patients with full-thickness wounds who were previously recommended for amputation and were treated with the combinatorial approach of muscle flap reconstruction and concentrated bone marrow aspirate, platelet-rich plasma, INTEGRA Wound matrix, vacuum-assisted closure, and split-thickness skin grafts were assessed retrospectively. The mean age of the patients identified was 48 years (range, 34–66 years). The average size of the defects was 19.6 cm². All defects were successfully covered with medial hemisoleus, lateral hemisoleus, or peroneus brevis muscle flaps combined with split-thickness skin grafts, concentrated bone marrow aspirate, and platelet-rich plasma. All flaps healed with an average time to fixator removal of 8.3 weeks; there was 1 above-knee amputation that occurred approximately after successful wound closing and fixator removal. The combinatorial approach described here including several regenerative medicine tools is an effective means of lower limb reconstruction to avoid amputation.

Challenges in the Treatment of Chronic Wounds

Significance: Chronic wounds include, but are not limited, to diabetic foot ulcers, venous leg ulcers, and pressure ulcers. They are a challenge to wound care professionals and consume a great deal of healthcare resources around the globe. This review discusses the pathophysiology of complex chronic wounds and the means and modalities currently available to achieve healing in such patients. Recent Advances: Although often difficult to treat, an understanding of the underlying pathophysiology and specific attention toward managing these perturbations can often lead to successful healing. Critical Issues: Overcoming the factors that contribute to delayed healing are key components of a comprehensive approach to wound care and present the primary challenges to the treatment of chronic wounds. When wounds fail to achieve sufficient healing after 4 weeks of standard care, reassessment of underlying pathology and consideration of the need for advanced therapeutic agents should be undertaken. However, selection of an appropriate therapy is often not evidence based. Future Directions: Basic tenets of care need to be routinely followed, and a systematic evaluation of patients and their wounds will also facilitate appropriate care. Underlying pathologies, which result in the failure of these wounds to heal, differ among various types of chronic wounds. A better understanding of the differences between various types of chronic wounds at the molecular and cellular levels should improve our treatment approaches, leading to better healing rates, and facilitate the development of new more effective therapies. More evidence for the efficacy of current and future advanced wound therapies is required for their appropriate use.

Progenitor cell therapy for sacral pressure sore: a pilot study with a novel human chronic wound model

Introduction

Chronic wounds are a major health-care issue, but research is limited by the complexity and heterogeneity in terms of wound etiology as well as patient-related factors. A suitable animal model that replicates the situation in humans is not available. Therefore, the aim of the present work is to present a standardized human wound model and the data of a pilot study of topically applied progenitor cells in a sacral pressure sore.

Methods

Three patients underwent cell harvest from the iliac crest at the time of the initial debridement. Forty-eight hours after bone marrow harvest and debridement, the CD34⁺ selected cell suspension was injected into the wound. With the aid of a laser scanner, three-dimensional analyses of wound morphometry were performed until the defect was reconstructed with a local flap 3 weeks after debridement.

Results

Decreases in volume to 60% ± 6% of baseline on the sham side and to 52% ± 3% of baseline on the cell side were measured. Histologic work-up revealed no signs of metaplastic, dysplastic, or neoplastic proliferation/differentiation after progenitor cell treatment. CD34⁺ cells were detected in the biopsies of day 0.

Conclusions

The pressure sore wound model allows investigation of the initial 3 weeks after cell-based therapy. Objective outcome analysis in terms of wound volume and histology can be performed without, or with, minimal additional morbidity, and the anatomy of the sacral area allows a control and study side in the same patient. Therefore, this model can serve as a standard for wound-healing studies.

Trial registration

ClinicalTrials.gov NCT00535548.

