Supply Of Growth Factors Research Articles

Deep learning reveals a damage signalling hierarchy that coordinates different cell behaviours driving wound re-epithelialisation.

One of the key tissue movements driving closure of a wound is re-epithelialisation. Earlier wound healing studies describe the dynamic cell behaviours that contribute to wound re-epithelialisation, including cell division, cell shape changes and cell migration, as well as the signals that might regulate these cell behaviours. Here, we have used a series of deep learning tools to quantify the contributions of each of these cell behaviours from movies of repairing wounds in the Drosophila pupal wing epithelium. We test how each is altered after knockdown of the conserved wound repair signals Ca2+ and JNK, as well as after ablation of macrophages that supply growth factor signals believed to orchestrate aspects of the repair process. Our genetic perturbation experiments provide quantifiable insights regarding how these wound signals impact cell behaviours. We find that Ca2+ signalling is a master regulator required for all contributing cell behaviours; JNK signalling primarily drives cell shape changes and divisions, whereas signals from macrophages largely regulate cell migration and proliferation. Our studies show deep learning to be a valuable tool for unravelling complex signalling hierarchies underlying tissue repair.

Application of combination chemotherapy in two dimensional tumor growth model with heterogeneous vasculature

We simulate the dynamics of a growing, vascular tumor with a heterogeneous vasculature and its behaviour under combination chemotherapy. The studied model includes two spatial dimensions, treating the system as a multiphase, viscous fluid. The vascular phase is split in young and mature vessels, in order to depict capillary formations in the tissue. Diffusible molecular species are considered, complementary to the fluid's phases, so as to simulate nutrient supply and vascular endothelial growth factor (VEGF) signaling in angiogenesis. Simulations succeed in recreating the spatial distribution of VEGF and underline the importance of chemotaxis to the tumor's nutrient supply. Furthermore, we simulate the effect of anti-VEGF therapy using the drug bevacizumab and combination therapy using bevacizumab with the cytotoxic agent docetaxel. Anti-VEGF treatment appears to slow tumor progression while, combination therapy manages to completely halt it and even leads to tumor shrinkage. Finally, we contemplate on the prospect of scheduling optimisation.

Accelerated wound healing using three-dimensional amniotic membrane scaffold in combination with adipose-derived stem cells in a diabetic rat model

The most important factors in the non-optimal healing of diabetic wounds are the lack of a suitable scaffold in the wound site for the migration and replacement of cells, as well as the lack of blood supply and effective growth factors in the wound site. Herein we investigated whether a bioengineered micro-porous three-dimensional decellularized amniotic membrane-scaffold (DAMS) in combination with adipose-derived stem cells (ASCs) could promote healing in ischemic wounds in diabetic type 1 rat. The diabetic animals were randomly divided into non-treated (untreated group), engraftment by DAMS (DAMS group), transplanted by ASCs (ASC group), and DAMS in combination with ASCs (DAMS+ASC group). Stereological, immunohistochemical, molecular, and tensiometrical assessments were performed on post-surgical days 7, 14, and 21. We found that the rate of wound closure, the volumes of new epidermis and dermis, the numerical density of fibroblasts and blood vessels, the numbers of proliferating cells and collagen deposition as well as biomechanical properties of the healed wounds were significantly higher in the treatment groups in comparison to the untreated group, and were the highest in DAMS+ASC ones. The transcripts for TGF-β and VEGF genes were significantly upregulated in all treatment regimens compared to the untreated group and were the highest for DAMS+ASC group. This is while expression of TNF-α and IL-1β as well as cell density of neutrophils decreased more significantly in DAMS+ASC group as compared with other groups. Overall, it was found that using both DAMS engraftment and ASC transplantation has more impact on diabetic wound healing.

