Platelet-derived growth factor receptor β-targeted positron emission tomography imaging for the noninvasive monitoring of liver fibrosis

PURPOSE

Noninvasive quantifying activated hepatic stellate cells (aHSCs) by molecular imaging is helpful for assessing disease progression and therapeutic responses of liver fibrosis. Our purpose is to develop platelet-derived growth factor receptor β (PDGFRβ)-targeted radioactive tracer for assessing liver fibrosis by positron emission tomography (PET) imaging of aHSCs.

METHODS

Comparative transcriptomics, immunofluorescence staining and flow cytometry were used to evaluate PDGFRβ as biomarker for human aHSCs and determine the correlation of PDGFRβ with the severity of liver fibrosis. The high affinity affibody for PDGFRβ (ZPDGFRβ) was labeled with gallium-68 (68Ga) for PET imaging of mice with carbon tetrachloride (CCl4)-induced liver fibrosis. Binding of the [68Ga]Ga-labeled ZPDGFRβ ([68Ga]Ga-DOTA-ZPDGFRβ) for aHSCs in human liver tissues was measured by autoradiography.

RESULTS

PDGFRβ overexpressed in aHSCs was highly correlated with the severity of liver fibrosis in patients and CCl4-treated mice. The 68Ga-labeled ZPDGFRβ affibody ([68Ga]Ga-DOTA-ZPDGFRβ) showed PDGFRβ-dependent binding to aHSCs. According to the PET imaging, hepatic uptake of [68Ga]Ga-DOTA-ZPDGFRβ increased with the accumulation of aHSCs and collagens in the fibrotic livers of mice. In contrast, hepatic uptake of [68Ga]Ga-DOTA-ZPDGFRβ decreased with spontaneous recovery or treatment of liver fibrosis, indicating that the progression and therapeutic responses of liver fibrosis in mice could be visualized by PDGFRβ-targeted PET imaging. [68Ga]Ga-DOTA-ZPDGFRβ also bound human aHSCs and visualized fibrosis in patient-derived liver tissues.

CONCLUSIONS

PDGFRβ is a reliable biomarker for both human and mouse aHSCs. PDGFRβ-targeted PET imaging could be used for noninvasive monitoring of liver fibrosis in mice and has great potential for clinical translation.

Retinal inflammation in murine models of type 1 and type 2 diabetes with diabetic retinopathy

AIMS/HYPOTHESIS

The loss of pericytes surrounding the retinal vasculature in early diabetic retinopathy underlies changes to the neurovascular unit that lead to more destructive forms of the disease. However, it is unclear which changes lead to loss of retinal pericytes. This study investigated the hypothesis that chronic increases in one or more inflammatory factors mitigate the signalling pathways needed for pericyte survival.

METHODS

Loss of pericytes and levels of inflammatory markers at the mRNA and protein levels were investigated in two genetic models of diabetes, Ins2Akita/+ (a model of type 1 diabetes) and Leprdb/db (a model of type 2 diabetes), at early stages of diabetic retinopathy. In addition, changes that accompany gliosis and the retinal vasculature were determined. Finally, changes in retinal pericytes chronically incubated with vehicle or increasing amounts of IFNγ were investigated to determine the effects on pericyte survival. The numbers of pericytes, microglia, astrocytes and endothelial cells in retinal flatmounts were determined by immunofluorescence. Protein and mRNA levels of inflammatory factors were determined using multiplex ELISAs and quantitative reverse transcription PCR (qRT-PCR). The effects of IFNγ on the murine retinal pericyte survival-related platelet-derived growth factor receptor β (PDGFRβ) signalling pathway were investigated by western blot analysis. Finally, the levels of cell death-associated protein kinase C isoform delta (PKCδ) and cleaved caspase 3 (CC3) in pericytes were determined by western blot analysis and immunocytochemistry.

RESULTS

The essential findings of this study were that both type 1 and 2 diabetes were accompanied by a similar progression of retinal pericyte loss, as well as gliosis. However, inflammatory factor expression was dissimilar in the two models of diabetes, with peak expression occurring at different ages for each model. Retinal vascular changes were more severe in the type 2 diabetes model. Chronic incubation of murine retinal pericytes with IFNγ decreased PDGFRβ signalling and increased the levels of active PKCδ and CC3.

CONCLUSIONS/INTERPRETATION

We conclude that retinal inflammation is involved in and sustains pericyte loss as diabetic retinopathy progresses. Moreover, IFNγ plays a critical role in reducing pericyte survival in the retina by reducing activation of the PDGFRβ signalling pathway and increasing PKCδ levels and pericyte apoptosis.