An in vitro skin model to study the effect of mesenchymal stem cells in wound healing and epidermal regeneration

The development of new wound therapies, such as bioengineered skin equivalents, is an ongoing process. Multi-potent mesenchymal stem cells (MSCs) give rise to many tissue lineages and have been implicated in wound healing making them a potential candidate for cell-based bioengineered products for injured tissue. In this study, we investigated the mesenchymal/epithelial interactions of cultured MSCs in comparison to cultured fibroblasts on epidermal proliferation, differentiation, and extracellular matrix (ECM) protein expression using a de-epidermalized dermis (DED) skin model. We also studied whether MSCs can transdifferentiate to keratinocytes using the same model. Keratinocytes were cultured on unseeded DED or DED populated with fibroblasts or MSCs at an air-liquid interface to induce epidermal differentiation. Fibroblasts or MSCs were also seeded on the papillary surface of the DED alone or on the reticular surface. General histology and immunostaining was performed on the skin equivalents to examine the expression of pan keratin (K) (K1, K5, K6, and K18) and protein markers for epidermal differentiation (K10), hyperproliferation (K6), proliferation (PCNA), ECM component (collagen type IV), and mesenchymal marker (vimentin). Keratinocyte-fibroblast skin model and keratinocyte-MSC skin model both displayed an epidermal phenotype similar to epidermis in vivo. Positive expression of proliferation, differentiation and ECM protein markers was observed. MSCs failed to adopt an epithelial phenotype in the DED skin model. Our findings highlight the potential use of MSCs in bioengineered tissue for the treatment of wounds.

Impacts of bone marrow aspirate and peripheral blood derived platelet-rich plasma on the wound healing in chronic ischaemic limb

Platelet rich plasma (PRP) has attracted attention as a safe and cost-effective source of growth factors that stimulate cells to regenerate tissue. Bone marrow cells are also estimated as an effective material for treating chronic ulcers. With the same technique to concentrate PRP from peripheral blood, bone marrow aspirate was processed and marrow cells were concentrated as well as platelets. Impact of PRP derived from bone marrow aspirate (bm-PRP) and that from peripheral blood (pb-PRP) on wound healing of persistent ischaemic rabbits' limbs were observed. Full thickness skin defects were made on the thighs, which had been treated to be persistent ischaemic status 3 weeks previously. Saline, pb-PRP, and bm-PRP were injected into the wound floor, respectively. Skin defected areas on ischaemic limbs were significantly wider than those on non-ischaemic limbs. bm-PRP injected wounds showed a significantly smaller skin defect area compared with pb-PRP and ischaemic-saline wounds at all time points. Fluorescently dyed cells of bm-PRP, injected into the wounds, could be traced 4 weeks after, whereas those of pb-PRP could be traced no more than 2 weeks. Wound healing on an ischaemic limb was accelerated with bm-PRP, whereas pb-PRP could not show any significance from saline. This difference can be attributed to the kind of cells contained in the PRPs. Injection of bm-PRP is a good candidate for treating wounds on ischaemic limbs.

Stem cell therapy for lower extremity diabetic ulcers: where do we stand?

The impairment of wound healing in diabetic patients is an important clinical problem affecting millions of patients worldwide. Various clinical and basic science studies show that stem cell therapy, as a regenerative medical therapy, can be a good solution. In this paper, we begin with an introduction of the cellular mechanism of the diabetic ulcer. We will then discuss the advantages and limitations of various stem cell therapies that have been under extensive recent study.

Marrow-derived stromal cell delivery on fibrin microbeads can correct radiation-induced wound-healing deficits

Skin that is exposed to radiation has an impaired ability to heal wounds. This is especially true for whole body irradiation, where even moderate non-lethal doses can result in wound healing deficits. Our previous attempts to administer dermal cells locally to wounds to correct radiation-induced deficits were hampered by poor cell retention. Here we improve the outcome by using biodegradable fibrin microbeads (FMB) to isolate a population of mesenchymal marrow-derived stromal cells (MSC) from murine bone marrow by their specific binding to the fibrin matrix, culture them to high density in vitro and deliver them as MSC on FMB at the wound site. MSC are retained and proliferate locally and assist wounds gain tensile strength in whole body irradiated mice with or without additional skin only exposure. MSC-FMB were effective in 2 different mouse strains but were ineffective across a major histocompatability barrier. Remarkably, irradiated mice whose wounds were treated with MSC-FMB showed enhanced hair regrowth suggesting indirect effect on the correction of radiation-induced follicular damage. Further studies showed that additional wound healing benefit could be gained by administration of G-CSF and AMD3100. Collagen strips coated with haptides and MSCs were also highly effective in correcting radiation-induced wound healing deficits.

