Platelet-derived Growth factor-CC Research Articles

Serum levels of PDGF-CC as a potential biomarker for the diagnosis of Kawasaki disease

BackgroundKawasaki disease (KD) is an acute systemic vasculitis of unknown etiology that predominantly affects children, and no specific diagnostic biomarkers for KD are available. Platelet-derived growth factor CC (PDGF-CC) is a peptide with angiogenic properties that has been amply demonstrated to play a critical role in the cardiovascular system. This study aimed to investigate the serum expression of PDGF-CC in children with KD and to evaluate the ability of PDGF-CC to diagnose KD.MethodsA total of 96 subjects, including 59 KD patients, 17 febrile controls (FC), and 20 healthy controls (HC), were enrolled. Serum levels of PDGF-CC were measured via enzyme-linked immunosorbent assay. The associations between PDGF-CC and clinical laboratory parameters were investigated by correlation analysis. The diagnostic performance was assessed by receiver operating characteristic (ROC) curve analysis.ResultsSerum PDGF-CC levels in the KD group were significantly higher than in the FC and HC groups. Serum PDGF-CC levels in the KD group were positively correlated with white blood cell counts, percentage of neutrophils, IL-2, IL-12p70, TNF-α, and IL-1β levels, and negatively correlated with the percentage of lymphocytes. In the analysis of ROC curves, the area under the curve was 0.796 (95% confidence interval 0.688–0.880; P < 0.0001) for PDGF-CC and increased to 0.900 (95% confidence interval 0.808–0.957; P < 0.0001) in combination with white blood cell counts and C-reactive protein.ConclusionsPDGF-CC is a potential biomarker for KD diagnosis, and the combination with white blood cell counts and C-reactive protein can further improve diagnostic performance.

25P Combining tissue microarray analysis with RNA-sequencing to explore platelet-derived growth factor-CC biology in primary triple-negative breast cancer

25P Combining tissue microarray analysis with RNA-sequencing to explore platelet-derived growth factor-CC biology in primary triple-negative breast cancer

Abstract P6-01-05: Platelet-derived growth factor-CC expression in primary triple-negative breast cancer is associated with the basal-like molecular subtype and increased immune infiltrate

Abstract Around 10-15% of all breast cancers are categorized clinically as triple-negative breast cancer (TNBC). TNBC is defined by lack of protein expression or over expression of treatment targets such as the Estrogen Receptor α (ER) and Human Epidermal Growth Factor Receptor-2 (HER2), and the prognostic factor PR (Progesterone Receptor). The negative definition of TNBC results in a heterogeneous mix of tumors with variable molecular characteristics and prognosis. Defining TNBC molecular subtypes in detail is of importance to improve prognostication and find new treatment options. Expression of Platelet-derived growth factor-CC (PDGF-CC) has previously been correlated with the TNBC subtype, and paracrine PDGF-CC signaling has been reported to be of importance for maintaining TNBC tumor cell phenotype. We aimed to characterize PDGF-CC expression within the TNBC patient population by combining studies of PDGF-CC in tissue microarrays (TMAs) with matching RNAseq data and clinical follow-up; all variables originating from the SCAN-B (Sweden Cancerome Analysis Network – Breast) clinical study (ClinicalTrials.gov: NCT02306096). TMAs constructed of primary TNBC patient samples were stained for PDGF-CC using the Dako PT Autostainer system. Tumor cell-specific expression of PDGF-CC intensity was scored as either absent (N=11), weak (N=86), intermediate (N=81) or strong (N=70), and the scores were used to create corresponding TNBC PDGF-CC subgroups. We then explored associations of these subgroups with clinicopathological variables and time-to-event outcomes. Intermediate and strong PDGF-CC scores were associated with Nottingham Histological Grade 3 (p=0.001), increased proliferation (p&amp;lt; 0.001) and younger patient age at diagnosis (p=0.002). RNAseq data corresponding to tumors included in the TMAs was then retrieved, and differentially expressed genes were identified and used to perform Gene Set Enrichment Analysis (GSEA) comparing the TMA-derived PDGF-CC subgroups. Immune-related signatures were found to be enriched in the strong PDGF-CC subgroup vs. intermediate. Interestingly, strong PDGF-CC intensity was associated with a decreased risk of recurrence in the chemotherapy treated patient group (HR 0.28, 95% CI 0.10-0.80, p=0.017). Finally, patient samples were assigned a PAM50 subtype and a TNBC molecular subtype by the TNBCtype algorithm. Ninety-four percent of tumors in the strong PDGF-CC subgroup were classified as basal-like, whereas the corresponding number in the weak and intermediate PDGF-CC subgroups were 51% and 84%, respectively. The TNBC molecular subtype termed ‘Immunomodulatory’ was more frequently represented in the strong PDGF-CC subgroup compared to weak and intermediate (33% vs. 13% and 16%, respectively). In conclusion, strong PDGF-CC protein expression identified basal-like TNBCs, with an increase in immune cell infiltrate shown by RNAseq analysis. Whether or not PDGF-CC has a direct effect on influx of immune cells into tumors remains to be investigated. Analyses are currently ongoing to better understand the improved outcome associated with strong PDGF-CC intensity and on the contrary, the worse outcome associated with weak and intermediate PDGF-CC intensity, and if paracrine PDGF-CC signaling may explain the discrepancy observed. Citation Format: Sophie Lehn, Gyula Pekar, Paulina Bolivar Balbas, Johan Staaf, Christina Möller, Kristina Lövgren, Anna Ehinger, Ana Bosch Campos, Åke Borg, Kristian Pietras. Platelet-derived growth factor-CC expression in primary triple-negative breast cancer is associated with the basal-like molecular subtype and increased immune infiltrate [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-01-05.