A small molecular multi-targeting tyrosine kinase inhibitor, anlotinib, inhibits pathological ocular neovascularization

Ocular neovascularization is a devastating pathology observed in numerous ocular diseases and is a major cause of blindness. However, all current treatments have their limitations. Hence, it is important to explore new therapeutic strategies. This study aimed to investigate the role of anlotinib, a small molecular multi-targeting tyrosine kinase inhibitor, in ocular neovascularization. Anlotinib administration did not induce any cytotoxicity and tissue toxicity at the tested concentrations. Cellular functional experiments demonstrated that anlotinib inhibited the viability, proliferation, migration, and tube formation ability of endothelial cells (ECs) and pericytes. Western blot analysis demonstrated that anlotinib significantly inhibited the phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2) and platelet-derived growth factor receptor β (PDGFR-β), as well as their downstream signaling pathways stimulated by VEGF or PDGF-BB, in a concentration-dependent manner in ECs and pericytes. Using an oxygen-induced retinopathy (OIR) model, our results demonstrated that injection of anlotinib reduced avascular areas and pathological neovascular tufts. Furthermore, using a laser-induced choroidal neovascularization (CNV) model, we observed that the combined treatment of anlotinib and Lucentis reduced the size and thickness of CNV lesions compared to Lucentis monotherapy alone. Taken together, our results suggest that anlotinib could be a promising drug candidate for ocular neovascularization.

Low-activity programming of the PDGFRβ/FAK pathway mediates H-type vessel dysplasia and high susceptibility to osteoporosis in female offspring rats after prenatal dexamethasone exposure

Dexamethasone is a common synthetic glucocorticoid drug that can promote foetal lung maturity. An increasing number of studies have shown that prenatal dexamethasone exposure (PDE) can cause a variety of short-term and long-term hazards to offspring, including bone development toxicity. H-type vessels are a newly discovered subtype of blood vessels associated with promoted bone formation and maintenance of bone mass. In this study, we aimed to explore whether H-type blood vessels are involved in PDE-induced long bone development toxicity in offspring and its mechanism. In vivo, we injected dexamethasone (0.2 mg/kg.d) subcutaneously at gestational days 9-20 and observed the H-type vessel abundance and bone mass at different time points in the offspring rats. In vitro, we investigated the effect of dexamethasone (0, 20, 100, and 500 nM) on the tube formation function of rat bone marrow-derived endothelial progenitor cells (EPCs) and explored its mechanism. Our results showed that the adult PDE female offspring rats were susceptible to osteoporosis. In addition, PDE inhibited bone mass, H-type vessel formation and the expression of bone platelet-derived growth factor receptor β (PDGFRβ)/focal adhesion kinase (FAK) pathway-related genes in antenatal and postnatal female offspring. Moreover, PDE promoted the expression of bone glucocorticoid receptor (GR), CCAAT and enhancer binding protein α (C/EBPα) and miR-34c in female foetuses. Dexamethasone suppressed the tube formation of rat bone marrow-derived EPCs and the activity of the PDGFRβ/FAK pathway, which was mediated by GR/C/EBPα/miR-34c signalling activation. In summary, PDE can cause H-type vessel dysplasia and high susceptibility to osteoporosis in female offspring, and its mechanism is related to the low-activity programming of the PDGFRβ/FAK pathway induced by GR/C/EBPα/miR-34c signalling activation. This study enhances the understanding of the molecular mechanism of dexamethasone-induced bone development toxicity and provides new insights for exploring the early intervention and therapeutic targets of foetal-derived osteoporosis.

[Successful treatment with imatinib for a patient with myeloid neoplasms with eosinophilia and abnormalities of PDGFRB due to t (5;14)(q33;q22)]

A 50-year old man with a 1-year history of eosinophilia presented with an eosinophil count exceeding 13,800/mm³ in the peripheral blood at the first visit. Bone marrow examination revealed that eosinophils accounted for 30% of the nucleated cell count, and G-band karyotyping analysis detected t (5;14)(q33;q22). Using peripheral blood FISH test, he was found to have platelet-derived growth factor receptor β (PDGFRB) locus rearrangement at 5q32-33. The level of eosinophils in the peripheral blood reduced markedly 3 days after the initiation of Imatinib mesylate, 400 mg daily. This treatment was administered for 2 years, after which the peripheral blood FISH test was negative for PDGFRB. In this disease, although most cases are with t (5;12), those with t (5;14) are relatively rare, and the long-term course of this translocation is unknown.

