Transplantation of ex vivo expanded endothelial progenitor cells for therapeutic neovascularization

Evaluation of ex vivo produced endothelial progenitor cells for autologous transplantation in primates

Background

Autologous transplantation of endothelial progenitor cells (EPCs) is a promising therapeutic approach in the treatment of various vascular diseases. We previously reported a two-step culture system for scalable generation of human EPCs derived from cord blood CD34⁺ cells ex vivo. Here, we now apply this culture system to expand and differentiate human and nonhuman primate EPCs from mobilized peripheral blood (PB) CD34⁺ cells for the therapeutic potential of autologous transplantation.

Methods

The human and nonhuman primate EPCs from mobilized PB CD34⁺ cells were cultured according to our previously reported system. The generated adherent cells were then characterized by the morphology, surface markers, nitric oxide (NO)/endothelial NO synthase (eNOS) levels and Dil-acetylated low-density lipoprotein (Dil-Ac-LDL) uptake/fluorescein isothiocyanate (FITC)-lectin binding actives. Furthermore, the efficacy and safety studies were performed by autologous transplantation via hepatic portal vein injection in a nonhuman primate model with acute liver sinusoidal endothelial cell injury.

Results

The mobilized PB CD34⁺ cells from both human and nonhuman primate were efficiently expanded and differentiated. Over 2 × 10⁸ adherent cells were generated from 20 mL mobilized primate PB (1.51 × 10⁶ ± 3.39 × 10⁵ CD34⁺ cells) by 36-day culture and more than 80% of the produced cells were identified as EPCs/endothelial cells (ECs). In the autologous transplant model, the injected EPC/ECs from nonhuman primate PB were scattered in the intercellular spaces of hepatocytes at the hepatic tissues 14 days post-transplantation, indicating successful migration and reconstitution in the liver structure as the functional EPCs/ECs.

Conclusions

We successfully applied our previous two-step culture system for the generation of primate EPCs from mobilized PB CD34⁺ cells, evaluated the phenotypes ex vivo, and transplanted autologous EPCs/ECs in a nonhuman primate model. Our study indicates that it may be possible for these ex-vivo high-efficient expanded EPCs to be used in clinical cell therapy.

Growth Factor-Free Pre-vascularization of Cell Sheets for Tissue Engineering

The therapeutic efficacy of tissue-engineered constructs is often compromised by inadequate inosculation and neo-vascularization. This problem is considered one of the biggest hurdles in the field and finding a solution is currently the focus of a great fraction of the research community. Many of the methodologies designed to address this issue propose the use of endothelial cells and angiogenic growth factors, or combinations of both, to accelerate neo-vascularization after transplantation. However, an adequate solution is still elusive. In this context, we describe a methodology that combines the use of the stromal vascular fraction (SVF) isolated from adipose tissue with low oxygen culture to produce pre-vascularized cell sheets as angiogenic tools for Tissue Engineering. The herein proposed approach takes advantage of the SVF angiogenic nature conferred by adipose stem cells, endothelial progenitors, endothelial and hematopoietic cells, and pericytes and further potentiates it using low oxygen, or hypoxic, culture. Freshly isolated nucleated SVF cells are cultured in hyperconfluent conditions under hypoxia (pO2 = 5 %) for up to 5 days in medium without extrinsic growth factors enabling the generation of contiguous sheets as described by the cell sheet engineering technique. Flow cytometry and immunocytochemistry allow confirming the phenotype of the different cell types composing the cell-sheets as well the organization of the CD31(+) cells in branched and highly complex tube-like structures. Overall, a simple and flexible approach to promote growth factor-free pre-vascularization of cell sheets for tissue engineering (TE) applications is described.

Angiogenic and osteogenic potentials of dental stem cells in bone tissue engineering

Manipulation of dental stem cells (DSCs) using current technologies in tissue engineering unveil promising prospect in regenerative medicine. DSCs have shown to possess angiogenic and osteogenic potential in both in vivo and in vitro. Neural crest derived DSCs can successfully be isolated from various dental tissues, exploiting their intrinsic great differentiation potential. In this article, researcher team intent to review the characteristics of DSCs, with focus on their angiogenic and osteogenic differentiation lineage. Clinical data on DSCs are still lacking to prove their restorative abilities despite extensive contemporary literature, warranting research to further validate their application for bone tissue engineering.

Harnessing Sphingosine-1-Phosphate Signaling and Nanotopographical Cues To Regulate Skeletal Muscle Maturation and Vascularization

Despite possessing substantial regenerative capacity, skeletal muscle can suffer from loss of function due to catastrophic traumatic injury or degenerative disease. In such cases, engineered tissue grafts hold the potential to restore function and improve patient quality of life. Requirements for successful integration of engineered tissue grafts with the host musculature include cell alignment that mimics host tissue architecture and directional functionality, as well as vascularization to ensure tissue survival. Here, we have developed biomimetic nanopatterned poly(lactic-co-glycolic acid) substrates conjugated with sphingosine-1-phosphate (S1P), a potent angiogenic and myogenic factor, to enhance myoblast and endothelial maturation. Primary muscle cells cultured on these functionalized S1P nanopatterned substrates developed a highly aligned and elongated morphology and exhibited higher expression levels of myosin heavy chain, in addition to genes characteristic of mature skeletal muscle. We also found that S1P enhanced angiogenic potential in these cultures, as evidenced by elevated expression of endothelial-related genes. Computational analyses of live-cell videos showed a significantly improved functionality of tissues cultured on S1P-functionalized nanopatterns as indicated by greater myotube contraction displacements and velocities. In summary, our study demonstrates that biomimetic nanotopography and S1P can be combined to synergistically regulate the maturation and vascularization of engineered skeletal muscles.

Simultaneous harvesting of endothelial progenitor cells and mesenchymal stem cells from the human umbilical cord

The human umbilical cord (UC) is usually discarded as biological waste. However, it has attracted interest as a source of cells including endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs), which have demonstrated enormous potential in regenerative medicine. The present study describes a convenient protocol that has been developed to sequentially extract these two cell types from a single UC. EPCs which had properties of progenitor cells were successfully isolated from the UC vein. These cells had cobble-shaped morphology and expressed Flt-1, KDR, VE-cadherin, von Willebrand factor and CD31 mRNA, in addition to CD73, CD105 and vascular endothelial growth factor receptor-2. In addition to absorbing fluorescent-labeled acetylated low density protein and binding to fluorescein isothiocyanate-UEA-l, they were able to form vascular tube-like structures on Matrigel. Typical fibroblast-like cells, which were isolated from the Wharton's jelly, were confirmed to be MSCs by their expression of CD73, CD90 and CD105, and their ability to differentiate into adipocytes and osteoblasts. Thus, the human UC-derived cells may be suitable for use in tissue engineering and cell therapy.

Identification of a novel angiogenic peptide from periostin

Angiogenic peptides have therapeutic potential for the treatment of chronic ischemic diseases. Periostin, an extracellular matrix protein expressed in injured tissues, promotes angiogenesis and tissue repair. We previously reported that in vivo administration of both recombinant full-length protein and the first FAS I domain of periostin alleviated peripheral artery occlusive disease by stimulating the migration of humane endothelial colony forming cells (ECFCs) and subsequent angiogenesis. In the present study, we ascertained the peptide sequence responsible for the periostin-induced angiogenesis. By serial deletion mapping of the first FAS I domain, we identified a peptide sequence (amino acids 142–151) of periostin for stimulation of chemotactic migration, adhesion, proliferation and endothelial tube formation of human ECFCs in vitro. Chemotactic migration of ECFCs induced by the periostin peptide was blocked by pre-incubation with an anti-β5 integrin neutralizing antibody. Treatment of ECFCs with the periostin peptide led to phosphorylation of both AKT and ERK, and pretreatment of ECFCs with the MEK-ERK pathway inhibitor U0126 or the PI3K-AKT pathway inhibitors, LY294002 or Wortmannin, blocked the periostin peptide-stimulated migration of ECFCs. These results suggest that the synthetic periostin peptide can be applied for stimulating angiogenic and therapeutic potentials of ECFCs.

