Human platelet concentrates: a source of solvent/detergent-treated highly enriched brain-derived neurotrophic factor

The Implications of Brain-Derived Neurotrophic Factor in the Biological Activities of Platelet-Rich Plasma

Platelet-rich plasma (PRP) is a biological blood-derived therapeutic obtained from whole blood that contains higher levels of platelets. PRP has been primarily used to mitigate joint degeneration and chronic pain in osteoarthritis (OA). This clinical applicability is based mechanistically on the release of several proteins by platelets that can restore joint homeostasis. Platelets are the primary source of brain-derived neurotrophic factor (BDNF) outside the central nervous system. Interestingly, BDNF and PRP share key biological activities with clinical applicability for OA management, such as anti-inflammatory, anti-apoptotic, and antioxidant. However, the role of BDNF in PRP therapeutic activities is still unknown. Thus, this work aimed to investigate the implications of BDNF in therapeutic outcomes provided by PRP therapy in vitro and in-vivo, using the MIA-OA animal model in male Wistar rats. Initially, the PRP was characterized, obtaining a leukocyte-poor-platelet-rich plasma (LP-PRP). Our assays indicated that platelets activated by Calcium release BDNF, and suppression of M1 macrophage polarization induced by LP-PRP depends on BDNF full-length receptor, Tropomyosin Kinase-B (TrkB). OA animals were given LP-PRP intra-articular and showed functional recovery in gait, joint pain, inflammation, and tissue damage caused by MIA. Immunohistochemistry for activating transcriptional factor-3 (ATF-3) on L4/L5 dorsal root ganglia showed the LP-PRP decreased the nerve injury induced by MIA. All these LP-PRP therapeutic activities were reversed in the presence of TrkB receptor antagonist. Our results suggest that the therapeutic effects of LP-PRP in alleviating OA symptoms in rats depend on BDNF/TrkB activity.

Brain-derived neurotrophic factor/tropomyosin receptor kinase B signaling in spinal muscular atrophy and amyotrophic lateral sclerosis

Tropomyosin receptor kinase B (TrkB) and its primary ligand brain-derived neurotrophic factor (BDNF) are expressed in the neuromuscular system, where they affect neuronal survival, differentiation, and functions. Changes in BDNF levels and full-length TrkB (TrkB-FL) signaling have been revealed in spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS), two common forms of motor neuron diseases that are characterized by defective neuromuscular junctions in early disease stages and subsequently progressive muscle weakness. This review summarizes the current understanding of BDNF/TrkB-FL-related research in SMA and ALS, with an emphasis on their alterations in the neuromuscular system and possible BDNF/TrkB-FL-targeting therapeutic strategies. The limitations of current studies and future directions are also discussed, giving the hope of discovering novel and effective treatments.

Blood neurofilament light chain as a biomarker for monitoring and predicting paclitaxel-induced peripheral neuropathy in patients with gynecological cancers

Objective

We aimed to evaluate the potential of serum neurofilament light chain (sNfL) and serum brain-derived neurotrophic factor (sBDNF) as reliable biomarkers for paclitaxel-induced peripheral neuropathy (PIPN).

Methods

Forty-eight patients with gynecologic cancer scheduled to undergo six cycles of paclitaxel-based chemotherapy at the National Cancer Center of Korea between September 2020 and January 2022 were prospectively assessed during and after chemotherapy.

Results

At the end of the chemotherapy, 12 (25%) patients were classified as having grade 3 PIPN according to the National Cancer Institute-Common Toxicity Criteria. The sNfL levels increased during paclitaxel treatment in all patients. After two, four, and six cycles, patients with grade 3 PIPN exhibited higher mean sNfL levels than those in the 0-2 grade range (p = 0.004, p = 001, and p < 0.001, respectively). For sNfL levels ≥ 124 pg/mL, after two cycles of chemotherapy, the sensitivity and specificity for predicting grade 3 PIPN at the end of treatment were 80% and 79%, respectively. Over the course of paclitaxel-based treatment, sBDNF levels continued to decrease regardless of the severity of PIPN. At the end of treatment and six months after chemotherapy, patients with grade 3 PIPN had lower sBDNF levels than those within the 0-2 grade range (p =0.037 and 0.02, respectively), and the patients in the latter group had better clinical symptoms six months after the end of treatment.