Activation of platelet-derived growth factor receptor β in the severe fever with thrombocytopenia syndrome virus infection

Severe fever with thrombocytopenia syndrome (SFTS), an emerging viral infectious disease with a high case fatality rate, is caused by the SFTS virus (SFTSV). Although several cellular molecules involved in viral entry have been identified, the entry mechanisms of SFTSV remain unclear. In this study, we screened the protein kinase inhibitors in inhibitory effects on the infection of Vero cells with SFTSV using InhibitorSelect™ Protein Kinase Library Series (Merck & Co., Inc., Kenilworth, NJ, USA). Several types of inhibitors targeted to platelet-derived growth factor receptor β (PDGFRβ) inhibited the infection of Vero, Huh7, and NIH3T3 cells with SFTSV in a dose-dependent manner within the noncytotoxic range. In addition, these protein kinase inhibitors also inhibited the infection of the target cells with SFTSV glycoprotein (SFTSV-GP) pseudotyped virus (SFTSVpv). Activation of PDGFRβ phosphorylation was detected in SFTSV-treated cells. The infectivities of SFTSVpv were specifically decreased not only in NIH3T3 cells treated with siRNA for PDGFRβ but also in NIH3T3 cells treated with anti-PDGFRβ neutralizing antibody in a dose-dependent manner. SFTSV growth and entry of SFTSVpv were also inhibited by Akt inhibitors. Activation of Akt phosphorylation was also detected in SFTSV-treated cells. These data indicate that PDGFRβ is one of the important host factors in the entry steps of SFTSV.

Gint4.T-Modified DNA Tetrahedrons Loaded with Doxorubicin Inhibits Glioma Cell Proliferation by Targeting PDGFRβ

Glioma is one of the deadliest intrinsic brain tumours due to its invasive growth. The effect of glioma treatment is poor because of the presence of the blood-brain barrier and blood tumour barrier and insufficient drug targeting. DNA tetrahedrons (TDN) show great potential for drug delivery and may be a novel therapeutic strategy for glioma. In this study, we used TDN to deliver doxorubicin (DOX) for the glioma therapy. Gint4.T, an aptamer that could recognize platelet-derived growth factor receptor β on tumour cell, was used to modify TDN (Apt-TDN) for targeted drug delivery. The TDN were self-assembled by one-step synthesis, which showed small size (10 nm) and negative charge. Fetal bovine serum test showed its stability as a drug delivery vehicle. Apt-TDN could be effectively taken up by U87MG cells. Compared with DOX and DOX@TDN (TDN loaded with DOX), the DOX@Apt-TDN (Gint4.T-modified TDN loaded with DOX) showed more early apoptosis rate, higher cell cycle arrest, and greater cytotoxicity towards U87MG cells. In conclusion, our findings indicated that DOX@Apt-TDN provides a novel therapy with promising clinical application for gliomas patients.

Plau/Plaur double-deficiency did not worsen lesion severity or vascular integrity after traumatic brain injury

Binding of urokinase-type plasminogen activator receptor (uPAR) to its ligand uPA or to its plasma membrane partner, platelet-derived growth factor receptor β (PDGFRβ), promotes neuroprotection, cell proliferation, and angiogenesis. Following injury, single deficiency in uPA or uPAR leads in increased tissue loss and compromised vascular remodeling. We hypothesized that double-deficiency of uPAR (Plaur) and uPA (Plau) would result in increased lesion area and poor vascular integrity after traumatic brain injury (TBI). TBI was induced by lateral fluid-percussion injury in Plau/Plaur double-knockout (dKO) and wild-type (Wt) mice. The cortical lesion area was quantified in unfolded cortical maps prepared from thionin-stained sections at 4 d or 30 d post-TBI. The density of PDGFRβ+ pericytes and blood vessels was calculated from immunostained sections. Blood-brain barrier leakage was analyzed using ImageJ® from IgG-immunostained sections. Genotype had no effect on the total area of the cortical lesion at 4 d or 30 d post-TBI (p > 0.05) or its progression as the overall lesion area was comparable at 4 d and 30 d post-TBI in both genotypes (p > 0.05). Subfield analysis, however, indicated that damage to the visual cortex at 4 d post-TBI in dKO-TBI mice was 53 % of that in Wt-TBI mice (p < 0.05). Both genotypes had a higher density of PDGFRβ-positive pericytes at 4 d than at 30 d post-TBI (p < 0.05), but no genotype effect was detected between these time-points (p > 0.05). TBI-induced increase in the density of PDGFRβ+ blood vessels at the region adjacent to the lesion core was comparable in both genotypes (p > 0.05). Genotype had no effect on TBI-induced IgG leakage into the perilesional cortical parenchyma (p > 0.05). Contrary to our expectations, Plau/Plaur double-deficiency did not aggravate TBI-related structural outcome.

