Recruitment Of Endothelial Progenitor Cells Research Articles

Vascular damage and excessive proliferation compromise liver function after extended hepatectomy in mice.

Surgical resection remains the gold standard for liver tumor treatment, yet the emergence of post-operative liver failure, known as the small for size syndrome (SFSS), poses a significant challenge. The activation of hypoxia sensors in a SFSS liver remnant initiated early angiogenesis, improving vascular architecture, safeguarding against liver failure and reducing mortality. The study aimed to elucidate vascular remodeling mechanisms in SFSS, its impact on hepatocyte function and subsequent liver failure. Mice underwent extended partial hepatectomy to induce SFSS, with a subset exposed to hypoxia immediately after surgery. Hypoxia bolstered post-hepatectomy survival rates. Early proliferation of liver sinusoidal cells, coupled with recruitment of putative endothelial progenitor cells (EPC), increased vascular density, improved lobular perfusion, and limited hemorrhagic events in the regenerating liver under hypoxia. Administration of granulocyte colony stimulating factor (G-CSF) in hepatectomized mice mimicked the effects of hypoxia on vascular remodeling and EPC recruitment, but failed to rescue survival. Compared to normoxia, hypoxia favored hepatocyte function over proliferation, promoting functional preservation in the regenerating remnant. Injection of AAV8-TBG-HNF4α virus for hepatocyte-specific overexpression of HNF4α, the master regulator of hepatocyte function, enforced functionality in proliferating hepatocytes but did not rescue survival. The combination of HNF4α overexpression and G-CSF treatment rescued survival after SFSS-setting hepatectomy. In summary, SFSS arises from an imbalance and desynchronized interplay between functional regeneration and vascular restructuring. To improve survival following SFSS-hepatectomy, it is essential to adopt a two-pronged strategy aimed at preserving the function of proliferating parenchymal cells and simultaneously attenuating vascular damage.

Transplantation of endothelial progenitor cells overexpressing mir-126-3p improves vascular repair in a diabetic rat model.

Transplantation of endothelial progenitor cells overexpressing mir-126-3p improves vascular repair in a diabetic rat model.

Nitric Oxide Generation and Endothelial Progenitor Cells Recruitment for Improving Hemocompatibility and Accelerating Endothelialization of Tissue Engineering Heart Valve (Adv. Funct. Mater. 9/2023)

Nitric Oxide Generation and Endothelial Progenitor Cells Recruitment for Improving Hemocompatibility and Accelerating Endothelialization of Tissue Engineering Heart Valve (Adv. Funct. Mater. 9/2023)

Nitric Oxide Generation and Endothelial Progenitor Cells Recruitment for Improving Hemocompatibility and Accelerating Endothelialization of Tissue Engineering Heart Valve

AbstractTissue engineering heart valve (TEHV) offers great potential to overcome the limitations of commercial artificial valves used in clinical practice as a permanent prosthetic valve. Currently, decellularized heart valve (DHV) is the most widely used scaffold for TEHV, but showed suboptimal performance due to difficulty of endothelialization. Facilitating endothelialization of DHV is indispensable for better valve performance, and excellent hemocompatibility guarantees enough time windows for endothelialization process. Herein, a dual‐functional TEHV scaffold with improving hemocompatibility and accelerating endothelialization is constructed by modifying DHV with copper ions (Cu) and growth differentiation factor 11 (GDF11). Results show the newly‐constructed scaffold successfully generates endogenous nitric oxide (NO) through catalysis of Cu, and possesses improved hemocompatibility by down‐regulating platelets activation and adhesion. Furthermore, GDF11 immobilization significantly accelerates scaffold endothelialization through facilitating recruitment, supporting growth, and alleviating apoptosis of endothelial progenitor cells . This TEHV scaffold shows favorable performance under in vivo hemodynamic environment with intact endothelial coverage and adaptive ECM remodeling, and without thrombus or calcification formation. This newly‐constructed TEHV scaffold is expected to make up for the shortcomings of currently available prosthetic valves in clinical practice and has the potential possibility of rapid translation to the clinic as a better prosthetic valve.

