Platelet derived growth factor and its receptor in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a common and highly disabling or fatal neurological disorder in adults. Recent studies have suggested that the platelet derived growth factor (PDGF) signaling pathway plays an important role in the development of ICH. PDGF is involved in vascular remodeling and can be used as a biomarker of cerebral amyloid angiopathy which is one of the major causes of ICH. PDGF and its receptors are involved in the mechanism of the secondary injury after ICH by affecting the integrity of the blood-brain barrier and inflammatory response. PDGF and its receptors may also participate in the mechanism of repair after ICH by promoting angiogenesis. This article reviews the latest research progress on the involvement of PDGF signaling pathway in the pathophysiology of intracerebral hemorrhage, and introduces the relevant antagonists using PDGFR as the therapeutic target, to provide information for the development of therapeutic options for intracerebral hemorrhage.

Platelet Rich Fibrin Membrane Grafting After Laser Excision for Oral Mucosal Lesions

Platelet rich fibrin (PRF) is a novel surgical biomaterial which has shown immense healing and regenerative potential with diverse clinical applications. Surgical excision is a routinely employed treatment modality for mucosal oral lesions with or without grafting or repair of the base of the wound. We proposed a hypothesis that covering of the base of excised lesion with this platelet rich fibrin membrane can accelerate the rate of physiological healing process and regeneration. To evaluate the role, efficacy, advantages and adverse effects if any, of placement of PRF membrane grafts over surgical excision sites of oral mucosal lesions. Platelet rich fibrin membrane graft was prepared as per recommendation and established protocols. Patients were selected for surgical excision of localized, superficial oral mucosal lesions after meticulous clinical and radiological considerations and informed consent was taken. After laser excision with safe margins, the base of wound was covered with PRF membrane graft, stitched in place by 3-0 vicryl sutures. The operated site was clinically evaluated at regular intervals and a healing score was calculated and statistically tabulated on the basis of various parameters of healing. A total of 34 patients were included in the study with a male preponderance (21 males and 13 females). Satisfactory and clinically acceptable wound healing was observed in most of the patient with minimal morbidities. Surgical site demonstrated good healing score and clinically complete healing with good epithelialisation was achieved in all patients. Platelet rich fibrin membrane is an effective grafting biomaterial after excision of oral mucosal lesions as it enhances the rate of healing with minimal complications. We recommend further multicentre studies with higher sample size to explore its utility and clinical applications in different avenues of oral and head neck surgery.

FDA-approved bone grafts and bone graft substitute devices in bone regeneration

To induce bone regeneration there is a complex cascade of growth factors. Growth factors such as recombinant BMP-2, BMP-7, and PDGF are FDA-approved therapies in bone regeneration. Although, BMP shows promising results as being an alternative to autograft, it also has its own downfalls. BMP-2 has many adverse effects such as inflammatory complications such as massive soft-tissue swelling that can compromise a patient's airway, ectopic bone formation, and tumor formation. BMP-2 may also be advantageous for patients not willing to give up smoking as it shows bone regeneration success with smokers. BMP-7 is no longer an option for bone regeneration as it has withdrawn off the market. PDGF-BB grafts in studies have shown PDGF had similar fusion rates to autologous grafts and fewer adverse effects. There is also an FDA-approved bioactive molecule for bone regeneration, a peptide P-15. P-15 was found to be effective, safe, and have similar outcomes to autograft at 2 years post-op for cervical radiculopathy due to cervical degenerative disc disease. Growth factors and bioactive molecules show some promising results in bone regeneration, although more research is needed to avoid their adverse effects and learn about the long-term effects of these therapies. There is a need of a bone regeneration method of similar quality of an autograft that is osteoconductive, osteoinductive, and osteogenic. This review covers all FDA-approved bone regeneration therapies such as the "gold standard" autografts, allografts, synthetic bone grafts, and the newer growth factors/bioactive molecules. It also covers international bone grafts not yet approved in the United States and upcoming technologies in bone grafts.

Immune responses to injury and their links to eye disease

The eye is regarded as an immune privileged site. Since the presence of a vasculature would impair vision, the vasculature of the eye is located outside of the central light path. As a result, many regions of the eye evolved mechanisms to deliver immune cells to sites of dysgenesis, injury, or in response to the many age-related pathologies. While the purpose of these immune responses is reparative or protective, cytokines released by immune cells compromise visual acuity by inducing inflammation and fibrosis. The response to traumatic or pathological injury is distinct in different regions of the eye. Age-related diseases impact both the anterior and posterior segment and lead to reduced quality of life and blindness. Here we focus attention on the role that inflammation and fibrosis play in the progression of age-related pathologies of the cornea and the lens as well as in glaucoma, the formation of epiretinal membranes, and in proliferative vitreoretinopathy.

Wettability of implant surfaces: Blood vs autologous platelet liquid (APL)

Physicochemical properties of titanium surfaces, such as wettability, influence protein binding, cell adhesion and proliferation, therefore osseointegration. The objective of this study was to investigate the wetting behaviour of two titanium surfaces, sandblasted and double acid etched (group S/E) and sandblasted (group S), using blood and Autologous Platelet Liquid (APL). Surface morphology and roughness were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The static contact angle (CA) was assessed with the sessile drop technique. The work also evaluates, with SEM observation, the fibrin clot structure that develops from blood and APL, knowing that a greater clot, firmly attached to an implant can facilitate cell migration to the implant interface. Both surfaces exhibited a hydrophobic behaviour, regardless of the wetting liquid used, but the S surface showed higher CA values for both the wetting fluids used. Lower CA values on the S/E surface are attributable to the different surface energy, which depends on different surface topography (the S surfaces were rougher) and on chemical composition. No statistically significant differences between the values of CA of blood and APL were found on the same surfaces. The clot obtained from whole blood differs from the APL clot due to a different cellular composition and fibrin density.

