PDGF signaling in cells and mice

Inhibition of myotube formation by platelet-derived growth factor subunit B in QM7 cells

OBJECTIVE

The primary objective of this study was to investigate the role and regulatory mechanisms of platelet-derived growth factor subunit B (PDGFB) in muscle differentiation.

METHODS

In this study, a vector for PDGFB was designed and transfected into quail muscle cells to investigate its role and regulatory mechanism during muscle formation. To investigate the inhibitory mechanisms of PDGFB on myogenic differentiation, the mRNA expression levels of various genes and the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK 1/2), both known to regulate muscle development and differentiation were compared.

RESULTS

PDGFB-overexpressed (OE) cells formed morphologically shorter and thinner myotubes and demonstrated a smaller total myotube area than did the control cells. This result was also confirmed at the molecular level by a reduced amount of myosin heavy chain protein in the PDGFB-OE cells. Therefore, PDGFB inhibits the differentiation of muscle cells. Additionally, the expression of myogenin (MYOG) significantly decreased in the PDGFBOE cells on days 2 and 4 compared with that in the control cells. The phosphorylation of ERK 1/2, an upstream protein that inhibits MYOG expression, increased in the PDGFB-OE cells on day 4 compared with that in the control cells. The decreased expression of MYOG in the PDGFB-OE cells increased by inhibition ERK 1/2 phosphorylation.

CONCLUSION

PDGFB may suppress myogenesis by reducing MYOG expression through ERK 1/2 phosphorylation. These findings can help understand muscle differentiation and potentially improve poultry meat production.

miR-1458 is inhibited by low concentrations of Vitamin B6 and targets TBX6 to promote the formation of spermatogonial stem cells in Rugao Yellow Chicken

Spermatogonial stem cells (SSCs) have vast application prospects in livestock and poultry production, genetic engineering, and medical research. However, the scarcity of SSCs and the complexity of their development limit the elucidation and verification of the mechanism of SSCs in vitro. Although miRNAs have been identified as critical players in germ cell development, upstream regulatory mechanisms by which miRNAs regulate SSCs formation are rarely reported. In this study, miR-1458, which was differentially expressed during SSCs formation, was selected by transcriptomic sequencing. We found that miR-1458, inhibited in an in vitro SSCs induction model, significantly upregulated the expression of germline marker genes (Cvh and integrin β1). Further analysis using Immunofluorescence and Flow Cytometry confirmed that miR-1458 inhibition promotes the formation of spermatogonial stem-like cells (SSCLCs). Immunohistochemical significantly increased the number of SSCs in the testis in vivo. However, significant upregulation of miR-1458 showed opposite results. High-throughput sequencing results showed that miR-1458 interacted with TBX6, one of the target genes of miR-1458, involved in affecting cell differentiation, and dual-luciferase reporter vectors confirmed the targeting relationship between the two. TBX6 overexpression and knockdown in vitro and in vivo have validated its function in SSCs formation. We found that overexpression of TBX6 promoted SSCs formation. Additionally, we identified Vitamin B6, a key metabolite affecting SSCs formation, as an upstream regulator of miR-1458 expression. The results showed that low concentrations of Vitamin B6 led to low expression of miR-1458 by decreasing histone demethylation levels. Overall, our findings suggest that miR-1458 is involved in SSCs formation, which is inhibited by low concentrations of Vitamin B6 and subsequently regulates the formation of SSCs by targeting TBX6, an essential gene involved in embryonic stem cell differentiation. Our study demonstrates the critical role of the Vitamin B6-miR-1458-TBX6 regulatory axis in spermatogonial stem cell formation in Rugao Yellow Chicken, providing new insights into the regulatory mechanisms by which miRNAs affect SSCs formation. It should be noted that most of the germline findings related to miRNAs were obtained by in vitro studies, and in vivo studies are needed to validate our results for clinical applications.

Correlation between PDGF-BB and M1-type macrophage in inflammatory bowel disease: a case-control study

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic disease in which macrophages play an important role in its pathogenesis. Platelet-derived growth factor-BB (PDGF-BB) secreted by macrophages is involved in the repair of vascular endothelial injury during inflammatory reactions.

METHODS

The expression levels of M1 macrophages and PDGF-BB in serum and colonic mucosa of 30 patients with Crohn's disease (CD) and 30 patients with ulcerative colitis (UC) were measured using enzyme-linked immunosorbent assays and immunohistochemistry. Logistic regression was used for univariate and multivariate analyses, and receiver operating characteristic curves were used to evaluate diagnostic value. Associations were evaluated using Spearman correlation analysis.

RESULTS

The expression of serum PDGF-BB and M1 macrophages with positive CXCL9 expression in patients with active-stage IBD [206.55(160.41,262.90)and 337.30(217.73,472.28) pg/ml] was higher than that in patients with remission stage [153.42(107.02,219.68)and 218.37(144.49,347.33)pg/ml] and controls [156.19(91.16,216.08)and 191.20(121.42,311.76)pg/ml](P < 0.05). The expression of PDGF-BB, CD86, and CXCL9 in the colon of patients with active-stage IBD [0.380(0.266,0.542) 0.663(0.480,0.591) and 0.564(0.378,0.765) /µm2] was higher than that in the remission stage [0.308(0.214,0.420), 0.376(0.206,0.591) and 0.413(0.275,0.570) /µm2] and controls [0.265(0.185,0.384), 0.416(0.269,0.534) and 0.497(0.415,0.642) /µm2] (P < 0.05). A positive correlation was observed between CD86 and PDGF-BB, and CXCL9 and PDGF-BB levels in patients with IBD (P < 0.05). CD86 and PDGF-BB in the colonic mucosa were independent risk factors for active IBD, and the area under the curve for their combined diagnosis was 0.754 (95%CI: 0.654-0.852, P < 0.05).

CONCLUSIONS

PDGF-BB was associated with M1 macrophages and has a potential diagnostic value for active IBD.

TRIAL REGISTRATION

Not applicable.

Suppressing PDGFRβ Signaling Enhances Myocyte Fusion to Promote Skeletal Muscle Regeneration

Muscle cell fusion is critical for forming and maintaining multinucleated myotubes during skeletal muscle development and regeneration. However, the molecular mechanisms directing cell-cell fusion are not fully understood. Here, we identify platelet-derived growth factor receptor beta (PDGFRβ) signaling as a key modulator of myocyte fusion in adult muscle cells. Our findings demonstrate that genetic deletion of Pdgfrβ enhances muscle regeneration and increases myofiber size, whereas PDGFRβ activation impairs muscle repair. Inhibition of PDGFRβ activity promotes myonuclear accretion in both mouse and human myotubes, whereas PDGFRβ activation stalls myotube development by preventing cell spreading to limit fusion potential. Transcriptomics analysis show that PDGFRβ signaling cooperates with TGFβ signaling to direct myocyte size and fusion. Mechanistically, PDGFRβ signaling requires STAT1 activation, and blocking STAT1 phosphorylation enhances myofiber repair and size during regeneration. Collectively, PDGFRβ signaling acts as a regenerative checkpoint and represents a potential clinical target to rapidly boost skeletal muscle repair.

Platelet-derived growth factor-stimulated pulmonary artery smooth muscle cells regulate pulmonary artery endothelial cell dysfunction through extracellular vesicle miR-409-5p

Platelet-derived growth factor (PDGF)-induced changes in vascular smooth muscle cells (VSMCs) stimulate vascular remodeling, resulting in vascular diseases such as pulmonary arterial hypertension. VSMCs communicate with endothelial cells through extracellular vesicles (EVs) carrying cargos, including microRNAs. To understand the molecular mechanisms through which PDGF-stimulated pulmonary artery smooth muscle cells (PASMCs) interact with pulmonary artery endothelial cells (PAECs) under pathological conditions, we investigated the crosstalk between PASMCs and PAECs via extracellular vesicle miR-409-5p under PDGF stimulation. miR-409-5p expression was upregulated in PASMCs upon PDGF signaling, and it was released into EVs. The elevated expression of miR-409-5p was transported to PAECs and led to their impaired function, including reduced NO release, which consequentially resulted in enhanced PASMC proliferation. We propose that the positive regulatory loop of PASMC-extracellular vesicle miR-409-5p-PAEC is a potential mechanism underlying the proliferation of PASMCs under PDGF stimulation. Therefore, miR-409-5p may be a novel therapeutic target for the treatment of vascular diseases, including pulmonary arterial hypertension.