Remote ischemic conditioning attenuates blood-brain barrier disruption after recombinant tissue plasminogen activator treatment via reducing PDGF-CC

Treatment of acute ischemic stroke with the recombinant tissue plasminogen activator (rtPA) is associated with increased blood–brain barrier (BBB) disruption and hemorrhagic transformation. Remote ischemic conditioning (RIC) has demonstrated neuroprotective effects against acute ischemic stroke. However, whether and how RIC regulates rtPA-associated BBB disruption remains unclear. Here, a rodent model of thromboembolic stroke followed by rtPA thrombolysis at different time points was performed with or without RIC. Brain infarction, neurological outcomes, BBB permeability, and intracerebral hemorrhage were assessed. The platelet-derived growth factor CC (PDGF-CC)/PDGFRα pathway in the brain tissue, PDGF-CC levels in the skeletal muscle and peripheral blood were also measured. Furthermore, impact of RIC on serum PDGF-CC levels were measured in healthy subjects and AIS patients. Our results showed that RIC substantially reduced BBB injury, intracerebral hemorrhage, cerebral infarction, and neurological deficits after stroke, even when rtPA was administrated in a delayed therapeutic time window. Mechanistically, RIC significantly decreased PDGFRα activation in ischemic brain tissue and reduced blood PDGF-CC levels, which partially resulted from PDGF-CC reduction in the skeletal muscle of RIC-applied hindlimbs and platelets. Intravenous or intraventricular recombinant PDGF-CC supplementation abolished RIC protective effects on BBB integrity. Moreover, similar changes of PDGF-CC in serum by RIC were also observed in healthy humans and acute ischemic stroke patients. Together, our study demonstrates that RIC can attenuate rtPA-aggravated BBB disruption after ischemic stroke via reducing the PDGF-CC/PDGFRα pathway and thus supports RIC as a potential approach for BBB disruption prevention or treatment following thrombolysis.

Serum Concentration of Selected Angiogenesis-Related Molecules Differs among Molecular Subtypes, Body Mass Index and Menopausal Status in Breast Cancer Patients

Background: Angiogenesis is a hallmark of breast cancer (BC) and is mediated by the vascular endothelial growth factor (VEGF) signaling axis. It is regulated by different proangiogenic factors, including platelet-derived growth factor-CC (PDGF-CC) and heparin-binding EGF-like growth factor (HB-EGF), as well as co-receptors, such as neuropilin-1, which could have prognostic implications in BC patients. Patients and methods: We assessed the serum levels of VEGF, HB-EGF, PDGF-CC and neuropilin-1 in 205 patients with early BC (invasive, n = 187; in situ, n = 18) and in 31 healthy donors (HD) and investigated the potential associations with clinical and histopathological parameters. Results: VEGF serum levels were significantly higher in patients with invasive versus ductal carcinomas in situ. PDGF-CC serum concentrations varied among BC molecular subtypes. Furthermore, we observed a differential expression of most biomarkers between overweight/obese (body mass index (BMI) ≥ 25 kg/m2) and non-obese patients among the BC molecular subtypes. Finally, the classification of subjects according to menopausal status revealed a significant difference in specific biomarker levels between patients and HD. Conclusion: The serum concentrations of angiogenic molecules differ among breast cancer molecular subtypes and are affected by the BMI and menopausal status, which could have possible clinical or prognostic implications.