Research progress on infiltrating zone and microvascular invasion of hepatic alveolar echinococcosis

Hepatic alveolar echinococcosis (AE) is a parasitic disease with biological characteristics similar to malignant tumor. It has no obvious clinical symptoms in the early stage. Most patients have complications such as jaundice, ascites and gastrointestinal bleeding when they see a doctor. At this time, the course of disease is at an advanced stage. In addition, the incomplete resection of the AE lesion(s) leads to a high postoperative recurrence rate, which has a serious impact on the physical and mental health of patients. Based on the summary of the latest research at home and abroad and the analysis of blood supply, microvascular invasion and vascular growth factor expression in the "infiltrating zone" adjacent to the lesions of hepatic AE, this article has a deep understanding of the occurrence and development process of hepatic AE, aiming to better guide clinical practice and improve the quality of life of patients.

The sponging effect of a lncRNA on a miRNA contributes to diabetic nephropathy

Vertebrate kidneys play a vital role in draining harmful metabolic waste products in urine, in addition to maintaining homeostasis. Kidneys are composed of a charge- and size-selective glomerular filtration barrier (GFB) that facilitates the excretion of small molecules and retains proteins and other macromolecules in the blood. The permselective GFB comprises three layers: endothelial cells, a basement membrane, and podocytes. Podocytes are highly specialized visceral epithelial cells, which provide coverage to the glomerular capillaries and supply growth factors for endothelium and matrix components to the basement membrane.

Effect of platelet-rich fibrin on the donor site of Split thickness skin graft in burn patients

Background: Patients with massive burn areas have now a greater chance of survival thanks to improved modalities of new treatments. In some patients it is necessary to harvest multiple skin grafts from the same donor site which is restricted by the quality of the skin and the time required to recover; this procedure can take a long time and may increase the danger of bacterial contamination, resulting in increased morbidity and mortality in these individuals. Platelet-rich fibrin is one of the newest autologous growth factors utilized for wound management. PRF application can significantly improve the wound's condition by supplying growth factors to the wound environment, which aid in the epithelialization process's acceleration, resulting in cost-effective wound management. This will allow multiple harvesting from the same donor site, reducing costs, hospitalization time, scars, and co-morbidities. Aim of the Work: To assess the role of PRF in accelerating wound healing in the donor site following skin grafting in burn patients.patients and Methods: This prospective, controlled, clinical trial study was done from April 2020 to April 2021 included 20 patients at the burn unit of El Demerdash Hospital Ain Shams University.Results: The current study showed that healing days in donor sites injected with PRF were lower than those of controlled areas with statistical significance. Mean epidermal thickness was lower in the control area than PRF injected areas with statistical significance.Conclusion: PRF can significantly decrease the time of donor wound healing compared to that of conventional treatment.

Scar free healing of full thickness diabetic wounds: A unique combination of silver nanoparticles as antimicrobial agent, calcium alginate nanoparticles as hemostatic agent, fresh blood as nutrient/growth factor supplier and chitosan as base matrix

Healing of diabetic wounds present a big challenge due to insufficient vascular supply and bacterial infection. We developed chitosan based biodegradable polymeric hydrogel containing silver nanoparticles (AgNPs) as antimicrobial agent and calcium alginate nanoparticles (Ca-AlgNps) as hemostatic agent to address this problem. The prepared Chitosan/Ca-AlgNps/AgNPs hydrogel showed broad spectrum antimicrobial properties against both Gram negative (E. coli, P. aeruginosa) and Gram positive (B. subtilis, S. aureus) bacteria. Taken into account the blood as a vital material containing various circulatory fibrocytes, growth factors, cytokines, platelets and macrophages etc., we incorporated the fresh blood of the same animal to the prepared Chitosan/Ca-Alg Nps/AgNPs hydrogel. In-vivo animal studies of Chitosan/Ca-AlgNps/AgNPs hydrogel and blood mixed Chitosan/Ca-AlgNps/AgNPs hydrogel exhibit 83.5 ± 4.4% and 99.8 ± 2.0% closure of wound respectively, on day 15 as compared to 41.5 ± 3.2% in diabetic control and 60.3 ± 2.2% in commercially available wound healing cream, Silverex Heal. The incorporation of fresh blood to the prepared hydrogel has advantage in terms of supplying growth factors, platelets, circulatory fibrocytes and cytokines which further enhanced the wound healing mechanism in diabetic rats. This work opens a novel idea to formulate hydrogels based dressings for diabetic wound healing.