Androgens and Androgen Receptors as Determinants of Vascular Sex Differences Across the Lifespan.

Androgens, including testosterone and its more potent metabolite dihydrotestosterone, exert multiple actions in the body. Physiologically, they play a critical role in male sex development. In addition, they influence vascular function, including arterial vasodilation and mediation of myogenic tone. Androgens are produced from 9 weeks' gestation in the human fetal testis, as well as in small amounts by the adrenal glands. Serum concentrations vary according to age and sex. The vasculature is a target for direct actions of androgens, which bind to various sex hormone receptors expressed in endothelial and vascular smooth muscle cells. Androgens exert both vasoprotective and vasoinjurious effects, depending on multiple factors including sex-specific effects of androgens, heterogeneity of the vascular endothelium, differential expression of androgen and sex hormone receptors in endothelial and vascular smooth muscle cells, and the chronicity of androgen administration. Long-term administration of androgens induces vasoconstriction and influences endothelial permeability, whereas acute administration may have opposite effects. At the cellular level, androgens stimulate endothelial cell production of nitric oxide and inhibit proinflammatory signalling pathways, inducing vasorelaxation and vasoprotection. However, androgens also activate endothelial production of vasoconstrictors and stimulate recruitment of endothelial progenitor cells. In humans, both androgen deficiency and androgen excess are associated with increased cardiovascular morbidity and mortality. This review discusses how androgens modulate vascular sex differences across the lifespan by considering the actions and production of androgens in both sexes and describes how cardiovascular risk is altered as levels of androgens change with aging.

Phosphomimetic endothelial nitric oxide synthase-loaded microbubbles-mediated cardiac shock wave transfection therapy for angiogenesis in the ischemic myocardium

Abstract Background Cardiac shock wave therapy is a potential and effective remedy to promote revascularization in the ischemic myocardium of patients with refractory coronary heart disease (CHD). Although gene therapy holds great promise as a treatment for coronary heart disease, current clinical application is hampered by the development of safe and efficient systems for local gene delivery to a specific tissue or organ. Purpose In this study, we developed an experimental pulsed- focused electrohydraulic shock wave therapy system and investigated its effectiveness on myocardial angiogenesis in the hypercholesterolemic rabbit accompanied by phosphomimetic endothelial nitric oxide synthase-loaded microbubbles administration, wherein a high resolution diagnostic ultrasound is adjuncted with the therapy system, with a goal of increased safety. Methods Briefly, New Zealand white rabbits underwent 2% cholesterol rich diet injury for sixteen weeks. Histopathology results showed the formation of foam cells-rich soft atherosclerotic plaques with severe stenosis in all of the rabbits' coronary arteries. Then treatment group underwent extracorporeal electrohydraulic pulsed-focused shock waves (25kV, 0.5Hz, 150 pulses) accompanied by phosphomimetic endothelial nitric oxide synthase-loaded PESDA (Perfluorocarbon Exposed Sonicated Dextrose Albumin) microbubbles (100 ml/kg, 2.5x105 bubbles/ml) administration. Results Results from ultrasonography and histopathology showed a significant increase in the mean value for myocardial neovessels density in the treatment group compared with the control group (p<0.05). Conclusion Enhanced angiogenesis and sonoporation effect of electrohydraulic shock wave therapy, induced by inertial collapsed microbubbles, accompanied by phosphomimetic endothelial nitric oxide synthase-mediated shock wave transfection therapy, can cause to enhance the nitric oxide synthesis and VEGF, interleukin8 (IL8), stromal cell- derived factor 1 (SDF1) and matrix metalloproteinase 9 (MMP9) secretion in the hypercholesterolemic rabbits' coronary arteries, resulting in the differentiation and recruitment of endothelial progenitor cells (EPCs), promotion of revascularization in the ischemic myocardium and improvement of the cardiac function. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Mehrad Research Lab