Conclusions

The sNfL levels during paclitaxel-based chemotherapy reflect ongoing neuroaxonal injury and serve as reliable biomarkers of PIPN severity. The sNfL levels during early treatment with paclitaxel might be prognostic indicators for PIPN progression. Low sBDNF levels 6 months after chemotherapy might adversely affect PIPN recovery.

Brain-derived neurotrophic factor in autoimmune inflammatory diseases (Review)

Numerous recent studies reported that brain-derived neurotrophic factor (BDNF) also exists in the peripheral blood to regulate the proliferation, differentiation and survival of lymphocytes. Besides the role of BDNF in neuron repair, circulatory BDNF also enhances the proliferation and reduces apoptosis of lymphocytes. Peripheral lymphocytes express both BDNF and its receptors. Increasing evidence has indicated that altered BDNF serum levels significantly affect patients with autoimmune inflammatory diseases and may also be linked to the pathogenesis of diseases. For instance, systemic lupus erythematosus, an autoimmune inflammatory disease involving multiple organs, is frequently linked to altered B lymphocyte function, imbalance of T-cell subpopulations and loss of immune tolerance, which dysregulates the immune regulatory network with excessive secretion of inflammatory cytokines. The present review summarized studies that suggest a potential link between circulatory BDNF and autoimmune inflammatory diseases.

The brain-derived neurotrophic factor prompts platelet aggregation and secretion

Brain-derived neurotrophic factor (BDNF) has both autocrine and paracrine roles in neurons, and its release and signaling mechanisms have been extensively studied in the central nervous system. Large quantities of BDNF have been reported in circulation, essentially stored in platelets with concentrations reaching 100- to 1000-fold those of neurons. Despite this abundance, the function of BDNF in platelet biology has not been explored. At low concentrations, BDNF primed platelets, acting synergistically with classical agonists. At high concentrations, BDNF induced complete biphasic platelet aggregation that in part relied on amplification from secondary mediators. Neurotrophin-4, but not nerve growth factor, and an activating antibody against the canonical BDNF receptor tropomyosin-related kinase B (TrkB) induced similar platelet responses to BDNF, suggesting TrkB could be the mediator. Platelets expressed, both at their surface and in their intracellular compartment, a truncated form of TrkB lacking its tyrosine kinase domain. BDNF-induced platelet aggregation was prevented by inhibitors of Ras-related C3 botulinum toxin substrate 1 (Rac1), protein kinase C, and phosphoinositide 3-kinase. BDNF-stimulated platelets secreted a panel of angiogenic and inflammatory cytokines, which may play a role in maintaining vascular homeostasis. Two families with autism spectrum disorder were found to carry rare missense variants in the BDNF gene. Platelet studies revealed defects in platelet aggregation to low concentrations of collagen, as well as reduced adenosine triphosphate secretion in response to adenosine diphosphate. In summary, circulating BDNF levels appear to regulate platelet activation, aggregation, and secretion through activation of a truncated TrkB receptor and downstream kinase-dependent signaling.

Investigation of the Roles of New Antiepileptic Drugs and Serum BDNF Levels in Efficacy and Safety Monitoring and Quality of Life: A Clinical Research

Objective: We aimed to determine the therapeutic drug monitoring (TDM) features and the relation to Brain-Derived Neurotrophic Factor (BDNF) of frequently used new antiepileptic drugs (NADs) including lamotrigine (LTG), oxcarbazepine (OXC), zonisamide (ZNS) and lacosamide (LCM). Moreover, we investigated their effect on the quality of life (QoL).

Methods: Eighty epileptic patients who had been using the NADs, and thirteen healthy participants were included in this cross-sectional study. The participants were randomized into groups. The QOLIE-31 test was used for the assessment of QoL. We also prepared and applied “Safety Test”. HPLC method for TDM, and ELISA method for BDNF measurements were used consecutively.

Results: In comparison to healthy participants, epileptic participants had lower marriage rate (p=0.049), education level (p˂0.001), alcohol use (p=0.002). BDNF levels were higher in patients with focal epilepsy (p=0.013) and in those with higher education level (p=0.016). There were negative correlations between serum BDNF levels and serum ZNS levels (p=0.042) with LTG-polytherapy, serum MHD levels (a 10-monohydroxy derivative of OXC, p=0.041) with OXC-monotherapy. There was no difference in BDNF according to monotherapy-polytherapy, drug-resistant groups, regarding seizure frequency. There was a positive correlation between total health status and QoL (p˂0.001). QOLIE-31 overall score (OS) was higher in those with OXC-monotherapy (76.5±14.5). OS (p˂0.001), seizure worry (SW, p=0.004), cognition (C, p˂0.001), social function (SF, p˂0.001) were different in the main groups. Forgetfulness was the most common unwanted effect.