A Simple and Effective Flow Cytometry-Based Method for Identification and Quantification of Tissue Infiltrated Leukocyte Subpopulations in a Mouse Model of Peripheral Arterial Disease.

Arteriogenesis, the growth of a natural bypass from pre-existing arteriolar collaterals, is an endogenous mechanism to compensate for the loss of an artery. Mechanistically, this process relies on a locally and temporally restricted perivascular infiltration of leukocyte subpopulations, which mediate arteriogenesis by supplying growth factors and cytokines. Currently, the state-of-the-art method to identify and quantify these leukocyte subpopulations in mouse models is immunohistology. However, this is a time consuming procedure. Here, we aimed to develop an optimized protocol to identify and quantify leukocyte subpopulations by means of flow cytometry in adductor muscles containing growing collateral arteries. For that purpose, adductor muscles of murine hindlimbs were isolated at day one and three after induction of arteriogenesis, enzymatically digested, and infiltrated leukocyte subpopulations were identified and quantified by flow cytometry, as exemplary shown for neutrophils and macrophages (defined as CD45+/CD11b+/Ly6G+ and CD45+/CD11b+/F4/80+ cells, respectively). In summary, we show that flow cytometry is a suitable method to identify and quantify leukocyte subpopulations in muscle tissue, and provide a detailed protocol. Flow cytometry constitutes a timesaving tool compared to histology, which might be used in addition for precise localization of leukocytes in tissue samples.

SIRT3 deficiency delays diabetic skin wound healing via oxidative stress and necroptosis enhancement.

Sirtuin 3 (SIRT3) plays a vital role in several dermatological diseases. However, the role and detailed mechanism of SIRT3 in diabetic wound healing are unknown well yet. To explore possible involvement of SIRT3 and necroptosis in diabetic skin wound healing, SIRT3 knockout (KO) mice and 129S1/SvImJ wild‐type (WT) mice were injected with streptozotocin (STZ), and mice skin fibroblasts were exposed to high glucose (HG). It was found that SIRT3 expression decreased in the skin of diabetic patients. SIRT3 deficiency delayed healing rate, reduced blood supply and vascular endothelial growth factor expression, promoted superoxide production, increased malondialdehyde (MDA) levels, decreased total antioxidant capacity (T‐AOC), reduced superoxide dismutase (SOD) activity and aggravated ultrastructure disorder in skin wound of diabetic mice. SIRT3 deficiency inhibited mice skin fibroblasts migration with HG stimulation, which was restored by SIRT3 overexpression. SIRT3 deficiency also suppressed α‐smooth muscle actin (α‐SMA) expression, enhanced superoxide production but decreased mitochondrial membrane potential with HG stimulation after scratch. SIRT3 deficiency further elevated receptor‐interacting protein kinase 3 (RIPK3), RIPK1 and caspase 3 expression both in vitro and in vivo. Collectively, SIRT3 deficiency delayed skin wound healing in diabetes, the mechanism might be related to impaired mitochondria function, enhanced oxidative stress and increased necroptosis. This may provide a novel therapeutic target to accelerate diabetic skin wound healing.

Extracellular RNA released due to shear stress controls natural bypass growth by mediating mechanotransduction in mice