Microfluidic 3D platform to evaluate endothelial progenitor cell recruitment by bioactive materials

Most of the conventional in vitro models to test biomaterial-driven vascularization are too simplistic to recapitulate the complex interactions taking place in the actual cell microenvironment, which results in a poor prediction of the in vivo performance of the material. However, during the last decade, cell culture models based on microfluidic technology have allowed attaining unprecedented levels of tissue biomimicry. In this work, we propose a microfluidic-based 3D model to evaluate the effect of bioactive biomaterials capable of releasing signaling cues (such as ions or proteins) in the recruitment of endogenous endothelial progenitor cells, a key step in the vascularization process. The usability of the platform is demonstrated using experimentally-validated finite element models and migration and proliferation studies with rat endothelial progenitor cells (rEPCs) and bone marrow-derived rat mesenchymal stromal cells (BM-rMSCs). As a proof of concept of biomaterial evaluation, the response of rEPCs to an electrospun composite made of polylactic acid with calcium phosphates nanoparticles (PLA+CaP) was compared in a co-culture microenvironment with BM-rMSC to a regular PLA control. Our results show a significantly higher rEPCs migration and the upregulation of several pro-inflammatory and proangiogenic proteins in the case of the PLA+CaP. The effects of osteopontin (OPN) on the rEPCs migratory response were also studied using this platform, suggesting its important role in mediating their recruitment to a calcium-rich microenvironment. This new tool could be applied to screen the capacity of a variety of bioactive scaffolds to induce vascularization and accelerate the preclinical testing of biomaterials. Statement of significanceFor many years researchers have used neovascularization models to evaluate bioactive biomaterials both in vitro, with low predictive results due to their poor biomimicry and minimal control over cell cues such as spatiotemporal biomolecule signaling, and in vivo models, presenting drawbacks such as being highly costly, time-consuming, poor human extrapolation, and ethically controversial. We describe a compact microphysiological platform designed for the evaluation of proangiogenesis in biomaterials through the quantification of the level of sprouting in a mimicked endothelium able to react to gradients of biomaterial-released signals in a fibrin-based extracellular matrix. This model is a useful tool to perform preclinical trustworthy studies in tissue regeneration and to better understand the different elements involved in the complex process of vascularization.

TLR4-SIRT3 Mechanism Modulates Mitochondrial and Redox Homeostasis and Promotes EPCs Recruitment and Survival.

The low survival rate of endothelial progenitor cells (EPCs) in vivo which are susceptible to adverse microenvironments including inflammation and oxidative stress has become one primary challenge of EPCs transplantation for regenerative therapy. Recent studies reported functional expression of toll-like receptor (TLR) 4 on EPCs and dose-dependent effects of lipopolysaccharide (LPS) on cellular oxidative stress and angiogenic properties. However, the involved mechanism has not yet been elucidated well, and the influence of TLR4 signaling on EPCs survival and function in vivo is unknown. In the present study, we observed the effects of LPS and TLR4/SIRT3 on EPCs mitochondrial permeability and intracellular mitochondrial superoxide. We employed the monocrotaline-induced pulmonary arteriolar injury model to observe the effects of TLR4/SIRT3 on the recruitment and survival of transplanted EPCs. We found the destructive effects of 10 μg/mL LPS on mitochondrial homeostasis, and cellular viability was mediated by TLR4/SIRT3 signals at least partially, and the TLR4 mediates the early-stage recruitment of transplanted EPCs in pulmonary arteriolar inflammation injury; however, SIRT3 has more contribution to the survival of incorporated EPCs and ameliorated arteriolar remodeling in lung vascular tissue. The study provides insights for the critical role of TLR4/SIRT3 in LPS-induced oxidative stress and mitochondrial disorder in EPCs in vitro and in vivo. The TLR4/SIRT3 signaling is important for EPCs resistance against inflammation and oxidative stress and may represent a new manipulating target for developing efficient cell therapy strategy.