Abstract 113: Lyve-1 expressing macrophages direct the expansion of pericytes within the perivascular niche to support angiogenesis in cancer

Abstract Despite the many pro-tumoral functions that have been described for the various stromal populations in cancer, it is becoming apparent that these cells are not working alone, but instead in concert with one another as part of a wider network of cross-communication to facilitate disease progression. Identifying non-redundant signaling pathways within the stromal network is desirable, as therapeutically targeting these signals could result in an unraveling of the stromal support network upon which the tumor cells rely. Tumor associated macrophages (TAMs) have been implicated in a variety of pro-tumoral processes and are polarized by signals in the tumor microenvironment (TME) to adopt a range of functionally distinct subsets to perform these tasks. Single-cell RNA-sequencing of the F4/80+ TAMs from the MMTV-PyMT murine model of mammary adenocarcinoma identified one subset selectively expressing Lyve-1 and adopting a CD206hiMHCIIlo phenotype. This population was identified to spatially reside in the niche proximal to blood vasculature within the tumor. We demonstrate that selective depletion of the Lyve-1+ TAM population using liposome-based approaches controlled tumor growth and was associated with a loss of perivascular alpha smooth muscle actin (αSMA)-expressing stromal cells. The αSMA+ stromal cells were characterized ex vivo and expressed a surface phenotype associated with pericytes (CD90+CD34-NG2+), highlighting a possible role for Lyve-1+ TAMs in maintaining the population. To exclude a role of Lyve-1+ TAMs in recruiting a pericyte-progenitor cell to the tumor, we selectively photo-labelled the TME using MMTV-PyMT mice ubiquitously expressing the photo-convertible green/red Kaede protein. Labelling the TME Kaede-red through exposure to ultraviolet light, demonstrated that pericytes and CD90+ mesenchymal cells more broadly, were not recruited from a peripheral site but instead suggested these populations must rely on local proliferation to maintain their prevalence in the TME. Indeed, we demonstrate through Edu incorporation, that loss of Lyve-1+ TAMs from the perivascular niche renders pericytes senescent. Using computational approaches, we characterized the signaling cross-talk in the perivascular niche between Lyve-1+ TAMs, pericytes and endothelial cells and identified a specific interaction involving platelet derived growth factor-CC (PDGF-CC) expression by Lyve-1+ TAMs and PDGF-receptor alpha (PDGFRα) on the pericytes. Using blocking antibodies to PDGF-CC in tumor bearing mice we demonstrate that blocking this axis of stromal crosstalk can render pericytes senescent. These data highlight that local expansion of pericytes in cancer is not an autonomous event, nor regulated by the endothelium alone, but tightly regulated by the perivascular Lyve-1+ TAM population, which dictates the success of angiogenesis in cancer. Citation Format: James W. Opzoomer, Joanne E. Anstee, Isaac Dean, Emily J. Hill, Ihssane Bouybayoune, Jonathan Caron, Tamara Muliaditan, Peter Gordon, Rosamond Nuamah, Sarah E. Pinder, Tony Ng, Francesco Dazzi, Shahram Kordasti, David R. Withers, Toby Lawrence, James N. Arnold. Lyve-1 expressing macrophages direct the expansion of pericytes within the perivascular niche to support angiogenesis in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 113.

HIV-1 Tat-Induced Astrocytic Extracellular Vesicle miR-7 Impairs Synaptic Architecture.

Although combination antiretroviral therapy (cART) has improved the health of millions of those living with HIV-1 (Human Immunodeficiency Virus, Type 1), the penetration into the central nervous system (CNS) of many such therapies is limited, thereby resulting in residual neurocognitive impairment commonly referred to as NeuroHIV. Additionally, while cART has successfully suppressed peripheral viremia, cytotoxicity associated with the presence of viral Transactivator of transcription (Tat) protein in tissues such as the brain, remains a significant concern. Our previous study has demonstrated that both HIV-1 Tat as well as opiates such as morphine, can directly induce synaptic alterations via independent pathways. Herein, we demonstrate that exposure of astrocytes to HIV-1 protein Tat mediates the induction and release of extracellular vesicle (EV) microRNA-7 (miR-7) that is taken up by neurons, leading in turn, to downregulation of neuronal neuroligin 2 (NLGN2) and ultimately to synaptic alterations. More importantly, we report that these impairments could be reversed by pretreatment of neurons with a neurotrophic factor platelet-derived growth factor-CC (PDGF-CC). Graphical

PDGF regulated migration of mesenchymal stem cells towards malignancy acts via the PI3K signaling pathway.