AbstractFluid shear stress in the vasculature is the driving force for natural bypass growth, a fundamental endogenous mechanism to counteract the detrimental consequences of vascular occlusive disease, such as stroke or myocardial infarction. This process, referred to as “arteriogenesis,” relies on local recruitment of leukocytes, which supply growth factors to preexisting collateral arterioles enabling them to grow. Although several mechanosensing proteins have been identified, the series of mechanotransduction events resulting in local leukocyte recruitment is not understood. In a mouse model of arteriogenesis (femoral artery ligation), we found that endothelial cells release RNA in response to increased fluid shear stress and that administration of RNase inhibitor blocking plasma RNases improved perfusion recovery. In contrast, treatment with bovine pancreatic RNase A or human recombinant RNase1 interfered with leukocyte recruitment and collateral artery growth. Our results indicated that extracellular RNA (eRNA) regulated leukocyte recruitment by engaging vascular endothelial growth factor receptor 2 (VEGFR2), which was confirmed by intravital microscopic studies in a murine cremaster model of inflammation. Moreover, we found that release of von Willebrand factor (VWF) as a result of shear stress is dependent on VEGFR2. Blocking VEGFR2, RNase application, or VWF deficiency interfered with platelet–neutrophil aggregate formation, which is essential for initiating the inflammatory process in arteriogenesis. Taken together, the results show that eRNA is released from endothelial cells in response to shear stress. We demonstrate this extracellular nucleic acid as a critical mediator of mechanotransduction by inducing the liberation of VWF, thereby initiating the multistep inflammatory process responsible for arteriogenesis.

Inflation dynamics in a dollarised economy: The case of Zimbabwe

This paper explores the dynamics of inflation in the dollarised Zimbabwean economy using the autoregressive distributed lag (ARDL) model with monthly data from 2009:1 to 2012:12. The main determinants of inflation were found to be the US dollar/South African rand exchange rate, international oil prices, lagged Zimbabwean inflation rate and South African inflation rate. During the local currency era, inflation dynamics in Zimbabwe were explained by excess growth in money supply, changes in import and administered prices, unit labour costs and output (Chhibber, Cottani, Firuzabadi & Walton 1989). According to Makochekanwa (2007), hyperinflation during the same era was attributed to excess money supply growth, lagged inflation and political factors. Coorey, Clausen, Funke, Munoz & Ould-Abdallah (2007) affirmed these findings by identifying excess money supply growth as a source of high inflation in Zimbabwe during the local currency era. In essence, the findings of this study point to a shift in inflation dynamics in Zimbabwe. This shift in inflation dynamics means that policies, which were used to respond to both internal and external shocks that have an impact on price formation, might not be applicable in a dollarised economy.

Treatment of lateral epicondylitis with autologous platelet rich plasma injection

Outcomes of traditional treatment methods of lateral epicondylitis are variable because of poor tendon healing properties secondary to poor vascularization. Platelet rich plasma provides locally high concentration of growth factors and have shown its efficacy in many tendinopathies and wound healing. We tried to measure the efficacy of locally injected autologous PRP, subjectively by functional oxford elbow score and pain score as well as objectively by ultrasonographic evaluation of the morphologic changes (focal hypoechoic, odema, tendon thickness, fraying, tear, cortical erosion, calcification) in common extensor origin in 30 patients with mean age of 39.3 years of recalcitrant lateral epicondylitis. The mean pain VAS Score improved from 7.7 before injection to 1.8 at final follow up i.e. after 6 months post injection. The Oxford elbow score improved from a mean of 19.2 prior to treatment to 41.3 after the injection at final follow. Ultrasonography of the involved elbow showed decrease in focal hypoechoic, decreased edema, improvement in thickness of the tendon and healing of the tear at the origin site. This study confirms that local PRP by supplying growth factors helps to enhance the stromal and mesenchymal stem cell proliferation and increases tendon vascularity and prevents angiofibroblastic degeneration and thus improves tendon repair and healing property by releasing growth factors and increasing vascularity, which can be documented by improved tendon morphology.