E-Selectin/AAV2/2 Gene Therapy Alters Angiogenesis and Inflammatory Gene Profiles in Mouse Gangrene Model

For patients with chronic limb-threatening ischemia and limited revascularization options, alternate means for therapeutic angiogenesis and limb salvage are needed. E-selectin is a cell adhesion molecule that is critical for inflammation and neovascularization in areas of wound healing and ischemia. Here, we tested the efficacy of modifying ischemic limb tissue by intramuscular administration of E-selectin/AAV2/2 (adeno-associated virus serotype 2/2) to modulate angiogenic and inflammatory responses in a murine hindlimb gangrene model. Limb appearance, reperfusion, and functional recovery were assessed for 3 weeks after induction of ischemia. Mice receiving E-selectin/AAV2/2 gene therapy had reduced gangrene severity, increased limb and footpad perfusion, enhanced recruitment of endothelial progenitor cells, and improved performance on treadmill testing compared to control group. Histologically, E-selectin/AAV2/2 gene therapy was associated with increased vascularity and preserved myofiber integrity. E-selectin/AAV2/2 gene therapy also upregulated a panel of pro-angiogenic genes yet downregulated another group of genes associated with the inflammatory response. This novel gene therapy did not induce adverse effects on coagulability, or hematologic, hepatic, and renal function. Our findings highlight the potential of E-selectin/AAV2/2 gene therapy for improving limb perfusion and function in patients with chronic limb-threatening ischemia.

IL-10 promotes endothelial progenitor cell infiltration and wound healing via STAT3.

Endothelial progenitor cells (EPCs) contribute tode novoangiogenesis, tissue regeneration, and remodeling. Interleukin 10 (IL-10), an anti-inflammatory cytokine that primarily signals via STAT3, has been shown to drive EPC recruitment to injured tissues. Our previous work demonstrated that overexpression of IL-10 in dermal wounds promotes regenerative tissue repair via STAT3-dependent regulation of fibroblast-specific hyaluronan synthesis. However, IL-10's role and specific mode of action on EPC recruitment, particularly in dermal wound healing and neovascularization in both normal and diabetic wounds, remain to be defined.Therefore, inducible skin-specific STAT3knockdown mice were studied to determine IL-10's impact on EPCs, dermal wound neovascularization and healing, and whether it is STAT3-dependent. We show that IL-10 overexpression significantly elevated EPC counts in the granulating wound bed, which was associated with robust capillary lumen density and enhanced re-epithelialization of both control and diabetic (db/db) wounds at day 7. We noted increased VEGF and high C-X-C motif chemokine 12 (CXCL12) levels in wounds and a favorable CXCL12gradient at day 3 that may support EPC mobilization and infiltration from bone marrow to wounds, an effect that was abrogated in STAT3knockdown wounds. These findings were supportedin vitro. IL-10 promoted VEGF and CXCL12synthesis in primary murine dermal fibroblasts, with blunted VEGF expression upon blocking CXCL12 in the media by antibody binding. IL-10-conditioned fibroblast media also significantly promoted endothelial sprouting and network formation. In conclusion, these studies demonstrate that overexpression of IL-10 in dermal wounds recruits EPCs and leads to increased vascular structures and faster re-epithelialization.

Regulation of Endothelial Progenitor Cell Functions in Ischemic Heart Disease: New Therapeutic Targets for Cardiac Remodeling and Repair.

Ischemic heart disease (IHD) is the leading cause of morbidity and mortality worldwide. Ischemia and hypoxia following myocardial infarction (MI) cause subsequent cardiomyocyte (CM) loss, cardiac remodeling, and heart failure. Endothelial progenitor cells (EPCs) are involved in vasculogenesis, angiogenesis and paracrine effects and thus have important clinical value in alternative processes for repairing damaged hearts. In fact, this study showed that the endogenous repair of EPCs may not be limited to a single cell type. EPC interactions with cardiac cell populations and mesenchymal stem cells (MSCs) in ischemic heart disease can attenuate cardiac inflammation and oxidative stress in a microenvironment, regulate cell survival and apoptosis, nourish CMs, enhance mature neovascularization, alleviate adverse ventricular remodeling after infarction and enhance ventricular function. In this review, we introduce the definition and discuss the origin and biological characteristics of EPCs and summarize the mechanisms of EPC recruitment in ischemic heart disease. We focus on the crosstalk between EPCs and endothelial cells (ECs), smooth muscle cells (SMCs), CMs, cardiac fibroblasts (CFs), cardiac progenitor cells (CPCs), and MSCs during cardiac remodeling and repair. Finally, we discuss the translation of EPC therapy to the clinic and treatment strategies.

