Platelet factors attenuate inflammation and rescue cognition in ageing.

Identifying therapeutics to delay, and potentially reverse, age-related cognitive decline is critical in light of the increased incidence of dementia-related disorders forecasted in the growing older population1. Here we show that platelet factors transfer the benefits of young blood to the ageing brain. Systemic exposure of aged male mice to a fraction of blood plasma from young mice containing platelets decreased neuroinflammation in the hippocampus at the transcriptional and cellular level and ameliorated hippocampal-dependent cognitive impairments. Circulating levels of the platelet-derived chemokine platelet factor 4 (PF4) (also known as CXCL4) were elevated in blood plasma preparations of young mice and humans relative to older individuals. Systemic administration of exogenous PF4 attenuated age-related hippocampal neuroinflammation, elicited synaptic-plasticity-related molecular changes and improved cognition in aged mice. We implicate decreased levels of circulating pro-ageing immune factors and restoration of the ageing peripheral immune system in the beneficial effects of systemic PF4 on the aged brain. Mechanistically, we identified CXCR3 as a chemokine receptor that, in part, mediates the cellular, molecular and cognitive benefits of systemic PF4 on the aged brain. Together, our data identify platelet-derived factors as potential therapeutic targets to abate inflammation and rescue cognition in old age.

When Will Fondaparinux Induce Thrombocytopenia?

The pentasaccharide Fondaparinux, a synthetic selective factor Xa inhibitor, is one of the safest anticoagulants in the heparin family that is recommended as an alternative drug for patients with hypersensitivity to other drugs such as heparin-induced thrombocytopenia (HIT). However, some observations of Fondaparinux-induced thrombocytopenia (FIT) have been reported while others claimed that FIT does not occur in patients with fondaparinux therapy, indicating that the mechanism of FIT remains controversial. Here, we utilized different methodologies including dynamic light scattering, immunosorbent and platelet aggregation assays, confocal laser scanning microscopy, and flow cytometry to gain insights into FIT. We found that at a certain concentration, Fondaparinux formed sufficient large and stable complexes with PF4 that facilitated binding of the HIT-like monoclonal KKO antibody and enhanced platelet aggregation and activation. We proposed a model to describe the role of Fondaparinux concentration in the formation of complexes with platelet factor 4 and how it promotes the binding of KKO. Our results clarify controversial observations of FIT in patients as each contains a dissimilar PF4:Fondaparinux concentration ratio.

Microvessel density and vascular endothelial growth factor receptors in breast carcinoma under the influence of rapamycin and platelet factor 4.

BACKGROUND: Vascular endothelial growth factor receptors (VEGFRs) are major endothelial growth factor receptors that influence the growth of a tumor. Microvessel density. (: MVD) is the quantification method of various aspects of tumor vasculature that indicates angiogenic activity. This study aims to analyze the correlation between MVD to the expression of VEGFRs on breast cancer tissue. MATERIALS AND METHOD: A total of 60 N-methyl-N-nitrosourea (MNU)-induced breast carcinomas in rats were suppressed by using antiangiogenic drugs. The rats were then sacrificed, and the tumor was fixed in 10% formalin, paraffin embedded, and immunohistochemistry stained using VEGFRs and CD34. RESULT: One-way ANOVA test showed a significant difference in all markers that have been used (P < 0.05) on MNU-breast tumor treated with rapamycin (M= 90.1664, SD= 7.4487), PF4 (M= 93.7946, SD= 7.1303) and rapamycin + PF4 (M= 93.6990, SD= 1.8432). We obtained a significant reduction of MVD count on breast carcinoma for rapamycin group (M= 25.6786, SD= 9.7075) and rapamycin + PF4 group (M= 30.5250, SD= 13.6928) while PF4 group (M=47.7985, SD=4.8892) showed slightly increase compared to control (M= 45.1875, SD= 4.4786). There was a moderately strong, positive correlation between angiogenic markers; Flt-1 (r= 0.544, n=60, P < 0.005) and Flt-4 (r= 0.555, n= 60, P < 0.005) while Flk-1 (r= 0.797, n= 60, P < 0.005) showed a strong, positive correlation with MVD. CONCLUSION: MVD was strongly correlated to the VEGFRs expression on breast carcinoma.