Portal vein thrombosis due to essential thrombocythemia with limited cutaneous systemic sclerosis

Portal vein thrombosis is caused by various diseases, including liver cirrhosis, cancer, abdominal infection, and myeloproliferative disorders. Essential thrombocythemia is one of the myeloproliferative disorders in which the bone marrow produces excessive amount of platelets and can be accompanied by various thrombotic diseases; however, essential thrombocythemia with limited cutaneous systemic sclerosis has not been reported yet. We herein report a case of extensive portal vein thrombosis due to essential thrombocythemia with limited cutaneous systemic sclerosis. A 49-year-old woman was referred to our hospital due to liver dysfunction. Extended portal vein thrombosis, splenomegaly, and thrombocytosis were founded. The examination of Janus kinase 2 V617F mutation in the bone marrow was positive. These findings resulted in the diagnosis of portal vein thrombosis due to essential thrombocythemia. Furthermore, Raynaud's phenomenon, finger's sclerosis, and positive anti-centromere antibody led to limited cutaneous systemic sclerosis. To further analyze the causal relationship between essential thrombocythemia and limited cutaneous systemic sclerosis, platelet-derived growth factor was examined. High level of serum platelet-derived growth factor, possibly caused by high platelet count due to essential thrombocythemia, was observed. As platelet-derived growth factor has been reportedly associated with the occurrence of systemic sclerosis, the present case indicates the possible causal link between essential thrombocythemia and limited cutaneous systemic sclerosis through high platelet-derived growth factor.

The importance of plasmin for the healing of the anterior cruciate ligament

Aims

The anterior cruciate ligament (ACL) is known to have a poor wound healing capacity, whereas other ligaments outside of the knee joint capsule such as the medial collateral ligament (MCL) apparently heal more easily. Plasmin has been identified as a major component in the synovial fluid that varies among patients. The aim of this study was to test whether plasmin, a component of synovial fluid, could be a main factor responsible for the poor wound healing capacity of the ACL.

Methods

The effects of increasing concentrations of plasmin (0, 0.1, 1, 10, and 50 µg/ml) onto the wound closing speed (WCS) of primary ACL-derived ligamentocytes (ACL-LCs) were tested using wound scratch assay and time-lapse phase-contrast microscopy. Additionally, relative expression changes (quantitative PCR (qPCR)) of major LC-relevant genes and catabolic genes were investigated. The positive controls were 10% fetal calf serum (FCS) and platelet-derived growth factor (PDGF).

Results

WCS did not differ significantly among no plasmin versus each of the tested concentrations (six donors). The positive controls with PDGF and with FCS differed significantly from the negative controls. However, we found a trend demonstrating that higher plasmin concentrations up-regulate the expression of matrix metalloproteinase 13 (MMP13), 3 (MMP3), and tenomodulin (TNMD).

Conclusion

The clinical relevance of this study is the possibility that it is not solely the plasmin, but also additional factors in the synovial fluid of the knee, that may be responsible for the poor healing capacity of the ACL.

Cite this article: Bone Joint Res 2020;9(9):543–553.

Angiotensin-(1-9) prevents vascular remodeling by decreasing vascular smooth muscle cell dedifferentiation through a FoxO1-dependent mechanism

The renin-angiotensin system, one of the main regulators of vascular function, controls vasoconstriction, inflammation and vascular remodeling. Antagonistic actions of the counter-regulatory renin-angiotensin system, which include vasodilation, anti-proliferative, anti-inflammatory and anti-remodeling effects, have also been described. However, little is known about the direct effects of angiotensin-(1-9), a peptide of the counter-regulatory renin-angiotensin system, on vascular smooth muscle cells. Here, we studied the anti-vascular remodeling effects of angiotensin-(1-9), with special focus on the control of vascular smooth muscle cell phenotype. Angiotensin-(1-9) decreased blood pressure and aorta media thickness in spontaneously hypertensive rats. Reduction of media thickness was associated with decreased vascular smooth muscle cell proliferation. In the A7r5 VSMC cell line and in primary cultures of rat aorta smooth muscle cells, angiotensin-(1-9) did not modify basal proliferation. However, angiotensin-(1-9) inhibited proliferation, migration and contractile protein decrease induced by platelet derived growth factor-BB. Moreover, angiotensin-(1-9) reduced Akt and FoxO1 phosphorylation at 30 min, followed by an increase of total FoxO1 protein content. Angiotensin-(1-9) effects were blocked by the AT2R antagonist PD123319, Akt-Myr overexpression and FoxO1 siRNA. These data suggest that angiotensin-(1-9) inhibits vascular smooth muscle cell dedifferentiation by an AT2R/Akt/FoxO1-dependent mechanism.

