Theiler's Murine Encephalomyelitis Virus Replicates in Primary Neuron Cultures and Impairs Spine Density Formation.

In this study, we examined infection with the highly neurovirulent GDVII, the less neurovirulent DA strains, and with a mutant DA, which lacks the L* protein (L*-1) involved in viral persistence and demyelinating disease, to analyze the direct effects of Theiler's murine encephalomyelitis virus (TMEV) replication using primary cultures of mouse brain hippocampal neurons. All viruses replicate in cultured neurons, with GDVII having the highest titers and L*-1 the lowest. Accordingly, all were positive for viral antigen staining 3 days postinfection (dpi), and DA and L*-1 were also positive after 12 dpi. NeuN + immunostaining showed an early and almost complete absence of positive cells in cultures infected with GDVII, an approximately 50% reduction in cultures infected with DA, and fewer changes in L*-1 strains at 3 dpi. Accordingly, staining with chloromethyltetramethylrosamine orange (Mitotracker OrangeTM) as a parameter for cell viability showed similar results. Moreover, at 1 dpi, the strain DA induced higher transcript levels of neuroprotective genes such as IFN-Iß, IRF7, and IRF8. At 3 dpi, strains GDVII and DA, but not the L*-1 mutant, showed lower PKR expression. In addition, confocal analysis showed that L*-1-infected neurons exhibited a decrease in spine density. Treatment with poly (I:C), which is structurally related to dsRNA and is known to trigger IFN type I synthesis, reduced spine density even more. These results confirmed the use of mouse hippocampal neuron cultures as a model to study neuronal responses after TMEV infection, particularly in the formation of spine density.

DNA extracellular traps as potential biomarker of chronic haemophilic synovitis and therapeutic perspective in patients treated with PRP: A pilot study.

INTRODUCTION: Hemarthrosis causes chronic haemophilic synovitis (CHS). Although neutrophils are major immune cells infiltrating joints after bleeding, their role on the pathogenesis of CHS is unknown. Neutrophils release extracellular DNA traps (ETs), structures of DNA with bound granular enzymes that were associated with tissue damage. AIMS: To evaluate the presence of ETs as pathogenic biomarker and the protective effect of intraarticular injection of platelet-rich plasma (PRP) in patients with CHS. METHODS: Haemophilia Joint Health Score (HJHS) and bleeding episodes (BE) were measured and correlated with ETs indicators (DNA/DNA-Elastase) in synovial fluids (SF), PRP and plasma of 21 patients. RESULTS: Soluble DNA and DNA-Elastase were detected in SF and plasma of patients. The synovial and plasma levels of DNA-Elastase positively correlated with worse HJHS/BE. Interestingly, remaining ETs-inducer factors were present in SF that induced the in vitro release of ETs from blood-isolated neutrophils. This phenomenon was impaired by adding plasma or PRP. Finally, preliminary data obtained from five patients indicate that levels of DNA-Elastase and HJHS/BE decreased after receiving intraarticular injection of PRP. CONCLUSIONS: The synovial and plasma levels of DNA-Elastase correlated with worse HJHS/BE suggesting that ETs formation could be a biomarker and potential therapeutic target for CHS. The intraarticular injection of PRP underlined a new potential alternative therapy, decreasing ETs formation in synovia of patients with CHS. However, our hypotheses must be confirmed in the future with better designed and more statistical power studies. Meanwhile, the use of intraarticular injections of PRP for the treatment of CHS remains controversial.

PRP in wound healing applications.

Platelets play a crucial role in hemostasis, tissue regeneration and host defense. Based on these settings, platelet-rich plasma (PRP) and its derivatives are therapeutically used to promote wound healing in several scenarios. This review summarizes the biological mechanisms underlying the most traditional as well as innovative applications of PRP in wound healing. These mechanisms involve the combined action of platelet-derived growth factors and cytokines, together with the role of plasma-derived fibrillar, antioxidant and homeostatic factors. In addition, regenerative treatments with PRP consist of personalized and non-standardized methods. Thus, the quality of PRP varies depending on endogenous factors (e.g., age; gender; concomitant medication; disease-associated systemic factors; nutrition) and exogenous factors (anticoagulants and cellular composition). This review also analyses whether these factors affect the biological mechanisms of PRP in wound healing applications.