Comparison of blood product use and costs with use of 3-factor versus 4-factor prothrombin complex concentrate for off-label indications.

PURPOSE: Results of a comparison of blood product use and cost outcomes with use of 3-factor versus 4-factor prothrombin complex concentrate (PCC) for indications other than warfarin reversal are presented. METHODS: Consecutive patients who received 3-factor PPC (PCC3) or 4-factor PCC (PCC4) for non-warfarin-related indications at 2 U.S. hospitals during a 19-month period were identified. The primary outcome was in-hospital blood product use, with a focus on plasma use. Total hemostasis costs, intensive care unit (ICU) and hospital lengths of stay, and other outcomes were evaluated. RESULTS: Indications for PCC3 use (n = 118) or PCC4 use (n = 64) included intraoperative bleeding, nonintraoperative bleeding, coagulopathy of liver disease, and reversal of direct-acting oral anticoagulant effects. The proportion of patients who received plasma was 56.8% with PCC3 use versus 53.1% with PCC4 use (p = 0.643); the corresponding median volumes of plasma received were 638 mL (interquartile range [IQR], 550-1,355 mL) and 656 mL (IQR, 532-1,136 mL), respectively. The median total hemostasis costs were $5,559 (IQR, $3,922-$8,159) with PCC3 use and $7,771 (IQR, $6,366-$9,205) with PCC4 use (p < 0.001). CONCLUSION: PCC3 use and PCC4 use were associated with similar blood product use, ICU length of stay, hospital length of stay, and in-hospital mortality when given for non-warfarin-related indications. However, relative to PCC3 use, PCC4 use was associated with an increase in costs that was primarily due to drug costs.

Movilización de progenitores hematopoyéticos a sangre periférica con plerixafor en pacientes malos movilizadores / Mobilization of peripheral blood stem cells with plerixafor in poor mobilizer patients

Fundamento y objetivo: El fracaso de movilización de progenitores hematopoyéticos a sangre periférica (células CD34+) desde el compartimento medular es una causa frecuente de no realización de trasplante autogénico de progenitores hematopoyéticos (TAPH) en pacientes con linfoma o mieloma. Plerixafor, un inhibidor reversible de la unión del factor derivado del estroma 1 con su receptor CXCR4, ha demostrado mayor movilización de progenitores hematopoyéticos cuando se administra junto con granulocyte colony stimulating factor (G-CSF, «factor estimulante de colonias granulocíticas»), respecto a la movilización con G-CSF solo, por lo que en la actualidad está indicado en pacientes con mieloma o linfoma y escasa capacidad de movilización. En los últimos años algunos estudios han señalado que una estrategia de administración anticipada de plerixafor durante la primera movilización, basada en el número de células CD34+ movilizadas a sangre periférica o en la celularidad obtenida en la primera aféresis, podría evitar fracasos de movilización y nuevas movilizaciones, así como el retraso del ulterior trasplante. El objetivo del presente consenso fue realizar una revisión de la bibliografía y establecer unas recomendaciones comunes para hospitales de Cataluña y Baleares para la utilización de una estrategia de administración anticipada de plerixafor. Métodos: Para la elaboración del documento de consenso se realizaron reuniones presenciales en las que se realizó una revisión de la bibliografía y de datos propios procedentes de los hospitales participantes. Para calificar el grado de la evidencia disponible y establecer las recomendaciones de uso anticipado de plerixafor se ha utilizado el sistema GRADE. Resultados y conclusiones: Tras la revisión de la bibliografía, el consenso de expertos definió que con un recuento inferior a 10 células CD34+/μl en sangre periférica (determinado en la mañana del día cuarto de la movilización con G-CSF solo o en el día de la recuperación hemoperiférica tras la movilización con quimioterapia seguida de G-CSF) se recomienda la administración anticipada de plerixafor (AU)