[Molecular tumor board-renal cell carcinoma]

The introduction of molecular targeted agents has fundamentally changed the treatment of metastatic renal cell carcinoma. A first wave of development was based on the improved understanding of tumor biology since the discovery of the importance of the von Hippel-Lindau gene as the key driver of the disease and paved the way for antiangiogenic agents. Of relevance is the overexpression of proangiogenic and proliferation-promoting factors (VEGF, vascular endothelial growth factor; PDGF, platelet-derived growth factor) as well as an overactivation of the PI3K-Akt signaling pathway: the target structure is the "mammalian target of rapamycin" (mTOR) molecule, which is involved in the regulation of cell proliferative processes. VEGF-, PDGF-, and mTOR-signals and signaling pathways are central targets of current targeted substances. A second wave is certainly to be seen in the development of therapeutic approaches with the targeted activation and modulation of the immune system, which has brought "immunotherapy" back into the focus of interest. Central development is the application of immune-checkpoint inhibitors, with the help of which (re-)activation of the cellular defense, especially of T cells, takes place, which per se holds the potential of a cytoreductive therapy by killing the tumor cells. Even though the prognosis has improved significantly due to the rapid development of recent years, treatment remains challenging as most patients experience progress, and long-term survival is only achieved in about 20% of cases because some patients are primarily refractory or do not respond. The more intensive interlocking of molecular biology, pathology, clinical research, and interdisciplinary uro-oncology, as is the claim of molecular tumor boards, can contribute to the individual selection of a suitable therapy strategy and, thus, establish the latest findings and developments for the benefit of patients in the clinic.

Effects of the CRMP2 activator lanthionine ketimine ethyl ester on oligodendrocyte progenitor cells

We previously showed LKE (lanthionine ketimine ester) reduces disease in the EAE model of multiple sclerosis, however whether LKE affects oligodendrocytes (OLGs) was not tested. In OLG progenitor cells (OPCs), LKE increased process number and area, but not PDGF-receptor-alpha expressing cells. In contrast, PDGF increased OPC numbers, but reduced process number and area. LKE increased collapsin response mediator protein-2 (CRMP2) expression, an LKE target, and CRMP2-expressing OLGs expressed myelin basic protein. LKE increased markers of OPC maturation, while PDGF, but not LKE, increased Sox2 expression. Our findings suggest that effects on OPCs may contribute to LKE beneficial actions in EAE.

Recombinant platelet derived growth factor-BB and hyaluronic acid effect in rat osteoarthritis models

Osteoarthritis (OA) arises from imbalance of cartilage metabolism between the synthesis and degradation of type II collagen by the chondrocyte. Collagen type II degradation is characterized by increase in the biomarker of C-telopeptide fragment of type II collagen (CTX-II), while the anabolic process of cartilage is characterized by an increase in the biosynthesis of procollagen amino terminal N-propeptide type IIA (PIIANP). Platelet derived growth factor (PDGF) with Hyaluronic Acid (HA) as a potent growth factor can be used to stimulate the higher formation of chondrocyte and PIIANP levels and lower CTX-II levels in mouse knee osteoarthritis model.

[Effect of cannabinoid receptor-2 agonist AM1241 on platelet-derived growth factor expression in the liver tissue of mice with hepatic fibrosis]

Objective: To investigate the effect of cannabinoid receptor-2 (CB2) agonist AM1241 on the mRNA and protein expression of platelet-derived growth factor (PDGF) and collagen-III (Col-III) in the liver tissue of mice with experimental liver fibrosis induced by carbon tetrachloride (CCl(4)). Methods: Totally 38 8-week-old male C57BL/6J mice were randomly divided into control group, model group, 3 mg/kg CB2 receptor agonist (AM1241) group, and 9 mg/kg AM1241 group. All mice, except for the control group, were treated with 30% CCl(4) (three times a week, 5 ml/kg body weight, 16 weeks) to establish a liver fibrosis model. Meanwhile, 3 and 9 mg/kg AM1421 was intraperitoneally injected for daily intervention, respectively. The dosage was adjusted according to actual body weight. The same solvent was given in the control group. The serum level of aspartate aminotransferase (AST) was measured by serum enzyme digestion. The liver inflammation and fibrosis were observed by HE staining of tissue slices. The mRNA and protein expression of PDGF and Col-III in hepatic tissue was determined by real-time PCR and immunohistochemistry. Results: Compared with the control group, the mice in model group showed severe liver fibrosis, significantly elevated serum AST level (742 ± 300.8 U/L vs 118.1 ± 31.1 U/L, P < 0.05), and significantly increased mRNA and protein expression of PDGF and Col-III in liver tissue (P < 0.05). Compared with the model group, the mice in 3 mg/kg AM1241 group and 9 mg/kg AM1241 group had less severe liver fibrosis, and significantly reduced serum AST levels (116.6 ± 13.68 U/L vs 742 ± 300.8 U/L, P < 0.05; 113.8 ± 16.01 U/L vs 742 ± 300.8 U/L, P < 0.05) and mRNA and protein expression of PDGF and Col-III in liver tissue (P < 0.05). Conclusion: CB2 receptor agonist AM1241 can inhibit the mRNA and protein expression of PDGF in the liver tissue of mice with hepatic fibrosis, and reduce extracellular matrix synthesis.