Microparticles Carrying Peroxisome Proliferator-Activated Receptor Alpha Restore the Reduced Differentiation and Functionality of Bone Marrow-Derived Cells Induced by High-Fat Diet

Metabolic pathologies such as diabetes and obesity are associated with decreased level of circulating and bone marrow (BM)-derived endothelial progenitor cells (EPCs). It is known that activation of peroxisome proliferator-activated receptor alpha (PPARα) may stimulate cell differentiation. In addition, microparticles (MPs), small membrane vesicles produced by activated and apoptotic cells, are able to reprogram EPCs. Here, we evaluated the role of MPs carrying PPARα on both phenotype and function of progenitor cells from mice fed with a high-fat diet (HFD). HFD reduced circulating EPCs and, after 7 days of culture, BM-derived EPCs and monocytic progenitor cells from HFD-fed mice displayed impaired differentiation. At the same time, we show that MPs bearing PPARα, MPs^PPARα+/+ , increased the differentiation of EPCs and monocytic progenitors from HFD-fed mice, whereas MPs taken from PPARα knockout mice (MPs^PPARα-/- ) had no effect on the differentiation of all types of progenitor cells. Furthermore, MPs^PPARα+/+ increased the ability of progenitor cells to promote in vivo angiogenesis in mice fed with HFD. The in vitro and in vivo effects of MPs^PPARα+/+ were abolished in presence of MK886, a specific inhibitor of PPARα. Collectively, these data highlight the ability of MPs carrying PPARα to restore the failed differentiation and functionality of BM-derived cells induced by HFD. Stem Cells Translational Medicine 2018;7:135-145.

Metabolic shift in density-dependent stem cell differentiation

BACKGROUND

Vascular progenitor cells (VPCs) derived from embryonic stem cells (ESCs) are a valuable source for cell- and tissue-based therapeutic strategies. During the optimization of endothelial cell (EC) inductions from mouse ESCs using our staged and chemically-defined induction methods, we found that cell seeding density but not VEGF treatment between 10 ng/mL and 40 ng/mL was a significant variable directing ESCs into FLK1⁺ VPCs during stage 1 induction. Here, we examine potential contributions from cell-to-cell signaling or cellular metabolism in the production of VPCs from ESCs seeded at different cell densities.

METHODS

Using 1D ¹H-NMR spectroscopy, transcriptomic arrays, and flow cytometry, we observed that the density-dependent differentiation of ESCs into FLK1⁺ VPCs positively correlated with a shift in metabolism and cellular growth.

RESULTS

Specifically, cell differentiation correlated with an earlier plateauing of exhaustive glycolysis, decreased lactate production, lower metabolite consumption, decreased cellular proliferation and an increase in cell size. In contrast, cells seeded at a lower density of 1,000 cells/cm² exhibited increased rates of glycolysis, lactate secretion, metabolite utilization, and proliferation over the same induction period. Gene expression analysis indicated that high cell seeding density correlated with up-regulation of several genes including cell adhesion molecules of the notch family (NOTCH1 and NOTCH4) and cadherin family (CDH5) related to vascular development.

CONCLUSIONS

These results confirm that a distinct metabolic phenotype correlates with cell differentiation of VPCs.

Mesenchymal stem/stromal cells enhance engraftment, vasculogenic and pro-angiogenic activities of endothelial colony forming cells in immunocompetent hosts

The clinical use of endothelial colony forming cells (ECFC) is hampered by their restricted engraftment. We aimed to assess engraftment, vasculogenic and pro-angiogenic activities of ECFC in immunocompetent (C57BL/6: WT) or immunodeficient (rag1 -/- C57BL/6: Rag1) mice. In addition, the impact of host immune system was investigated where ECFC were co-implanted with mesenchymal stem/stromal cells (MSC) from adult bone marrow (AdBM-MSC), fetal bone marrow (fBM-MSC), fetal placental (fPL-MSC), or maternal placental (MPL-MSC). Transplantation of ECFCs in Matrigel plugs resulted in less cell engraftment in WT mice compared to Rag1 mice. Co-implantation with different MSCs resulted in a significant increase in cell engraftment up to 9 fold in WT mice reaching levels of engraftment observed when using ECFCs alone in Rag1 mice but well below levels of engraftment with MSC-ECFC combination in Rag1 recipients. Furthermore, MSCs did not reduce murine splenic T cell proliferation in response to ECFCs in vitro. ECFCs enhanced the murine neo-vascularization through paracrine effect, but with no difference between Rag1 and WT mice. In conclusions, the host adaptive immune system affects the engraftment of ECFCs. MSC co-implantation improves ECFC engraftment and function even in immunocompetent hosts mostly through non-immune mechanisms.

Fresh Noncultured Endothelial Progenitor Cells Improve Neonatal Lung Hyperoxia-Induced Alveolar Injury

Treatment of preterm human infants with high oxygen can result in disrupted lung alveolar and vascular development. Local or systemic administration of endothelial progenitor cells (EPCs) is reported to remedy such disruption in animal models. In this study, the effects of both fresh (enriched for KDR) and cultured bone marrow (BM)-derived cell populations with EPC characteristics were examined following hyperoxia in neonatal mouse lungs. Intraperitoneal injection of fresh EPCs into five-day-old mice treated with 90% oxygen resulted in full recovery of hyperoxia-induced alveolar disruption by 56 days of age. Partial recovery in septal number following hyperoxia was observed following injection of short-term cultured EPCs, yet aberrant tissue growths appeared following injection of long-term cultured cells. Fresh and long-term cultured cells had no impact on blood vessel development. Short-term cultured cells increased blood vessel number in normoxic and hyperoxic mice by 28 days but had no impact on day 56. Injection of fresh EPCs into normoxic mice significantly reduced alveolarization compared with phosphate buffered saline-injected normoxic controls. These results indicate that fresh BM EPCs have a higher and safer corrective profile in a hyperoxia-induced lung injury model compared with cultured BM EPCs but may be detrimental to the normoxic lung. The appearance of aberrant tissue growths and other side effects following injection of cultured EPCs warrants further investigation. Stem Cells Translational Medicine 2017;6:2094-2105.

Stem cell-based peripheral vascular regeneration

Chronic critical limb ischemia (CLI) represents an end-stage manifestation of peripheral arterial disease (PAD). CLI patients are at very high risk of amputation and cardiovascular complications, leading to severe morbidity and mortality. Because many patients with CLI are ineligible for conventional revascularization procedures, it is urgently needed to explore alternative strategies to improve blood supply in the ischemic tissue. Although researchers initially focused on gene/protein therapy using proangiogenic growth factors/cytokines, recent discovery of somatic stem/progenitor cells including bone marrow (BM)-derived endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) has drastically developed the field of therapeutic angiogenesis for CLI. Overall, early phase clinical trials demonstrated that stem/progenitor cell therapies may be safe, feasible and potentially effective. However, only few late-phase clinical trials have been conducted. This review provides an overview of the preclinical and clinical reports to demonstrate the usefulness and the current limitations of the cell-based therapies.

The angiogenic properties of human adipose-derived stem cells (HASCs) are modulated by the High mobility group box protein 1 (HMGB1)

Peripheral arterial disease (PAD), is a major health problem. Many studies have been focused on the possibilities of treatment offered by vascular regeneration. Human adipose-derived stem cells (HASCs), multipotent CD34+ stem cells found in the stromal-vascular fraction of adipose tissues, which are capable to differentiate into multiple mesenchymal cell types. The High mobility group box 1 protein (HMGB1) is a nuclear protein involved in angiogenesis. The aim of the study was to define the role of HMGB1 in cell therapy with HASCs, in an animal model of PAD. We induced unilateral ischemia in mice and we treated them with HASCs, with the specific HMGB1-inihibitor BoxA, with HMGB1 protein, and with the specific VEGF inhibitor sFlt1, alternately or concurrently. We measured the blood flow recovery in all mice. Immunohistochemical and ELISA analyses was performed to evaluate the number of vessels and the VEGF tissue content. None auto-amputation occurred and there have been no rejection reactions to the administration of HASCs. Animals co-treated with HASCs and HMGB1 protein had an improved blood flow recovery, compared to HASCs-treated mice. The post-ischemic angiogenesis was reduced when the HMGB1 pathway was blocked or when the VEGF activity was inhibited, in mice co-treated with HASCs and HMGB1. In conclusion, the HASCs treatment can be used in a mouse model of PAD to induce post-ischemic angiogenesis, modulating angiogenesis by HMGB1. This effect is mediated by VEGF activity. Although further data are needed, these findings shed light on possible new cell treatments for patients with PAD.