Progress in stem cell therapy for the diabetic foot

The diabetic foot is a common and severe complication of diabetes comprising a group of lesions including vasculopathy, neuropathy, tissue damage and infection. Vasculopathy due to ischemia is a major contributor to the pathogenesis, natural history and outcome of the diabetic foot. Despite conventional revascularization interventions including angioplasty, stenting, atherectomy and bypass grafts to vessels, a high incidence of amputation persists. The need to develop alternative therapeutic options is compelling; stem cell therapy aims to increase revascularization and alleviate limb ischemia or improve wound healing by stimulating new blood vessel formation, and brings new hope for the treatment of the diabetic foot.

Comprehensive review of the clinical application of autologous mesenchymal stem cells in the treatment of chronic wounds and diabetic bone healing

Chronic ulcerations are a physical and financial burden to the health and economic establishment in the United States and Worldwide. Improvements in biotechnology and knowledge in stem cell applications have progressed and basic science results are making their way slowly into the clinical arena. Chronic wounds and diabetic bone healing are the key components in the limb salvage of the common diabetic foot. We have examined the current available literature and present the latest on stem cells applications as a novel clinical technique in the treatment of chronic wound and diabetic bone healing and their impact in the treatment paradigm of patients.

Bone marrow mesenchymal cells: how do they contribute to tissue repair and are they really stem cells?

Adult stem cells typically generate the cell types of the tissue in which they reside, and thus the range of their differentiation is considered limited. Bone marrow mesenchymal stem cells (MSCs) are different from other somatic stem cells in that they differentiate not only into the same mesodermal-lineage such as bone, cartilage, and adipocytes but also into other lineages of ectodermal and endodermal cells. Thus, MSCs are a unique type of adult stem cells. In addition, MSCs home to damaged sites, differentiate into cells specific to the tissue and contribute to tissue repair. Therefore, application of MSCs in the treatment of various diseases, including liver dysfunction, myocardial infarction, and central nervous system repair, has been initiated. Because MSCs are generally harvested as adherent cells from bone marrow aspirates, however, they comprise heterogeneous cell populations and their wide-ranging differentiation ability and repair functions are not yet clear. Recent evidence suggests that a very small subpopulation of cells that assume a repair function with the ability to differentiate into trilineage cells resides among human MSCs and effective utilization of such cells is expected to improve the repair effect of MSCs. This review summarizes recent advances in the clarification of MSC properties and discusses future perspectives.

Treatment of non-healing wounds with autologous bone marrow cells, platelets, fibrin glue and collagen matrix

BACKGROUND AIMS

Recalcitrant diabetic wounds are not responsive to the most common treatments. Bone marrow-derived stem cell transplantation is used for the healing of chronic lower extremity wounds.

METHODS

We report on the treatment of eight patients with aggressive, refractory diabetic wounds. The marrow-derived cells were injected/applied topically into the wound along with platelets, fibrin glue and bone marrow-impregnated collagen matrix.

RESULTS

Four weeks after treatment, the wound was completely closed in three patients and significantly reduced in the remaining five patients.

CONCLUSIONS

Our study suggests that the combination of the components mentioned can be used safely in order to synergize the effect of chronic wound healing.

Adipose-derived stem cells for skin regeneration

Intractable skin ulcers resulting from diabetes, ischemia and collagen diseases represent significant problems with few solutions. Cell-based therapy may hold promise in overcoming such disorders. In order to establish a suitable experimental model for the treatment of such ulcers using stem cells, this chapter describes detailed methods for: (1) isolation of stem cells from adipose tissue, termed adipose-derived stem cells (ASCs), (2) preparing a hybrid-type artificial dermis that consists of a type I collagen sponge and ASCs, (3) preparing intractable ulcers using Mitomycin C, and (4) evaluating the effect of wound healing histologically. ASCs seeded onto a type I collagen sponge are applied to intractable ulcers induced by topical application of Mitomycin C. Histological evaluation after 1 and 2 weeks revealed an increase in capillary density and granulation thickness of the hybrid-type artificial dermis. These findings suggest that ASCs may have a positive effect on wound healing and may be a useful tool for future cell-based therapy.