[Altered expression and clinical significance of plasma PDGF in patients with myasthnia gravis]

Objective: To evaluate the expression and clinical significance of plasma platelet derived growth factor (PDGF) in the patients with myasthenia gravis (MG). Methods: Plasma samples from 44 MG patients and 34 healthy people were collected from August 2015 to December 2016 from the Second Affiliated Hospital of Harbin Medical University. The expression of PDGF was detected by MILLIPLEX MAP Reagent kit. Furthermore, we analyzed the associations between PDGF expression level and quantitative myasthenia gravis score (QMG). Result: The expression of PDGF in plasma was significant lower in MG patients (5.8±1.3) compared with control group (10.1±2.2), and the difference was statistically significant (t'=-9.767, P<0.001). Meanwhile it was positively related to QMG (r=0.777, P<0.01). However, no significant difference in expression of PDGF in MG subgroups was observed. Conclusion: The expression of PDGF decreases in MG patients, has positive correlation with MG severity, and is not related to age, sex and the pathology of thymus samples.

Recombinant human platelet-derived growth factor-BB versus autologous bone graft in foot and ankle fusion: A systematic review and meta-analysis

Today, autogenous bone graft (ABG) is still considered as the gold standard for joint fusion. Recombinant human platelet-derived growth factor-BB (rhPDGF-BB) which is of chemotactic and mitogenic to mesenchymal stem cells and possesses outstanding osteogenetic potentials has been used for ankle and foot fusion in recent years. The goal of this article is to evaluate the safety and efficacy of rhPDGF-BB versus ABG in foot and ankle fusion. The PubMed MEDLINE, EMBASE, Web of Science, and Cochrane Library were systematic searched. Finally, three randomized controlled trials (RCTs) with 634 patients were enrolled in this study. Results of radiologic effectiveness which included CT and radiographic union rates revealed that there was no significant difference between rhPDGF-BB approach and ABG approach. Analysis of clinical results held the same outcomes expect that ABG group was superior in long-term Short Form-12 physical component scores. The pooled results also demonstrated that rhPDGF-BB was as safe as ABG in foot and ankle surgery. However, autograft harvesting procedure has some drawbacks such as donor-site pain and morbidity, additional operation time, blood loss, and scarring, which can be overcome by rhPDGF-BB. Thus, rhPDGF-BB is a viable alternative to autograft in foot and ankle fusion surgery. Yet, more high-quality RCTs with long-term follow-up are still required to make the final conclusion.

Antileukemic effects of midostaurin in acute myeloid leukemia - the possible importance of multikinase inhibition in leukemic as well as nonleukemic stromal cells

INTRODUCTION

Midostaurin is a multikinase inhibitor that inhibits receptor tyrosine kinases (Flt3, CD117/c-kit, platelet-derived growth factor receptor, vascular endothelial growth factor receptor 2) as well as non-receptor tyrosine kinases (Frg, Src, Syk, Protein kinase C). Combination of midostaurin with conventional intensive chemotherapy followed by one year maintenance monotherapy was recently reported to improve the survival of acute myeloid leukemia (AML) patients with Flt3 mutations. Areas covered: Relevant publications were identified through literature searches in the PubMed database. We searched for (i) original articles describing the results from clinical studies; (ii) published articles describing the importance of midostaurin-inhibited kinases for leukemogenesis and chemosensitivity. Expert opinion: Midostaurin monotherapy is well tolerated, combined with conventional chemotherapy gastrointestinal toxicity increases significantly. Midostaurin alters anthracycline pharmacokinetics. Furthermore, its antileukemic effects may not only be mediated through Flt3 inhibition alone; the inhibition of other kinases may also be important for the overall antileukemic effect. Midostaurin may then have direct effects on the leukemic cells but also indirect antileukemic effects through inhibition of the AML-supporting effects of neighboring stromal cells in the bone marrow microenvironment. Midostaurin may thus be used in combination with intensive chemotherapy, as maintenance treatment or as disease-stabilizing treatment for elderly unfit patients.

Vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) levels in the cerebrospinal fluid of children with influenza-associated encephalopathy

INTRODUCTION

To search for an index of neurologic prognosis of children with influenza-associated encephalopathy (IAE), involvement of angiogenesis-related growth factors in the pathology was investigated.

PATIENTS AND METHODS

The subjects were 11 IAE patients, 6 patients with bacterial meningitis (BM), and 24 patients with non-central nervous system infection as a control group admitted to our hospital. The correlation between the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) levels in cerebrospinal fluid and the relationship with an index of inflammatory marker, interleukin (IL)-6, were investigated. Using the Pediatric Cerebral Performance Categories (PCPC) score as a prognostic indicator, we evaluated the association between the biomarkers and neurologic prognosis.

RESULT

PDGF significantly increased in the IAE group compared with that in the BM group. Cerebrospinal fluid VEGF and PDGF increased in all IAE and BM patients compared with that in the control group, and VEGF and PDGF were positively correlated in the 2 groups. No correlation was found between the cerebrospinal fluid VEGF and PDGF levels and IL-6 level in the IAE group, whereas a correlation was found in the BM group. All these factors increased in patients with poor neurologic prognosis.

DISCUSSION

It is possible that the disease state of IAE can be evaluated based on vascular endothelial disorder-related markers.