Background and objective: Poor mobilization of peripheral blood stem cells (CD34+ cells) from bone marrow is a frequent reason for not reaching the autologous stem cell trasplantation (SCT) procedure in patients diagnosed with lymphoma or myeloma. Plerixafor, a reversible inhibitor of the binding of stromal cell-derived factor 1 to its cognate receptor CXCR4, has demonstrated a higher capacity for the mobilization of peripheral blood stem cells in combination with granulocyte colony stimulating factor (G-CSF) compared with G-CSF alone. For this reason, plerixafor is now indicated for poor mobilizer myeloma or lymphoma patients. Some studies have recently indicated that a pre-emptive strategy of plerixafor use during first mobilization, according to the number of CD34+ mobilized cells in peripheral blood or to the harvested CD34+ cells after first apheresis, could avoid mobilization failures and re-mobilizations, as well as the delay of autologous SCT. The aim of this consensus was to perform a review of published studies on pre-emptive strategy and to establish common recommendations for hospitals in Catalonia and Balearics on the use of pre-emptive plerixafor. Methods: For the Consensus, physicians from participant hospitals met to review previous studies as well as previous own data about plerixafor use. The GRADE system was used to qualify the available evidence and to establish recommendations on the use of pre-emptive plerixafor. Results and conclusions: After a review of the literature, the expert consensus recommended the administration of pre-emptive plerixafor for multiple myeloma or lymphoma patients with a CD34+ cell count lower than 10 cells/μL in peripheral blood (measured in the morning of day 4 of mobilization with G-CSF or after haematopietic recovery in the case of mobilization with chemotherapy plus G-CSF) (AU)

The Chemokine Platelet Factor-4 Variant (PF-4var)/CXCL4L1 Inhibits Diabetes-Induced Blood-Retinal Barrier Breakdown.

PURPOSE: To investigate the expression of platelet factor-4 variant (PF-4var/CXCL4L1) in epiretinal membranes from patients with proliferative diabetic retinopathy (PDR) and the role of PF-4var/CXCL4L1 in the regulation of blood-retinal barrier (BRB) breakdown in diabetic rat retinas and human retinal microvascular endothelial cells (HRMEC). METHODS: Rats were treated intravitreally with PF-4var/CXCL4L1 or the anti-vascular endothelial growth factor (VEGF) agent bevacizumab on the first day after diabetes induction. Blood-retinal barrier breakdown was assessed in vivo with fluorescein isothiocyanate (FITC)-conjugated dextran and in vitro in HRMEC by transendothelial electrical resistance and FITC-conjugated dextran cell permeability assay. Occludin, vascular endothelial (VE)-cadherin, hypoxia-inducible factor (HIF)-1α, VEGF, tumor necrosis factor (TNF)-α, receptor for advanced glycation end products (RAGE), caspase-3 levels, and generation of reactive oxygen species (ROS) were assessed by Western blot, enzyme-linked immunosorbent assays, or spectrophotometry. RESULTS: In epiretinal membranes, vascular endothelial cells and stromal cells expressed PF-4var/CXCL4L1. In vitro, HRMEC produced PF-4var/CXCL4L1 after stimulation with a combination of interleukin (IL)-1ß and TNF-α, and PF-4var/CXCL4L1 inhibited VEGF-mediated hyperpermeability in HRMEC. In rats, PF-4var/CXCL4L1 was as potent as bevacizumab in attenuating diabetes-induced BRB breakdown. This effect was associated with upregulation of occludin and VE-cadherin and downregulation of HIF-1α, VEGF, TNF-α, RAGE, and caspase-3, whereas ROS generation was not altered. CONCLUSIONS: Our findings suggest that increasing the intraocular PF-4var/CXCL4L1 levels early after the onset of diabetes protects against diabetes-induced BRB breakdown.

Platelet factor 4 protects kidney allograft in a rat kidney transplantation model.

Platelets are the cellular mediator of thrombosis, but it is becoming increasingly evident that platelets actively participate in inflammation and immune responses. A recent paper indicated that platelet factor 4 (PF4) alleviated cardiac allograft rejection in mice. But the role of PF4 on kidney transplantation has never been investigated. In our current experiment, PF4 administration alleviates immune responses to kidney transplantation. PF4 significantly alleviates vascular and glomerular changes, as well as interstitial inflammation, fibrosis, and tubular atrophy at day 56 after transplantation. PF4 decreases interleukin (IL)-17 production in vivo and also limits Th17 differentiation in vitro. Furthermore, the alleviated chronic vasculopathy and tubulointerstitial inflammation induced by PF4 were abolished with additional IL-17 administration. Meanwhile, decreased serum creatinine and urea induced by PF4 were also reversed by recombinant mouse IL-17 (rmIL-17). In conclusion, PF4 plays a protective role in chronic kidney allograft and this was associated with inhibition of IL-17 production.