Conclusion: While TDM helps the clinician to use more effective and safe NADs, BDNF may assist in TDM for reaching the therapeutic target in epilepsy.

Tissue-Specificity of Antibodies Raised Against TrkB and p75NTR Receptors; Implications for Platelets as Models of Neurodegenerative Diseases

Platelets and neurons share many similarities including comparable secretory granule types with homologous calcium-dependent secretory mechanisms as well as internalization, sequestration and secretion of many neurotransmitters. Thus, platelets present a high potential to be used as peripheral biomarkers to reflect neuronal pathologies. The brain-derived neurotrophic factor (BDNF) acts as a neuronal growth factor involved in learning and memory through the binding of two receptors, the tropomyosin receptor kinase B (TrkB) and the 75 kDa pan-neurotrophic receptor (p75^NTR). In addition to its expression in the central nervous system, BDNF is found in much greater quantities in blood circulation, where it is largely stored within platelets. Levels 100- to 1,000-fold those of neurons make platelets the most important peripheral reservoir of BDNF. This led us to hypothesize that platelets would express canonical BDNF receptors, i.e., TrkB and p75^NTR, and that the receptors on platelets would bear significant resemblance to the ones found in the brain. However, herein we report discrepancies regarding detection of these receptors using antibody-based assays, with antibodies displaying important tissue-specificity. The currently available antibodies raised against TrkB and p75^NTR should therefore be used with caution to study platelets as models for neurological disorders. Rigorous characterization of antibodies and bioassays appears critical to understand the interplay between platelet and neuronal biology of BDNF.

Platelets Selectively Regulate the Release of BDNF, But Not That of Its Precursor Protein, proBDNF

Background

Brain-derived neurotrophic factor (BDNF) plays a role in synaptic plasticity and neuroprotection. BDNF has well-established pro-survival effects, whereas its precursor protein, proBDNF, induces apoptosis. Thus, it has been suggested that the proBDNF/BDNF ratio could be an indicator of neuronal health. Access to neurons is, understandably, limited. Because of their similarities, platelets have been put forward as a non-invasive biomarker of neuronal health; indeed, they store large quantities of BDNF and can release it into circulation upon activation, similarly to neurons. However, whether platelets also express the precursor proBDNF protein remains unknown. We therefore sought to characterize proBDNF levels in human platelets and plasma.

Methods

The presence of proBDNF was assessed by immunoblotting, cell fractionation, flow cytometry, and confocal microscopy in washed platelets from 10 healthy volunteers. Platelets from 20 independent healthy volunteers were activated with several classical agonists and the release of BDNF and proBDNF into plasma was quantified by ELISA.

Results

Platelets expressed detectable levels of proBDNF (21 ± 13 fmol/250 x 10⁶ platelets). ProBDNF expression was mainly localized in the intracellular compartment. The proBDNF to BDNF molar ratio was ~1:5 in platelets and 10:1 in plasma. In stark contrast to the release of BDNF during platelet activation, intraplatelet and plasma concentrations of proBDNF remained stable following stimulation with classical platelet agonists, consistent with non-granular expression.

Conclusions

Platelets express both the mature and the precursor form of BDNF. Whether the intraplatelet proBDNF to BDNF ratio could be used as a non-invasive biomarker of cognitive health warrants further investigation.

The neuroprotective activity of heat-treated human platelet lysate biomaterials manufactured from outdated pathogen-reduced (amotosalen/UVA) platelet concentrates

Background

Effective neurorestorative therapies of neurodegenerative diseases must be developed. There is increasing interest in using human platelet lysates, rich in neurotrophic factors, as novel disease-modifying strategy of neurodegeneration. To ensure virus safety, pathogen reduction treatments should be incorporated in the preparation process of the platelet concentrates used as source material. We therefore investigated whether platelet concentrates (PC) pathogen-inactivated using a licensed photo-inactivation treatment combining photosensitive psoralen (amotosalen) and UVA irradiation (Intercept) can serve as source material to prepare platelet lysates with preserved neuroprotective activity in Parkinson’s disease models.