CSF evidence of pericyte damage in Alzheimer's disease is associated with markers of blood-brain barrier dysfunction and disease pathology

Background

We aimed to assess the relationship between levels of a cerebrospinal fluid (CSF) marker of pericyte damage, soluble platelet-derived growth factor receptor β (sPDGFRβ) and CSF markers of blood-brain barrier (BBB) integrity (CSF albumin and CSF/serum albumin ratio) and disease pathology (reduced CSF Aβ42 and elevated CSF total and phosphorylated tau) in Alzheimer’s disease (AD).

Methods

sPDGFRβ and albumin were measured by sandwich ELISA in ante-mortem CSF from 39 AD and 39 age-matched controls that were grouped according to their biomarker profile (i.e. AD cases t-tau > 400 pg/mL, p-tau > 60 pg/mL and Aβ42 < 550 pg/mL). sPDGFRβ was also measured in matched serum and CSF samples (n = 23) in a separate neurologically normal group for which the CSF/serum albumin ratio had been determined.

Results

CSF sPDGFRβ level was significantly increased in AD (p = 0.0038) and correlated positively with albumin (r = 0.45, p = 0.007), total tau (r = 0.50, p = 0.0017) and phosphorylated tau (r = 0.41, p = 0.013) in AD but not in controls. CSF sPDGFRβ did not correlate with Aβ42. Serum and CSF sPDGFRβ were positively correlated (r = 0.547, p = 0.0085) in the independent neurologically normal CSF/serum matched samples.

Conclusions

We provide further evidence of an association between pericyte injury and BBB breakdown in AD and novel evidence that a CSF marker of pericyte injury is related to the severity of AD pathology.

Electronic supplementary material

The online version of this article (10.1186/s13195-019-0534-8) contains supplementary material, which is available to authorized users.

MicroRNA-30c contributes to the development of hypoxia pulmonary hypertension by inhibiting platelet-derived growth factor receptor β expression

Pulmonary arterial hypertension (PAH) is characterized by excessive proliferation and resistance to apoptosis of pulmonary artery smooth muscle cells (PASMCs). MicroRNAs have been implicated in the regulation of cell proliferation and might be implicated in the etiology of PAH. Data from in vivo and in vitro cell culture models showed that hypoxia inhibits microRNA-30c (miR-30c) expression in PASMCs. Inhibition of miR-30c by either hypoxia or AMO-30c results in PASMC proliferation (cell viability, 5-bromo-2-deoxyuridine (BrdU) incorporation, proliferating cell nuclear antigen, Ki67, and tubulin polymerization) and the inhibition of apoptosis (cell cycle progression, Cyclin A and Cyclin D, and TUNEL staining). Moreover, down-regulation of miR-30c also results in the phenotype switch from contractile to synthetic PASMC (SM22α and Calponin, osteopontin expression, and wound healing assay). In contrast, these effects were reversed by the application of an miR-30c mimetic under hypoxic conditions. Mechanically, miR-30c inhibited the platelet-derived growth factor receptor β (PDGFRβ) expression by directly binding to the 3' untranslated region of PDGFRβ mRNA (luciferase reporter assays, and PDGFRβ-masking antisense oligodeoxynucleotides). Pharmacological inhibition of PDGFR by AG-1296 displayed similar effects to the miR-30c mimetic. These data suggest that the down-regulation of miR-30c accounts for the up-regulation of PDGFRβ expression, and subsequent activation of PDGF signaling results in the hypoxia-induced PASMC proliferation and phenotype switching. Therefore, increasing miR-30c expression levels could be explored as a potential new therapy for hypoxia-induced PAH.

Involvement of platelet-derived growth factor receptor β in fibrosis through extracellular matrix protein production after ischemic stroke