miRNA Regulation of Cell Phenotype and Parietal Remodeling in Atherosclerotic and Non-Atherosclerotic Aortic Aneurysms: Differences and Similarities

Aortic aneurysms are a serious health concern as their rupture leads to high morbidity and mortality. Abdominal aortic aneurysms (AAAs) and thoracic aortic aneurysms (TAAs) exhibit differences and similarities in their pathophysiological and pathogenetic features. AAA is a multifactorial disease, mainly associated with atherosclerosis, characterized by a relevant inflammatory response and calcification. TAA is rarely associated with atherosclerosis and in some cases is associated with genetic mutations such as Marfan syndrome (MFS) and bicuspid aortic valve (BAV). MFS-related and non-genetic or sporadic TAA share aortic degeneration with endothelial-to-mesenchymal transition (End-Mt) and fibrosis, whereas in BAV TAA, aortic degeneration with calcification prevails. microRNA (miRNAs) contribute to the regulation of aneurysmatic aortic remodeling. miRNAs are a class of non-coding RNAs, which post-transcriptionally regulate gene expression. In this review, we report the involvement of deregulated miRNAs in the different aortic remodeling characterizing AAAs and TAAs. In AAA, miRNA deregulation appears to be involved in parietal inflammatory response, smooth muscle cell (SMC) apoptosis and aortic wall calcification. In sporadic and MFS-related TAA, miRNA deregulation promotes End-Mt, SMC myofibroblastic phenotypic switching and fibrosis with glycosaminoglycan accumulation. In BAV TAA, miRNA deregulation sustains aortic calcification. Those differences may support the development of more personalized therapeutic approaches.

Hepatocellular Carcinoma: Old and Emerging Therapeutic Targets

Liver cancer, predominantly hepatocellular carcinoma (HCC), globally ranks sixth in incidence and third in cancer-related deaths. HCC risk factors include non-viral hepatitis, alcohol abuse, environmental exposures, and genetic factors. No specific genetic alterations are unequivocally linked to HCC tumorigenesis. Current standard therapies include surgical options, systemic chemotherapy, and kinase inhibitors, like sorafenib and regorafenib. Immunotherapy, targeting immune checkpoints, represents a promising avenue. FDA-approved checkpoint inhibitors, such as atezolizumab and pembrolizumab, show efficacy, and combination therapies enhance clinical responses. Despite this, the treatment of hepatocellular carcinoma (HCC) remains a challenge, as the complex tumor ecosystem and the immunosuppressive microenvironment associated with it hamper the efficacy of the available therapeutic approaches. This review explores current and advanced approaches to treat HCC, considering both known and new potential targets, especially derived from proteomic analysis, which is today considered as the most promising approach. Exploring novel strategies, this review discusses antibody drug conjugates (ADCs), chimeric antigen receptor T-cell therapy (CAR-T), and engineered antibodies. It then reports a systematic analysis of the main ligand/receptor pairs and molecular pathways reported to be overexpressed in tumor cells, highlighting their potential and limitations. Finally, it discusses TGFβ, one of the most promising targets of the HCC microenvironment.

Mechanistic characterization of a Drosophila model of paraneoplastic nephrotic syndrome

Paraneoplastic syndromes occur in cancer patients and originate from dysfunction of organs at a distance from the tumor or its metastasis. A wide range of organs can be affected in paraneoplastic syndromes; however, the pathological mechanisms by which tumors influence host organs are poorly understood. Recent studies in the fly uncovered that tumor secreted factors target host organs, leading to pathological effects. In this study, using a Drosophila gut tumor model, we characterize a mechanism of tumor-induced kidney dysfunction. Specifically, we find that Pvf1, a PDGF/VEGF signaling ligand, secreted by gut tumors activates the PvR/JNK/Jra signaling pathway in the principal cells of the kidney, leading to mis-expression of renal genes and paraneoplastic renal syndrome-like phenotypes. Our study describes an important mechanism by which gut tumors perturb the function of the kidney, which might be of clinical relevance for the treatment of paraneoplastic syndromes.

Growth factors and their peptide mimetics for treatment of traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of disability in adults, caused by a physical insult damaging the brain. Growth factor-based therapies have the potential to reduce the effects of secondary injury and improve outcomes by providing neuroprotection against glutamate excitotoxicity, oxidative damage, hypoxia, and ischemia, as well as promoting neurite outgrowth and the formation of new blood vessels. Despite promising evidence in preclinical studies, few neurotrophic factors have been tested in clinical trials for TBI. Translation to the clinic is not trivial and is limited by the short in vivo half-life of the protein, the inability to cross the blood-brain barrier and human delivery systems. Synthetic peptide mimetics have the potential to be used in place of recombinant growth factors, activating the same downstream signalling pathways, with a decrease in size and more favourable pharmacokinetic properties. In this review, we will discuss growth factors with the potential to modulate damage caused by secondary injury mechanisms following a traumatic brain injury that have been trialled in other indications including spinal cord injury, stroke and neurodegenerative diseases. Peptide mimetics of nerve growth factor (NGF), hepatocyte growth factor (HGF), glial cell line-derived growth factor (GDNF), brain-derived neurotrophic factor (BDNF), platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) will be highlighted, most of which have not yet been tested in preclinical or clinical models of TBI.

Exposure to real-ambient particulate matter induced vascular hypertrophy through activation of PDGFRβ

BACKGROUND

Vascular toxicity induced by particulate matter (PM) exposure exacerbates the onset and development of cardiovascular diseases; however, its detailed mechanism remains unclear. Platelet-derived growth factor receptor β (PDGFRβ) acts as a mitogen for vascular smooth muscle cells (VSMCs) and is therefore essential for normal vasoformation. However, the potential effects of PDGFRβ on VSMCs in PM-induced vascular toxicity have not yet been elucidated.

METHODS

To reveal the potential roles of PDGFRβ signalling in vascular toxicity, individually ventilated cage (IVC)-based real-ambient PM exposure system mouse models and PDGFRβ overexpression mouse models were established in vivo, along with in vitro VSMCs models.

RESULTS

Vascular hypertrophy was observed following PM-induced PDGFRβ activation in C57/B6 mice, and the regulation of hypertrophy-related genes led to vascular wall thickening. Enhanced PDGFRβ expression in VSMCs aggravated PM-induced smooth muscle hypertrophy, which was attenuated by inhibiting the PDGFRβ and janus kinase 2 /signal transducer and activator of transcription 3 (JAK2/STAT3) pathways.

CONCLUSION

Our study identified the PDGFRβ gene as a potential biomarker of PM-induced vascular toxicity. PDGFRβ induced hypertrophic effects through the activation of the JAK2/STAT3 pathway, which may be a biological target for the vascular toxic effects caused by PM exposure.

Age-dependent Pdgfrβ signaling drives adipocyte progenitor dysfunction to alter the beige adipogenic niche in male mice

Perivascular adipocyte progenitor cells (APCs) can generate cold temperature-induced thermogenic beige adipocytes within white adipose tissue (WAT), an effect that could counteract excess fat mass and metabolic pathologies. Yet, the ability to generate beige adipocytes declines with age, creating a key challenge for their therapeutic potential. Here we show that ageing beige APCs overexpress platelet derived growth factor receptor beta (Pdgfrβ) to prevent beige adipogenesis. We show that genetically deleting Pdgfrβ, in adult male mice, restores beige adipocyte generation whereas activating Pdgfrβ in juvenile mice blocks beige fat formation. Mechanistically, we find that Stat1 phosphorylation mediates Pdgfrβ beige APC signaling to suppress IL-33 induction, which dampens immunological genes such as IL-13 and IL-5. Moreover, pharmacologically targeting Pdgfrβ signaling restores beige adipocyte development by rejuvenating the immunological niche. Thus, targeting Pdgfrβ signaling could be a strategy to restore WAT immune cell function to stimulate beige fat in adult mammals.