Methods

Intercept treated-PCs were centrifuged, when reaching expiry day (7 days after collection), to remove plasma and platelet additive solution. The platelet pellet was re-suspended and concentrated in phosphate buffer saline, subjected to 3 freeze-thaw cycles (− 80 °C/37 °C) then centrifuged to remove cell debris. The supernatant was recovered and further purified, or not, by heat-treatment as in our previous investigations. The content in proteins and neurotrophic factors was determined and the toxicity and neuroprotective activity of the platelet lysates towards LUHMES cells or primary cortical/hippocampal neurons were assessed using ELISA, flow cytometry, cell viability and cytotoxicity assays and proteins analysis by Western blot.

Results

Platelet lysates contained the expected level of total proteins (ca. 7–14 mg/mL) and neurotrophic factors. Virally inactivated and heat-treated platelet lysates did not exert detectable toxic effects on neither Lund human mesencephalic dopaminergic LUHMES cell line nor primary neurons. When used at doses of 5 and 0.5%, they enhanced the expression of tyrosine hydroxylase and neuron-specific enolase in LUHMES cells and did not significantly impact synaptic protein expression in primary neurons, respectively. Furthermore, virally-inactivated platelet lysates tested were found to exert very strong neuroprotection effects on both LUHMES and primary neurons exposed to erastin, an inducer of ferroptosis cell death.

Conclusion

Outdated Intercept pathogen-reduced platelet concentrates can be used to prepare safe and highly neuroprotective human heat-treated platelet pellet lysates. These data open reassuring perspectives in the possibility to develop an effective biotherapy using virally-inactivated platelet lysates rich in functional neurotrophins for neuroregenerative medicine, and for further bio-industrial development. However, the data should be confirmed in animal models.

Graphical abstract

[Brain-derived neurotrophic factor in multiple sclerosis]

The review presents data on brain-derived neurotrophic factor (BDNF), its structure and functions, the effect on the pathogenesis of experimental autoimmune encephalomyelitis and multiple sclerosis (MS). The correlation of BDNF level with clinical manifestations of MS and the changes of its level during disease-modifying therapy is considered.

Effects of a Pasty Bone Cement Containing Brain-Derived Neurotrophic Factor-Functionalized Mesoporous Bioactive Glass Particles on Metaphyseal Healing in a New Murine Osteoporotic Fracture Model

The development of new and better implant materials adapted to osteoporotic bone is still urgently required. Therefore, osteoporotic muscarinic acetylcholine receptor M3 (M3 mAChR) knockout (KO) and corresponding wild type (WT) mice underwent osteotomy in the distal femoral metaphysis. Fracture gaps were filled with a pasty α-tricalcium phosphate (α-TCP)-based hydroxyapatite (HA)-forming bone cement containing mesoporous bioactive CaP-SiO₂ glass particles (cement/MBG composite) with or without Brain-Derived Neurotrophic Factor (BDNF) and healing analyzed after 35 days. Histologically, bone formation was significantly increased in WT mice that received the BDNF-functionalized cement/MBG composite compared to control WT mice without BDNF. Cement/MBG composite without BDNF increased bone formation in M3 mAChR KO mice compared to equally treated WT mice. Mass spectrometric imaging showed that the BDNF-functionalized cement/MBG composite implanted in M3 mAChR KO mice was infiltrated by newly formed tissue. Leukocyte numbers were significantly lower in M3 mAChR KO mice treated with BDNF-functionalized cement/MBG composite compared to controls without BDNF. C-reactive protein (CRP) concentrations were significantly lower in M3 mAChR KO mice that received the cement/MBG composite without BDNF when compared to WT mice treated the same. Whereas alkaline phosphatase (ALP) concentrations in callus were significantly increased in M3 mAChR KO mice, ALP activity was significantly higher in WT mice. Due to a stronger effect of BDNF in non osteoporotic mice, higher BDNF concentrations might be needed for osteoporotic fracture healing. Nevertheless, the BDNF-functionalized cement/MBG composite promoted fracture healing in non osteoporotic bone.