Acceleration of diabetic wound healing by low-dose radiation is associated with peripheral mobilization of bone marrow stem cells

In this study we investigated the effect of repeated low-dose radiation exposure (75 mGy X ray) on skin wound healing in a rat model of diabetes. A skin wound was made on the backs of diabetic and age-matched control rats 60 days after diabetes was induced by a single injection of streptozotocin. Rats with skin wounds were immediately treated with whole-body radiation daily for 5, 10 or 15 days with a 2-day break every 5 days. Wound size was estimated 5, 10 and 15 days after wound formation. Repeated exposure of diabetic rats to low-dose radiation significantly accelerated skin wound healing compared to the nonirradiated diabetic group. Furthermore, low-dose radiation-induced improvement in healing was associated with increases in bone marrow and circulating CD31(+)/CD34(+) stem cells, vessel regeneration and cell proliferation in the wound tissue, and matrix metalloproteinase 2 and 9 expression. Therefore, we conclude that the acceleration of wound healing in diabetic rats by repeated exposure to low-dose radiation is associated with stimulation of bone marrow stem cell proliferation and peripheral mobilization.

Diabetic foot ulcers: effects of hyperoxia and SDF-1α on endothelial progenitor cells

Diabetes mellitus is a common disease afflicting many people. In addition to coronary artery disease, diabetic retinopathy and renal failure, diabetic patients face abnormal wound healing and have increased lower extremity ulcers and amputations. In diabetes, wound healing is altered due to both macrovascular and microvascular processes. While the former can be addressed with surgical intervention, the latter is more difficult to correct. Neovascularization within the granulation tissue via angiogenesis and vasculogenesis is critical for wound healing. Endothelial progenitor cells (EPCs) have been implicated in vasculogenesis. Mobilization of EPCs from the bone marrow is impaired in diabetes and homing of EPCs to the wound is also abnormal. Recent studies show that hyperoxia and administration of exogenous stromal-derived factor-1α increases circulatory and wound levels of EPCs and improves wound healing in diabetic mice. These findings have great potential for translation into human counterparts as the treatment for this prevalent disease matures.

Notch pathway modulation on bone marrow-derived vascular precursor cells regulates their angiogenic and wound healing potential

Bone marrow (BM) derived vascular precursor cells (BM-PC, endothelial progenitors) are involved in normal and malignant angiogenesis, in ischemia and in wound healing. However, the mechanisms by which BM-PC stimulate the pre-existing endothelial cells at sites of vascular remodelling/recovery, and their contribution towards the formation of new blood vessels are still undisclosed. In the present report, we exploited the possibility that members of the Notch signalling pathway, expressed by BM-PC during endothelial differentiation, might regulate their pro-angiogenic or pro-wound healing properties. We demonstrate that Notch pathway modulates the adhesion of BM-PC to extracellular matrix (ECM) in vitro via regulation of integrin alpha3beta1; and that Notch pathway inhibition on BM-PC impairs their capacity to stimulate endothelial cell tube formation on matrigel and to promote endothelial monolayer recovery following wounding in vitro. Moreover, we show that activation of Notch pathway on BM-PC improved wound healing in vivo through angiogenesis induction. Conversely, inoculation of BM-PC pre-treated with a gamma secretase inhibitor (GSI) into wounded mice failed to induce angiogenesis at the wound site and did not promote wound healing, presumably due to a lower frequency of BM-PC at the wound area. Our data suggests that Notch pathway regulates BM-PC adhesion to ECM at sites of vascular repair and that it also regulates the capacity of BM-PC to stimulate angiogenesis and to promote wound healing. Drug targeting of the Notch pathway on BM-PC may thus represent a novel strategy to modulate neo-angiogenesis and vessel repair.