Ela Shai

Involvement of platelet derived microparticles in tumor metastasis and tissue regeneration

Platelets play a major role in hemostasis, but are also involved in vascular biology processes such as angiogenesis and tumor metastasis. Activated platelets release many proteins favoring wound healing and promoting angiogenesis. Microparticles (MP) are small plasma membrane vesicles shed from cells upon their activation or apoptosis. Platelet-derived microparticles (PMP) constitute the majority of the pool of MP circulating in the blood. PMP express and may transfer functional receptors, stimulate the release of cytokines, activate intracellular signaling pathways, promote angiogenesis, and are involved in tissue regeneration and cancer metastasis. We investigated the effect of PMP on cancer cells metastasis and their potential beneficial effect in an ischemic stroke model.

Platelet Microparticles Induce Angiogenesis and Neurogenesis after Cerebral Ischemia

Activated platelets shed microparticles, which contain a variety of growth factors central to angiogenesis and neurogenesis. The aim of this study was to explore whether platelet derived microparticles (PMP) can boost endogenous neural stem cells dependent repair mechanisms following stroke in a rat model. To examine the effects of PMP therapy in-vivo, we delivered PMP or vehicle via a biodegradable polymer to the brain surface after permanent middle cerebral artery occlusion (PMCAO) in rats. Rats were tested with the neurological severity score and infarct volumes were measured at 90 days post-ischemia. Immunohistochemistry was used to determine the fate of newborn cells and to count blood vessels in the ischemic brain. The results show that PMP led to a dose dependent increase in cell proliferation, neurogenesis and angiogenesis at the infarct boundary zone and significantly improved behavioral deficits.

Platelet Microparticles Promote Neural Stem Cell Proliferation, Survival and Differentiation

Platelet microparticles (PMP) are small subcellular fragments, shed upon platelet activation. PMP host a variety of cytokines and growth factor that were previously shown to affect angiogenesis and postischemic tissue regeneration. This study attempted to explore the effect of PMP on neural stem cell (NSC) proliferation, survival and differentiation. Cells were grown as neurospheres and treated with PMP, or relevant growth factors, sphere size and cell fates were evaluated. PMP treatment led to larger neurospheres with increased cell survival. PMP treatment was comparable with the effect of acceptable single growth factors such as fibroblastic growth factor (FGF), vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF). PMP treatment also increased the differentiation potential of NSC to glia and neurons. Specific growth factor inhibitors only partly blocked these effects, which were associated with increments in ERK and Akt phosphorylation. In this study, we show that various growth factors contained within the PMP promote neuronal cell proliferation, survival and differentiation. The results suggest a role for platelet microparticles in augmenting endogenous neural progenitor and stem cells angiogenesis and neurogenesis that might be utilized for treatment following brain injury.

Development, Cell Differentiation, Angiogenesis—Microparticles and Their Roles in Angiogenesis

Cells of various types release small membrane vesicles called microparticles (MP) on their activation, as well as during the process of apoptosis. The properties and roles of MP generated in different contexts are diverse and are determined by their parent cell and the pathway of their generation, which affects their content. MP are involved in multiple cellular functions, including immunomodulation, inflammation, coagulation, and intercellular communication. MP are able to deliver molecular signals in the form of lipids, proteins, nucleic acids, or functional transmembrane proteins from the parent cell to distantly located targets. In this review, we summarize some of the current knowledge regarding MP and their functional roles in transfer of proteins, nucleic acids, and signal transduction stimulators between cells of different origins in different settings. We will focus on the ability of MP to mediate angiogenesis-related signals and their effect on cell development. The investigation of MP could elucidate new cellular communication pathways and may lead to better understanding of pathophysiological processes. From a clinical point of view, MP may serve as biomarkers for disease status and may be found useful for developing novel therapeutic strategies targeting angiogenesis-related conditions.