Treatment of Cutaneous Ulcers with Multilayered Mixed Sheets of Autologous Fibroblasts and Peripheral Blood Mononuclear Cells

Background/Aims: We have developed a mixed-cell sheet consisting of autologous fibroblasts and peripheral blood mononuclear cells with a high potency for angiogenesis and wound healing against refractory cutaneous ulcers in mouse and rabbit models. To increase the effectiveness of the mixed sheet, we developed a multilayered mixed sheet. Methods: We assessed the therapeutic effects of multilayered sheets on cutaneous ulcers in mice. Growth factors and chemokines were assessed by enzyme-linked immunosorbent assay. Angiogenesis and fibroblast migration were measured by using tube formation and migration assays. Wound healing rate of cutaneous ulcers was evaluated in mice with diabetes mellitus. Results: The concentration of secreted vascular endothelial growth factor, hepatocyte growth factor, transforming growth factor, C-X-C motif chemokine ligand (CXCL)-1, and CXCL-2 in multilayered sheets was much higher than that in single-layered mixed-cell sheets (single-layered sheets) and multilayered sheets of fibroblasts alone (fibroblast sheets). The supernatant in multilayered sheets enhanced angiogenic potency and fibroblast migration compared with single-layered and fibroblast sheets in an in vitro experiment. The wound healing rate in the multilayered sheet-treated group was higher compared with the no-treatment group (control) at the early stage of healing. Moreover, both vessel lumen area and microvessel density in tissues treated with multilayered sheets were significantly increased compared with tissues in the control group. Conclusion: Multilayered sheets promoted wound healing and microvascular angiogenesis in the skin by supplying growth factors and cytokines. Accordingly, our data suggest that multilayered sheets may be a promising therapeutic material for refractory cutaneous ulcers.

Utilization of concentrated growth factor as a sole sinus augmentation material

Posterior maxillary tooth loss frequently coincides with loss of available bone volume for implant placement due to both atrophy of the residual crestal bone and enlargement of the maxillary sinus. The longer the teeth have been missing, the greater the loss of osseous structure that may house implants. This necessitates augmentation of the maxillary sinus to provide adequate bone to place implants. Maxillary sinus augmentation with various bone graft material have become routine treatment over the past 38 years. Various materials have been utilized including allografts, xenografts and synthetics with varying levels of success as measured by the amount of graft maturation and its density to support implants following healing. As the use of autogenous blood products has increased in dental surgery for both soft and hard tissue applications, those materials have expanded into use when augmenting the sinus. As blood biology has grown in use with regard to grafting using the patients own blood to supply growth factors and other patient derived products, grafting has improved the clinical results we are able to achieve. These blood derived products have been mixed with packed osseous graft materials to help improve the quality and quantity of the resulting graft following healing. The case presented in this article demonstrates graft maturation as evidenced by density can be achieved using CGF alone with no added osseous graft materials. The benefit of this approach is no issues with the potential of a patient reaction to the packaged osseous graft material that are typically used and cost of treatment is reduced as packaged products are not utilized in the sinus augmentation procedure.

Meniscus ECM-functionalised hydrogels containing infrapatellar fat pad-derived stem cells for bioprinting of regionally defined meniscal tissue.

Injuries to the meniscus of the knee commonly lead to osteoarthritis. Current therapies for meniscus regeneration, including meniscectomies and scaffold implantation, fail to achieve complete functional regeneration of the tissue. This has led to increased interest in cell and gene therapies and tissue engineering approaches to meniscus regeneration. The implantation of a biomimetic implant, incorporating cells, growth factors, and extracellular matrix (ECM)-derived proteins, represents a promising approach to functional meniscus regeneration. The objective of this study was to develop a range of ECM-functionalised bioinks suitable for 3D bioprinting of meniscal tissue. To this end, alginate hydrogels were functionalised with ECM derived from the inner and outer regions of the meniscus and loaded with infrapatellar fat pad-derived stem cells. In the absence of exogenously supplied growth factors, inner meniscus ECM promoted chondrogenesis of fat pad-derived stem cells, whereas outer meniscus ECM promoted a more elongated cell morphology and the development of a more fibroblastic phenotype. With exogenous growth factors supplementation, a more fibrogenic phenotype was observed in outer ECM-functionalised hydrogels supplemented with connective tissue growth factor, whereas inner ECM-functionalised hydrogels supplemented with TGFβ3 supported the highest levels of Sox-9 and type II collagen gene expression and sulfated glycosaminoglycans (sGAG) deposition. The final phase of the study demonstrated the printability of these ECM-functionalised hydrogels, demonstrating that their codeposition with polycaprolactone microfibres dramatically improved the mechanical properties of the 3D bioprinted constructs with no noticeable loss in cell viability. These bioprinted constructs represent an exciting new approach to tissue engineering of functional meniscal grafts.