SCF-KIT signaling induces endothelin-3 synthesis and secretion: Thereby activates and regulates endothelin-B-receptor for generating temporally- and spatially-precise nitric oxide to modulate SCF- and or KIT-expressing cell functions

We demonstrate that SCF-KIT signaling induces synthesis and secretion of endothelin-3 (ET3) in human umbilical vein endothelial cells and melanoma cells in vitro, gastrointestinal stromal tumors, human sun-exposed skin, and myenteric plexus of human colon post-fasting in vivo. This is the first report of a physiological mechanism of ET3 induction. Integrating our finding with supporting data from literature leads us to discover a previously unreported pathway of nitric oxide (NO) generation derived from physiological endothelial NO synthase (eNOS) or neuronal NOS (nNOS) activation (referred to as the KIT-ET3-NO pathway). It involves: (1) SCF-expressing cells communicate with neighboring KIT-expressing cells directly or indirectly (cleaved soluble SCF). (2) SCF-KIT signaling induces timely local ET3 synthesis and secretion. (3) ET3 binds to ETBR on both sides of intercellular space. (4) ET3-binding-initiated-ETBR activation increases cytosolic Ca²⁺, activates cell-specific eNOS or nNOS. (5) Temporally- and spatially-precise NO generation. NO diffuses into neighboring cells, thus acts in both SCF- and KIT-expressing cells. (6) NO modulates diverse cell-specific functions by NO/cGMP pathway, controlling transcriptional factors, or other mechanisms. We demonstrate the critical physiological role of the KIT-ET3-NO pathway in fulfilling high demand (exceeding basal level) of endothelium-dependent NO generation for coping with atherosclerosis, pregnancy, and aging. The KIT-ET3-NO pathway most likely also play critical roles in other cell functions that involve dual requirement of SCF-KIT signaling and NO. New strategies (e.g. enhancing the KIT-ET3-NO pathway) to harness the benefit of endogenous eNOS and nNOS activation and precise NO generation for correcting pathophysiology and restoring functions warrant investigation.

Endothelial and cardiac progenitor cells for cardiovascular repair: A controversial paradigm in cell therapy

Stem cells have the potential to differentiate into cardiovascular cell lineages and to stimulate tissue regeneration in a paracrine/autocrine manner; thus, they have been extensively studied as candidate cell sources for cardiovascular regeneration. Several preclinical and clinical studies addressing the therapeutic potential of endothelial progenitor cells (EPCs) and cardiac progenitor cells (CPCs) in cardiovascular diseases have been performed. For instance, autologous EPC transplantation and EPC mobilization through pharmacological agents contributed to vascular repair and neovascularization in different animal models of limb ischemia and myocardial infarction. Also, CPC administration and in situ stimulation of resident CPCs have been shown to improve myocardial survival and function in experimental models of ischemic heart disease. However, clinical studies using EPC- and CPC-based therapeutic approaches have produced mixed results. In this regard, intracoronary, intra-myocardial or intramuscular injection of either bone marrow-derived or peripheral blood progenitor cells has improved pathological features of tissue ischemia in humans, despite modest or no clinical benefit has been observed in most cases. Also, the intriguing scientific background surrounding the potential clinical applications of EPC capture stenting is still waiting for a confirmatory proof. Moreover, clinical findings on the efficacy of CPC-based cell therapy in heart diseases are still very preliminary and based on small-size studies. Despite promising evidence, widespread clinical application of both EPCs and CPCs remains delayed due to several unresolved issues. The present review provides a summary of the different applications of EPCs and CPCs for cardiovascular cell therapy and underlies their advantages and limitations.

Increased levels of circulating CD34+ cells in neovascular age-related macular degeneration: relation with clinical and OCT features

PURPOSE

To investigate the levels of circulating CD34+ stem cells in patients with neovascular type age-related macular degeneration (AMD) and its relation with clinical and optical coherence tomography (OCT) findings.

METHODS

The study consisted of 55 patients: 28 patients (18 male and 10 female) with neovascular type AMD as a study group and 27 patients (12 male and 15 female) scheduled for cataract surgery as a control group. The level of CD34+ stem cells was measured by flow cytometry. Demographic and clinical data were recorded.

RESULTS

The mean ages of patients in the study and control groups were 71 ± 8 and 68 ± 6 years, respectively. There was no statistically significant difference in terms of age, sex, or systemic disease association between study and control groups. However, smoking status was significantly higher in the study group (67.9% vs 37.0%; p = 0.02). Stem cell levels were significantly higher in the study group (1.5 ± 0.9 vs 0.5 ± 0.3; p<0.001), but there was no relation between stem cell levels and clinical and OCT findings.

CONCLUSIONS

Increased circulating CD34+ stem cell levels were observed in patients with choroidal neovascular membrane associated with AMD, but no significant relation was found between cell levels and clinical and OCT findings.

Curcumin induces therapeutic angiogenesis in a diabetic mouse hindlimb ischemia model via modulating the function of endothelial progenitor cells

Background

Neovascularization is impaired in diabetes mellitus, which leads to the development of peripheral arterial disease and is mainly attributed to the dysfunction of endothelial progenitor cells (EPCs). Previous studies proved the promotional effect of curcumin on neovascularization in wound healing of diabetes. Thus, we hypothesize that curcumin could promote neovascularization at sites of hindlimb ischemia in diabetes and might take effect via modulating the function of EPCs.

Methods

Streptozotocin-induced type 1 diabetic mice and nondiabetic mice both received unilateral hindlimb ischemic surgery. Curcumin was then administrated to the mice by lavage for 14 days consecutively. Laser Doppler perfusion imaging was conducted to demonstrate the blood flow reperfusion. Capillary density was measured in the ischemic gastrocnemius muscle. In addition, angiogenesis, migration, proliferation abilities, and senescence were determined in EPCs isolated from diabetic and nondiabetic mice. Quantitative PCR was then used to determine the mRNA expression of vascular endothelial growth factor (VEGF) and angiopoetin-1 (Ang-1) in EPCs.

Results

Curcumin application to type 1 diabetic mice significantly improved blood reperfusion and increased the capillary density in ischemic hindlimbs. The in-vitro study also revealed that the angiogenesis, migration, and proliferation abilities of EPCs and the number of senescent EPCs were reversed by curcumin application. Quantitative PCR confirmed the overexpression of VEGF-A and Ang-1 in EPCs after curcumin treatment.

Conclusion

Curcumin could enhance neovascularization via promoting the function of EPCs in a diabetic mouse hindlimb ischemia model.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0636-9) contains supplementary material, which is available to authorized users.

Angiogenic conditioning of peripheral blood mononuclear cells promotes fracture healing

Objectives

The objective of this study was to investigate the therapeutic effect of peripheral blood mononuclear cells (PBMNCs) treated with quality and quantity control culture (QQ-culture) to expand and fortify angiogenic cells on the acceleration of fracture healing.

Methods

Human PBMNCs were cultured for seven days with the QQ-culture method using a serum-free medium containing five specific cytokines and growth factors. The QQ-cultured PBMNCs (QQMNCs) obtained were counted and characterised by flow cytometry and real-time polymerase chain reaction (RT-PCR). Angiogenic and osteo-inductive potentials were evaluated using tube formation assays and co-culture with mesenchymal stem cells with osteo-inductive medium in vitro. In order to evaluate the therapeutic potential of QQMNCs, cells were transplanted into an immunodeficient rat femur nonunion model. The rats were randomised into three groups: control; PBMNCs; and QQMNCs. The fracture healing was evaluated radiographically and histologically.

Results

The total number of PBMNCs was decreased after QQ-culture, however, the number of CD34+ and CD206+ cells were found to have increased as assessed by flow cytometry analysis. In addition, gene expression of angiogenic factors was upregulated in QQMNCs. In the animal model, the rate of bone union was higher in the QQMNC group than in the other groups. Radiographic scores and bone volume were significantly associated with the enhancement of angiogenesis in the QQMNC group.