VEGF Induces Expression of Genes That Either Promote or Limit Relaxation of the Retinal Endothelial Barrier

The purpose of this study was to identify genes that mediate VEGF-induced permeability. We performed RNA-Seq analysis on primary human retinal endothelial cells (HRECs) cultured in normal (5 mM) and high glucose (30 mM) conditions that were treated with vehicle, VEGF, or VEGF then anti-VEGF. We filtered our RNA-Seq dataset to identify genes with the following four characteristics: (1) regulated by VEGF, (2) VEGF regulation reversed by anti-VEGF, (3) regulated by VEGF in both normal and high glucose conditions, and (4) known contribution to vascular homeostasis. Of the resultant 18 genes, members of the Notch signaling pathway and ANGPT2 (Ang2) were selected for further study. Permeability assays revealed that while the Notch pathway was dispensable for relaxing the barrier, it contributed to maintaining an open barrier. In contrast, Ang2 limited the extent of barrier relaxation in response to VEGF. These findings indicate that VEGF engages distinct sets of genes to induce and sustain barrier relaxation. Furthermore, VEGF induces expression of genes that limit the extent of barrier relaxation. Together, these observations begin to elucidate the elegance of VEGF-mediated transcriptional regulation of permeability.

Thermogenic adipose tissue in energy regulation and metabolic health

The ability to generate thermogenic fat could be a targeted therapy to thwart obesity and improve metabolic health. Brown and beige adipocytes are two types of thermogenic fat cells that regulate energy balance. Both adipocytes share common morphological, biochemical, and thermogenic properties. Yet, recent evidence suggests unique features exist between brown and beige adipocytes, such as their cellular origin and thermogenic regulatory processes. Beige adipocytes also appear highly plastic, responding to environmental stimuli and interconverting between beige and white adipocyte states. Additionally, beige adipocytes appear to be metabolically heterogenic and have substrate specificity. Nevertheless, obese and aged individuals cannot develop beige adipocytes in response to thermogenic fat-inducers, creating a key clinical hurdle to their therapeutic promise. Thus, elucidating the underlying developmental, molecular, and functional mechanisms that govern thermogenic fat cells will improve our understanding of systemic energy regulation and strive for new targeted therapies to generate thermogenic fat. This review will examine the recent advances in thermogenic fat biogenesis, molecular regulation, and the potential mechanisms for their failure.

Bioinformatic analysis of biological pathways in coronary heart disease and Alzheimer’s disease

Aim. Using bioinformatic tools, to perform a pathway enrichment analysis in Alzheimer’s disease and coronary heart disease (CHD).

Materials and methods. Genes contributing to susceptibility to CHD and Alzheimer’s disease were obtained from the public database DisGeNET (Database of Gene – Disease Associations). A pathway enrichment analysis was performed in the ClueGO Cytoscape plug-in (version 3.6.0) using hypergeometric distribution and the KEGG and Reactome databases.

Results. The identified genes contributing to susceptibility to Alzheimer’s disease and CHD are included in 69 common signaling pathways, grouped into the following subgroups: cell death signaling pathways (1); signaling pathways regulating immune responses (2); signaling pathways responsible for fatty acid metabolism (3); signaling pathways involved in the functioning of the nervous system (4), cardiovascular system (5), and endocrine system (6).

Conclusion. Following the performed analysis, we identified possible associations between processes involving genetic factors and their products in CHD and Alzheimer’s disease. In particular, we assumed that susceptibility genes involved in the implementation of these pathways regulate apoptosis, production of inflammatory cytokines and chemokines, lipid metabolism, β-amyloid formation, and angiogenesis.

Novel therapeutic perspectives for crescentic glomerulonephritis through targeting parietal epithelial cell activation and proliferation

INTRODUCTION

Kidney injury is clinically classified as crescentic glomerulonephritis (CrGN) when ≥50% of the glomeruli in a biopsy sample contain crescentic lesions. However, current strategies, such as systemic immunosuppressive therapy and plasmapheresis for CrGN, are partially effective, and these drugs have considerable systemic side effects. Hence, targeted therapy to prevent glomerular crescent formation and expansion remains an unmet clinical need.

AREAS COVERED

Hyperproliferative parietal epithelial cells (PECs) are the main constituent cells of the glomerular crescent with cell-tracing evidence. Crescents obstruct the flow of primary urine, pressure the capillaries, and degenerate the affected nephrons. We reviewed the markers of PEC activation and proliferation, potential therapeutic effects of thrombin and thrombin receptor inhibitors, and how podocytes cross-talk with PECs. These experiments may help identify potential early specific targets for the prevention and treatment of glomerular crescentic injury.

EXPERT OPINION

Inhibiting PEC activation and proliferation in CrGN can alleviate glomerular crescent progression, which has been supported by preclinical studies with evidence of genetic deletion. Clarifying the outcome of PEC transformation to the podocyte phenotype and suppressing thrombin, thrombin receptors, and PEC hyperproliferation in early therapeutic strategies will be the research goals in the next ten years.

miR-335-5p regulates the proliferation, migration and phenotypic switching of vascular smooth muscle cells in aortic dissection by directly regulating SP1

Uncontrolled proliferation, migration and phenotypic switching of vascular smooth muscle cells (VSMCs) are important steps in the development and progression of aortic dissection (AD). The function and potential mechanism of miR-335-5p in the pathogenesis of AD are explored in this study. Specifically, the biological function of miR-335-5p is explored in vitro through CCK-8, Transwell, immunofluorescence, EdU, wound-healing, RT-qPCR and western blotting assays. In addition, an AD model induced by angiotensin II is used to investigate the function of miR-335-5p in vivo. A dual-luciferase assay is performed to verify the targeting relationship between miR-335-5p and specificity protein 1 (SP1). Experiments involving the loss of SP1 function are performed to demonstrate the function of SP1 in the miR-335-5p-mediated regulation of human aortic-VSMCs (HA-VSMCs). AD tissues and platelet-derived growth factor BB (PDGF-BB)-stimulated HA-VSMCs show significant downregulation of miR-335-5p expression and upregulated SP1 expression. Overexpression of miR-335-5p effectively suppresses cell proliferation, migration and synthetic phenotype markers and enhances contractile phenotype markers induced by PDGF-BB treatment. Additionally, SP1 is identified as a target gene downstream of miR-335-5p, and its expression is negatively correlated with miR-335-5p in AD. Upregulation of SP1 partially reverses the inhibitory effect of miR-335-5p on HA-VSMCs, whereas the downregulation of SP1 has the opposite effect. Furthermore, Ad-miR-335-5p clearly suppresses aorta dilatation and vascular media degeneration in the AD model. Our results suggest that miR-335-5p inhibits HA-VSMC proliferation, migration and phenotypic switching by negatively regulating SP1, and indicate that miR-335-5p may be a potential therapeutic target in AD.

Theaflavin-3,3′-Digallate from Black Tea Inhibits Neointima Formation Through Suppression of the PDGFRβ Pathway in Vascular Smooth Muscle Cells

The abnormal neointima formation caused by the phenotypic switching of vascular smooth cells (VSMCs) into a synthetic state plays a key role in the pathogenesis of various vascular diseases, including atherosclerosis and postangioplasty restenosis. Theaflavin-3,3′-digallate (TF3) in black tea has been reported to exert antiinflammatory and anticancer effects, but its role in neointima formation remains unclear. Here, we delineated a remarkable effect of TF3 in suppressing neointima formation of VSMCs in vivo as well as the ability of primary rat aortic smooth cells (RASMCs) to proliferate and migrate in vitro. Further study confirmed that the effects of TF3 on PDGF-BB–induced RASMCs were due to reduced phosphorylation of PDGFRβ, which led to the repression of downstream pathways. We concluded that TF3 may act as a repressor in the progression of neointima formation and serve as a potential therapeutic candidate for excessive phenotypic switching of VSMCs.

RNA-Seq Profiling of Neutrophil-Derived Microvesicles in Alzheimer's Disease Patients Identifies a miRNA Signature That May Impact Blood-Brain Barrier Integrity

(1) Background: Systemic infection is associated with increased neuroinflammation and accelerated cognitive decline in AD patients. Activated neutrophils produce neutrophil-derived microvesicles (NMV), which are internalised by human brain microvascular endothelial cells and increase their permeability in vitro, suggesting that NMV play a role in blood-brain barrier (BBB) integrity during infection. The current study investigated whether microRNA content of NMV from AD patients is significantly different compared to healthy controls and could impact cerebrovascular integrity. (2) Methods: Neutrophils isolated from peripheral blood samples of five AD and five healthy control donors without systemic infection were stimulated to produce NMV. MicroRNAs isolated from NMV were analysed by RNA-Seq, and online bioinformatic tools were used to identify significantly differentially expressed microRNAs in the NMV. Target and pathway analyses were performed to predict the impact of the candidate microRNAs on vascular integrity. (3) Results: There was no significant difference in either the number of neutrophils (p = 0.309) or the number of NMV (p = 0.3434) isolated from AD donors compared to control. However, 158 microRNAs were significantly dysregulated in AD NMV compared to controls, some of which were associated with BBB dysfunction, including miR-210, miR-20b-5p and miR-126-5p. Pathway analysis revealed numerous significantly affected pathways involved in regulating vascular integrity, including the TGFβ and PDGFB pathways, as well as Hippo, IL-2 and DNA damage signalling. (4) Conclusions: NMV from AD patients contain miRNAs that may alter the integrity of the BBB and represent a novel neutrophil-mediated mechanism for BBB dysfunction in AD and the accelerated cognitive decline seen as a result of a systemic infection.