CXCL12 regulates bone marrow–derived endothelial progenitor cells to promote aortic aneurysm recovery

Bone marrow-derived endothelial progenitor cells (EPCs) have been proven to participate in the recovery of aortic aneurysm. CXCL12 promotes EPC recruitment and revascularization. Therefore, this study was dedicated to fathoming out whether EPCs regulated by CXCL12 can participate in the recovery of aneurysm. The morphology and maker protein activity of EPCs derived from bone marrow were separately detected by microscopic examination and immunofluorescence. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot were performed to detect the transfection efficiency of CXCL12. Lumen formation, viability, and migration were determined by lumen formation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and wound-healing assays, respectively. The aneurysm tissues in rat model of artery aneurysm were used for histopathological observation by haematoxylin-eosin (HE) staining, α-SMA was detected by immunohistochemistry, and the expressions of VEGF, IGF1, FGF, PDGF and matrix metalloproteinase-2/9 (MMP-2/9) were measured by RT-qPCR and western blot assays. As a result, some EPCs showed fusiform on day 6, while others showed a cord-like structure. On day 17, cells presented a paving stone-like pattern. The expressions of CD34, CD133 and VEGFR2 were positive. CXCL12 overexpression promoted lumen formation, viability and migration of EPCs, and further facilitated growth of smooth muscle-like cells in the aneurysm cavity and VEGF expression, while inhibiting MMP-2/9 expression in the aneurysm tissues in vivo. The present study suggested that CXCL12 overexpression strengthened the lumen formation, viability, and migration of EPCs, and CXCL12-primed EPCs had better effects on aneurysm recovery than unmodified EPCs did.

SDF-1α loaded bioengineered human amniotic membrane-derived scaffold transplantation in combination with hyperbaric oxygen improved diabetic wound healing

Based on its multifactorial nature, successful treatment of diabetic wounds requires combinatorial approach. In this regard, we hypothesized that engraftment of a bioengineered micro-porous three-dimensional human amniotic membrane-scaffold (HAMS) loaded by SDF-1α (SHAMS) in combination with hyperbaric oxygen (HBO), throughout mobilization and recruitment of endothelial progenitor cells (EPCs), could accelerate wound healing in rats with type 1 diabetes mellitus. To test this hypothesis, 30 days after inducting diabetes, an ischemic wound was created in rat skin and treatments were performed for 21 days. In addition to wounded non-diabetic (ND) group, diabetic animals were randomly divided into non-treated (NT-D), HBO-treated (HBO-D), HBO-treated plus HAMS transplantation (HBO+HAMS-D) or HBO-treated in combination with SHAMS transplantation (HBO+SHAMS-D) groups. Our results on post-wounding days 7, 14 and 21 showed that the wound closure, volume of new dermis and epidermis, numerical density of basal cells of epidermis, fibroblasts and blood vessels, number of proliferating cells, deposition of collagen and biomechanical properties of healed wound were considerably higher in both HBO+HAMS-D and HBO+SHAMS-D groups in comparison to those of the NT-D and HBO-D groups, and were the highest in HBO+SHAMS-D ones. The transcripts for Vegf, bFgf, and Tgf-β genes were significantly upregulated in all treatment regimens compared to NT-D group and were the highest for HBO+SHAMS-D group. This is while expression of Tnf-α and Il-1β as well as cell density of neutrophil and macrophage decreased more significantly in HBO+SHAMS-D group as compared with NT-D or HBO-D groups. Overall, it was found that using both HAMS transplantation and HBO treatment has more impact on diabetic wound healing. Moreover, SDF-1α loading on HAMS could transiently improve the wound healing process, as compared with the HBO+HAMS-D group on day 7 only.