Conclusion

We have demonstrated that QQMNCs have superior potential to accelerate fracture healing compared with PBMNCs. The QQMNCs could be a promising option for fracture nonunion.

Cite this article: K. Mifuji, M. Ishikawa, N. Kamei, R. Tanaka, K. Arita, H. Mizuno, T. Asahara, N. Adachi, M. Ochi. Angiogenic conditioning of peripheral blood mononuclear cells promotes fracture healing. Bone Joint Res 2017;6: 489–498. DOI: 10.1302/2046-3758.68.BJR-2016-0338.R1.

Circulating endothelial progenitors in vascular repair

Endothelial Colony Forming Cells (ECFCs) are obtained in culture from Circulating Endothelial Progenitor Cells. They display all characteristics of endothelial cells and they display stem cells features. Cord blood-derived ECFCs (CB-ECFCs) have a high clonogenic and proliferative potentials, and exhibit vascular repair capabilities useful for the treatment of ischemic diseases. However, the link between immaturity and functional properties of CB-ECFCs is still poorly defined. We showed that these cells have a high clonogenic potential and are capable to be efficiently reprogrammed into induced pluripotent stem cells. Moreover, we analyzed the expression of a broad panel of genes involved in embryonic stem cell properties. We define a novel stem cell transcriptional signature for CB-ECFCs fora better characterization and stratification according to their stem cell profile. We then improved the yield of CB-ECFC production for obtaining cells more functional in fewer passages. We used Glycosaminoglycans (GAG), components from the extracellular matrix which potentiate heparin binding growth factor activities. GAG mimetics were designed, having the capacity to increase the yield of ECFC during the isolation process, to increase the number of colonies, improve adhesion, proliferation, migration and self-renewal. GAG mimetics have thus great interest for vascular regeneration in combination with ECFC. Our results show that CB-ECFC are immature cells harboring specific functions such as formation of colonies, proliferation and formation of vascular structures in vitro and in vivo.

Endothelial progenitor cells and hypertension: current concepts and future implications

The discovery of endothelial progenitor cells (EPCs), a group of cells that play important roles in angiogenesis and the maintenance of vascular endothelial integrity, has led to considerable improvements in our understanding of the circulatory system and the regulatory mechanisms of vascular homoeostasis. Despite lingering disputes over where EPCs actually originate and how they facilitate angiogenesis, extensive research in the past decade has brought about significant advancements in this field of research, establishing EPCs as an essential element in the pathogenesis of various diseases. EPC and hypertensive disorders, especially essential hypertension (EH, also known as primary hypertension), represent one of the most appealing branches in this area of research. Chronic hypertension remains a major threat to public health, and the exact pathologic mechanisms of EH have never been fully elucidated. Is there a relationship between EPC and hypertension? If so, what is the nature of such relationship-is it mediated by blood pressure alterations, or other factors that lie in between? How can our current knowledge about EPCs be utilized to advance the prevention and clinical management of hypertension? In this review, we set out to answer these questions by summarizing the current concepts about EPC pathophysiology in the context of hypertension, while attempting to point out directions for future research on this subject.

Specific recruitment of circulating angiogenic cells using biomaterials as filters

Endogenous recruitment of circulating angiogenic cells (CACs) is an emerging strategy to induce angiogenesis within a defect site, and multiple recent strategies have deployed soluble protein releasing biomaterials for this purpose. However, the way in which the design of biomaterials affects CAC recruitment and invasion are poorly understood. Here we used an enhanced-throughput cell invasion assay to systematically examine the effects of biomaterial design on CAC recruitment. The screens co-optimized hydrogel presentation of a stromal-derived factor-1α (SDF-1α) gradient, hydrogel degradability, and hydrogel stiffness for maximal CAC invasion. We also examined the specificity of this invasion by assessing dermal fibroblast, mesenchymal stem cell, and lymphocyte invasion individually and in co-culture with CACs to identify hydrogels specific to CAC invasion. These screens suggested a subset of MMP-degradable hydrogels presenting a specific range of SDF-1α gradient slopes that induced specific invasion of CACs, and we posit that the design parameters of this subset of hydrogels may serve as instructive templates for the future design of biomaterials to specifically recruit CACs. We also posit that this design concept may be applied more broadly in that it may be possible to utilize these specific subsets of biomaterials as "filters" to control which types of cell populations invade into and populate the biomaterial.

STATEMENT OF SIGNIFICANCE

The recruitment of specific cell types for cell-based therapies in vivo is of great interest to the regenerative medicine community. Circulating angiogenic cells (CACs), CD133+ cells derived from the blood stream, are of particular interest for induction of angiogenesis in ischemic tissues, and recent studies utilizing soluble-factor releasing biomaterials to recruit these cells in vivo show great promise. However, these studies are largely "proof of concept" and are not systematic in nature. Thus, little is currently known about how biomaterial design affects the recruitment of CACs. In the present work, we use a high throughput cell invasion screening platform to systematically examine the effects of biomaterial design on circulating angiogenic cell (CAC) recruitment, and we successfully screened 263 conditions at 3 replicates each. Our results identify a particular subset of conditions that robustly recruit CACs. Additionally, we found that these conditions also specifically recruited CACs and excluded the other tested cells types of dermal fibroblasts, mesenchymal stem cells, and lymphocytes. This suggests an intriguing new role for biomaterials as "filters" to control the types of cells that invade and populate that biomaterial.

Harnessing cAMP signaling in musculoskeletal regenerative engineering

This paper reviews the most recent findings in the search for small molecule cyclic AMP analogues regarding their potential use in musculoskeletal regenerative engineering.

Tissue engineering and surgery: from translational studies to human trials

Tissue engineering was introduced as an innovative and promising field in the mid-1980s. The capacity of cells to migrate and proliferate in growth-inducing medium induced great expectancies on generating custom-shaped bioconstructs for tissue regeneration. Tissue engineering represents a unique multidisciplinary translational forum where the principles of biomaterial engineering, the molecular biology of cells and genes, and the clinical sciences of reconstruction would interact intensively through the combined efforts of scientists, engineers, and clinicians. The anticipated possibilities of cell engineering, matrix development, and growth factor therapies are extensive and would largely expand our clinical reconstructive armamentarium. Application of proangiogenic proteins may stimulate wound repair, restore avascular wound beds, or reverse hypoxia in flaps. Autologous cells procured from biopsies may generate an ‘autologous’ dermal and epidermal laminated cover on extensive burn wounds. Three-dimensional printing may generate ‘custom-made’ preshaped scaffolds – shaped as a nose, an ear, or a mandible – in which these cells can be seeded. The paucity of optimal donor tissues may be solved with off-the-shelf tissues using tissue engineering strategies. However, despite the expectations, the speed of translation of in vitro tissue engineering sciences into clinical reality is very slow due to the intrinsic complexity of human tissues. This review focuses on the transition from translational protocols towards current clinical applications of tissue engineering strategies in surgery.

The Role of Endothelial Progenitor Cells in Ischemic Cerebral and Heart Diseases

Ischemic heart and cerebral diseases are complex clinical syndromes. Endothelial dysfunction caused by dysfunctional endothelial progenitor cells (EPCs) is thought to play a major role in pathophysiology of both types of disease. Healthy EPCs may be able to replace the dysfunctional endothelium through endogenous repair mechanisms. EPC levels are changed in patients with ischemic cerebrovascular and cardiovascular disease and EPCs may play a role in the pathophysiology of these diseases. EPCs are also a marker for preventive and therapeutic interventions. Homing of EPCs to ischemic sites is a mechanism of ischemic tissue repair, and molecules such as stromal-derived factor-1 and integrin may play a role in EPC homing in ischemic disease. Potentiation of the function and numbers of EPCs as well as combining EPCs with other pharmaceutical agents may improve the condition of ischemia patients. However, the precise role of EPCs in ischemic heart and cerebral disease and their therapeutic potential still remain to be explored. Here, we discuss the identification, mobilization, and clinical implications of EPCs in ischemic diseases.