Local administration of platelet-derived growth factor B (PDGFB) improves follicular development and ovarian angiogenesis in a rat model of Polycystic Ovary Syndrome

Alterations in ovarian angiogenesis are common features in Polycystic Ovary Syndrome (PCOS) patients; the most studied of these alterations is the increase in vascular endothelial growth factor (VEGF) production by ovarian cells. Platelet-derived growth factor B (PDGFB) and D (PDGFD) are decreased in follicular fluid of PCOS patients and in the ovaries of a rat model of PCOS. In the present study, we aimed to analyze the effects of local administration of PDGFB on ovarian angiogenesis, follicular development and ovulation in a DHEA-induced PCOS rat model. Ovarian PDGFB administration to PCOS rats partially restored follicular development, decreased the percentage of cysts, increased the percentage of corpora lutea, and decreased the production of anti-Müllerian hormone. In addition, PDGFB administration improved ovarian angiogenesis by reversing the increase in periendothelial cell area and restoring VEGF levels. Our results shed light into the mechanisms that lead to altered ovarian function in PCOS and provide new data for potential therapeutic strategies.

Imatinib alters cell viability but not growth factors levels in TM4 Sertoli cells

BACKGROUND

The anticancer agent imatinib (IM) is a small molecular analog of ATP that inhibits tyrosine kinase activity of platelet derived growth factors (PDGFs) and stem cell factor (SCF) receptor in cancer cells. However these factors have a key role in regulating growth and development of normal Sertoli, Leydig and germ cells.

OBJECTIVE

The aim of this study was to determine cell viability, PDGF and SCF levels in mouse normal Sertoli cells exposed to IM.

MATERIALS AND METHODS

In this experimental study, the mouse TM4 Sertoli cells were treated with 0, 2.5, 5, 10 and 20 μM IM for 2, 4 or 6 days. The cell viability and growth factors levels were assessed by MTT and ELISA methods, respectively. For statistical analysis, One-Way ANOVA was performed.

RESULTS

IM showed significant decrease in Sertoli cell viability compared to control group (p=0.001). However, IM increased PDGF and SCF level insignificantly (p>0.05).

CONCLUSION

Results suggested that IM treatment induced a dose dependent reduction of cell viability in Sertoli cells. It seems that treatment with this anticancer drug is involved in the fertility process. Further studies are needed to evaluate the role of PDGF and SCF in this cell.

Functional Interference in the Bone Marrow Microenvironment by Disseminated Breast Cancer Cells

Skeletal metastasis of breast cancer is associated with a poor prognosis and significant morbidity. Investigations in other solid tumors have revealed an impairment in hematopoietic function upon bone marrow invasion. However, the interaction between disseminated breast cancer cells and the bone marrow microenvironment which harbors them has not been addressed comprehensively. Employing advanced co-culture assays, proteomic studies, organotypic models as well as in vivo xenotransplant models, we define the consequences of this interaction on the stromal compartment of bone marrow, affected molecular pathways and subsequent effects on the hematopoietic stem and progenitor cells (HSPCs). The results showed a basic fibroblast growth factor (bFGF)-mediated, synergistic increase in proliferation of breast cancer cells and mesenchymal stromal cells (MSCs) in co-culture. The stromal induction was associated with elevated phosphoinositide-3 kinase (PI3K) signaling in the stroma, which coupled with elevated bFGF levels resulted in increased migration of breast cancer cells towards the MSCs. The perturbed cytokine profile in the stroma led to reduction in the osteogenic differentiation of MSCs via downregulation of platelet-derived growth factor-BB (PDGF-BB). Long term co-cultures of breast cancer cells, HSPCs, MSCs and in vivo studies in NOD.Cg-Prkdc(scid) Il2rg(tm1Wjl) /SzJ (NSG) mice showed a reduced support for HSPCs in the altered niche. The resultant non- conducive phenotype of the niche for HSPC support emphasizes the importance of the affected molecular pathways in the stroma as clinical targets. These findings can be a platform for further development of therapeutic strategies aiming at the blockade of bone marrow support to disseminated breast cancer cells. Stem Cells 2016;34:2224-2235.

The Effects of Imatinib Mesylate on Cellular Viability, Platelet Derived Growth Factor and Stem Cell Factor in Mouse Testicular Normal Leydig Cells

BACKGROUND

Growth factors play an essential role in the development of tumor and normal cells like testicular leydig cells. Treatment of cancer with anti-cancer agents like imatinib mesylate may interfere with normal leydig cell activity, growth and fertility through failure in growth factors' production or their signaling pathways. The purpose of the study was to determine cellular viability and the levels of, platelet derived growth factor (PDGF) and stem cell factor (SCF) in normal mouse leydig cells exposed to imatinib, and addressing the effect of imatinib on fertility potential.

METHODS

The mouse TM3 leydig cells were treated with 0 (control), 2.5, 5, 10 and 20 μM imatinib for 2, 4 and 6 days. Each experiment was repeated three times (15 experiments in each day).The cellular viability and growth factors levels were assessed by MTT and ELISA methods, respectively. For statistical analysis, one-way ANOVA with Tukey's post hoc and Kruskal-Wallis test were performed. A p-value less than 0.05 was considered statistically significant.

RESULTS

With increasing drug concentration, cellular viability decreased significantly (p<0.05) and in contrast, PDGF levels increased (p<0.05). Different imatinib concentrations had no significant effect on SCF level. Increasing the duration of treatment from 2 to 6 days had no obvious effect on cellular viability, PDGF and SCF levels.