Platelet factor 4 inhibits IL-17/Stat3 pathway via upregulation of SOCS3 expression in melanoma.

Platelet factor 4 (PF4) was the first discovered CXC chemokine and is found in platelet granules at very high concentration. Now, it is becoming increasingly evident that PF4 actively participates in inflammation and immune response. Recent paper demonstrated that PF4 limits the development and response of the Th17 cells and assisted in regulatory T cell development in transplantation. But, the immunoregulatory role of PF4 in tumor has little known and needs to be further investigated. In our current study, wild-type mice are inoculated with melanoma cell line B16-F10 (1 × 10(6)/mouse) and treated with PF4. PF4 inhibits B16 tumor growth and decreases γδ cell infiltration. The expression of interleukin (IL)-17, IL-6, and p-signal transducer and activator of transcription-3 (Stat3) was markedly decreased with treatment of PF4 compared with control in vivo and in vitro. And, the suppressed tumor growth induced by PF4 is abolished by additional treatment of recombinant mouse IL (rmIL)-17. PF4 also induces suppressor of cytokine signaling 3 (SOCS3) upregulations, and PF4 fails to suppress expression of p-Stat3, IL-17, and IL-6 in cells transfected with SOCS3 short interfering RNA (siRNA). In conclusion, PF4 inhibits IL-17/Stat3 pathway via upregulation of SOCS3 expression and may contribute to suppressing tumor growth in murine models of melanoma.

Platelet factor-4 (CXCL4/PF-4): an angiostatic chemokine for cancer therapy.

Platelet factor-4 (CXCL4/PF-4) is the first chemokine identified to have several biological functions. Notably, CXCL4/PF-4 inhibits endothelial cell proliferation and migration, leading to suppression of angiogenesis. Since angiogenesis is essential for the growth of most primary tumors and their subsequent metastases, it is a target for cancer therapy; due to its multiple functions, CXCL4/PF-4 is a potential clinical anti-tumor agent. This report reviews the mechanisms of CXCL4/PF-4 angiostatic activity, including interference with angiogenic growth factors bFGF-2 and VEGF165, activation of CXCR3B, interactions with integrins, interference with cell cycle, interactions with factors such as VEGF121 and CXCL8/IL-8, and derived molecules of CXCL4/PF-4 with angiostatic and anti-tumoral activities in different models in vivo or in vitro.

A case series of recombinant platelet factor 4 for heparin reversal after cardiopulmonary bypass.

BACKGROUND: Platelet factor 4 (PF4) is released by activated platelets and has a strong affinity for heparin. Recombinant PF4 (rPF4) has been previously considered as an alternative to protamine for heparin reversal. However, it has been demonstrated that antibodies directed against the PF4/heparin moiety are important in the pathophysiologic development of heparin-induced thrombocytopenia, a prothrombotic complication for which cardiac bypass patients are at increased risk. METHODS: We retrospectively analyzed a case series from an open-label, comparative phase I-II study of rPF4 and protamine after cardiac surgery to determine the heparin-reversal activity of different doses of IV rPF4. Sixteen patients received rPF4, and 5 received protamine. Activated clotting time (ACT) was used to monitor heparin reversal, with reversal defined as ACT <150 seconds. Platelets, white blood cells, C3a, C5a, fibrinopeptide A, von Willebrand factor antigen, and prothrombin fragment 1.2 were monitored postoperatively as indicators of coagulation and inflammation. RESULTS: Heparin reversal was successful by 10 minutes after administration of rPF4 as measured by ACT in all 16 patients. Specifically, a dose of 5 mg/kg rPF4 resulted in ACT <150 seconds after 5 minutes in 10 of 10 patients. For both treatment groups, there were no bleeding or thrombotic complications, no clinical thrombocytopenia after day 5, and no deaths within the 30-day study period. CONCLUSIONS: Our case series demonstrates that heparin anticoagulation was effectively reversed by the administration of rPF4 without serious complications. Additional studies are needed to further validate the safety and efficacy of exogenous rPF4 administration.