Regenerative Therapy for Stroke

Stroke remains a leading cause of death and disability worldwide. An increasing number of animal studies and preclinical trials have, however, provided evidence that regenerative cell-based therapies can lead to functional recovery in stroke patients. Stem cells can differentiate into neural lineages to replace lost neurons. Moreover, they provide trophic support to tissue at risk in the penumbra surrounding the infarct area, enhance vasculogenesis, and help promote survival, migration, and differentiation of the endogenous precursor cells after stroke. Stem cells are highly migratory and seem to be attracted to areas of brain pathology such as ischemic regions. The pathotropism may follow the paradigm of stem cell homing to bone marrow and leukocytes migrating to inflammatory tissue. The molecular signaling therefore may involve various chemokines, cytokines, and integrins. Among these, stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor-4 (CXCR4) signaling is required for the interaction of stem cells and ischemia-damaged host tissues. SDF-1 is secreted primarily by bone marrow fibroblasts and is required for BMSC homing to bone marrow. Overexpression of SDF-1 in ischemic tissues has been found to enhance stem cell recruitment from peripheral blood and to induce neoangiogenesis. Furthermore, SDF-1 expression in the lesioned area peaked within 7 days postischemia, in concordance with the time window of G-CSF therapy for stroke. Recent data have shown that SDF-1 expression is directly proportional to reduced tissue oxygen tension. SDF-1 gene expression is regulated by hypoxic-inducible factor-1 (HIF-1), a hypoxia-dependent stabilization transcription factor. Thus, ischemic tissue may recruit circulating progenitors regulated by hypoxia through differential expression of HIF-1α and SDF-1. In addition to SDF-1, β2-integrins also play a role in the homing of hematopoietic progenitor cells to sites of ischemia and are critical for their neovascularization capacity. In our recent report, increased expression of β1-integrins apparently contributed to the local neovasculization of the ischemic brain as well as its functional recovery. Identification of the molecular pathways involved in stem cell homing into the ischemic areas could pave the way for the development of new treatment regimens, perhaps using small molecules, designed to enhance endogeneous mobilization of stem cells in various disease states, including chronic stroke and other neurodegenerative diseases. For maximal functional recovery, however, regenerative therapy may need to follow combinatorial approaches, which may include cell replacement, trophic support, protection from oxidative stress, and the neutralization of the growth-inhibitory components for endogenous neuronal stem cells.

MicroRNA-containing extracellular vesicles released from endothelial colony-forming cells modulate angiogenesis during ischaemic retinopathy

Endothelial colony‐forming cells (ECFCs) are a defined subtype of endothelial progenitors that modulate vascular repair and promote perfusion in ischaemic tissues. Their paracrine activity on resident vasculature is ill‐defined, but mediated, at least in part, by the transfer of extracellular vesicles (EVs). To evaluate the potential of isolated EVs to provide an alternative to cell‐based therapies, we first performed a physical and molecular characterization of those released by ECFCs. Their effects upon endothelial cells in vitro and angiogenesis in vivo in a model of proliferative retinopathy were assessed. The EVs expressed typical markers CD9 and CD63 and formed a heterogeneous population ranging in size from ~60 to 1500 nm by electron microscopy. ECFC EVs were taken up by endothelial cells and increased cell migration. This was reflected by microarray analyses which showed significant changes in expression of genes associated with angiogenesis. Sequencing of small RNAs in ECFCs and their EVs showed that multiple microRNAs are highly expressed and concentrated in EVs. The functional categories significantly enriched for the predicted target genes of these microRNAs included angiogenesis. Intravitreally delivered ECFC EVs were associated with the vasculature and significantly reduced the avascular area in a mouse oxygen‐induced retinopathy model. Our findings confirm the potential of isolated EVs to influence endothelial cell function and act as a therapy to modulate angiogenesis. The functions associated with the specific microRNAs detected in ECFC EVs support a role for microRNA transfer in mediating the observed effects.

Decreased phosphorylation of PDGFR-β impairs the angiogenic potential of expanded endothelial progenitor cells via the inhibition of PI3K/Akt signaling

Human umbilical cord blood-derived endothelial progenitor cells (EPCs) have been proven to contribute to post-natal angiogenesis, and have been applied in various models of ischemia. However, to date, to the best of our knowledge, there is no available data on the angiogenic properties of EPCs during the process of in vitro expansion. In this study, we expanded EPCs to obtain cells at different passages, and analyzed their cellular properties and angiogenic ability. In the process of expansion, no changes were observed in cell cobblestone-like morphology, apoptotic rate and telomere length. However, the cell proliferative ability was significantly decreased. Additionally, the expression of CD144, CD90 and KDR was significantly downregulated in the later-passage cells. Vascular formation assay in vitro revealed that EPCs at passage 4 and 6 formed more integrated and organized capillary-like networks. In a murine model of hind limb ischemia, the transplantation of EPCs at passage 4 and 6 more effectively promoted perfusion recovery in the limbs on days 7 and 14, and promoted limb salvage and histological recovery. Furthermore, the phosphorylation levels of platelet‑derived growth factor receptor-β (PDGFR-β) were found to be significantly decreased with the in vitro expansion process, accompanied by the decreased activation of the PI3K/Akt signaling pathway. When PDGFR inhibitor was used to treat the EPCs, the differences in the angiogenic potential and migratory ability among the EPCs at different passages were no longer observed; no significant differences were also observed in the levels of phosphorylated PI3K/Akt between the EPCs at different passages following treatment with the inhibitor. On the whole, our findings indicate that the levels of phosphorylated PDGFR-β are decreased in EPCs with the in vitro expansion process, which impairs their angiogenic potential by inhibiting PI3K/Akt signaling. Our findings may aid in the more effective selection of EPCs of different passages for the clinical therapy of ischemic disease.

Increase in acid sphingomyelinase level in human retinal endothelial cells and CD34+ circulating angiogenic cells isolated from diabetic individuals is associated with dysfunctional retinal vasculature and vascular repair process in diabetes

BACKGROUND

Diabetic retinopathy is a microvascular disease that results from retinal vascular degeneration and defective repair due to diabetes-induced endothelial progenitor dysfunction.

OBJECTIVE

Understanding key molecular factors involved in vascular degeneration and repair is paramount for developing effective diabetic retinopathy treatment strategies. We propose that diabetes-induced activation of acid sphingomyelinase (ASM) plays essential role in retinal endothelial and CD34+ circulating angiogenic cell (CAC) dysfunction in diabetes.

METHODS

Human retinal endothelial cells (HRECs) isolated from control and diabetic donor tissue and human CD34+ CACs from control and diabetic patients were used in this study. ASM messenger RNA and protein expression were assessed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. To evaluate the effect of diabetes-induced ASM on HRECs and CD34+ CACs function, tube formation, CAC incorporation into endothelial tubes, and diurnal release of CD34+ CACs in diabetic individuals were determined.

RESULTS

ASM expression level was significantly increased in HRECs isolated from diabetic compared with control donor tissue, as well as CD34+ CACs and plasma of diabetic patients. A significant decrease in tube area was observed in HRECs from diabetic donors compared with control HRECs. The tube formation deficiency was associated with increased expression of ASM in diabetic HRECs. Moreover, diabetic CD34+ CACs with high ASM showed defective incorporation into endothelial tubes. Diurnal release of CD34+ CACs was disrupted with the rhythmicity lost in diabetic patients.

CONCLUSION

Collectively, these findings support that diabetes-induced ASM upregulation has a marked detrimental effect on both retinal endothelial cells and CACs.

Delivery of growth factor-based therapeutics in vascular diseases: Challenges and strategies

Either cardiovascular or peripheral vascular diseases have become the major cause of morbidity and mortality worldwide. Recently, growth factors therapeutics, whatever administrated in form of exogenous growth factors or their relevant genes have been discovered to be an effective strategy for the prevention and therapy of vascular diseases, because of their promoting angiogenesis. Besides, as an alternative, stem cell-based therapy has been also developed in view of their paracrine-mediated effect or ability of differentiation toward angiogenesis-related cells under assistance of growth factors. Despite of being specific and potent, no matter growth factors or stem cells-based therapy, their full clinical transformation is limited from bench to bedside. In this review, the potential choices of therapeutic modes based on types of different growth factors or stem cells were firstly summarized for vascular diseases. The confronted various challenges such as lack of non-invasive delivery method, the physiochemical challenge, the short half-life time, and poor cell survival, were carefully analyzed for these therapeutic modes. Various strategies to overcome these limitations are put forward from the perspective of drug delivery. The expertised design of a suitable delivery form will undoubtedly provide valuable insight into their clinical application in the regenerative medicine.