Differential expression of serum biomarkers in hemodialysis patients with mild cognitive decline: A prospective single-center cohort study

Studies suggest that hemodialysis patients are at a higher risk for cognitive decline than healthy individuals; however, underlying mechanisms have not been fully elucidated. We aimed to investigate the roles of serum biomarkers, such as brain-derived neurotrophic factor (BDNF), inflammatory cytokines, fibroblast growth factor (FGF)-23 and its co-receptor α-klotho and platelet (PLT) count in mild cognitive decline (MCD) of patients undergoing hemodialysis in this prospective cohort study. Serum levels of BDNF, tumour necrosis factor (TNF)-α, interleukin (IL)-6 and the number of PLT were significantly altered in the MCD group compared with those in healthy controls (HCs) or those with normal cognitive function (NCF). Although serum α-klotho and FGF-23 levels were significantly altered in the MCD group, there were no statistical differences between the MCD and NCF groups. Serum BDNF levels and PLT counts were significantly correlated with cognitive test scores. Receiver operating characteristic (ROC) curves demonstrated that BDNF and PLT were potential biomarkers for improved MCD diagnosis in patients with hemodialysis. These findings suggest that hemodialysis-related MCD is associated with altered BDNF, TNF-α and IL-6 levels as well as PLT counts and that serum BDNF levels and PLT counts are potential biomarkers for hemodialysis-related MCD diagnosis.

Brain-derived Neurotrophic Factor in Megakaryocytes

The biosynthesis of endogenous brain-derived neurotrophic factor (BDNF) has thus far been examined in neurons where it is expressed at very low levels, in an activity-dependent fashion. In humans, BDNF has long been known to accumulate in circulating platelets, at levels far higher than in the brain. During the process of blood coagulation, BDNF is released from platelets, which has led to its extensive use as a readily accessible biomarker, under the assumption that serum levels may somehow reflect brain levels. To identify the cellular origin of BDNF in platelets, we established primary cultures of megakaryocytes, the progenitors of platelets, and we found that human and rat megakaryocytes express the BDNF gene. Surprisingly, the pattern of mRNA transcripts is similar to neurons. In the presence of thapsigargin and external calcium, the levels of the mRNA species leading to efficient BDNF translation rapidly increase. Under these conditions, pro-BDNF, the obligatory precursor of biologically active BDNF, becomes readily detectable. Megakaryocytes store BDNF in α-granules, with more than 80% of them also containing platelet factor 4. By contrast, BDNF is undetectable in mouse megakaryocytes, in line with the absence of BDNF in mouse serum. These findings suggest that alterations of BDNF levels in human serum as reported in studies dealing with depression or physical exercise may primarily reflect changes occurring in megakaryocytes and platelets, including the ability of the latter to retain and release BDNF.

Are the changes in the peripheral brain-derived neurotrophic factor levels due to platelet activation?

Brain-derived neurotrophic factor (BDNF) plays an important role in central nervous system development, neurogenesis and neuronal plasticity. BDNF is also expressed in several non-neuronal tissues, and it could play an important role in other processes, such as cancer, angiogenesis, etc. Platelets are the major source of peripheral BDNF. However, platelets also contain high amounts of serotonin; they express specific surface receptors during activation, and a multitude of pro-inflammatory and immunomodulatory bioactive compounds are secreted from the granules. Until recently, there was insufficient knowledge regarding the relationship between BDNF and platelets. Recent studies showed that BDNF is present in two distinct pools in platelets, in α-granules and in the cytoplasm, and only the BDNF in the granules is secreted following stimulation, representing 30% of the total BDNF in platelets. BDNF has an important role in the pathophysiology of depression. Low levels of serum BDNF have been described in patients with major depressive disorder, and BDNF levels increased with chronic antidepressant treatment. Interestingly, there is an association between depression and platelet function. This review analyzed studies that evaluated the relationship between BDNF and platelet activation and the effect of treatments on both parameters. Only a few studies consider this possible confounding factor, and it could be very important in diseases such as depression, which show changes in both parameters.

Multifaceted regenerative lives of expired platelets in the second decade of the 21st century

A traditional concept in transfusion medicine is the expiration of platelet concentrates 5-7 days after collection due to storage conditions that favor the risks of bacterial contamination and may lead to a gradual alteration of platelet hemostatic power. Newer findings are strongly suggesting that, after their supposed expiration date, platelet concentrates still contain multiple functional growth factors and cytokines and actually have unaltered power for application in regenerative medicine and cell therapy. Expired platelets can be a valuable source of growth factors to promote the healing of wounds, and can be used for ex vivo expansion of stem cells. There is also preliminary evidence that infusible platelet membrane (IPM) from outdated platelet concentrates and thrombosomes have potential clinical applications as hemostatic products. Experimental work is certainly needed to further validate and standardize the clinical potential of "expired" platelet blood products in human clinical medicine. However, strong evidence accumulates toward a potential for further manufacturing avenues of expired platelet concentrates into valuable therapeutic and clinically relevant products.