Diverse roles of tumor-stromal PDGFB-to-PDGFRβ signaling in breast cancer growth and metastasis

Over the last couple of decades, it has become increasingly apparent that the tumor microenvironment (TME) mediates every step of cancer progression and solid tumors are only able to metastasize with a permissive TME. This intricate interaction of cancer cells with their surrounding TME, or stroma, is becoming more understood with an ever greater knowledge of tumor-stromal signaling pairs such as platelet-derived growth factors (PDGF) and their cognate receptors. We and others have focused our research efforts on understanding how tumor-derived PDGFB activates platelet-derived growth factor receptor beta (PDGFRβ) signaling specifically in the breast cancer TME. In this chapter, we broadly discuss PDGF and PDGFR expression patterns and signaling in normal physiology and breast cancer. We then detail the expansive roles played by the PDGFB-to-PDGFRβ signaling pathway in modulating breast tumor growth and metastasis with a focus on specific cellular populations within the TME, which are responsive to tumor-derived PDGFB. Given the increasingly appreciated importance of PDGFB-to-PDGFRβ signaling in breast cancer progression, specifically in promoting metastasis, we end by discussing how therapeutic targeting of PDGFB-to-PDGFRβ signaling holds great promise for improving current breast cancer treatment strategies.

PDGF/PDGFR: A Possible Molecular Target in Scleroderma Fibrosis

Systemic sclerosis (SSc) is a clinically heterogeneous disorder of the connective tissue characterized by vascular alterations, immune/inflammatory manifestations, and organ fibrosis. SSc pathogenesis is complex and still poorly understood. Therefore, effective therapies are lacking and remain nonspecific and limited to disease symptoms. In the last few years, many molecular and cellular mediators of SSc fibrosis have been described, providing new potential options for targeted therapies. In this review: (i) we focused on the PDGF/PDGFR pathway as key signaling molecules in the development of tissue fibrosis; (ii) we highlighted the possible role of stimulatory anti-PDGFRα autoantibodies in the pathogenesis of SSc; (iii) we reported the most promising PDGF/PDGFR targeting therapies.

Pharmacological inhibition of epidermal growth factor receptor attenuates intracranial aneurysm formation by modulating the phenotype of vascular smooth muscle cells

AIM

To study the effect of pharmacological inhibition of epidermal growth factor receptor (EGFR) on intracranial aneurysm (IA) initiation.

METHODS

Human IA samples were analyzed for the expression of p-EGFR and alpha smooth muscle actin (α-SMA) by immunofluorescence (IF). Rat models of IA were established to evaluate the ability of the EGFR inhibitor, erlotinib, to attenuate the incidence of IA. We analyzed anterior cerebral artery tissues by pathological and proteomic detection for the expression of p-EGFR and relevant proteins, and vessel casting was used to evaluate the incidence of aneurysms in each group. Rat vascular smooth muscle cells (VSMCs) and endothelial cells were extracted and used to establish an in vitro co-culture model in a flow chamber with or without erlotinib treatment. We determined p-EGFR and relevant protein expression in VSMCs by immunoblotting analysis.

RESULTS

Epidermal growth factor receptor activation was found in human IA vessel walls and rat anterior cerebral artery walls. Treatment with erlotinib markedly attenuated the incidence of IA by inhibiting vascular remodeling and pro-inflammatory transformation of VSMC in rat IA vessel walls. Activation of EGFR in rat VSMCs and phenotypic modulation of rat VSMCs were correlated with the strength of shear stress in vitro, and treatment with erlotinib reduced phenotypic modulation of rat VSMCs. In vitro experiments also revealed that EGFR activation could be induced by TNF-α in human brain VSMCs.

CONCLUSIONS

These results suggest that EGFR plays a critical role in the initiation of IA and that the EGFR inhibitor erlotinib protects rats from IA initiation by regulating phenotypic modulation of VSMCs.

Skeletal stem cell fate defects caused by Pdgfrb activating mutation

Autosomal dominant PDGFRβ gain-of-function mutations in mice and humans cause a spectrum of wasting and overgrowth disorders afflicting the skeleton and other connective tissues, but the cellular origin of these disorders remains unknown. We demonstrate that skeletal stem cells (SSCs) isolated from mice with a gain-of-function D849V point mutation in PDGFRβ exhibit colony formation defects that parallel the wasting or overgrowth phenotypes of the mice. Single-cell RNA transcriptomics with SSC-derived polyclonal colonies demonstrates alterations in osteogenic and chondrogenic precursors caused by PDGFRβD849V. Mutant cells undergo poor osteogenesis in vitro with increased expression of Sox9 and other chondrogenic markers. Mice with PDGFRβD849V exhibit osteopenia. Increased STAT5 phosphorylation and overexpression of Igf1 and Socs2 in PDGFRβD849V cells suggests that overgrowth in mice involves PDGFRβD849V activating the STAT5-IGF1 axis locally in the skeleton. Our study establishes that PDGFRβD849V causes osteopenic skeletal phenotypes that are associated with intrinsic changes in SSCs, promoting chondrogenesis over osteogenesis.

MicroRNA-663 prevents monocrotaline-induced pulmonary arterial hypertension by targeting TGF-β1/smad2/3 signaling

OBJECTIVE

Pulmonary vascular remodeling due to excessive growth factor production and pulmonary artery smooth muscle cells (PASMCs) proliferation is the hallmark feature of pulmonary arterial hypertension (PAH). Recent studies suggest that miR-663 is a potent modulator for tumorigenesis and atherosclerosis. However, whether miR-663 involves in pulmonary vascular remodeling is still unclear.

METHODS AND RESULTS

By using quantitative RT-PCR, we found that miR-663 was highly expressed in normal human PASMCs. In contrast, circulating level of miR-663 dramatically reduced in PAH patients. In addition, in situ hybridization showed that expression of miR-663 was decreased in pulmonary vasculature of PAH patients. Furthermore, MTT and cell scratch-wound assay showed that transfection of miR-663 mimics significantly inhibited platelet derived growth factor (PDGF)-induced PASMCs proliferation and migration, while knockdown of miR-663 expression enhanced these effects. Mechanistically, dual-luciferase reporter assay revealed that miR-663 directly targets the 3'UTR of TGF-β1. Moreover, western blots and ELISA results showed that miR-663 decreased PDGF-induced TGF-β1 expression and secretion, which in turn suppressed the downstream smad2/3 phosphorylation and collagen I expression. Finally, intratracheal instillation of adeno-miR-663 efficiently inhibited the development of pulmonary vascular remodeling and right ventricular hypertrophy in monocrotaline (MCT)-induced PAH rat models.

CONCLUSION

These results indicate that miR-663 is a potential biomarker for PAH. MiR-663 decreases PDGF-BB-induced PASMCs proliferation and prevents pulmonary vascular remodeling and right ventricular hypertrophy in MCT-PAH by targeting TGF-β1/smad2/3 signaling. These findings suggest that miR-663 may represent as an attractive approach for the diagnosis and treatment for PAH.

Wound healing potential of licorice extract in rat model: Antioxidants, histopathological, immunohistochemical and gene expression evidences

Wound healing is a public health concern. Licorice gained a great attention for its antioxidant and anti-inflammatory properties which expand its valuable effects as a herbal medicine. In this study, we pointed out to the wound healing potential and the mechanism by which licorice alcoholic extract can modulate cutaneous wound healing through immune, antioxidant, histopathological, immunohistochemical (IHC) and molecular studies. 24 Wister rats were assigned into 3 groups (n = 8 each); control group, topical and oral supplied groups. Licorice extract administration significantly increased total and differential leucocyte counts, phagocytic activity of neutrophils, antioxidant biomarkers as superoxide dismutase (SOD), glutathione peroxidase activities (GPx) and reduced glutathione (GSH) content with a notable reduction in oxidative stress marker malondialdehyde (MDA). Moreover, histopathological findings detected complete re-epithelialization with increasing collagen synthesis while IHC results revealed a significant enhancement in the expression of α-SMA, PDGFR-α, FGFR1 and Cytokeratin 14 in licorice treated groups compared with the control group. Licorice extract supplementation accelerated wound healing by increasing angiogenesis and collagen deposition through up-regulation of bFGF, VEGF and TGF-β gene expression levels compared with the control group. UPLC-PDA-MS/MS aided to authenticate the studied Glycyrrihza species and recognized 101 potential constituents that may be responsible for licorice-exhibited potentials. Based on our observations we concluded that licorice enhanced cutaneous wound healing via its free radical-scavenging potential, potent antioxidant activities, and anti-inflammatory actions. Therefore, licorice could be used as a potential alternative therapy for wound injury which could overcome the associated limitations of modern therapeutic products.