Trimodal rescue of hind limb ischemia with growth factors, cells, and nanocarriers: fundamentals to clinical trials

Peripheral artery disease is a severe medical condition commonly characterized by critical or acute limb ischemia. Gradual accumulation of thrombotic plaques in peripheral arteries of the lower limb may lead to intermittent claudication or ischemia in muscle tissue. Ischemic muscle tissue with lesions may become infected, resulting in a non-healing wound. Stable progression of the non-healing wound associated with severe ischemia might lead to functional deterioration of the limb, which, depending on the severity, can result in amputation. Immediate rescue of ischemic muscles through revascularization strategies is considered the gold standard to treat critical limb ischemia. Growth factors offer multiple levels of protection in revascularization of ischemic tissue. In this review, the basic mechanism through which growth factors exert their beneficial properties to rescue the ischemic limb is extensively discussed. Moreover, clinical trials based on growth factor and stem cell therapy to treat critical limb ischemia are considered. The clinical utility of stem cell therapy for the treatment of limb ischemia is explained and recent advances in nanocarrier technology for selective growth factor and stem cell supplementation are summarized.

Perinatal Brain Injury As a Consequence of Preterm Birth and Intrauterine Inflammation: Designing Targeted Stem Cell Therapies

Chorioamnionitis is a major cause of preterm birth and brain injury. Bacterial invasion of the chorion and amnion, and/or the placenta, can lead to a fetal inflammatory response, which in turn has significant adverse consequences for the developing fetal brain. Accordingly, there is a strong causal link between chorioamnionitis, preterm brain injury and the pathogenesis of severe postnatal neurological deficits and cerebral palsy. Currently there are no treatments to protect or repair against brain injury in preterm infants born after pregnancy compromised by intrauterine infection. This review describes the injurious cascade of events in the preterm brain in response to a severe fetal inflammatory event. We will highlight specific periods of increased vulnerability, and the potential effects of therapeutic intervention with cell-based therapies. Many clinical trials are underway to investigate the efficacy of stem cells to treat patients with cerebral palsy. Stem cells, obtained from umbilical cord tissue and cord blood, normally discarded after birth, are emerging as a safe and potentially effective therapy. It is not yet known, however, which stem cell type(s) are the most efficacious for administration to preterm infants to treat brain injury-mediated inflammation. Individual stem cell populations found in cord blood and tissue, such as mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs), have a number of potential benefits that may specifically target preterm inflammatory-induced brain injury. MSCs have strong immunomodulatory potential, protecting against global and local neuroinflammatory cascades triggered during infection to the fetus. EPCs have angiogenic and vascular reparative qualities that make them ideal for neurovascular repair. A combined therapy using both MSCs and EPCs to target inflammation and promote angiogenesis for re-establishment of vital vessel networks is a treatment concept that warrants further investigation.

The acute impact of high-dose lipid-lowering treatment on endothelial progenitor cells in patients with coronary artery disease-The REMEDY-EPC early substudy

RATIONALE AND OBJECTIVE

Endothelial progenitor cells (EPCs) play a role in vascular repair, while circulating endothelial cells (CECs) are biomarkers of vascular damage and regeneration. Statins may promote EPC/CEC mobilization in the peripheral blood. We evaluated whether pre-procedural exposure to different lipid-lowering drugs (statins±ezetimibe) can acutely increase levels/activity of EPCs/CECs in patients with stable coronary artery disease (CAD).

METHODS

In a planned sub-analysis of the Rosuvastatin For REduction Of Myocardial DamagE During Coronary AngioplastY (REMEDY) trial, 38 patients with stable CAD on chronic low-dose statin therapy were randomized, in a double-blind, placebo-controlled design, into 4 groups before PCI: i. placebo (n = 11); ii. atorvastatin (80 mg+40 mg, n = 9); iii. rosuvastatin (40 mg twice, n = 9); and iv. rosuvastatin (5 mg) and ezetimibe (10 mg) twice, (n = 9). At baseline and 24 h after treatment-before PCI-, patients underwent blinded analyses of EPCs [colony forming units-endothelial cells (CFU-ECs), endothelial colony-forming cells (ECFCs) and tubulization activity] and CECs in peripheral blood.

RESULTS

We found no significant treatment effects on parameters investigated such as number of CECs [Median (IQR): i. 0(0), ii. 4.5(27), iii. 1.9(2.3), iv. 1.9(2.3)], CFU-ECs [Median (IQR): i. 27(11), ii. 19(31), iii. 47(36), iv. 30(98)], and ECFCs [Median (IQR): i. 86(84), ii. 7(84), iii. 8/(42.5), iv. 5(2)], as well as tubulization activity [total tubuli (well), Median (IQR): i. 19(7), ii. 5(4), iii. 25(13), iv. 15(24)].

CONCLUSIONS

In this study, we found no evidence of acute changes in levels or activity of EPCs and CECs after high-dose lipid-lowering therapy in stable CAD patients.

Rationale and design of the MarrowStim PAD Kit for the Treatment of Critical Limb Ischemia in Subjects with Severe Peripheral Arterial Disease (MOBILE) trial investigating autologous bone marrow cell therapy for critical limb ischemia

OBJECTIVE

Critical limb ischemia (CLI) continues to place a significant encumbrance on patients and the health care system as it progresses to limb loss and long-term disability. Traditional methods of revascularization offer a significant benefit; however, for one-third of CLI patients, these surgical options are not technically possible or patency is severely limited by disease burden (deemed "poor-option" for revascularization). In a previous phase I trial, we demonstrated intramuscular injection of concentrated bone marrow aspirate (cBMA) via MarrowStim (Zimmer Biomet, Warsaw, Ind) harvest is safe and may decrease major amputation in patients with CLI unfit for surgical revascularization. Therefore, we describe and rationalize the MarrowStim PAD Kit for the Treatment of Critical Limb Ischemia in Subjects with Severe Peripheral Arterial Disease (MOBILE) trial, a study geared to provide the pivotal proof of efficacy of cBMA in CLI.

METHODS

MOBILE is a multicenter, randomized, double-blind, placebo-controlled trial designed to assess the efficacy of intramuscular injections of cBMA in promoting amputation-free survival in patients with poor-option CLI. Patients (aged >21 years) with rest pain or tissue loss resulting from advanced peripheral arterial disease, as characterized by ankle-brachial index (<0.6), toe-brachial index (<0.4), or transcutaneous pressure of oxygen (<50 mm Hg), were eligible for inclusion if surgical revascularization was not possible secondary to advanced disease.

RESULTS

Treatment and 1-year follow-up of 152 patients enrolled in MOBILE are completed. Long-term follow-up is ongoing. Currently, we are in the process of unblinding the initial results for preliminary data analysis.

CONCLUSIONS

If successful, MOBILE could add definitive, high-quality evidence in support of cBMA for the treatment of poor-option CLI patients and provide an additional modality for patients who face amputation secondary to advanced limb ischemia.

Use of p53-Silenced Endothelial Progenitor Cells to Treat Ischemia in Diabetic Peripheral Vascular Disease

BACKGROUND

Peripheral vascular disease is a major diabetes mellitus-related complication. In this study, we noted that expressions of proapoptotic p53 gene and its downstream cascade gene such as p21 are upregulated in hyperglycemia. Therefore, we investigated whether p53- and p21-silenced endothelial progenitor cells (EPCs) were able to survive in hyperglycemic milieu, and whether transplantation of either p53 knockout (KO) or p21KO or p53- and p21-silenced EPCs could improve collateral vessel formation and blood flow in diabetic vaso-occlusive peripheral vascular disease mouse models.