Ex vivo expansion of bovine corneal endothelial cells in xeno-free medium supplemented with platelet releasate

Clinical-grade ex vivo expansion of corneal endothelial cells can increase the availability of corneal tissues for transplantation and treatment of corneal blindness. However, these cells have very limited proliferative capacity. Successful propagation has required so far to use very complex growth media supplemented with fetal bovine serum and other xenocomponents. We hypothesized that human platelet releasates rich in multiple growth factors, and in particular neurotrophins, could potentially be a useful supplement for ex vivo expansion of corneal endothelium cells due to their neural crest origin. Platelet releasates were prepared by calcium salt activation of apheresis platelet concentrates, subjected or not to complement inactivation by heat treatment at 56°C for 30 minutes. Platelet releasates were characterized for their content in proteins and were found to contain high amount of growth factors including platelet-derived growth factor-AB (30.56 to 39.08 ng/ml) and brain-derived neurotrophic factor (30.57 to 37.11 ng/ml) neurotrophins. We compared the growth and viability of corneal endothelium cells in DMEM-F12 medium supplemented with different combinations of components, including 2.5%∼10% of the platelet releasates. Corneal endothelium cells expanded in platelet releasates exhibited good adhesion and a typical hexagonal morphology. Their growth and viability were enhanced when using the complement-inactivated platelet releasate at a concentration of 10%. Immunostaining and Western blots showed that CECs maintained the expressions of four important membrane markers: Na-K ATPase α1, zona occludens-1, phospho-connexin 43 and N-cadherin. In conclusion, our study provides the first proof-of-concept that human platelet releasates can be used for exvivo expansion of corneal endothelium cells. These findings open a new paradigm for exvivo propagation protocols of corneal endothelium cells in compliance with good tissue culture practices and regulatory recommendations to limit the use of xenogenic materials.

GSK3β, CREB, and BDNF in peripheral blood of patients with Alzheimer's disease and depression

BACKGROUND

Glycogen synthase kinase-3β (GSK3β), cAMP-response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) play critical roles in neuronal survival, synaptic plasticity and memory and participate in the pathophysiology of both depressive disorder and Alzheimer's disease (AD).

METHODS

This study was designed to determine the association of GSK3β activity, CREB activity and BDNF concentration in peripheral blood of patients with AD with or without depressive symptoms and in depressive patients without AD. GSK3β activity in platelets, CREB activity in lymphocytes and BDNF concentration in plasma, platelet-rich plasma or platelets were measured in 85 AD patients (36 of whom displayed co-morbid depressive symptoms), 65 non-AD patients with depressive disorder and 96 healthy controls. AD patients were clinically assessed for stage of dementia, cognitive impairment and severity of depressive symptoms. Depressive patients were clinically assessed for severity of depression.

RESULTS

We observed increased CREB activity and GSK3β activity in AD with depressive symptoms or in AD at mild stage of dementia. Decreased BDNF concentration was found in platelet-rich plasma of AD patients at moderate to severe stages of dementia or in AD without depressive symptoms. An association was revealed of the severity of cognitive impairment with the increase of GSK3β in the platelets of AD patients with mild dementia. In depressive patients, a lower concentration of phosphorylated GSK3β was associated with a higher severity of depression. Association was confirmed between severity of depression, CREB activation, and BDNF concentration in drug-naïve depressive patients.

CONCLUSION

Our data demonstrated that AD is accompanied by increased CREB activity in lymphocytes and a decreased concentration of BDNF in platelet-rich plasma. The decreased BDNF concentration appears to correlate with moderate to severe stages of dementia in AD. Observation of decreased phosphorylation of GSK3β in platelets of both AD patients with depressive symptoms and depressive patients after treatment confirms the role of increased GSK3β activity in the pathophysiology of both AD and depressive disorder. Associations were confirmed between AD and platelet GSK3β activity, lymphocyte CREB activity and plasma BDNF. CREB activity and platelet BDNF concentration seems to be related to depressive disorder.