The role of the CXC chemokines platelet factor-4 (CXCL4/PF-4) and its variant (CXCL4L1/PF-4var) in inflammation, angiogenesis and cancer.

Chemokines are chemotactic cytokines which recruit leukocytes to inflammatory sites. They also affect tumor development and metastasis by acting as growth factor, by attracting pro- or anti-tumoral leukocytes or by influencing angiogenesis. Platelet factor-4 (CXCL4/PF-4) was the first chemokine shown to inhibit angiogenesis. CXCL4L1/PF-4var, recently isolated from thrombin-stimulated platelets, differing from authentic CXCL4/PF-4 in three carboxy-terminally located amino acids, was found to be more potent than CXCL4/PF-4 in inhibiting angiogenesis and tumor growth. Both glycosaminoglycans (GAG) and CXCR3 are implicated in the activities of the PF-4 variants. This report reviews the current knowledge on the role of CXCL4/PF-4 and CXCL4L1/PF-4var in physiological and pathological processes. In particular, the role of CXCL4/PF-4 in cancer, heparin-induced thrombocytopenia and atherosclerosis is described.

Recombinant platelet factor 4: a therapeutic, anti-neoplastic chimera?

Angiogenesis plays a pivotal role in many serious and life-threatening disorders (e.g., cancer, atherosclerosis, diabetes, arthritis, psoriasis, nephropathy, and retinopathy) and is regulated by a delicate equilibrium between a variety of pro- and anti-angiogenic factors. Although recombinant platelet factor 4 (PF4) was originally developed and evaluated as a clinical alternative to protamine for heparin neutralization, the current scientific evidence supports a role for this protein and derivative peptides in inhibiting tumor growth and spread, by suppression of tumor-induced neovascularization in many different types of solid tumors. As a heparin-binding tetramer, recombinant PF4 interferes with several steps of endothelial cell proliferation, migration, and angiogenesis, regulates apoptotic death through activation of distinct signal transduction pathways, inhibits growth factor receptor binding, amplifies the inflammatory response of natural killer cells through regulation of cytokines production, and induces and maintains a nonspecific immune response to cancer cells. These biological evidences paved the way for the development and marketing of novel PF4-based angiostatic agents characterized by reduced toxicity and improved bioavailability, thus raising the possibility of an alternative approach for preventing and treating growth and metastasis of tumors. Some PF4-derived molecules such as carboxyl-terminal fragments of recombinant human PF4 and modified and chimeric peptides have already been developed that exhibit stronger anti-angiogenic properties than the parent molecule and may serve as leads for further therapeutic developments. Newer means of delivering of this anti-angiogenic agent are also being attempted, including PF4-bearing polymeric microspheres, vector-mediated PF4 transduction, transgene transfection into oncolytic viruses, and molecular targeting therapy against PF4 and rHuPF4 conjugates. These delivery systems aim to produce high concentrations of the therapeutic agent in a local area for a sustained period, thereby avoiding the typical problems encountered with long-term administration of recombinant proteins.

In vivo fate and therapeutic efficacy of PF-4/CTF microspheres in an orthotopic human glioblastoma model.

The correlation between glioma grade and angiogenesis suggests that antiangiogenic therapies are potentially therapeutically effective for these tumors. However, to achieve tumor suppression, antiangiogenic therapies need to be administered daily using high systemic quantities. We designed a biodegradable polymeric device that overcomes those barriers by providing sustained local delivery of a C-terminal fragment of platelet factor 4 (PF-4/CTF), an antiangiogenic agent. Fluorescent-labeled microspheres composed of poly lactic-coglycolic acid (PLGA) were loaded with rhodamine-labeled PF-4/CTF and formulated to release their contents over time. Fluorescent labeling enabled the correlation between the in vitro to the in vivo kinetic and release studies. PF-4/CTF microspheres were injected into established intracranial human glioma tumors in nude mice. Noninvasive magnetic resonance imaging (MRI) was used to assess the therapeutic response. Tumor size, microvessel density, proliferation, and apoptosis rate were measured by histological analysis. Intracranially, the microspheres were located throughout the tumor bed and continuously released PF-4/CTF during the entire experimental period. MRI and histological studies showed that a single injection of microspheres containing PF-4/CTF caused a 65.2% and 72% reduction in tumor volume, respectively, with a significant decrease in angiogenesis and an increase in apoptosis. Our data demonstrate that polymeric microspheres are an effective therapeutic approach for delivering antiangiogenic agents that result in the inhibition of glioma tumor growth.