Vascular smooth muscle cell dysfunction contribute to neuroinflammation and Tau hyperphosphorylation in Alzheimer disease

Despite the emerging evidence implying early vascular contributions to neurodegenerative syndromes, the role of vascular smooth muscle cells (VSMCs) in the pathogenesis of Alzheimer disease (AD) is still not well understood. Herein, we show that VSMCs in brains of patients with AD and animal models of the disease are deficient in multiple VSMC contractile markers which correlated with Tau accumulation in brain arterioles. Ex vivo and in vitro experiments demonstrated that VSMCs undergo dramatic phenotypic transitions under AD-like conditions, adopting pro-inflammatory phenotypes. Notably, these changes coincided with Tau hyperphosphorylation at residues Y18, T205, and S262. We also observed that VSMC dysfunction occurred in an age-dependent manner and that expression of Sm22α protein was inversely correlated with CD68 and Tau expression in brain arterioles of the 3xTg-AD and 5xFAD mice. Together, these findings further support the contribution of dysfunctional VSMCs in AD pathogenesis and nominate VSMCs as a potential therapeutic target in AD.

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Loss of VSMC contractile phenotypes correlates with Tau accumulation in brain arterioles

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VSMC dysfunction promotes the hyperphosphorylation of Tau protein at multiple residues

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VSMC dysfunction occurs in an age-dependent manner in brain arterioles of patients with AD

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Vascular smooth muscle cell is a promising therapeutic target in AD

PDGF-PDGFR network differentially regulates the fate, migration, proliferation, and cell cycle progression of myogenic cells

Platelet-derived growth factors (PDGFs) regulate embryonic development, tissue regeneration, and wound healing through their binding to PDGF receptors, PDGFRα and PDGFRβ. However, the role of PDGF signaling in regulating muscle development and regeneration remains elusive, and the cellular and molecular responses of myogenic cells are understudied. Here, we explore the PDGF-PDGFR gene expression changes and their involvement in skeletal muscle myogenesis and myogenic fate. By surveying bulk RNA sequencing and single-cell profiling data of skeletal muscle stem cells, we show that myogenic progenitors and muscle stem cells differentially express PDGF ligands and PDGF receptors during myogenesis. Quiescent adult muscle stem cells and myoblasts preferentially express PDGFRβ over PDGFRα. Remarkably, cell culture- and injury-induced muscle stem cell activation altered PDGF family gene expression. In myoblasts, PDGF-AB and PDGF-BB treatments activate two pro-chemotactic and pro-mitogenic downstream transducers, RAS-ERK1/2 and PI3K-AKT. PDGFRs inhibitor AG1296 inhibited ERK1/2 and AKT activation, myoblast migration, proliferation, and cell cycle progression induced by PDGF-AB and PDGF-BB. We also found that AG1296 causes myoblast G0/G1 cell cycle arrest. Remarkably, PDGF-AA did not promote a noticeable ERK1/2 or AKT activation, myoblast migration, or expansion. Also, myogenic differentiation reduced the expression of both PDGFRα and PDGFRβ, whereas forced PDGFRα expression impaired myogenesis. Thus, our data highlight PDGF signaling pathway to stimulate satellite cell proliferation aiming to enhance skeletal muscle regeneration and provide a deeper understanding of the role of PDGF signaling in non-fibroblastic cells.

Quantifying information accumulation encoded in the dynamics of biochemical signaling

Cellular responses to environmental changes are encoded in the complex temporal patterns of signaling proteins. However, quantifying the accumulation of information over time to direct cellular decision-making remains an unsolved challenge. This is, in part, due to the combinatorial explosion of possible configurations that need to be evaluated for information in time-course measurements. Here, we develop a quantitative framework, based on inferred trajectory probabilities, to calculate the mutual information encoded in signaling dynamics while accounting for cell-cell variability. We use it to understand NFκB transcriptional dynamics in response to different immune threats, and reveal that some threats are distinguished faster than others. Our analyses also suggest specific temporal phases during which information distinguishing threats becomes available to immune response genes; one specific phase could be mapped to the functionality of the IκBα negative feedback circuit. The framework is generally applicable to single-cell time series measurements, and enables understanding how temporal regulatory codes transmit information over time.

The infantile myofibromatosis NOTCH3 L1519P mutation leads to hyperactivated ligand-independent Notch signaling and increased PDGFRB expression

Infantile myofibromatosis (IMF) is a benign tumor form characterized by the development of nonmetastatic tumors in skin, bone, muscle and sometimes viscera. Autosomal dominant forms of IMF are caused by mutations in the PDGFRB gene, but a family carrying a L1519P mutation in the NOTCH3 gene has also recently been identified. In this report, we address the molecular consequences of the NOTCH3L1519P mutation and the relationship between the NOTCH and PDGFRB signaling in IMF. The NOTCH3L1519P receptor generates enhanced downstream signaling in a ligand-independent manner. Despite the enhanced signaling, the NOTCH3L1519P receptor is absent from the cell surface and instead accumulates in the endoplasmic reticulum. Furthermore, the localization of the NOTCH3L1519P receptor in the bipartite, heterodimeric state is altered, combined with avid secretion of the mutated extracellular domain from the cell. Chloroquine treatment strongly reduces the amount of secreted NOTCH3L1519P extracellular domain and decreases signaling. Finally, NOTCH3L1519P upregulates PDGFRB expression in fibroblasts, supporting a functional link between Notch and PDGF dysregulation in IMF. Collectively, our data define a NOTCH3-PDGFRB axis in IMF, where an IMF-mutated NOTCH3 receptor elevates PDGFRB expression. The functional characterization of a ligand-independent gain-of-function NOTCH3 mutation is important for Notch therapy considerations for IMF, including strategies aimed at altering lysosome function.

Biomaterials for Bioprinting Microvasculature

Microvasculature functions at the tissue and cell level, regulating local mass exchange of oxygen and nutrient-rich blood. While there has been considerable success in the biofabrication of large- and small-vessel replacements, functional microvasculature has been particularly challenging to engineer due to its size and complexity. Recently, three-dimensional bioprinting has expanded the possibilities of fabricating sophisticated microvascular systems by enabling precise spatiotemporal placement of cells and biomaterials based on computer-aided design. However, there are still significant challenges facing the development of printable biomaterials that promote robust formation and controlled 3D organization of microvascular networks. This review provides a thorough examination and critical evaluation of contemporary biomaterials and their specific roles in bioprinting microvasculature. We first provide an overview of bioprinting methods and techniques that enable the fabrication of microvessels. We then offer an in-depth critical analysis on the use of hydrogel bioinks for printing microvascularized constructs within the framework of current bioprinting modalities. We end with a review of recent applications of bioprinted microvasculature for disease modeling, drug testing, and tissue engineering, and conclude with an outlook on the challenges facing the evolution of biomaterials design for bioprinting microvasculature with physiological complexity.

Hepatic Stellate Cell-Specific Platelet-Derived Growth Factor Receptor-α Loss Reduces Fibrosis and Promotes Repair after Hepatocellular Injury

Platelet-derived growth factor receptor (PDGFR)-α plays roles in cell survival, proliferation, and differentiation; however, its function in chronic liver injury sequelae, such as fibrosis, is unknown. Hepatic stellate cells (HSCs), the primary mediators of fibrosis, undergo activation, which entails differentiation to myofibroblasts, proliferation, migration, and collagen deposition, partially in response to PDGFs. To examine the role of PDGFR-α in HSCs, Lrat-Cre recombinase and Pdgfra-floxed mice were bred to generate Lrat-CrePdgfra-/- (knockout) animals, which were subjected to chronic liver injury through carbon tetrachloride treatment, bile duct ligation, and 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine. Although no major difference was observed after other types of liver injury, PDGFR-α loss in HSCs led to a significant albeit transient reduction in fibrosis after carbon tetrachloride injury, associated with increased HSC death and reduced migration. There was continued alleviation of hepatocellular injury in knockout mice despite ongoing carbon tetrachloride insult, associated with increased numbers of CD68 and F480 macrophages and increased clearance of damaged hepatocytes. Altogether our findings support a profibrotic role of PDGFR-α in HSCs during chronic liver injury in vivo via regulation of HSC survival and migration and affect the immune microenvironment, especially macrophages in clearing dying hepatocytes. Thus, our study provides a preclinical foundation for the future testing of therapeutic PDGFR-α inhibition in hepatic fibrosis, especially in combination with other therapies.