Engagement of the CXCL12-CXCR4 Axis in the Interaction of Endothelial Progenitor Cell and Smooth Muscle Cell to Promote Phenotype Control and Guard Vascular Homeostasis.

Endothelial progenitor cells (EPCs) are involved in vascular repair and modulate properties of smooth muscle cells (SMCs) relevant for their contribution to neointima formation following injury. Considering the relevant role of the CXCL12–CXCR4 axis in vascular homeostasis and the potential of EPCs and SMCs to release CXCL12 and express CXCR4, we analyzed the engagement of the CXCL12–CXCR4 axis in various modes of EPC–SMC interaction relevant for injury- and lipid-induced atherosclerosis. We now demonstrate that the expression and release of CXCL12 is synergistically increased in a CXCR4-dependent mechanism following EPC–SMC interaction during co-cultivation or in response to recombinant CXCL12, thus establishing an amplifying feedback loop Additionally, mechanical injury of SMCs induces increased release of CXCL12, resulting in enhanced CXCR4-dependent recruitment of EPCs to SMCs. The CXCL12–CXCR4 axis is crucially engaged in the EPC-triggered augmentation of SMC migration and the attenuation of SMC apoptosis but not in the EPC-mediated increase in SMC proliferation. Compared to EPCs alone, the alliance of EPC–SMC is superior in promoting the CXCR4-dependent proliferation and migration of endothelial cells. When direct cell–cell contact is established, EPCs protect the contractile phenotype of SMCs via CXCL12–CXCR4 and reverse cholesterol-induced transdifferentiation toward a synthetic, macrophage-like phenotype. In conclusion we show that the interaction of EPCs and SMCs unleashes a CXCL12–CXCR4-based autoregulatory feedback loop promoting regenerative processes and mediating SMC phenotype control to potentially guard vascular homeostasis.

Role of Stromal Cell-Derived Factor-1 in Endothelial Progenitor Cell-Mediated Vascular Repair and Regeneration.

Endothelial progenitor cells (EPCs) are immature endothelial cells that participate in vascular repair and postnatal neovascularization and provide a novel and promising therapy for the treatment of vascular disease. Studies in different animal models have shown that EPC mobilization through pharmacological agents and autologous EPC transplantation contribute to restoring blood supply and tissue regeneration after ischemic injury. However, these effects of the progenitor cells in clinical studies exhibitmixed results. The therapeutic efficacy of EPCs is closely associated with the number of the progenitor cells recruited into ischemic regions and their functional abilities and survival in injury tissues. In this review, we discussed the regulating role ofstromal cell-derived factor-1(also known CXCL12, SDF-1) in EPC mobilization, recruitment, homing, vascular repair and neovascularization, and analyzedthe underlying machemisms of these functions. Application of SDF-1 to improve the regenerative function of EPCs following vascular injurywas also discussed. SDF-1plays a crucial role in mobilizing EPC from bone marrowinto peripheral circulation, recruiting the progenitor cells to target tissue and protecting against cell death under pathological conditions; thus improve EPC regenerative capacity. SDF-1 are crucial for regulating EPC regenerative function, andprovide a potential target for improve therapeutic efficacy of the progenitor cells in treatment of vascular disease.

Perivascular cell-derived extracellular vesicles stimulate colorectal cancer revascularization after withdrawal of antiangiogenic drugs.