METHODS AND RESULTS

We transplanted p53 and p21KO mouse EPCs (mEPCs) into streptozotocin-induced diabetic (type 1 diabetes mellitus model) C57BL/6J and db/db (B6.BKS(D)-Leprdb/J) (type 2 model) post-femoral artery occlusion. Similarly, Ad-p53-silenced and Ad-p21-silenced human EPCs (CD34+) cells were transplanted into streptozotocin-induced diabetic NOD.CB17-Prkdcscid/J mice. We measured blood flow at 3, 7, and 10 days and hindlimb muscles were obtained postsacrifice for mRNA estimation and CD31 staining. Enhanced blood flow was noted with delivery of p53 and p21KO mEPCs in streptozotocin-induced diabetic C57BL/6J mice. Similar results were obtained when human Ad-p53shEPCs(CD34+) and Ad-p21shEPCs(CD34+) were transplanted into streptozotocin-induced nonobese diabetic severe combined immunodeficiency mice. Gene expression analysis of p53 and p21KO EPCs transplanted hindlimb muscles showed increased expression of endothelial markers such as endothelial nitric oxide synthase, vascular endothelial growth factor A, and platelet endothelial cell adhesion molecule 1. Similarly, quantitative reverse transcriptase polymerase chain reaction of human Ad-p53shEPCs (CD34+)- and Ad-p21shEPCs (CD34+)-transplanted hindlimb muscles also showed increased expression of endothelial markers such as vascular endothelial growth factor A, noted primarily in the p53-silenced EPCs group. However, such beneficial effect was not noted in the db/db type 2 diabetic mouse models.

CONCLUSIONS

Transient silencing of p53 using adenoviral vector in EPCs may have a therapeutic role in diabetic peripheral vascular disease.

Role of NADPH Oxidase-4 in Human Endothelial Progenitor Cells

Introduction: Endothelial progenitor cells (EPCs) display a unique ability to promote angiogenesis and restore endothelial function in injured blood vessels. NADPH oxidase 4 (NOX4)-derived hydrogen peroxide (H₂O₂) serves as a signaling molecule and promotes endothelial cell proliferation and migration as well as protecting against cell death. However, the role of NOX4 in EPC function is not completely understood. Methods: EPCs were isolated from human saphenous vein and mammary artery discarded during bypass surgery. NOX4 gene and protein expression in EPCs were measured by real time-PCR and Western blot analysis respectively. NOX4 gene expression was inhibited using an adenoviral vector expressing human NOX4 shRNA (Ad-NOX4i). H₂O₂ production was measured by Amplex red assay. EPC migration was evaluated using a transwell migration assay. EPC proliferation and viability were measured using trypan blue counts. Results: Inhibition of NOX4 using Ad-NOX4i reduced Nox4 gene and protein expression as well as H₂O₂ formation in EPCs. Inhibition of NOX4-derived H₂O₂ decreased both proliferation and migration of EPCs. Interestingly, pro-inflammatory cytokine tumor necrosis factor alpha (TNFα) decreased NOX4 expression and reduced survival of EPCs. However, the survival of EPCs was further diminished by TNF-α in NOX4-knockdown cells, suggesting that NOX4 has a protective role in EPCs. Conclusion: These findings suggest that NOX4-type NADPH oxidase is important for proliferation and migration functions of EPCs and protects against pro-inflammatory cytokine induced EPC death. These properties of NOX4 may facilitate the efficient function of EPCs which is vital for successful neovascularization.

Metformin inhibits endothelial progenitor cell migration by decreasing matrix metalloproteinases, MMP-2 and MMP-9, via the AMPK/mTOR/autophagy pathway

The aim of the present study was to investigate the effect of metformin on endothelial progenitor cell (EPC) migration and to explore the possible mechanisms. EPCs were treated with metformin, and the migration of EPCs was evaluated by wound healing and Matrigel invasion assays. We also examined the expression levels of of MMP-2 and MMP-9 in EPCs with or without metformin treatment via RT-PCR and western blot analysis, and activities of MMP-2 and MMP-9 in EPCs under different conditions was examined by zymography. Moreover, we also assessed the AMPK/mTOR/autophagy pathway to explore the possible mechanisms. Metformin treatment significantly downregulated matrix metalloproteinase-2 (MMP-2) and MMP-9 expression, and subsequently decreased the migration of EPCs. Increased levels of phosphorylated (p)-AMPK and LC3II expression, as well as decreased levels of p-mTOR and p62 contributed to this phenomenon. The AMPK inhibitor compound C reversed the effect exerted by metformin. In conclusion, our results showed that metformin inhibited the migration of EPCs by decreasing MMP-2 and MMP-9. The AMPK/mTOR/autophagy pathway was demonstrated to be involved in the regulatory mechanisms.

Multiparametric evaluation of hindlimb ischemia using time-series indocyanine green fluorescence imaging

Peripheral arterial disease (PAD) can further cause lower limb ischemia. Quantitative evaluation of the vascular perfusion in the ischemic limb contributes to diagnosis of PAD and preclinical development of new drug. In vivo time-series indocyanine green (ICG) fluorescence imaging can noninvasively monitor blood flow and has a deep tissue penetration. The perfusion rate estimated from the time-series ICG images is not enough for the evaluation of hindlimb ischemia. The information relevant to the vascular density is also important, because angiogenesis is an essential mechanism for post-ischemic recovery. In this paper, a multiparametric evaluation method is proposed for simultaneous estimation of multiple vascular perfusion parameters, including not only the perfusion rate but also the vascular perfusion density and the time-varying ICG concentration in veins. The target method is based on a mathematical model of ICG pharmacokinetics in the mouse hindlimb. The regression analysis performed on the time-series ICG images obtained from a dynamic reflectance fluorescence imaging system. The results demonstrate that the estimated multiple parameters are effective to quantitatively evaluate the vascular perfusion and distinguish hypo-perfused tissues from well-perfused tissues in the mouse hindlimb. The proposed multiparametric evaluation method could be useful for PAD diagnosis. The estimated perfusion rate and vascular perfusion density maps (left) and the time-varying ICG concentration in veins of the ankle region (right) of the normal and ischemic hindlimbs.

Therapeutic strategies for cell-based neovascularization in critical limb ischemia

Critical limb ischemia (CLI) causes severe ischemic rest pain, ulcer, and gangrene in the lower limbs. In spite of angioplasty and surgery, CLI patients without suitable artery inflow or enough vascular bed in the lesions are often forced to undergo amputation of a major limb. Cell-based therapeutic angiogenesis has the potential to treat ischemic lesions by promoting the formation of collateral vessel networks and the vascular bed. Peripheral blood mononuclear cells and bone marrow-derived mononuclear cells are the most frequently employed cell types in CLI clinical trials. However, the clinical outcomes of cell-based therapeutic angiogenesis using these cells have not provided the promised benefits for CLI patients, reinforcing the need for novel cell-based therapeutic angiogenesis strategies to cure untreatable CLI patients. Recent studies have demonstrated the possible enhancement of therapeutic efficacy in ischemic diseases by preconditioned graft cells. Moreover, judging from past clinical trials, the identification of adequate transplant timing and responders to cell-based therapy is important for improving therapeutic outcomes in CLI patients in clinical settings. Thus, to establish cell-based therapeutic angiogenesis as one of the most promising therapeutic strategies for CLI patients, its advantages and limitations should be taken into account.

Marrow-isolated adult multilineage inducible cells embedded within a biologically-inspired construct promote recovery in a mouse model of peripheral vascular disease

Peripheral vascular disease is one of the major vascular complications in individuals suffering from diabetes and in the elderly that is associated with significant burden in terms of morbidity and mortality. Stem cell therapy is being tested as an attractive alternative to traditional surgery to prevent and treat this disorder. The goal of this study was to enhance the protective and reparative potential of marrow-isolated adult multilineage inducible (MIAMI) cells by incorporating them within a bio-inspired construct (BIC) made of two layers of gelatin B electrospun nanofibers. We hypothesized that the BIC would enhance MIAMI cell survival and engraftment, ultimately leading to a better functional recovery of the injured limb in our mouse model of critical limb ischemia compared to MIAMI cells used alone. Our study demonstrated that MIAMI cell-seeded BIC resulted in a wide range of positive outcomes with an almost full recovery of blood flow in the injured limb, thereby limiting the extent of ischemia and necrosis. Functional recovery was also the greatest when MIAMI cells were combined with BICs, compared to MIAMI cells alone or BICs in the absence of cells. Histology was performed 28 days after grafting the animals to explore the mechanisms at the source of these positive outcomes. We observed that our critical limb ischemia model induces an extensive loss of muscular fibers that are replaced by intermuscular adipose tissue (IMAT), together with a highly disorganized vascular structure. The use of MIAMI cells-seeded BIC prevented IMAT infiltration with some clear evidence of muscular fibers regeneration.