Mesenchymal stem cells (MSCs) have been described in breast cancer models to migrate towards carcinoma and integrate into tumor associated stroma supporting tumor growth, increasing their metastatic potency and contributing to tumor-angiogenesis. Platelet-derived growth factor (PDGF) isoforms (AA, BB, CC) stimulate growth, survival and motility of MSCs and certain other cell types. Noteworthy, breast carcinomas are known to express PDGF. We aim to further shed light on i) the relevance of the different PDGF isoforms on adipose tissue derived stem cells (ASCs) migration and ii) the underlying pathway dependent on PDGF stimulation. Breast cancer cell lines were purchased and ASC's were isolated from murine subcutaneous adipose tissue. The transmigration of ASC's towards the PDGF-isoforms was assessed by using recombinant human PDGF-AA, PDGF-BB and PDGF-CC in a trans-well culture dish system. Transmigrated ASC's were quantified in 5 randomly selected fields per condition using fluorescence microscopy after calcein-staining. PDGF-BB depended transmigration of ASC's was verified by downregulation and overexpression of PDGF-BB in breast cancer cell line using lentiviral vectors. In addition, a PI3-kinase inhibitor (LY294002) and a MAP-kinase inhibitor (PD98059) were used to identify the pathway involved in the PDGF-BB mediated migration of ASC's towards tumor. ASC's transmigration significantly increased towards PDGF AA at 50 ng and only showed further increase by 500 ng which was similar to cell behavior when exposed to PDGF CC. In comparison, PDGF-BB significantly increased ASC's transmigration already at a low level of 5 ng with further significant increase for 20 ng and 40 ng. Cell transmigration was blocked with PDGFR-α antibodies but only for PDGF-AA and PDGF-CC whereas PDGFR-β blockage showed a significant effect on transmigration for PDGF-BB and PDGF-CC but not for PDGF-AA. Neutralizing antibodies in combination with PDGF receptor blockage confirmed findings. In addition, only PI3-kinase inhibitor but not the MEK-1 selective inhibitor caused a significant decrease of transmigration for ASCs towards breast cancer cells. The transmigration of ASC's is most significantly enhanced by PDGF-BB via the PI3-kinase pathway. This data support that PI3-kinase is an important key player for MSC migration towards malignancy which need further research to prevent tumor progression in early disease stage.

Preclinical toxicological assessment of a novel monoclonal antibody targeting human platelet-derived growth factor CC (PDGF-CC) in PDGF-CChum mice.

Platelet-derived growth factor CC (PDGF-CC) is important during foetal development but also in pathogenesis of neurologic diseases, cancer and fibrosis. We have previously demonstrated that blocking the PDGF-CC/PDGF receptor alpha (PDGFRα) axis resulted in reduction of stroke volume and cerebrovascular permeability after experimentally induced stroke. Recently, we could translate these findings into the clinic showing that imatinib, a small tyrosine kinase inhibitor targeting PDGF receptors, can significantly improve neurological outcome after ischemic stroke in human. Herein we report preclinical toxicological analyses of our newly generated monoclonal anti-human PDGF-CC antibody 6B3 (mAb 6B3) in PDGF-CC humanized mice. Beside histological organ assessment, we also analysed serum, urine, haematological parameters and the general health status of the treated mice. We could not find any indications that mAb 6B3 is toxic or has other significant side effects neither in short, nor in long treatment regimens. Our results indicate that mAb 6B3 can be further developed for clinical use. This opens up the possibility to assess the therapeutic potential of blocking PDGF-CC in diverse pathological conditions such as neurologic diseases, cancer and fibrosis.

Abstract 5199: Microenvironmental control of breast cancer subtype elicited by paracrine platelet-derived growth factor-CC signaling