Characterization of Murine Autologous Salivary Gland Graft Cells: A Model for Use with an Artificial Salivary Gland

The purpose of this study was to examine the growth and key functional abilities of primary cultures of salivary epithelial cells toward developing an artificial salivary gland. Cultures of epithelial cells originating from submandibular glands of BALB/c mice were established. Parenchymal cells were isolated by a Percoll gradient technique and thereafter seeded on irradiated NIH 3T3 fibroblasts serving as a feeder layer. The isolated cells were termed autologous salivary gland epithelial (ASGE) cells and could be cultivated for at least five passages (time limit of experiments). ASGE cells presented the typical organizational behavior of epithelial cells and electron microscopy, as well as immunostaining for cytokeratins, confirmed their epithelial origin. Furthermore, measurements of transepithelial resistance and water permeability indicated the ability of the ASGE cells to form a functional epithelial barrier. This study suggests that primary salivary epithelial cells can be obtained that exhibit critical characteristics needed for use with an artificial secretory device.

Underdiagnosed Menorrhagia in Adolescents is Associated with Underdiagnosed Anemia

OBJECTIVE To test the hypothesis that adolescent girls with menorrhagia rarely seek medical attention. STUDY DESIGN A total of 705 adolescent girls attended a lecture on menorrhagia, completed an initial anonymous questionnaire, and were asked to participate in a more comprehensive study comprising a detailed bleeding questionnaire, a pictorial blood loss assessment chart, and blood tests. RESULTS A total of 105 adolescents (15%) reported they had heavy periods on the initial questionnaire. Among the 94 girls who completed the full questionnaire, 34 reported menorrhagia (36%; 95% CI, 26.5%-46.7%). Almost one-third (11 of 34) of these girls did not perceive having menorrhagia according to their response to the initial questionnaire. Menorrhagia was not related to age, years since menarche, or family history of menorrhagia. Among the 62 girls who consented to blood testing, 6 had anemia (9.6%; 95% CI, 3.6%-19.6%), all of whom had bleeding symptoms. CONCLUSION Using standardized questionnaires, we were able to identify adolescents with menorrhagia associated with anemia. Importantly, some of these adolescents were not aware of having menorrhagia and/or anemia. Screening programs for menorrhagia in schools could result in better detection of menorrhagia among adolescents and consequent appropriate referral for medical consultation.

The Role of Platelets and their Microparticles in Rehabilitation of Ischemic Brain Tissue

Stroke is a leading cause of mortality and chronic disability. Therapies aimed at reducing stroke related morbidity are currently limited. Therefore it is very important to develop effective treatments that will maximize rehabilitation after stroke. Current efforts in the field of cellular therapy focus on stem cell transplantations. This approach involves biological and ethical complications and therefore, the use of endogenous neural stem cells (eNSC) for repairing damage in various neurological disorders has been suggested. eNSCs reside in specialized vascular niches in defined regions, such as the subventricular zone (SVZ) of the lateral ventricle. These cells have an unlimited potential to create newborn cells. Interrelations between newborn neural and endothelial cells have an important role in eNSC survival, maturation, migration and differentiation and neurogenesis occurs in close spatio-temporal association with vessel growth in these niches. Previous studies have shown that application of external factors can boost long-term endogenous repair mechanisms in the cerebral cortex. Activated platelets and their microparticles contain a variety of growth and trophic factors essential to angiogenesis and neurogenesis and may therefore serve as novel therapeutic agents for brain injury. Specifically, factors from platelets and their microparticles may promote neurogenesis by stimulating eNSC proliferation, migration and differentiation, and by stimulating niche angiogenesis and the release of neurogenic signals from endothelial cells and astrocytes. In this review we will show that combined augmentation of angiogenesis, neurogenesis and neuroprotection using platelets and their microparticles is feasible and results in improved functional gain after stroke.