Molecular pathways of angiogenesis inhibition.

A large body of evidence now demonstrates that angiostatic therapy represents a promising way to fight cancer. This research recently resulted in the approval of the first angiostatic agent for clinical treatment of cancer. Progress has been achieved in decrypting the cellular signaling in endothelial cells induced by angiostatic agents. These agents predominantly interfere with the molecular pathways involved in migration, proliferation and endothelial cell survival. In the current review, these pathways are discussed. A thorough understanding of the mechanism of action of angiostatic agents is required to develop efficient anti-tumor therapies.

Continuous delivery of endogenous inhibitors from poly(lactic-co-glycolic acid) polymeric microspheres inhibits glioma tumor growth.

PURPOSE: There is an urgent need for modalities that can localize and prolong the administration of the antitumor agents, particularly antiangiogenic, to achieve long-term tumor inhibition. However, one of the major obstacles is designing a device in which the biological activity of sensitive endogenous inhibitors is retained. We have designed a biodegradable polymeric device, which provides a unique and practical means of localizing and continuously delivering hemopexin (PEX) or platelet factor 4 fragment (PF-4/CTF) at the tumor site while maintaining their biological activity. The potential and efficacy of this system is shown in vitro and in vivo in a human glioma mouse model. EXPERIMENTAL DESIGN: Polymeric microspheres made of poly(lactic-co-glycolic acid) (PLGA) were loaded with very low amounts of PEX and PF-4/CTF. The release profiles of these factors from PLGA and their biological activity were confirmed in vitro using proliferation assays done on endothelial and tumor cells. Tumor inhibition using this system was studied in nude mice bearing a human s.c. glioma. RESULTS: PEX and PF-4/CTF released in vitro from PLGA microspheres were biologically active and significantly inhibited the proliferation of human umbilical vein endothelial cells, bovine capillary endothelial cells, and U87-MG cells. A single local s.c. injection of PLGA microspheres loaded with low amounts of PEX or PF-4/CTF resulted in an 88% and 95% reduction in glioma tumor volume 30 days post-treatment. Immunohistochemical analysis of the treated tumors showed a marked decrease in tumor vessel density compared with untreated tumors. CONCLUSION: Our findings show that polymeric microspheres are a very promising approach to locally and efficiently deliver endogenous inhibitors to the tumor site leading to a significant inhibition of the tumor.

Recombinant platelet factor 4 for heparin neutralization.

Protamine sulfate has been used for many years to reverse the effects of unfractionated heparin, but it can cause hemodynamic changes and other serious side effects. Platelet factor 4 (PF4) is a naturally occurring protein synthesized in megakaryocytes and eventually stored in the alpha granules of platelets for later release. Although the complete physiologic role of PF4 is unknown, it is highly effective for the neutralization of heparin anticoagulation. Several preliminary animal studies and trials using blood obtained from cardiopulmonary bypass circuits suggested recombinant PF4 (rPF4) would be an effective alternative to protamine. In the first open-label, phase 1 human study, patients received rPF4 in doses of 0.5, 1.0, 2.5, or 5.0 mg/kg over 3 minutes to reverse heparin anticoagulation after diagnostic cardiac catheterization. There were no important hemodynamic changes and the rPF4 was highly effective in neutralizing heparin. Serial measurements of rPF4 levels showed a monophasic elimination pattern with a serum half-life of 25.5 +/- 13.5 minutes that was independent of dose administered. A randomized and blinded trial comparing rPF4 to protamine confirmed the safety and effectiveness of rPF4. Although rPF4 was initially being evaluated as a clinical alternative to protamine, it is not currently being developed for general clinical use.