CONCLUSION

Imatinib may reduce fertility potential especially at higher concentrations in patients treated with this drug by decreasing cellular viability. The effect of imatinib on leydig cells is associated with PDGF stimulation. Of course future studies can be helpful in exploring the long term effects of this drug.

Controlled release of fibrin matrix-conjugated platelet derived growth factor improves ischemic tissue regeneration by functional angiogenesis

Sustained, local, low dose growth factor stimulus of target tissues/cells is believed to be of imminent importance in tissue regeneration and engineering. Recently, a technology was developed to bind growth factors to a fibrin matrix using the transglutaminase (TG) activity of factor XIIIa, thus allowing prolonged release through enzymatic cleavage. In this study we aimed to determine whether TG-PDGF.AB in fibrin could improve tissue regeneration in a standard ischemic flap model. In vitro determination of binding and release kinetics of TG-PDGF.AB allowed proof of concept of the developed binding technology. A single spray application of TG-PDGF.AB in fibrin matrix at a concentration of 10 and 100ng/ml significantly reduced ischemia-induced flap tissue necrosis in vivo on day 7 after ischemic impact compared to controls. TG-PDGF.AB at a concentration of 100ng/ml fibrin induced distinct angiogenesis as reflected by significantly improved tissue perfusion assessed by laser Doppler imaging as well as enhanced von Willebrand factor (vWF) protein expression determined by immunohistochemical means. In addition, significantly more mature microvessels were observed with 100ng/ml TG-PDGF.AB in fibrin compared to control and vehicle groups as evidenced by an improved smooth muscle actin (sma)/vWF protein ratio. In conclusion, PDGF.AB in a conjugated fibrin matrix effectively reduced ischemia-induced tissue necrosis, increased tissue perfusion and induced the growth of a mature and functional neovasculature. The sealing properties of the fibrin matrix in conjunction with the prolonged growth factor stimulus enabled by the TG-hook binding technology may present an innovative and suitable tool in tissue regeneration.

STATEMENT OF SIGNIFICANCE

In our experimental study we elucidated recombinant platelet derived growth factor (PDGF) as a potential candidate in inducing angiogenesis. To avoid preterm growth factor degradation in vivo PDGF.AB was covalently linked to a fibrin scaffold using a bi-domain functionalized peptide (FXIII substrate site and plasmin cleavage site). This allowed PDGF binding to fibrin during spray application to the donor site and subsequent prolonged release via endogenous plasmin. This resulted in a mature vascular network thus enhancing tissue perfusion and consequently improved clinical outcome. With our present work we could certainly provide researchers and clinicians with an innovative versatile and reproducible technology not only to induce functional vascularity but also to improve attempts in tissue engineering in general by e.g. using different growth factors. Hence, we believe that this approach studied in the present work may provide a valuable input in an effort to drive the aim forward bringing experimental work in tissue engineering to clinic by using a clinically well characterized and used fibrin scaffold in combination with a human recombinant growth factor (fibrin scaffold linked with the specific binding technology).

Safe dose of intravitreal imatinib and its effect on laser-induced choroidal neovascularization: a rat-model experiment

Background

This two-phase experimental study was conducted to determine the maximum safe dose of intravitreal imatinib (IVI) and its inhibitory effect on a rat model of choroidal neovascularization (CNV).

Methods

In phase I, 60 rats were divided into six groups (A to F); five of which received IVI with concentrations of 330 (A), 250 (B), 165 (C), 80 (D), and 40 (E) µg/5 µl, and the control group (F) received balanced salt solution (BSS). In addition to electroretinography (ERG), routine histopathological analysis and immunohistochemistry for glial fibrillary acidic protein were performed. In phase II, CNV was induced by laser photocoagulation in 25 rats and the animals were divided into two groups. One group received the maximum safe dose of IVI, determined in phase I, and the other received intravitreal BSS. After 4 weeks, the groups were compared in terms of mean scores of fluorescein leakage in fluorescein angiography and the mean CNV areas in histopathological sections.

Results

In phase I, ERG and the histopathological findings revealed retinal toxicity in groups A to D and A to C, respectively; therefore, a dose of 40 µg/5 µl imatinib was specified as the maximum safe dose for phase II. In phase II, late phase fluorescein leakage and the CNV areas were not significantly different between the imatinib-treated eyes and the controls (p = 0.62 and p = 0.5, respectively).

Conclusions

Despite the safety of IVI with a dose of 40 µg/5 µl, no inhibitory effect on laser-induced CNV was observed. Further studies are required to investigate the possible synergistic effects of Imatinib with conventional anti-CNV drugs.

Platelet derived growth factor inhibitors: A potential therapeutic approach for ocular neovascularization

Retinochoroidal vascular diseases are the leading causes of blindness in the developed world. They include diabetic retinopathy (DR), retinal vein occlusion, retinopathy of prematurity, age-related macular degeneration (AMD), and pathological myopia, among many others. Several different therapies are currently under consideration for the aforementioned disorders. In the following section, agents targeting platelet-derived growth factor (PDGF) are discussed as a potential therapeutic option for retinochoroidal vascular diseases. PDGF plays an important role in the angiogenesis cascade that is activated in retinochoroidal vascular diseases. The mechanism of action, side effects, efficacy, and the potential synergistic role of these agents in combination with other treatment options is discussed. The future of treatment of retinochoroidal vascular diseases, particularly AMD, has become more exciting due to agents such as PDGF antagonists.