Reduced Expression of Gamma Interferon in Serum and Marked Lymphoid Depletion Induced by Porphyromonas gingivalis Increase Murine Morbidity and Mortality due to Cytomegalovirus Infection

ABSTRACT Porphyromonas gingivalis, a gram-negative anaerobe, is a major etiological agent of severe forms of periodontal disease. Although periodontal disease is considered a localized disease, accumulating evidence indicates that it may lead to a predisposition to a decline in immunocompetence. Human cytomegalovirus (CMV) commonly infects all human populations without producing significant clinical symptoms. Immunocompromised patients usually develop a primary or reactivated CMV infection, which is associated with high rates of morbidity and mortality. The aim of this study was to determine whether P. gingivalis increases animal susceptibility to CMV infection. Mice were inoculated with CMV and infected locally with P. gingivalis 3 days after the virus inoculation. Mortality rates were monitored, and traces of viral DNA and bacterial infection were detected systemically by using real-time PCR. Local and systemic cytokine secretion was measured, and histological sections were used to assess the pathological state of infected organs. P. gingivalis- and CMV-coinfected mice showed dramatically higher mortality rates than mice infected with P. gingivalis or CMV only. Although the organs of coinfected mice exhibited decreased viral titers, distinct necrosis and tissue damage were more evident in the livers and spleens of these mice than in those of mice infected with CMV only. Furthermore, systemic gamma interferon levels were decreased in coinfected mice, and marked lymphoid depletion was observed in their necrotic organs. In parallel control Escherichia coli-CMV coinfection experiments, the mortality and pathological results were the same as those found in mice infected with CMV only. Our results suggest a specific influence of P. gingivalis on the mouse immune response, causing increased susceptibility to CMV infection.

Interferon-gamma deficiency attenuates local P. gingivalis-induced inflammation.

Infection with the periodontal pathogen Porphyromonas gingivalis causes a strong local inflammatory reaction. Using IFNγ-deficient mice, we tested the hypothesis that the absence of IFNγ would result in a reduction of the local pro-inflammatory response to P. gingivalis. Cytokine secretion by macrophages from IFNγ-/- animals was significantly attenuated. Addition of IFNγ restored cytokine secretion. In vivo injection of P. gingivalis into subcutaneous chambers increased the intra-chamber leukocyte counts and TNFα and IL-1β levels. This increase was significantly lower in the IFNγ-/- mice. Local reconstitution of IFNγ-/- mice at the site of inflammation with the IFNγ gene increased the levels of TNFα and decreased the IL-10 levels. Anti-P. gingivalis IgG1 levels, a marker of Th2 response, were higher in immunized IFNγ-/- than in IFNγ+/+ mice. The results suggest that lack of IFNγ reduced the amplitude of the local pro-inflammatory response without decreasing the humoral protective response. The higher IgG1/IgG2a ratio observed supports the possibility of a Th2-dominant response in IFNγ-deficient animals.

Platelet lysates stimulate angiogenesis, neurogenesis and neuroprotection after stroke

Platelets contain chemo-attractants and mitogens that have a major role in tissue repair. Therefore we hypothesised that tissue regeneration secondary to activation of endogenous neural stem cells (eNSC) can be enhanced by delivering platelets to the ischaemic brain. To examine these potential therapeutic effects we injected platelet-poor plasma (PPP), fibroblast growth factor (FGF2) and platelet lysate (PLT) to the lateral ventricles after permanent middle cerebral artery occlusion (PMCAO) in rats. The animals were tested with the neurological severity score, and infarct volumes were measured at 90 days post-PMCAO. Immunohistochemistry was used to determine the fate of newborn cells and to count blood vessels in the ischaemic brain. Platelets significantly increased eNSC proliferation and angiogenesis in the subventricular zone (SVZ) and in the peri-lesion cortex. Functional outcome was significantly improved and injury size was significantly reduced in rats treated with PLT suggesting additional neuroprotective effects. In conclusion, local delivery of PLT to the lateral ventricles induces angiogenesis, neurogenesis and neuroprotection and reduces behavioural deficits after brain ischaemia.