Abstract Aim: Breast tumors of the basal-like, hormone receptor-negative subtype, remain an unmet clinical challenge, as patients exhibit the highest recurrence rate, the shortest time to recurrence and the worst overall survival rate due to a paucity of therapeutic targets. Also, as tumors develop, the surrounding microenvironment co-evolves into an activated state through continuous paracrine communication, creating a dynamic signaling circuitry that promotes malignant progression. Thus, novel treatment approaches that also include the targeting of stromal components are urgently required. Methods: We used experimental mouse models of cancer (transgenic, syngeneic, human cell lines and patient-derived xenografts) for knockout studies and preclinical trials, immunostaining, in vitro assays, western-blot, gene expression analysis and RNA-sequencing, patient cohorts, data mining and bioinformatics analysis. Results and discussion: We identified a paracrine crosstalk between cancer cells expressing platelet-derived growth factor (PDGF)-CC and cancer-associated fibroblasts (CAFs) expressing the cognate receptors in human basal-like mammary carcinomas. In translational efforts, we found that PDGF-CC expression in the malignant epithelium of breast cancer was associated with a hormone receptor-negative state. We then generated a mouse model to characterise the functional role of PDGF-CC in tumorigenesis. Moreover, we identified and validated factors secreted by CAFs to maintain a basal-like phenotype, e.g. Stanniocalcin (STC)-1, Hepatocyte Growth Factor (HGF) and Insulin Growth Factor Binding Protein (IGFBP)-3. Genetic or pharmacological targeting of PDGF-CC in experimental mouse models resulted in the transcriptional reprogramming and conversion of basal-like breast tumors into a luminal-like state characterised by Estrogen Receptor (ER)-α positivity, that conferred sensitivity to endocrine therapy in previously intrinsically unresponsive tumors. Conclusions: Specification of the basal-like subtype of breast cancer is under microenvironmental control and therapeutically actionable in order to achieve sensitivity to endocrine therapy. Our work sheds light on previously unknown mechanisms that define breast cancer subtype and has significant therapeutic implications for patients with basal-like breast tumors. Citation Format: Matteo Bocci, Michael Bartoschek, Pernilla Roswall, Kristian Pietras. Microenvironmental control of breast cancer subtype elicited by paracrine platelet-derived growth factor-CC signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5199.

Microenvironmental control of breast cancer subtype elicited through paracrine platelet-derived growth factor-CC signaling.

Breast tumors of the basal-like, hormone receptor-negative, subtype remain an unmet clinical challenge, as patients exhibit a high rate of recurrence and poor survival. Co-evolution of the malignant mammary epithelium and its underlying stroma instigates cancer-associated fibroblasts (CAFs) to endorse most, if not all, hallmarks of cancer progression. Here, we delineate a previously unappreciated role for CAFs as determinants of the molecular subtype of breast cancer. We identified a paracrine cross-talk between cancer cells expressing platelet-derived growth factor (PDGF)-CC and CAFs expressing the cognate receptors in human basal-like mammary carcinomas. Genetic or pharmacological intervention with PDGF-CC activity in mouse models of cancer resulted in conversion of basal-like breast cancers into a hormone receptor-positive state that conferred sensitivity to endocrine therapy in previously impervious tumors. We conclude that specification of the basal-like subtype of breast cancer is under microenvironmental control and therapeutically actionable in order to achieve sensitivity to endocrine therapy.

Microglial-mediated PDGF-CC activation increases cerebrovascular permeability during ischemic stroke

Treatment of acute ischemic stroke with the thrombolytic tissue plasminogen activator (tPA) can significantly improve neurological outcomes; however, thrombolytic therapy is associated with an increased risk of intra-cerebral hemorrhage (ICH). Previously, we demonstrated that during stroke tPA acting on the parenchymal side of the neurovascular unit (NVU) can increase blood–brain barrier (BBB) permeability and ICH through activation of latent platelet-derived growth factor-CC (PDGF-CC) and signaling by the PDGF receptor-α (PDGFRα). However, in vitro, activation of PDGF-CC by tPA is very inefficient and the mechanism of PDGF-CC activation in the NVU is not known. Here, we show that the integrin Mac-1, expressed on brain microglia/macrophages (denoted microglia throughout), acts together with the endocytic receptor LRP1 in the NVU to promote tPA-mediated activation of PDGF-CC. Mac-1-deficient mice (Mac-1−/−) are protected from tPA-induced BBB permeability but not from permeability induced by intracerebroventricular injection of active PDGF-CC. Immunofluorescence analysis demonstrates that Mac-1, LRP1, and the PDGFRα all localize to the NVU of arterioles, and following middle cerebral artery occlusion (MCAO) Mac-1−/− mice show significantly less PDGFRα phosphorylation, BBB permeability, and infarct volume compared to wild-type mice. Bone-marrow transplantation studies indicate that resident CD11b+ cells, but not bone-marrow-derived leukocytes, mediate the early activation of PDGF-CC by tPA after MCAO. Finally, using a model of thrombotic stroke with late thrombolysis, we show that wild-type mice have an increased incidence of spontaneous ICH following thrombolysis with tPA 5 h after MCAO, whereas Mac-1−/− mice are resistant to the development of ICH even with late tPA treatment. Together, these results indicate that Mac-1 and LRP1 act as co-factors for the activation of PDGF-CC by tPA in the NVU, and suggest a novel mechanism for tightly regulating PDGFRα signaling in the NVU and controlling BBB permeability.