BDNF Val 66 Met and 5-HTTLPR genotype moderate the impact of early psychosocial adversity on plasma brain-derived neurotrophic factor and depressive symptoms: a prospective study

Recent studies have emphasized an important role for neurotrophins, such as brain-derived neurotrophic factor (BDNF), in regulating the plasticity of neural circuits involved in the pathophysiology of stress-related diseases. The aim of the present study was to examine the interplay of the BDNF Val⁶⁶Met and the serotonin transporter promoter (5-HTTLPR) polymorphisms in moderating the impact of early-life adversity on BDNF plasma concentration and depressive symptoms. Participants were taken from an epidemiological cohort study following the long-term outcome of early risk factors from birth into young adulthood. In 259 individuals (119 males, 140 females), genotyped for the BDNF Val⁶⁶Met and the 5-HTTLPR polymorphisms, plasma BDNF was assessed at the age of 19 years. In addition, participants completed the Beck Depression Inventory (BDI). Early adversity was determined according to a family adversity index assessed at 3 months of age. Results indicated that individuals homozygous for both the BDNF Val and the 5-HTTLPR L allele showed significantly reduced BDNF levels following exposure to high adversity. In contrast, BDNF levels appeared to be unaffected by early psychosocial adversity in carriers of the BDNF Met or the 5-HTTLPR S allele. While the former group appeared to be most susceptible to depressive symptoms, the impact of early adversity was less pronounced in the latter group. This is the first preliminary evidence indicating that early-life adverse experiences may have lasting sequelae for plasma BDNF levels in humans, highlighting that the susceptibility to this effect is moderated by BDNF Val⁶⁶Met and 5-HTTLPR genotype.

Virally inactivated human platelet concentrate lysate induces regulatory T cells and immunosuppressive effect in a murine asthma model

BACKGROUND

Platelet concentrate lysates (PCLs) are increasingly used in regenerative medicine. We have developed a solvent/detergent (S/D)-treated PCL. The functional properties of this preparation should be unveiled. We hypothesized that, due to transforming growth factor-β1 (TGF-β1) content, PCLs may exert immunosuppressive and anti-inflammatory functions.

STUDY DESIGN AND METHODS

PCL was prepared by S/D treatment, oil extraction, and hydrophobic interaction chromatography. The content of TGF-β in PCL was determined by enzyme-linked immunosorbent assay. Cultured CD4+ T cells were used to investigate the effects of PCL on expression of transcription factor forkhead box P3 (Foxp3), the inhibition of T-cell proliferation, and cytokine production. The regulatory function of PCL-converted CD4+ T cells was analyzed by suppressive assay. The BALB/c mice were given PCL-converted CD4+ T cells before ovalbumin (OVA) sensitization and challenge using an asthma model. Inflammatory parameters, such as the level of immunoglobulin E (IgE), airway hyperresponsiveness (AHR), bronchial lavage fluid eosinophils, and cytokines were assayed. Recombinant human (rHu) TGF-β1 was used as control.

RESULTS

PCL significantly enhanced the development of CD4+Foxp3+-induced regulatory T cells (iTregs). Converted iTregs produced neither Th1 nor Th2 cytokines and inhibited normal T-cell proliferation. PCL- and rHuTGF-β-converted CD4+ T cells prevented OVA-induced asthma. PCL- and rHuTGF-β-modified T cells both significantly reduced expression levels of OVA-specific IgE and significantly inhibited the development of AHR, airway eosinophilia, and Th2 responses in mice.

CONCLUSION

S/D-treated PCL promotes Foxp3+ iTregs and exerts immunosuppressive and anti-inflammatory properties. This finding may help to understand the clinical properties of platelet lysates.

BDNF, produced by a TPO-stimulated megakaryocytic cell line, regulates autocrine proliferation

While human platelets release endogenous brain-derived neurotrophic factor (BDNF) upon activation, a previous report on MEG-01, a megakaryocytic cell line, found no trace of BDNF production, and the pathophysiological function of platelet BDNF has remained elusive. In the present study, we demonstrate that MEG-01 produces BDNF in the presence of TPO and that this serves to potentiate cell proliferation. Our in vitro findings suggest that BDNF regulates MEG-01 proliferation in an autocrine manner, and we suggest that BDNF may be a physiological autocrine regulator of megakaryocyte progenitors.