Response to imatinib as a function of target kinase expression in recurrent glioblastoma

BACKGROUND

Despite some progress in the treatment of glioblastoma, most patients experience tumor recurrence. Imatinib mesylate, a tyrosine kinase inhibitor of platelet derived growth factor receptor-alpha and -beta, c-fms, c-kit, abl and arg kinase (imatinib targets), has been shown to prevent tumor progression in early studies of recurrent gliomas, but has shown weak activity in randomized controlled trials. We studied the response to oral imatinib in 24 patients with recurrent glioblastoma who showed immunohistochemical expression of these imatinib targets in the initially resected tumor tissue.

METHODS

We offered oral imatinib, 400 mg once daily treatment to 24 recurrent glioblastoma patients whose initial biopsy showed presence of at least one imatinib inhibitable tyrosine kinase.

RESULTS

Six imatinib treated patients survived over one year. Twelve patients achieved at least tumor stabilisations from 2.6 months to 13.4 months. Median progression free survival was 3 months and median overall survival was 6 months. Imatinib was well tolerated. We found evidence, though not statistically significant, that arg kinase [Abl-2] immunopositivity had shorter survival [5 months] than the arg kinase immunonegative group [9 months].

CONCLUSIONS

Responses to imatinib observed in this patient series where imatinib inhibitable tyrosine kinases were documented on the original biopsy are marginally better than that previously reported in imatinib treatment of unselected recurrent glioblastoma patients. We thus present a suggestion for defining a patient sub-population who might potentially benefit from imatinib.

Crosstalk between tyrosine kinase receptors, GSK3 and BMP2 signaling during osteoblastic differentiation of human mesenchymal stem cells

Bone morphogenic proteins (BMPs) promote mesenchymal stem cell (MSC) osteogenic differentiation, whereas platelet derived growth factor (PDGF) and fibroblast growth factor (FGF) activate their proliferation through receptors tyrosine kinase (RTK). The effects of PDGF or FGF receptor signaling pathway on BMP2-induced osteoblastic differentiation was investigated in human MSC (HMSC). Inhibition of PDGF or/and FGF receptors enhanced BMP2-induced alkaline phosphatase (ALP) activity, expression of Osterix, ALP and Bone sialoprotein, and matrix calcification. These effects were associated with increased Smad-1 activity, indicating that mitogenic factors interfere with Smad signaling in HMSC differentiation. RTK activate MAPK and inhibit GSK3 through the PI3K/Akt pathway. Biochemical analysis indicated that MAPK JNK and GSK3 especially are potential signaling molecules regulating BMP-induced osteoblastic HMSC differentiation. These observations highlight that the osteogenic effects of BMP2 are modulated by mitogenic factors acting through RTK.

Mesenchymal stem cell secreted platelet derived growth factor exerts a pro-migratory effect on resident Cardiac Atrial appendage Stem Cells

Mesenchymal stem cells (MSCs) modulate cardiac healing after myocardial injury through the release of paracrine factors, but the exact mechanisms are still unknown. One possible mechanism is through mobilization of endogenous cardiac stem cells (CSCs). This study aimed to test the pro-migratory effect of MSC conditioned medium (MSC-CM) on endogenous CSCs from human cardiac tissue. By using a three-dimensional collagen assay, we found that MSC-CM improved migration of cells from human cardiac tissue. Cell counts, perimeter and area measurements were utilized to quantify migration effects. To examine whether resident stem cells were among the migrating cells, specific stem cell properties were investigated. The migrating cells displayed strong similarities with resident Cardiac Atrial appendage Stem Cells (CASCs), including a clonogenic potential of ~21.5% and expression of pluripotency associated genes like Oct-4, Nanog, c-Myc and Klf-4. Similar to CASCs, migrating cells demonstrated high aldehyde dehydrogenase activity and were able to differentiate towards cardiomyocytes. Receptor tyrosine kinase analysis and collagen assays performed with recombinant platelet derived growth factor (PDGF)-AA and Imatinib Mesylate, a PDGF receptor inhibitor, suggested a role for the PDGF-AA/PDGF receptor α axis in enhancing the migration process of CASCs. In conclusion, our findings demonstrate that factors present in MSC-CM improve migration of resident stem cells from human cardiac tissue. These data open doors towards future therapies in which MSC secreted factors, like PDGF-AA, can be utilized to enhance the recruitment of CASCs towards the site of myocardial injury.