Sex-gender-related therapeutic approaches for cardiovascular complications associated with diabetes

Diabetes is a chronic disease associated with micro- and macrovascular complications and is a well-established risk factor for cardiovascular disease. Cardiovascular complications associated with diabetes are among the most important causes of death in diabetic patients. Interestingly, several sex-gender differences have been reported to significantly impact in the pathophysiology of diabetes. In particular, sex-gender differences have been reported to affect diabetes epidemiology, risk factors, as well as cardiovascular complications associated with diabetes. This suggests that different therapeutic approaches are needed for managing diabetes-associated cardiovascular complications in men and women. In this review, we will discuss about the sex-gender differences that are known to impact on diabetes, mainly focusing on the cardiovascular complications associated with the disease. We will then discuss the therapeutic approaches for managing diabetes-associated cardiovascular complications and how differences in sex-gender can influence the existing therapeutic approaches.

Endothelial differentiation of bone marrow mesenchyme stem cells applicable to hypoxia and increased migration through Akt and NFκB signals

BACKGROUND

Bone marrow mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) are used to repair hypoxic or ischemic tissue. However, the underlining mechanism of resistance in the hypoxic microenvironment and the efficacy of migration to the injured tissue are still unknown. The current study aims to understand the hypoxia resistance and migration ability of MSCs during differentiation toward endothelial lineages by biochemical and mechanical stimuli.

METHOD

MSCs were harvested from the bone marrow of 6-8-week-old Sprague-Dawley rats. The endothelial growth medium (EGM) was added to MSCs for 3 days to initiate endothelial differentiation. Laminar shear stress was used as the fluid mechanical stimulation.

RESULTS

Application of EGM facilitated the early endothelial lineage cells (eELCs) to express EPC markers. When treating the hypoxic mimetic desferrioxamine, both MSCs and eELCs showed resistance to hypoxia as compared with the occurrence of apoptosis in rat fibroblasts. The eELCs under hypoxia increased the wound closure and C-X-C chemokine receptor type 4 (CXCR4) gene expression. Although the shear stress promoted eELC maturation and aligned cells parallel to the flow direction, their migration ability was not superior to that of eELCs either under normoxia or hypoxia. The eELCs showed higher protein expressions of CXCR4, phosphorylated Akt (pAkt), and endogenous NFκB and IκBα than MSCs under both normoxia and hypoxia conditions. The potential migratory signals were discovered by inhibiting either Akt or NFκB using specific inhibitors and revealed decreases of wound closure and transmigration ability in eELCs.

CONCLUSION

The Akt and NFκB pathways are important to regulate the early endothelial differentiation and its migratory ability under a hypoxic microenvironment.

Progenitor cells from atria, ventricle and peripheral blood of the same patients exhibit functional differences associated with cardiac repair

AIM

Deciding the best cell type for cardiac regeneration remains a big challenge. No studies have directly compared the functional efficacy of cardiac progenitor cells (CPCs) with extra-cardiac stem cells isolated from the same patient.

METHODS AND RESULTS

We compared the functional characteristics of endothelial progenitor cells (EPCs), right atrial (RAA) CPCs and left ventricular (LV) CPCs isolated from the same patients (n=14). Within the same heart, RAA and LV CPCs exhibited marked differences in surface marker expression, with RAA CPCs exhibiting better expansion potential and migration properties. When subjected to hypoxia and serum starvation to simulate in vivo ischemic environment, RAA and LV CPCs exhibited similar pattern of resistance to apoptotic cell death under ischemia. Interestingly, EPCs exhibited highest resistance to apoptotic cell death, however, they also showed the lowest proliferation under hypoxia. RT-profiler array showed comparable gene expression pattern in RAA and LV CPCs, while they were differentially expressed in EPCs. Further, treating human umbilical vein endothelial cells with conditioned medium (CM) from LV showed maximum angiogenic potential, while cardiomyocytes treated with CM from RAA showed greatest survival under hypoxic conditions.

CONCLUSIONS

Results from this study provide the first evidence that progenitor cells from different regions exhibit functional differences within the same patient.

Elevating CXCR7 Improves Angiogenic Function of EPCs via Akt/GSK-3β/Fyn-Mediated Nrf2 Activation in Diabetic Limb Ischemia

RATIONALE

Endothelial progenitor cells (EPCs) respond to stromal cell-derived factor 1 (SDF-1) through chemokine receptors CXCR7 and CXCR4. Whether SDF-1 receptors involves in diabetes mellitus-induced EPCs dysfunction remains unknown.

OBJECTIVE

To determine the role of SDF-1 receptors in diabetic EPCs dysfunction.

METHODS AND RESULTS

CXCR7 expression, but not CXCR4 was reduced in EPCs from db/db mice, which coincided with impaired tube formation. Knockdown of CXCR7 impaired tube formation of EPCs from normal mice, whereas upregulation of CXCR7 rescued angiogenic function of EPCs from db/db mice. In normal EPCs treated with oxidized low-density lipoprotein or high glucose also reduced CXCR7 expression, impaired tube formation, and increased oxidative stress and apoptosis. The damaging effects of oxidized low-density lipoprotein or high glucose were markedly reduced by SDF-1 pretreatment in EPCs transduced with CXCR7 lentivirus but not in EPCs transduced with control lentivirus. Most importantly, EPCs transduced with CXCR7 lentivirus were superior to EPCs transduced with control lentivirus for therapy of ischemic limbs in db/db mice. Mechanistic studies demonstrated that oxidized low-density lipoprotein or high glucose inhibited protein kinase B and glycogen synthase kinase-3β phosphorylation, nuclear export of Fyn and nuclear localization of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), blunting Nrf2 downstream target genes heme oxygenase-1, NAD(P)H dehydrogenase (quinone 1) and catalase, and inducing an increase in EPC oxidative stress. This destructive cascade was blocked by SDF-1 treatment in EPCs transduced with CXCR7 lentivirus. Furthermore, inhibition of phosphatidylinositol 3-kinase/protein kinase B prevented SDF-1/CXCR7-mediated Nrf2 activation and blocked angiogenic repair. Moreover, Nrf2 knockdown almost completely abolished the protective effects of SDF-1/CXCR7 on EPC function in vitro and in vivo.

CONCLUSIONS

Elevated expression of CXCR7 enhances EPC resistance to diabetes mellitus-induced oxidative damage and improves therapeutic efficacy of EPCs in treating diabetic limb ischemia. The benefits of CXCR7 are mediated predominantly by a protein kinase B/glycogen synthase kinase-3β/Fyn pathway via increased activity of Nrf2.

Stem cell therapy: An emerging modality in glomerular diseases

The kidney has been considered a highly terminally differentiated organ with low proliferative potential and thus unlikely to undergo regeneration. Glomerular disease progresses to end-stage renal disease (ESRD), which requires dialysis or renal transplantation for better quality of life for patients with ESRD. Because of the shortage of implantable kidneys and complications such as immune rejection, septicemia and toxicity of immunosuppression, kidney transplantation remains a challenge. Therapeutic options available for glomerular disease include symptomatic treatment and strategies to delay progression. In an attempt to develop innovative treatments by promoting the limited capability of regeneration and repair after kidney injury and overcome the progressive pathological process that is uncontrolled with conventional treatment modalities, stem cell-based therapy has emerged as novel intervention due to its ability to inhibit inflammation and promote regeneration. Recent developments in cell therapy have demonstrated promising therapeutic outcomes in terms of restoration of renal structure and function. This review focuses on stem cell therapy approaches for the treatment of glomerular disease, including the various cell sources used and recent advances in preclinical and clinical studies.