Fibrosis is concomitant with repair processes following injuries in the central nervous system (CNS). Pericytes are considered as an origin of fibrosis-forming cells in the CNS. Here, we examined whether platelet-derived growth factor receptor β (PDGFRβ), a well-known indispensable molecule for migration, proliferation, and survival of pericytes, was involved in the production of extracellular matrix proteins, fibronectin and collagen type I, which is crucial for fibrosis after ischemic stroke. Immunohistochemistry demonstrated induction of PDGFRβ expression in vascular cells of peri-infarct areas at 3-7days in a mouse stroke model. The PDGFRβ-expressing cells extended from peri-infarct areas toward the ischemic core after day 7 while expressing fibronectin and collagen type I in the infarct areas. In contrast, desmin and α-smooth muscle actin, markers of pericytes, were only expressed in vascular cells. In PDGFRβ heterozygous knockout mice, the expression of fibronectin and collagen type I was attenuated at both mRNA and protein levels with an enlargement of the infarct volume after ischemic stroke compared with that in wild-type littermates. In cultured brain pericytes, the expression of PDGF-B, PDGFRβ, fibronectin, and collagen type I, but not desmin, was significantly increased by serum depletion (SD). The SD-induced upregulation of fibronectin and collagen type I was suppressed by SU11652, an inhibitor of PDGFRβ, while PDGF-B further increased the SD-induced upregulation. In conclusion, the expression level of PDGFRβ may be a crucial determinant of fibrosis after ischemic stroke. Moreover, PDGFRβ signaling participates in the production of fibronectin and collagen type I after ischemic stroke.

Effect of Danshao Huaxian capsule on the expression of platelet-derived growth factor receptor β and phosphorylation events of the ERK1/2 in rats with experimental hepatic fibrosis

AIM: To investigate the effects of Danshao Huaxian capsule (DSHX) on the expression of platelet-derived growth factor receptor β and phosphorylated ERK1/2 (p-ERK1/2) in rats with experimental hepatic fibrosis, and to explore the anti-fibrosis mechanism of DSHX.

METHODS: A total of 55 male Sprague Dawley rats were randomly divided into group A, B, and C. The rats in group A served as normal controls, and those in group B and C were treated with carbon tetrachloride, ethanol and high-fat diet to establish the model of liver fibrosis. Meanwhile, the rats in group C were intragastrically administered with 0.8 g/kg DSHX once per day for 8 weeks. HE staining was used to observe the pathological changes of liver tissues. The expression of PDGFR-β and p-ERK1/2 in fibrosis tissues were detected by immunohistochemistry and Western blot, respectively. Biochemical examination were performed to determine the serum levels of hyaluronic acid (HA), laminin (LN), type Ⅲ procollagen peptide (PⅢP), albumin (ALB), total protein (TP), and the ratio of albumin to globulin (A/G) was also calculated.

RESULTS: Pathological examination confirmed that the model of rat hepatic fibrosis was induced successfully at the end of the 8^th week. As compared with those in group A, the expression of PDGFR-β, p-ERK1/2 in liver tissues, the serum levels of HA, LN, and PⅢP were significantly increased (PDGFR-β: 184.6 ± 8.5 vs 89.6 ± 5.8, P < 0.05; p-ERK1/2: 360.0 ± 14.5 vs 15.4 ± 2.1, P < 0.05; HA: 517.5 ± 91.5 μg/L vs 254.4 ± 33.1 μg/L, P < 0.05; LN: 58.4 ± 11.3 μg/L vs 37.3 ± 9.8 μg/L, P < 0.05; PⅢP: 36.9 ± 5.6 μg/L vs 4.7 ± 1.5 μg/L, P < 0.05) in group B, while the serum level of ALB and the value of A/G were markedly decreased (ALB: 27.4 ± 4.9 g/L vs 42.1 ± 1.6 g/L, P < 0.05; A/G: 0.89 ± 0.08 vs 1.38 ± 0.09, P < 0.05). However, in group C, the expression of PDGFR-b, p-ERK1/2 in liver tissues, the serum levels of HA, LN, and PⅢP were markedly decreased (PDGFR-β: 91.1 ± 6.3 vs 184.6 ± 8.5, P < 0.05; p-ERK1/2: 253.8 ± 18.2 vs 360.0 ± 14.5, P < 0.05; HA: 322.9 ± 41.4 vs 517.5 ± 91.5 μg/L, P < 0.05; LN: 46.0 ± 9.4 vs 58.4 ± 11.3 μg/L, P < 0.05; PⅢP: 14.5 ± 2.4 vs 36.9 ± 5.6 μg/L, P < 0.05), while the serum level of ALB and the value of A/G were notably increased (ALB: 37.2 ± 2.8 g/L vs 27.4 ± 4.9 g/L, P < 0.05; A/G: 1.18 ± 0.13 vs 0.89 ± 0.08, P < 0.05) in comparison with those in group B.

CONCLUSION: PDGFR-β and p-ERK1/2 may play pivotal roles in the pathogenesis of liver fibrosis, and DSHX can prevent liver from fibrosis by decreasing the expression of PDGFR-β and p-ERK1/2.