SHP-2-Mediated Upregulation of ZEB1 Is Important for PDGF-B-Induced Cell Proliferation and Metastatic Phenotype in Triple Negative Breast Cancer

Background: Triple negative breast cancer (TNBC), a fatal malignant tumor, is characterized by a lack of estrogen and progesterone hormone receptors and overexpression of HER2. Due to its characteristics, there are no effective targeted therapies for TNBC. Therefore, it is critical to identify the crucial factors that participate in modulating TNBC progression and explore the underlying molecular mechanism. Methods: CCK-8, bromodeoxyuridine incorporation, western blotting, qPCR, and transwell assays were utilized to evaluate breast cancer cell proliferation, migration, and invasion. Results: Activation of platelet-derived growth factor (PDGF)-B/PDGF receptor (PDGFR) promoted the proliferation and metastatic phenotype of TNBC cells; however, these effects were attenuated by SHP-2 knockdown. Moreover, PDGF-B promoted the expression of zinc finger E-box binding homeobox 1 (ZEB1) by downregulating the expression of miR-200. Furthermore, knockdown of ZEB1 mitigated the promoting effects of PDGF-B on cell proliferation and migration. In addition, the regulatory effects of PDGF-B on miR-200 and ZEB1 were mediated through the SHP-2/Akt pathway. Conclusion: Our findings highlight the important roles of PDGF-B/PDGFR and their downstream signaling pathways in regulating cell proliferation and metastatic phenotype in TNBC. Hence, these molecules may serve as novel therapeutic targets for TNBC in the future.

Uveal Melanoma Cells Elicit Retinal Pericyte Phenotypical and Biochemical Changes in an in Vitro Model of Coculture

Vascular pericytes are an important cellular component in the tumor microenvironment, however, their role in supporting cancer invasion is poorly understood. We hypothesized that PDGF-BB could be involved in the transition of human retinal pericytes (HRPC) in cancer-activated fibroblasts (CAF), induced by the 92.1 uveal melanoma (UM) cell line. In our model system, HRPC were conditioned by co-culturing with 92.1UM for 6 days (cHRPC), in the presence or absence of imatinib, to block PDGF receptor-β (PDGFRβ). The effects of the treatments were tested by wound healing assay, proliferation assay, RT-PCR, high-content screening, Western blot analysis, and invasion assay. Results showed profound changes in cHRPC shape, with increased proliferation and motility, reduction of NG2 and increase of TGF-β1, α-SMA, vimentin, and FSP-1 protein levels, modulation of PDGF isoform mRNA levels, phospho-PDGFRβ, and PDGFRβ, as well as phospho-STAT3 increases. A reduction of IL-1β and IFNγ and an increase in TNFα, IL10, and TGF-β1, CXCL11, CCL18, and VEGF mRNA in cHRPC were found. Imatinib was effective in preventing all the 92.1UM-induced changes. Moreover, cHRPC elicited a significant increase of 92.1UM cell invasion and active MMP9 protein levels. Our data suggest that retinal microvascular pericytes could promote 92.1UM growth through the acquisition of the CAF phenotype.

Role of platelet-derived growth factor in type II diabetes mellitus and its complications

Type 2 diabetes mellitus is a type of metabolic disorder characterized by hyperglycaemia with multiple serious complications, such as diabetic neuropathies, diabetic nephropathy, diabetic retinopathy, and diabetic foot. Platelet-derived growth factors are growth factors that regulate cell growth and division, playing a critical role in diabetes and its harmful complications. This review focused on the cellular mechanism of platelet-derived growth factors and their receptors on diabetes development. Furthermore, we raise some proper therapeutic molecular targets for the treatment of diabetes and its complications.

Downregulation of HDAC1 suppresses media degeneration by inhibiting the migration and phenotypic switch of aortic vascular smooth muscle cells in aortic dissection

Although much progress has been made in the diagnosis and treatment of thoracic aortic dissection (TAD), the overall morbidity and mortality rates of TAD are still high. Therefore, the molecular pathogenesis and etiology of TAD need to be elucidated. In this study, we found that histone deacetylase 1 (HDAC1) expression is dramatically higher in the aortic wall of patients with TAD (than that in a normal group) and negatively correlates with the levels of the vascular smooth muscle cell (SMC) contractile-phenotype markers. Knockdown of HDAC1 upregulated both smooth muscle 22 α (SM22α) and α-smooth muscle actin (α-SMA) in platelet-derived growth factor (PDGF)-BB-treated and -untreated SMCs. In addition, the knockdown of HDAC1 markedly decreased SMC viability and migration in contrast to the control group under the conditions of quiescence and PDGF-BB treatment. We also showed that the expression of polycystic kidney disease 1 (PKD1) is decreased in the aortic wall of patients with TAD and negatively correlates with HDAC1 expression. Overexpressed PKD1 obviously increased SM22α and α-SMA expression and reduced the viability and migration of SMCs, but these effects were attenuated by HDAC1. Furthermore, we demonstrated that HDAC1 serves as an important modulator of the migration and phenotypic switch of SMCs by suppressing the PKD1- mammalian target of the rapamycin signaling pathway. HDAC1 downregulation inhibited media degeneration and attenuated the loss of elastic-fiber integrity in a mouse model of TAD. Our results suggest that HDAC1 might be a new target for the treatment of a macrovascular disease such as TAD.

Lung developmental arrest caused by PDGF-A deletion: consequences for the adult mouse lung

PDGF-A is a key contributor to lung development in mice. Its expression is needed for secondary septation of the alveoli and deletion of the gene leads to abnormally enlarged alveolar air spaces in mice. In humans, the same phenotype is the hallmark of bronchopulmonary dysplasia (BPD), a disease that affects premature babies and may have long lasting consequences in adulthood. So far, the knowledge regarding adult effects of developmental arrest in the lung is limited. This is attributable to few follow-up studies of BPD survivors and lack of good experimental models that could help predict the outcomes of this early age disease for the adult individual. In this study, we used the constitutive lung-specific Pdgfa deletion mouse model to analyze the consequences of developmental lung defects in adult mice. We assessed lung morphology, physiology, cellular content, ECM composition and proteomics data in mature mice, that perinatally exhibited lungs with a BPD-like morphology. Histological and physiological analyses both revealed that enlarged alveolar air spaces remained until adulthood, resulting in higher lung compliance and higher respiratory volume in knockout mice. Still, no or only small differences were seen in cellular, ECM and protein content when comparing knockout and control mice. Taken together, our results indicate that Pdgfa deletion-induced lung developmental arrest has consequences for the adult lung at the morphological and functional level. In addition, these mice can reach adulthood with a BPD-like phenotype, which makes them a robust model to further investigate the pathophysiological progression of the disease and test putative regenerative therapies.

Dysregulated mesenchymal PDGFR-β drives kidney fibrosis

Kidney fibrosis is characterized by expansion and activation of platelet-derived growth factor receptor-β (PDGFR-β)-positive mesenchymal cells. To study the consequences of PDGFR-β activation, we developed a model of primary renal fibrosis using transgenic mice with PDGFR-β activation specifically in renal mesenchymal cells, driving their pathological proliferation and phenotypic switch toward myofibroblasts. This resulted in progressive mesangioproliferative glomerulonephritis, mesangial sclerosis, and interstitial fibrosis with progressive anemia due to loss of erythropoietin production by fibroblasts. Fibrosis induced secondary tubular epithelial injury at later stages, coinciding with microinflammation, and aggravated the progression of hypertensive and obstructive nephropathy. Inhibition of PDGFR activation reversed fibrosis more effectively in the tubulointerstitium compared to glomeruli. Gene expression signatures in mice with PDGFR-β activation resembled those found in patients. In conclusion, PDGFR-β activation alone is sufficient to induce progressive renal fibrosis and failure, mimicking key aspects of chronic kidney disease in humans. Our data provide direct proof that fibrosis per se can drive chronic organ damage and establish a model of primary fibrosis allowing specific studies targeting fibrosis progression and regression.