Antiangiogenic tyrosine kinase inhibitors (AA‐TKIs) have become a promising therapeutic strategy for colorectal cancer (CRC). In clinical practice, a significant proportion of cancer patients temporarily discontinue AA‐TKI treatment due to recurrent toxicities, economic burden or acquired resistance. However, AA‐TKI therapy withdrawal‐induced tumour revascularization frequently occurs, hampering the clinical application of AA‐TKIs. Here, this study demonstrates that tumour perivascular cells mediate tumour revascularization after withdrawal of AA‐TKI therapy. Pharmacological inhibition and genetic ablation of perivascular cells largely attenuate the rebound effect of CRC vascularization in the AA‐TKI cessation experimental settings. Mechanistically, tumour perivascular cell‐derived extracellular vehicles (TPC‐EVs) contain Gas6 that instigates the recruitment of endothelial progenitor cells (EPCs) for tumour revascularization via activating the Axl pathway. Gas6 silence and an Axl inhibitor markedly inhibit tumour revascularization by impairing EPC recruitment. Consequently, combination therapy of regorafenib with the Axl inhibitor improves overall survival in mice metastatic CRC model by inhibiting tumour growth. Together, these data shed new mechanistic insights into perivascular cells in off‐AA‐TKI‐induced tumour revascularization and indicate that blocking the Axl signalling may provide an attractive anticancer approach for sustaining long‐lasting angiostatic effects to improve the therapeutic outcomes of antiangiogenic drugs in CRC.

The Effect of Platelet-Rich Plasma on Endothelial Progenitor Cell Functionality.

Platelets mediate circulating endothelial progenitor cell (EPC) recruitment and maturation, participating in vascular repair, however the underlying mechanism(s) remain unclear. We investigated the effect of platelet-rich plasma (PRP) on the functionality of CD34+-derived late-outgrowth endothelial cells (OECs) in culture. Confluent OECs were coincubated with PRP under platelet aggregation (with adenosine diphosphate; ADP) and nonaggregation conditions, in the presence/absence of the reversible P2Y12 platelet receptor antagonist ticagrelor. Outgrowth endothelial cell activation was evaluated by determining prostacyclin (PGI2) and monocyte chemoattractant protein-1 (MCP-1) release and intercellular adhesion molecule-1 (ICAM-1) membrane expression. Similar experiments were performed using human umbilical vein endothelial cells (HUVECs). Platelet-rich plasma increased ICAM-1 expression and PGI2 and MCP-1 secretion compared with autologous platelet-poor plasma, whereas ADP-aggregated platelets in PRP did not exhibit any effect. Platelet-rich plasma pretreated with ticagrelor prior to activation with ADP increased all markers to a similar extent as PRP. Similar results were obtained using HUVECs. In conclusion, PRP induces OEC activation, a phenomenon not observed when platelets are aggregated with ADP. Platelet inhibition with ticagrelor restores the PRP capability to activate OECs. Since EPC activation is important for endothelial regeneration and angiogenesis, we suggest that agents inhibiting platelet aggregation, such as ticagrelor, may promote platelet-EPC interaction and EPC function.

The Combination of Tissue-Engineered Blood Vessel Constructs and Parallel Flow Chamber Provides a Potential Alternative to In Vivo Drug Testing Models.

Cardiovascular disease is a major cause of death globally. This has led to significant efforts to develop new anti-thrombotic therapies or re-purpose existing drugs to treat cardiovascular diseases. Due to difficulties of obtaining healthy human blood vessel tissues to recreate in vivo conditions, pre-clinical testing of these drugs currently requires significant use of animal experimentation, however, the successful translation of drugs from animal tests to use in humans is poor. Developing humanised drug test models that better replicate the human vasculature will help to develop anti-thrombotic therapies more rapidly. Tissue-engineered human blood vessel (TEBV) models were fabricated with biomimetic matrix and cellular components. The pro- and anti-aggregatory properties of both intact and FeCl3-injured TEBVs were assessed under physiological flow conditions using a modified parallel-plate flow chamber. These were perfused with fluorescently labelled human platelets and endothelial progenitor cells (EPCs), and their responses were monitored in real-time using fluorescent imaging. An endothelium-free TEBV exhibited the capacity to trigger platelet activation and aggregation in a shear stress-dependent manner, similar to the responses observed in vivo. Ketamine is commonly used as an anaesthetic in current in vivo models, but this drug significantly inhibited platelet aggregation on the injured TEBV. Atorvastatin was also shown to enhance EPC attachment on the injured TEBV. The TEBV, when perfused with human blood or blood components under physiological conditions, provides a powerful alternative to current in vivo drug testing models to assess their effects on thrombus formation and EPC recruitment.