Inhibition of Fenton reaction is a novel mechanism to explain the therapeutic effect of intra-articular injection of PRP in patients with chronic haemophilic synovitis.

INTRODUCTION AND AIM: Haemarthroses cause major morbidity in haemophilia resulting in chronic haemophilic synovitis (CHS) and arthropathy. Oxidation of haemoglobin-coupled iron released in synovium after haemolysis induces chondrocytes death and cartilage damage, allowing postulate using iron-chelating drugs as potential therapeutic tool for haemophilic joint damage. Considering that albumin, the most abundant plasma protein, is a physiologic iron chelator, we aim to demonstrate that impediment of haemoglobin oxidation is exerted by plasma as a mechanism involved in the therapeutic effect of intra-articular injection of platelet-rich plasma in CHS. METHODS: Oxidation of haemoglobin (Hb) to methaemoglobin (MeHb) through Fenton reaction was induced in vitro by addition of potassium ferricyanide in the presence or absence of peripheral blood-derived platelets-rich or platelets-poor plasma (PRP/PPP) or albumin. The relevance of in vitro findings was analysed in synovial fluid (SF) samples from one patient with CHS obtained before and after 6 months of PRP intra-articular injection. RESULTS: MeHb formation was completely impaired either by of PPP, PRP or albumin indicating that PRP exerts an anti-oxidative effect, probably due by plasma albumin. Analysis of SF samples revealed the presence of MeHb levels and haemosiderin-laden macrophages in SF obtained before PRP treatment. Reduction of synovial MeHb, normalization of cellular composition and improvement of health joint haemophilic score, pain and bleeding episodes were registered after 6 months of PRP intra-articular injection. CONCLUSION: Inhibition of Fenton reaction and the consequent normalization of joint cellular composition is a noncanonical mechanism underlying the therapeutic effect of PRP intra-articular injection in CHS.

Anticoagulants Interfere With the Angiogenic and Regenerative Responses Mediated by Platelets.

BACKGROUND AND AIMS: Platelet rich plasma (PRP) obtained from blood anticoagulated with acid-citrate-dextrose (ACD) or sodium-citrate (SC) is used for regenerative medicine as source of platelet-derived growth factors. Allergic reactions against citrate were reported in patients after local injection of PRP allowing us to hypothesize that anticoagulants exert a harmful and local effect that interferes with the regenerative proprieties of platelets. Herein we test this hypothesis by analyzing the effect of ACD and SC on angiogenic and regenerative responses mediated by platelets. METHODS: PRP was obtained from SC- or ACD-anticoagulated blood; platelets were lysed to release growth factors; and PRP releasates (PRPr) were used to induce in vitro endothelial proliferation and 2D-migration, and regeneration of mouse skin wounds. RESULTS: We first compared proliferation and migration of endothelial cells mediated by anticoagulated-PRPr supplemented or not with CaCl2. Alteration of endothelial adhesion and impediment of proliferation and migration was observed without CaCl2. Although endothelial morphology was normalized in SC- and ACD-PRPr after calcium restitution, angiogenic responses were only markedly induced by SC-PRPr. In vivo studies revealed a delay in mouse skin regeneration after treatment with anticoagulated-PRPr without CaCl2. Healing was only induced after calcium restitution in SC- but ACD-PRPr. Moreover, the development of inflammatory intradermal papules was evidenced after injection of ACD-PRPr. Supplementation of SC-PRPr with the equivalent concentration of dextrose (D-Glucose, 18 mM) present in ACD-PRPr resulted in reduction of endothelial proliferation and migration, delay of mouse skin regeneration and development of intradermal papules. Finally, collecting blood with half amount of SC significantly improved all the angiogenic and regenerative responses mediated by PRPr. In contrast, the delay of skin regeneration and the development of inflammatory papules remained stable after dilution of ACD. CONCLUSION: Our findings indicate that (1) calcium restitution is required to impair the cellular and tissue alterations induced by citrated-anticoagulants contained in PRP; (2) ACD-derived dextrose confers anti-angiogenic, anti-regenerative and pro-inflammatory proprieties to PRP; and (3) half concentration of SC improves the angiogenesis and regeneration mediated by PRP.