Suppression of tumor growth by viral vector-mediated gene transfer of N-terminal truncated platelet factor 4.

Platelet factor four (PF4), an inhibitor of endothelial cell proliferation in vitro, inhibits angiogenesis and tumor growth in vivo in experimental animals. The present study was designed to determine whether gene therapy-mediated expression of a form of PF4 lacking 16 amino acids of N-terminus from tumor cells could inhibit angiogenesis and tumor growth in vivo. Two replication-defective recombinant retroviral vectors were constructed. One encodes human PF4 (rRV-PF4) and the other encodes the N-truncated peptide (rRVp17-70). These vectors were then used to transduce KB cells, a human head and neck squamous carcinoma cell line. Expression of PF4 and p17-70 transgenes was confirmed by Western blot analysis. In vitro, both rRV-PF4 and rRVp17-70 were able to inhibit selectively the proliferation of human umbilical vascular endothelial cells (HUVEC) but not KB cells. In vivo activity was assessed by injecting 10(7) KB cells subcutaneously into nude mice and by monitoring subsequent tumor growth, xenograft vascular histochemistry, and animal survival. Viral vector-mediated cDNA transfer of PF4 and p17-70 resulted in inhibiting solid tumors through an anti-angiogenic action in vivo. Our data indicate that targeting tumor angiogenesis using viral-mediated gene transfer of full-length and N-terminal truncated PF4 represents a promising strategy for cancer gene therapy.

Is platelet-rich plasma the perfect enhancement factor? A current review.

Guided bone regeneration is an accepted surgical method employed in implant dentistry to increase the quantity and quality of the host bone in areas of localized alveolar defects. The lack of predictability in osseous regenerative procedures with various grafting materials suggests that improvement in the osteoinductive properties of these materials is highly desirable. Platelet-rich plasma (PRP), a modification of fibrin glue made from autologous blood, is being used to deliver growth factors in high concentration to sites requiring osseous grafting. Growth factors released from the platelets include platelet-derived growth factor, transforming growth factor beta, platelet-derived epidermal growth factor, platelet-derived angiogenesis factor, insulin-like growth factor 1, and platelet factor 4. These factors signal the local mesenchymal and epithelial cells to migrate, divide, and increase collagen and matrix synthesis. PRP has been suggested for use to increase the rate of bone deposition and quality of bone regeneration when augmenting sites prior to or in conjunction with dental implant placement Only 6 human studies using PRP have been found in the dental implant literature and 5 were case series or reports. Thus, there is clearly a lack of scientific evidence to support the use of PRP in combination with bone grafts during augmentation procedures. This novel and potentially promising technique requires well-designed, controlled studies to provide evidence of efficacy.

[Transfer of cDNAs of platelet factor 4 and N-truncated peptide inhibits solid tumor growth in vivo].

OBJECTIVE: Determine the anti-tumor angiogenic effect of PF4 and p17 - 70 using virally mediated gene transfer. METHODS: Full-length PF4 cDNA and p17 - 70 cDNA were cloned into retroviral vector (pLXSN). KB was incubated with the supernatant of transfected PA317. PCR, RT-PCR and Western blotting analysis was used to determine the integration and expression of foreign gene. By MTT method the effects of the supernatants of PA317-PF4s and KB-PF4s on the proliferation of human umbilical vein endothelial cells (HUVEC) were studied. Tumorigenecity of KB-PF4 and KBp17 - 70 cells was assayed with xenograft tumor growth in isogenous nude mice by examining the growth rate of xenograft, survival, and histochemistry of xenograft tumor. RESULTS: Recombinant PF4 and p17 - 70 were able to inhibit selectively HUVEC proliferation. Animal survival was significantly prolonged. Furthermore, p17 - 70 significantly prolonged animal survival compared with PF4 group (P < 0.05). CONCLUSION: Transduction of p17 - 70 inhibits solid tumor growth through an anti-angiogensis mechanism. Targeted anti-angiogenesis, using retroviral-mediated PF4 gene transfer, especially p17 - 70 represents a promising strategy for cancer gene therapy.