Imatinib treatment reduces brain injury in a murine model of traumatic brain injury.

Current therapies for Traumatic brain injury (TBI) focus on stabilizing individuals and on preventing further damage from the secondary consequences of TBI. A major complication of TBI is cerebral edema, which can be caused by the loss of blood brain barrier (BBB) integrity. Recent studies in several CNS pathologies have shown that activation of latent platelet derived growth factor-CC (PDGF-CC) within the brain can promote BBB permeability through PDGF receptor α (PDGFRα) signaling, and that blocking this pathway improves outcomes. In this study we examine the efficacy for the treatment of TBI of an FDA approved antagonist of the PDGFRα, Imatinib. Using a murine model we show that Imatinib treatment, begun 45 min after TBI and given twice daily for 5 days, significantly reduces BBB dysfunction. This is associated with significantly reduced lesion size 24 h, 7 days, and 21 days after TBI, reduced cerebral edema, determined from apparent diffusion co-efficient (ADC) measurements, and with the preservation of cognitive function. Finally, analysis of cerebrospinal fluid (CSF) from human TBI patients suggests a possible correlation between high PDGF-CC levels and increased injury severity. Thus, our data suggests a novel strategy for the treatment of TBI with an existing FDA approved antagonist of the PDGFRα.

Role of Platelet-Derived Growth Factor-CC in Capillary Rarefaction in Renal Fibrosis

We have identified platelet-derived growth factor (PDGF)-CC as a potent profibrotic mediator in kidney fibrosis and pro-angiogenic mediator in glomeruli. Because renal fibrosis is associated with progressive capillary rarefaction, we asked whether PDGF-CC neutralization in fibrosis might have detrimental anti-angiogenic effects leading to aggravated peritubular capillary loss. We analyzed capillary rarefaction in mice with and without PDGF-CC neutralization (using genetically deficient mice and neutralizing antibodies), in three different models of renal interstitial fibrosis, unilateral ureteral obstruction, unilateral ischemia-reperfusion, Col4a3-deficient (Alport) mice, and healthy animals. Independent of the effect of PDGF-CC neutralization on renal fibrosis, we found no difference in capillary rarefaction between PDGF-CC-neutralized mice and mice with intact PDGF-CC. We also found no differences in microvascular leakage (determined by extravasation of Evans Blue Dye) and in renal relative blood volume quantified using invivo microcomputed tomography. PDGF-CC neutralization had no effects on renal microvasculature in healthy animals. Capillary endothelium did not express PDGF receptor-α, suggesting that potential PDGF-CC effects would have to be indirect. PDGF-CC neutralization or deficiency was not associated with preservation or accelerated loss of peritubular capillaries, suggesting no significant pro-angiogenic effects of PDGF-CC during renal fibrosis. From a clinical perspective, the profibrotic effects of PDGF-CC outweigh the pro-angiogenic effects and, thus, do not limit apotential therapeutic use of PDGF-CC inhibition in renal fibrosis.

Understanding the functions of endogenous and exogenous tissue-type plasminogen activator during stroke.

Alteplase (Actilyse or Activase) is the gold standard acute treatment of ischemic stroke1 and receives attention for hematoma resolution in hemorrhagic stroke. The active principle of Alteplase is the recombinant form of an endogenous protease, tissue-type plasminogen activator (tPA). Its intravascular thrombolytic activity is well known, but less are its multifaceted functions in the central nervous system (CNS). Endogenous tPA is not only released in the blood by endothelial cells but also expressed by many cells within the brain parenchyma (online-only Data Supplement), and it can act on all cell types of the brain virtually. Endogenous tPA has been involved in an ever-increasing number of brain functions, of which several are highly relevant during and after stroke. Importantly, knowledge on the mechanisms of action of endogenous tPA may hold true for recombinant tPA. In this review, we provide an up-to-date overview of the current knowledge on the enzymatic or cytokine-like effects of action of tPA in the CNS, its various molecular substrates or receptors, focusing on the processes occurring during and after ischemic or hemorrhagic stroke, including excitotoxicity, apoptosis, blood–brain barrier breakdown, inflammation, axonal damage, and demyelination. tPA is a mosaic protease of 527 amino acids consisting of 5 distinct modules: a Finger domain, an epidermal growth factor (EGF)–like domain, 2 kringle domains (K1 and K2), and a serine protease proteolytic domain. Through these domains, tPA can interact with a variety of binding proteins and receptors in the brain parenchyma, thus extending its functions above the conversion of plasminogen into plasmin (Figure 1). Figure 1. Main cellular and molecular targets of tissue-type plasminogen activator in the central nervous system. BBB indicates blood–brain barrier, EGFR, epidermal growth factor receptor; LRP, low-density lipoprotein receptor–related protein; NMDAR, N-methyl-d-aspartate receptors; and PDGFR, platelet-derived growth factor receptor. tPA is not fibrinolytic by itself. …