MiR-222-3p downregulation prompted the migration, invasion and recruitment of endothelial progenitor cells via ADIPOR1 expression increase-induced AMKP activation

BackgroundClinical data show that aneurysm rupture causes high mortality in aged men. MicroRNAs (miRNAs) were reported to regulate endothelial progenitor cells (EPCs) which play a vital role in repairing endothelial damage and maintaining vascular integrity. This study identified a novel miRNA regulator for the functions of EPCs in aneurysm repair. MethodsAbdominal aortic aneurysm (AAA) model was established on Sprague-Dawley rats which later underwent antagomiR-222 treatment. The histopathological changes of AAA rats were examined by hematoxylin-eosin staining. Flow cytometry was performed to quantify EPCs in peripheral blood and identify EPCs isolated from the rat femur. The potential target of miR-222-3p was predicted by TargetScan v7.2 and validated by Dual-luciferase reporter assay. The effects of miR-222-3p and ADIPOR1 on the migration, invasion and tube formation of EPCs were evaluated by wound healing, Transwell and tube formation assays. The expressions of miR-222-3p and ADIPOR1 in aortic aneurysm tissues and EPCs were assessed by qRT-PCR or Western blot. ResultsAAA exhibited histopathological abnormality, a decreased number of EPCs in the peripheral blood and an increased miR-222-3p expression. AntagomiR-222 injection reversed all these phenomena in AAA rats. Upregulating miR-222-3p expression inhibited the migration, invasion, and tube formation of EPCs, and the expressions of ADIPOR1 and phosphorylated-AMKP, while downregulating miR-222-3p expression exerted opposite effects in EPCs. ADIPOR1 was identified as a target gene of miR-222-3p. Overexpressing ADIPOR1 abrogated the effects of miR-222-3p upregulation on EPCs. ConclusionDownregulated miR-222-3p prompted the migration, invasion and recruitment of EPCs by targeting ADIPOR1-induced AMKP activation.

An update to the advances in understanding distraction histogenesis: From biological mechanisms to novel clinical applications

Over the past 3 decades, Ilizarov technique namely distraction histogenesis (DH) technique has been widely accepted and applied in orthopaedics and traumatology with outstanding clinical outcomes and emerging novel applications. This review focuses on the recent advances in understanding the biological mechanisms of DH, new methods for promoting bone consolidation in DH procedures and novel clinical applications of DH techniques. Tension stress regulates many genes during DH, including signaling transduction molecules, BMPs, inflammatory and angiogenic factors as well as epigenetic factors. DH also triggers systemic responses such as recruitment of mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs). These activities play important roles in regulating bone regeneration and remodeling during DH. To promote bone formation in DH is still a clinical challenge, and minimal or non-invasive means for promoting bone consolidation are preferable, such as weight-bearing exercise, ultrasound and electromagnetic stimuli; whereas systemic administration of anabolic agents and hormones may also achieve better outcomes. Local cell transplantation and application of various biological factors at the right time may also be the choices. With better understanding of the biological mechanisms, applications of DH technique have now been extended for managing skin wound, joint disorders and avascular diseases. However, more basic or clinical researches are still needed to unravel the “magic” of DH technique. DH technique awakens and promotes human body’s self-regeneration potentials and leads to many novel treatment strategies. A substantial number of methods have been found to promote bone consolidation in DH to shorten the treatment duration and make the application of DH easier. Novel clinical applications of DH technique have now been extended to management of soft-tissue repair disorders, avascular diseases and others, with many more new biological mechanisms yet to be defined. A full understanding of DH technique may facilitate its wider and more appropriate clinical applications.