The Exometabolome of Two Model Strains of the Roseobacter Group: A Marketplace of Microbial Metabolites.

Recent studies applying Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) showed that the exometabolome of marine bacteria is composed of a surprisingly high molecular diversity. To shed more light on how this diversity is generated we examined the exometabolome of two model strains of the Roseobacter group, Phaeobacter inhibens and Dinoroseobacter shibae, grown on glutamate, glucose, acetate or succinate by FT-ICR-MS. We detected 2,767 and 3,354 molecular formulas in the exometabolome of each strain and 67 and 84 matched genome-predicted metabolites of P. inhibens and D. shibae, respectively. The annotated compounds include late precursors of biosynthetic pathways of vitamins B1, B2, B5, B6, B7, B12, amino acids, quorum sensing-related compounds, indole acetic acid and methyl-(indole-3-yl) acetic acid. Several formulas were also found in phytoplankton blooms. To shed more light on the effects of some of the precursors we supplemented two B1 prototrophic diatoms with the detected precursor of vitamin B1 HET (4-methyl-5-(β-hydroxyethyl)thiazole) and HMP (4-amino-5-hydroxymethyl-2-methylpyrimidine) and found that their growth was stimulated. Our findings indicate that both strains and other bacteria excreting a similar wealth of metabolites may function as important helpers to auxotrophic and prototrophic marine microbes by supplying growth factors and biosynthetic precursors.

Angiogenic potential of human mesenchymal stromal cell and circulating mononuclear cell cocultures is reflected in the expression profiles of proangiogenic factors leading to endothelial cell and pericyte differentiation.

Endothelial progenitors found among the peripheral blood (PB) mononuclear cells (MNCs) are interesting cells for their angiogenic properties. Mesenchymal stromal cells (MSCs) in turn can produce proangiogenic factors as well as differentiate into mural pericytes, making MSCs and MNCs an attractive coculture setup for regenerative medicine. In this study, human bone marrow-derived MSCs and PB-derived MNCs were cocultured in basal or osteoblastic medium without exogenously supplied growth factors to demonstrate endothelial cell, pericyte and osteoblastic differentiation. The expression levels of various proangiogenic factors, as well as endothelial cell, pericyte and osteoblast markers in cocultures were determined by quantitative polymerase chain reaction. Immunocytochemistry for vascular endothelial growth factor receptor-1 and α-smooth muscle actin as well as staining for alkaline phosphatase were performed after 10 and 14days. Messenger ribonucleic acid expression of endothelial cell markers was highly upregulated in both basal and osteoblastic conditions after 5days of coculture, indicating an endothelial cell differentiation, which was supported by immunocytochemistry for vascular endothelial growth factor receptor-1. Stromal derived factor-1 and vascular endothelial growth factor were highly expressed in MSC-MNC coculture in basal medium but not in osteoblastic medium. On the contrary, the expression levels of bone morphogenetic protein-2 and angiopoietin-1 were significantly higher in osteoblastic medium. Pericyte markers were highly expressed in both cocultures after 5days. In conclusion, it was demonstrated endothelial cell and pericyte differentiation in MSC-MNC cocultures both in basal and osteoblastic medium indicating a potential for neovascularization for tissue engineering applications.