Progranulin Deficiency Promotes Post-Ischemic Blood–Brain Barrier Disruption

Loss-of-function mutations of progranulin (PGRN) have been linked to frontotemporal dementia, but little is known about the effects of PGRN deficiency on the brain in health and disease. PGRN has been implicated in neurovascular development, inflammation, and Wnt signaling, a pathway involved in the formation of the blood-brain barrier (BBB). Because BBB alterations and inflammation contribute to ischemic brain injury, we examined the role of PGRN in the brain damage produced by ischemia-reperfusion. PGRN(+/-) and PGRN(-/-) mice underwent middle cerebral artery occlusion (MCAO) with monitoring of cerebral blood flow. Infarct volume and motor deficits were assessed 72 h later. Post-ischemic inflammation was examined by expression of inflammatory genes and flow cytometry. BBB structure and permeability were examined by electron microscopy (EM) and Evans blue (EB) extravasation, respectively. MCAO resulted in ~60% larger infarcts in PGRN(+/-) and PGRN(-/-) mice, an effect independent of hemodynamic factors or post-ischemic inflammation. Rather, massive hemorrhages and post-ischemic BBB disruption were observed, unrelated to degradation of tight junction (TJ) proteins or matrix metalloproteinases (MMPs). By EM, TJ were 30-52% shorter, fewer, and less interlocking, suggesting a weaker seal between endothelial cells. Intracerebral injection of platelet-derived growth factor-CC (PDGF-CC), which increases BBB permeability, resulted in a more severe BBB breakdown in PGRN(+/-) and PGRN(-/-) than wild-type mice. We describe a previously unrecognized involvement of PGRN in the expression of key ultrastructural features of the BBB. Such a novel vasoprotective role of PGRN may contribute to brain dysfunction and damage in conditions associated with reduced PGRN function.

In vitro comparative evaluation of recombinant growth factors for tissue engineering of bladder in patients with neurogenic bladder

BackgroundTo compare the effects of various recombinant growth factors on bladder regeneration and angiogenesis for tissue engineering of bladder in patients with neurogenic bladder through in vitro cellular biological methods. Materials and methodsHuman bladder smooth muscle cells (HBSMCs) and human bladder urothelial cells (HBUCs) were cultured from patients with neurogenic bladder and used for comparative evaluations of various growth factors. Human umbilical vein endothelial cells (HUVECs) were also used. Eight potential growth factors, platelet-derived growth factor BB (PDGF-BB), platelet-derived growth factor CC (PDGF-CC), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), insulin-like growth factor 1 (IGF-1), hepatocyte growth factor (HGF), and transforming growth factor beta 1 (TGF-β1), were selected and their effects on the proliferation, migration, and wound healing of HBSMCs, HBUCs, and HUVECs were compared. ResultsPDGF-BB, PDGF-CC, bFGF, VEGF, IGF-1, or HGF enhanced the proliferation, migration, and wound healing of HBSMCs, whereas TGF-β1 inhibited their proliferation. Proliferation, migration, and wound healing of HBUCs and HUVECs were enhanced by bFGF, VEGF, EGF, IGF-1, or HGF, whereas inhibited by TGF-β1. PDGF-BB failed to enhance cell activity of HUVECs, whereas PDGF-CC could enhance their migration and wound healing. PDGF-BB, EGF, and VEGF were the most potent factors for stimulating the activities of HBSMCs, HBUCs, and HUVECs, respectively. ConclusionsOur findings suggest the potential use of a combination of PDGF-BB, EGF, and VEGF for bladder regeneration and angiogenesis. The synergetic effects of the three growth factors on cell activities in a three-dimensional scaffold and an animal model with neurogenic bladder need to be further evaluated.