Development and gene expression of C57BL/6 mouse embryo palate shelves in rotary organ culture

The aim of the present study was to improve methods for the suspension culture of mouse palatal shelves by comparing the expression of platelet-derived growth factor receptor (PDGFR)-α in palatal shelves in vivo, to that in vitro. The palatal shelves of C57BL/6 mouse embryos were obtained on gestation days (GDs) 13.5, 14.5, 15.0 and 15.5 for in vivo experiments. The palatal shelves were removed and observed under a stereomicroscope to investigate palatal development. For in vitro experiments, the palatal shelves were dissected under a stereomicroscope on GD 13.5 and then subjected to rotary culture for 0, 24, 36 or 48 h. The expression of PDGFR-α at different time points was detected by immunohistochemical staining and western blot analysis. Both methods of analysis displayed PDGFR-α expression in mesenchymal and epithelial cells at GD 13.5, 14.5, 15.0 and 15.5, in vivo and in vitro. The level of PDGFR-α expression peaked on GD 14.5. The expression of PDGFR-α in palatal shelves in in vitro rotary culture was consistent with that in vivo. Therefore, the novel technique of palatal rotary organ culture presented in the current study could provide a good model for studying the mechanism of pathological palatal fusion in vitro. Additionally, the present study further confirmed that PDGFR-α gene expression was associated with the development of palatal shelves.

Lipopolysaccharide-Induced Matrix Metalloproteinase-9 Expression Associated with Cell Migration in Rat Brain Astrocytes

Neuroinflammation is a landmark of neuroinflammatory and neurodegenerative diseases. Matrix metalloproteinase (MMP)-9, one member of MMPs, has been shown to contribute to the pathology of these brain diseases. Several experimental models have demonstrated that lipopolysaccharide (LPS) exerts a pathological role through Toll-like receptors (TLRs) in neuroinflammation and neurodegeneration. However, the mechanisms underlying LPS-induced MMP-9 expression in rat brain astrocytes (RBA-1) are not completely understood. Here, we applied pharmacological inhibitors and siRNA transfection to assess the levels of MMP-9 protein, mRNA, and promoter activity, as well as protein kinase phosphorylation in RBA-1 cells triggered by LPS. We found that LPS-induced expression of pro-form MMP-9 and cell migration were mediated through TLR4, proto-oncogene tyrosine-protein kinase (c-Src), proline-rich tyrosine kinase 2 (Pyk2), platelet-derived growth factor receptor (PDGFR), phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt), p38 mitogen-activated protein kinase (MAPK), and Jun amino-terminal kinase (JNK)1/2 signaling molecules in RBA-1 cells. In addition, LPS-stimulated binding of c-Jun to the MMP-9 promoter was confirmed by chromatin immunoprecipitation (ChIP) assay, which was blocked by pretreatment with c-Src inhibitor II, PF431396, AG1296, LY294002, Akt inhibitor VIII, p38 MAP kinase inhibitor VIII, SP600125, and tanshinone IIA. These results suggest that in RBA-1 cells, LPS activates a TLR4/c-Src/Pyk2/PDGFR/PI3K/Akt/p38 MAPK and JNK1/2 pathway, which in turn triggers activator protein 1 (AP-1) activation and ultimately induces MMP-9 expression and cell migration.

Pericytes: Problems and Promises for CNS Repair

Microvascular complications are often associated with slow and progressive damage of various organs. Pericytes are multi-functional mural cells of the microcirculation that control blood flow, vascular permeability and homeostasis. Whereas accumulating evidence suggests that these cells are also implicated in a variety of diseases, pericytes represent promising targets that can be manipulated for therapeutic gain. Here, we review the role of pericytes in angiogenesis, blood-brain barrier (BBB) function, neuroinflammation, tissue fibrosis, axon regeneration failure, and neurodegeneration. In addition, we outline strategies altering pericyte behavior to point out problems and promises for axon regeneration and central nervous system (CNS) repair following injury or disease.

Novel PDGFRB rearrangement in multifocal infantile myofibromatosis is tumorigenic and sensitive to imatinib

Infantile myofibromatosis (IM) is an aggressive neoplasm composed of myofibroblast-like cells in children. Although typically localized, it can also present as multifocal disease, which represents a challenge for effective treatment. IM has previously been linked to activating somatic and germline point mutations in the PDGFRβ tyrosine kinase encoded by the PDGFRB gene. Clinical panel-based targeted tumor sequencing of a tumor from a newborn with multifocal IM revealed a novel PDGFRB rearrangement, which was reported as being of unclear significance. Additional sequencing of cDNA from tumor and germline DNA confirmed a complex somatic/mosaic PDGFRB rearrangement with an apparent partial tandem duplication disrupting the juxtamembrane domain. Ectopic expression of cDNA encoding the mutant form of PDGFRB markedly enhanced cell proliferation of mouse embryo fibroblasts (MEFs) compared to wild-type PDGFRB and conferred tumor-forming capacity on nontumorigenic 10T1/2 fibroblasts. The mutated protein enhanced MAPK activation and retained sensitivity to the PDGFRβ inhibitor imatinib. Our findings reveal a new mechanism by which PDGFRB can be activated in IM, suggest that therapy with tyrosine kinase inhibitors including imatinib may be beneficial, and raise the possibility that this receptor tyrosine kinase might be altered in a similar fashion in additional cases that would similarly present annotation challenges in clinical DNA sequencing analysis pipelines.

Platelet-derived growth factor receptor-α is essential for cardiac fibroblast survival

Platelet-derived growth factor receptor α (PDGFRα), a receptor tyrosine kinase required for cardiac fibroblast development, is uniquely expressed by fibroblasts in the adult heart. Despite the consensus that PDGFRα is expressed in adult cardiac fibroblasts, we know little about its function when these cells are at rest. Here, we demonstrate that loss of PDGFRα in cardiac fibroblasts resulted in a rapid reduction of resident fibroblasts. Furthermore, we observe that phosphatidylinositol 3-kinase signaling was required for PDGFRα-dependent fibroblast maintenance. Interestingly, this reduced number of fibroblasts was maintained long-term, suggesting that there is no homeostatic mechanism to monitor fibroblast numbers and restore hearts to wild-type levels. Although we did not observe any systolic functional changes in hearts with depleted fibroblasts, the basement membrane and microvasculature of these hearts were perturbed. Through in vitro analyses, we showed that PDGFRα signaling inhibition resulted in an increase in fibroblast cell death, and PDGFRα stimulation led to increased levels of the cell survival factor activating transcription factor 3. Our data reveal a unique role for PDGFRα signaling in fibroblast maintenance and illustrate that a 50% loss in cardiac fibroblasts does not result in lethality.NEW & NOTEWORTHY Platelet-derived growth factor receptor α (PDGFRα) is required in developing cardiac fibroblasts, but a functional role in adult, quiescent fibroblasts has not been identified. Here, we demonstrate that PDGFRα signaling is essential for cardiac fibroblast maintenance and that there are no homeostatic mechanisms to regulate fibroblast numbers in the heart. PDGFR signaling is generally considered mitogenic in fibroblasts, but these data suggest that this receptor may direct different cellular processes depending on the cell's maturation and activation status.

PDGFR-β restores blood-brain barrier functions in a mouse model of focal cerebral ischemia

Although platelet-derived growth factor receptor beta (PDGFR-β) mediates the recruitment of vascular pericytes into ischemic lesion to restore the blood-brain barrier (BBB) dysfunction, its mechanisms still remain elusive. Compared with control PDGFR-β^{floxed/floxed} mice (Floxed), postnatally induced systemic PDGFR-β knockout mice (Esr-KO) not only showed severe brain edema, neurologic functional deficits, decreased expression of tight junction (TJ) proteins, abundant endothelial transcytosis, and deformed TJs in the BBB, but also showed reduced expression of transforming growth factor-β (TGF-β) protein after photothrombotic middle cerebral artery occlusion (MCAO). In endothelial-pericyte co-culture, an in vitro model of BBB, the increment in the barrier function of endothelial monolayer induced by pericyte co-culture was completely cancelled by silencing PDGFR-β gene expression in pericytes, and was additively improved by PDGFR-β and TGF-β receptor signals under hypoxia condition. Exogenous PDGF-BB increased the expression of p-Smad2/3, while anti-TGF-β1 antibody at least partially inhibited the phosphorylation of Smad2/3 after PDGF-BB treatment in vitro. Furthermore, pre-administration of TGF-β1 partially alleviated edema formation, neurologic dysfunction, and TJs reduction in Esr-KO mice after MCAO. Accordingly, PDGFR-β signalling, via TGF-β signalling, may be crucial for restoration of BBB integrity after cerebral ischemia and therefore represents a novel potential therapeutic target.