The enhancement of bone regeneration by gene activated matrix encoding for platelet derived growth factor

Gene therapy using non-viral vectors that are safe and efficient in transfecting target cells is an effective approach to overcome the shortcomings of protein delivery of growth factors. The objective of this study was to develop and test a non-viral gene delivery system for bone regeneration utilizing a collagen scaffold to deliver polyethylenimine (PEI)-plasmid DNA (pDNA) [encoding platelet derived growth factor-B (PDGF-B)] complexes. The PEI-pPDGF-B complexes were fabricated at amine (N) to phosphate (P) ratio of 10 and characterized for size, surface charge, and in vitro cytotoxicity and transfection efficacy in human bone marrow stromal cells (BMSCs). The influence of the complex-loaded collagen scaffold on cellular attachment and recruitment was evaluated in vitro using microscopy techniques. The in vivo regenerative capacity of the gene delivery system was assessed in 5 mm diameter critical-sized calvarial defects in Fisher 344 rats. The complexes were ~100 nm in size with a positive surface charge. Complexes prepared at an N/P ratio of 10 displayed low cytotoxicity as assessed by a cell viability assay. Confocal microscopy revealed significant proliferation of BMSCs on complex-loaded collagen scaffolds compared to empty scaffolds. In vivo studies showed significantly higher new bone volume/total volume (BV/TV) % in calvarial defects treated with the complex-activated scaffolds following 4 weeks of implantation (14- and 44-fold higher) when compared to empty defects or empty scaffolds, respectively. Together, these findings suggest that non-viral PDGF-B gene-activated scaffolds are effective for bone regeneration and are an attractive gene delivery system with significant potential for clinical translation.

Matrix Producing Cells in Chronic Kidney Disease: Origin, Regulation, and Activation

Chronic injury to the kidney causes kidney fibrosis with irreversible loss of functional renal parenchyma and leads to the clinical syndromes of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Regardless of the type of initial injury, kidney disease progression follows the same pathophysiologic processes characterized by interstitial fibrosis, capillary rarefaction and tubular atrophy. Myofibroblasts play a pivotal role in fibrosis by driving excessive extracellular matrix (ECM) deposition. Targeting these cells in order to prevent the progression of CKD is a promising therapeutic strategy, however, the cellular source of these cells is still controversial. In recent years, a growing amount of evidence points to resident mesenchymal cells such as pericytes and perivascular fibroblasts, which form extensive networks around the renal vasculature, as major contributors to the pool of myofibroblasts in renal fibrogenesis. Identifying the cellular origin of myofibroblasts and the key regulatory pathways that drive myofibroblast proliferation and transdifferentiation as well as capillary rarefaction is the first step to developing novel anti-fibrotic therapeutics to slow or even reverse CKD progression and ultimately reduce the prevalence of ESRD. This review will summarize recent findings concerning the cellular source of myofibroblasts and highlight recent discoveries concerning the key regulatory signaling pathways that drive their expansion and progression in CKD.

Micromechanical PDGF recognition via lab-on-a-disc aptasensor arrays

A plug-and-play CD-like platform is used to perform a statistical detection of platelet derived growth factor (PDGF) proteins through aptamer-based surface functionalization of multiple microcantilever arrays. When PDGF proteins bind to aptamer coatings, the cantilevers deflect. The deflection response is monitored by optical read-out units from a commercial DVD-ROM device. We report on the use of an improved sensing platform which facilitates measurements under continuous liquid flow and with temperature control. Also, the mechanical wobbling of the DVD-ROM platform has been minimized and the scanning system has been optimized in order to detect cantilever deflections in liquid with nanometer scale resolution. The capability of the sensing platform is demonstrated by detection of clinically relevant concentrations of PDGF proteins. We present statistical measurements on 100 microcantilevers at different concentrations of PDGF, ranging from 10 nM to 400 nM. Hereby it is possible to reliably characterize the averaged mechanical response of cantilevers as a function of protein concentration.

Tyrosine kinase inhibitors: Multi-targeted or single-targeted?

Since in most tumors multiple signaling pathways are involved, many of the inhibitors in clinical development are designed to affect a wide range of targeted kinases. The most important tyrosine kinase families in the development of tyrosine kinase inhibitors are the ABL, SCR, platelet derived growth factor, vascular endothelial growth factor receptor and epidermal growth factor receptor families. Both multi-kinase inhibitors and single-kinase inhibitors have advantages and disadvantages, which are related to potential resistance mechanisms, pharmacokinetics, selectivity and tumor environment. In different malignancies various tyrosine kinases are mutated or overexpressed and several resistance mechanisms exist. Pharmacokinetics is influenced by interindividual differences and differs for two single targeted inhibitors or between patients treated by the same tyrosine kinase inhibitor. Different tyrosine kinase inhibitors have various mechanisms to achieve selectivity, while differences in gene expression exist between tumor and stromal cells. Considering these aspects, one type of inhibitor can generally not be preferred above the other, but will depend on the specific genetic constitution of the patient and the tumor, allowing personalized therapy. The most effective way of cancer treatment by using tyrosine kinase inhibitors is to consider each patient/tumor individually and to determine the strategy that specifically targets the consequences of altered (epi)genetics of the tumor. This strategy might result in treatment by a single multi kinase inhibitor for one patient, but in treatment by a couple of single kinase inhibitors for other patients.

New perspectives on diabetic vascular complications: the loss of endogenous protective factors induced by hyperglycemia

Diabetic vascular complications are among the leading causes of morbidity and mortality in diabetic patients. In the past, many studies have focused on the mechanisms of hyperglycemia-induced chronic vascular complications via the formation of toxic metabolites such as oxidative stress, advanced glycosylated end products, persistent activation of protein kinase C, and increased sorbitol concentrations. However, vascular complications result from imbalances caused by increases in systemic toxic metabolites, such as those that occur under conditions of hyperglycemia and dyslipidemia, and by reductions in endogenous protective factors such as insulin, vascular endothelial growth factor, and platelet derived growth factor. This review outlines some of the evidence supporting the importance of enhancing endogenous regenerative factors.