Platelet derived growth factor-CC isoform is associated with hemorrhagic transformation in ischemic stroke patients treated with tissue plasminogen activator

ObjectivePlatelet derived growth factor-CC (PDGF–CC) isoform is activated by tissue plasminogen activator (tPA) regulating blood brain barrier permeability after ischemia. We aimed to study the association of PDGF isoforms serum levels with hemorrhagic transformation (HT) and edema after thrombolytic treatment in ischemic stroke. MethodsWe studied 129 patients with ischemic stroke treated with tPA within the first 4.5 h (h) from stroke onset. CT was performed on admission and at 24–36 h. On the 2nd CT, HT was classified according to ECASS II criteria, and severe brain edema was diagnosed if extensive swelling causing any shifting of the structures of the midline was detected. PDGF-AA, PDGF-AB, PDGF–BB and PDGF–CC serum levels were analyzed by ELISA on admission (before tPA bolus), at 24 and 72 h. ResultsPatients who developed HT showed only higher levels of PDGF–CC isoform on admission and at 24 h (all p < 0.0001). In the multivariate analysis, PDGF–CC levels on admission (OR, 1.02; CI 95%, 1.00–1.04) and at 24 h (OR, 1.05; CI 95%, 1.02–1.08) were independently associated with HT after adjustment by confounding factors. On the other hand, patients with severe edema showed also higher levels of PDGF–CC on admission and at 24 h (p < 0.0001), but this statistical association was lost in the logistic regression analysis. PDGF–CC levels ≥ 175 ng/mL at 24 h predict the development of PH with a sensitivity of 90% and specificity of 88% (area under the curve 0.936; p < 0.0001). ConclusionIncreased PDGF–CC levels after tPA treatment is associated with HT.

Platelet derived growth factor-CC secreted by M2 macrophages induces alpha-smooth muscle actin expression by dermal and gingival fibroblasts

Dermal wounds can heal detrimentally by formation of excess fibrosis or hypertrophic scarring. These phenomena are normally absent in the oral mucosa. Macrophages play an important role in wound repair, have a marked heterogeneity and are thought to contribute to fibrosis. To investigate to what extend macrophages are involved in the occurrence of fibrosis, the effect of differently activated macrophages on dermal and gingival fibroblasts was studied in vitro. Macrophages were differentiated into a classical (M1) or alternative (M2) phenotype, which was assessed by receptor expression (CD40/mannose receptor) and cytokine secretion (interleukin-4 and -12). Fibroblasts were exposed to these macrophages and/or conditioned medium (cm), and differentiation into α-SMA-expressing myofibroblasts was quantified. M2, but not M1 macrophages induced α-SMA expression in both dermal and gingival fibroblasts. Blocking of transforming growth factor-β1 did not decrease the α-SMA expression mediated by M2 macrophages. It appeared that this induction was mediated by platelet derived growth factor-CC (PDGF-CC), produced by M2 macrophages. The expression and role of this growth factor was confirmed by ELISA, RT-PCR, and blocking experiments. Our results indicate that M2 macrophages are able to induce myofibroblast differentiation via production of PDGF-CC. Based on our findings we conclude that PDGF-CC may play a hitherto unknown role in the differentiation of myofibroblasts.

Platelet-Derived Growth Factor CC-Mediated Neuroprotection against HIV Tat Involves TRPC-Mediated Inactivation of GSK 3beta

Platelet-derived growth factor-CC (PDGF-CC) is the third member of the PDGF family, and has been implicated both in embryogenesis and development of the CNS. The biological function of this isoform however, remains largely unexplored in the context of HIV-associated dementia (HAD). In the present study, we demonstrate that exposure of human neuroblastoma cells SH-SY5Y to HIV transactivator protein Tat resulted in decreased intrinsic expression of PDGF-CC as evidenced by RT-PCR and western blot assays. Reciprocally, pretreatment of SH-SY5Y cells with PDGF-CC abrogated Tat-mediated neurotoxicity by mitigating apoptosis and neurite & MAP-2 loss. Using pharmacological and loss of function approaches we identified the role of phosphatidylinositol 3-kinase (PI3K)/Akt signaling in PDGF-CC-mediated neuroprotection. We report herein a novel role about the involvement of transient receptor potential canonical (TRPC) channel 1 in modulation of calcium transients in PDGF-CC-mediated neuroprotection. Furthermore we also demonstrated PDGF-CC-mediated inactivation of the downstream mediator - glycogen synthase kinase 3β (GSK3β) evidenced by its phosphorylation at Ser-9. This was further validated by gain and loss of function studies using cells transfected with either the wild type or mutant GSK3β constructs. Intriguingly, pretreatment of cells with either the PI3K inhibitor or TRPC blocker resulted in failure of PDGF-CC to inactivate GSK3β, thereby suggesting the intersection of PI3K and TRPC signaling at GSK3β. Taken together our findings lead to the suggestion that PDGF-CC could be developed as a therapeutic target to reverse Tat-mediated neurotoxicity with implications for HAD.