Abstract 166: Acceleration of Diabetic Wound Healing With Adipose Derived Stem Cells, Endothelial Differentiated Stem Cells and Topical Conditioned Medium Therapy in a Swine Model

Objectives: The goal of our study is to investigate the effect of adipose derived stem cells (ASCs), endothelial differentiated (ED) ASCs, and various conditioned medium (CM) on wound healing in a diabetic swine model. Methods: Diabetes was induced in 4 male Yorkshire pigs via intravenous injection of 150 mg/kg Streptozotocin. Pig ASCs were harvested and cultured in either M199 or EGM-2 medium with 30 mm glucose. Fourteen circular dorsal wounds (5 cm diameter; 5 mm depth) were created. Duplicate wounds were treated with one of 4 cell-based therapies by injection of 5 million (M) ASCs, 10M ASCs, 5M ED ASCs, or 10M ED ASCs on day 0 and half the initial dose on day 15. Wounds assigned to the topical CM therapy were covered with 2 cc of either serum free M199 primed by ASCs or Human Umbilical Vein Endothelial Cells every 3 days. One set of wound was designated as control. Wounds were assessed at day 0, 10, 15, 20 and 28. Animals were sacrificed on day 28. Image J software was used to evaluate percent wound healing. Results: On day 10, 15, 20 and 28 there was a significant increase in percent wound closure rates in both cell-based treatments when compared to control (p<0.05, Figure 1 ). All treatments displayed significant increase in wound closure rates on day 28 when compared to control. Histology revealed a decrease in dermal inflammatory cells and improved restoration of normal skin architecture in therapeutic treatment groups when compared to untreated controls. Conclusions: Cellular therapy with ASCs, ED ASCs and topical CM accelerate diabetic wound healing in the swine model. Cellular therapy may provide the greatest benefit, as cells may continuously supply growth factors and adapt to the evolving microcellular environment as the wound progresses through the various phases of healing

The Toll-like receptor 4-activated neuroprotective microglia subpopulation survives via granulocyte macrophage colony-stimulating factor and JAK2/STAT5 signaling

Toll-like receptor (TLR) 4 mediates inflammation and is also known to trigger apoptosis in microglia. Our time-lapse observations showed that lipopolysaccharide (LPS) stimulation induced rapid death in primary cultures of rat microglia, while a portion of the microglia escaped from death and survived for much longer than 2 days, in which time, all of the control cells had died. However, it remains unclear how the LPS-stimulated microglia subpopulation could continue to survive in the absence of any supplied growth factors. In the present study, to clarify the mechanism underlying the LPS-stimulated survival, we investigated whether microglia could produce their own survival factors in response to LPS, focusing on macrophage colony-stimulating factor (M-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-34, which are mainly supplied by astrocytes or neurons. The LPS-stimulated microglia drastically induced the expression of the GM-CSF mRNA and protein, while M-CSF and IL-34 levels were unchanged. The surviving microglia also significantly upregulated the expression of GM-CSF receptor (GM-CSFR) mRNA without affecting M-CSFR. As for the GM-CSFR downstream signal, LPS resulted in the phosphorylation of STAT5 and its translocation to the nucleus in the surviving microglia. Moreover, a specific JAK2 inhibitor, NVP-BSK805, suppressed STAT5 phosphorylation and microglia survival in response to LPS, indicating a critical role of the JAK2/STAT5 pathway in this survival mechanism. Together, these results suggest that a subpopulation of TLR4-activated microglia may survive by producing GM-CSF and up-regulating GM-CSFR. This autocrine GM-CSF pathway may activate the JAK2/STAT5 signaling pathway, which controls the transcription of survival-related genes. Finally, these surviving microglia may have neuroprotective functions because the neurons remained viable in co-cultures with these microglia.

Monocyte dysfunction as a previously unrecognized pathophysiological mechanism in ApoE −/− mice contributing to impaired arteriogenesis

Hyperlipidemia (HL) is a major cardiovascular risk factor promoting atherogenesis leading to coronary and peripheral artery disease. Collateral vessel development, a crucial compensatory mechanism in peripheral artery disease, is negatively influenced by HL [1]. Monocytes and tissue-resident macrophages accelerate both atherogenesis and arteriogenesis by supplying growth factors, cytokines and proteolytic enzymes [2]. The decreased monocyte/macrophage accumulation around growing collateral vessels in HL is associated with jeopardized arteriogenesis [1].