MicroRNA‑132 mediates proliferation and migration of pulmonary smooth muscle cells via targeting PTEN

Pulmonary arterial hypertension (PAH) is a severe and progressive disease characterized by the remodeling of small pulmonary arteries. The aberrant proliferation of pulmonary arterial smooth muscle cells (PASMCs) is the primary feature of PAH. MicroRNA (miR)‑132 has been demonstrated to inhibit the proliferation of vascular smooth muscle cells and repress neointimal formation. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a direct target of miR‑132 that has been revealed to be involved in the development of PAH. However, the role of miR‑132 in PAH remains unclear. The present study demonstrated that miR‑132 expression was upregulated in monocrotaline‑induced PAH rats and platelet‑derived growth factor‑induced PASMCs. In addition, treatment of PASMCs with miR‑132 mimics inhibited their proliferation, whereas miR‑132 inhibition exhibited the opposite effects. Furthermore, miR‑132 mimics promoted cell migration and maintained the PASMC contractile phenotype. Finally, the expression levels of PTEN were significantly decreased in PAH and PASMCs treated with miR‑132 mimics. Taken collectively, the data suggested that miR‑132 regulated PASMC function via PTEN and that it may be used as a potential target for the treatment of PAH.

MicroRNA-134-5p Regulates Media Degeneration through Inhibiting VSMC Phenotypic Switch and Migration in Thoracic Aortic Dissection

Abnormal phenotypic switch, migration, and proliferation of vascular smooth muscle cells (VSMCs) are hallmarks for pathogenesis of thoracic aortic dissection (TAD). In the current study, we identified miR-134-5p as a critical regulator controlling human VSMC phenotypic switch and migration to investigate whether miR-134-5p affects human VSMC functions and development of TAD. Using miRNA microarray of aorta specimens from 12 TAD and 12 controls, we identified miR-134-5p, which was significantly downregulated in TAD tissues. With qPCR detection, we found that miR-134-5p was also evidently decreased in human AoSMCs. Ectopic expression of miR-134-5p obviously promoted VSMC differentiation and expression of contractile markers, such as α-SMA, SM22α, and MYH11. miR-134-5p potently inhibited PDGF-BB-induced VSMC phenotypic switch and migration. We further identified STAT5B and ITGB1 as downstream targets of miR-134-5p in human VSMCs and proved them to be mediators in VSMC phenotypic switch and progression of TAD. Finally, Ad-miR-134-5p obviously suppressed the aorta dilatation and vascular media degeneration by 39% in TAD mice after vascular injury induced by Ang II. Our findings revealed that miR-134-5p was a novel regulator in vascular remodeling and pathological progress of TAD via targeting STAT5B/ITGB1 expression. Targeting miR-134-5p or its downstream molecules in VSMCs might develop new avenues in clinical treatment of TAD.

PDGF Modulates BMP2-Induced Osteogenesis in Periosteal Progenitor Cells

BMPs are used in various clinical applications to promote bone formation. The limited success of the BMPs in clinical settings and supraphysiological doses required for their effects prompted us to evaluate the influence of other signaling molecules, specifically platelet‐derived growth factor (PDGF) on BMP2‐induced osteogenesis. Periosteal cells make a major contribution to fracture healing. We detected broad expression of PDGF receptor beta (PDGFRβ) within the intact periosteum and healing callus during fracture repair. In vitro, periosteum‐derived progenitor cells were highly responsive to PDGF as demonstrated by increased proliferation and decreased apoptosis. However, PDGF blocked BMP2‐induced osteogenesis by inhibiting the canonical BMP2/Smad pathway and downstream target gene expression. This effect is mediated via PDGFRβ and involves ERK1/2 MAPK and PI3K/AKT signaling pathways. Therapeutic targeting of the PDGFRβ pathway in periosteum‐mediated bone repair might have profound implications in the treatment of bone disease in the future. © 2018 The Authors JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Exosomes from mesenchymal stem cells expressing miR-125b inhibit neointimal hyperplasia via myosin IE

Intercellular communication between mesenchymal stem cells (MSCs) and their target cells in the perivascular environment is modulated by exosomes derived from MSCs. However, the potential role of exosome-mediated microRNA transfer in neointimal hyperplasia remains to be investigated. To evaluate the effects of MSC-derived exosomes (MSC-Exo) on neointimal hyperplasia, their effects upon vascular smooth muscle cell (VSMC) growth in vitro and neointimal hyperplasia in vivo were assessed in a model of balloon-induced vascular injury. Our results showed that MSC-Exo were internalised by VSMCs and inhibited proliferation and migration in vitro. Further analysis revealed that miR-125b was enriched in MSC-Exo, and repressed the expression of myosin 1E (Myo1e) by targeting its 3' untranslated region. Additionally, MSC-Exo and exosomally transferred miR-125b repressed Myo1e expression and suppressed VSMC proliferation and migration and neointimal hyperplasia in vivo. In summary, our findings revealed that MSC-Exo can transfer miR-125b to VSMCs and inhibit VSMC proliferation and migration in vitro and neointimal hyperplasia in vivo by repressing Myo1e, indicating that miR-125b may be a therapeutic target in the treatment of vascular diseases.

Crosstalk between receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCR) in the brain: Focus on heteroreceptor complexes and related functional neurotrophic effects

Neuronal events are regulated by the integration of several complex signaling networks in which G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) are considered key players of an intense bidirectional cross-communication in the cell, generating signaling mechanisms that, at the same time, connect and diversify the traditional signal transduction pathways activated by the single receptor. For this receptor-receptor crosstalk, the two classes of receptors form heteroreceptor complexes resulting in RTKs transactivation and in growth-promoting signals. In this review, we describe heteroreceptor complexes between GPCR and RTKs in the central nervous system (CNS) and their functional effects in controlling a variety of neuronal effects, ranging from development, proliferation, differentiation and migration, to survival, repair, synaptic transmission and plasticity. In this interaction, RTKs can also recruit components of the G protein signaling cascade, creating a bidirectional intricate interplay that provides complex control over multiple cellular events. These heteroreceptor complexes, by the integration of different signals, have recently attracted a growing interest as novel molecular target for depressive disorders. This article is part of the Special Issue entitled 'Receptor heteromers and their allosteric receptor-receptor interactions'.

Toll-like receptor 9 negatively regulates pancreatic islet beta cell growth and function in a mouse model of type 1 diabetes

AIMS/HYPOTHESIS

Innate immune effectors interact with the environment to contribute to the pathogenesis of the autoimmune disease, type 1 diabetes. Although recent studies have suggested that innate immune Toll-like receptors (TLRs) are involved in tissue development, little is known about the role of TLRs in tissue development, compared with autoimmunity. We aimed to fill the knowledge gap by investigating the role of TLR9 in the development and function of islet beta cells in type 1 diabetes, using NOD mice.

METHODS

We generated Tlr9^-/- NOD mice and examined them for type 1 diabetes development and beta cell function, including insulin secretion and glucose tolerance. We assessed islet and beta cell number and characterised CD140a expression on beta cells by flow cytometry. We also tested beta cell function in Tlr9^-/- C57BL/6 mice. Finally, we used TLR9 antagonists to block TLR9 signalling in wild-type NOD mice to verify the role of TLR9 in beta cell development and function.

RESULTS

TLR9 deficiency promoted pancreatic islet development and beta cell differentiation, leading to enhanced glucose tolerance, improved insulin sensitivity and enhanced first-phase insulin secretory response. This was, in part, mediated by upregulation of CD140a (also known as platelet-derived growth factor receptor-α [PDGFRα]). In the absence of TLR9, induced by either genetic targeting or treatment with TLR9 antagonists, which had similar effects on ontogenesis and function of beta cells, NOD mice were protected from diabetes.

CONCLUSIONS/INTERPRETATION

Our study links TLR9 and the CD140a pathway in regulating islet beta cell development and function and indicates a potential therapeutic target for diabetes prevention and/or treatment.