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Platelets are small anucleated blood cells primarily known for their vital hemostatic role. Allogeneic platelet concentrates (PCs) collected from healthy donors are an essential cellular product transfused by hospitals to control or prevent bleeding in patients affected by thrombocytopenia or platelet dysfunctions. Platelets fulfill additional essential functions in innate and adaptive immunity and inflammation, as well as in wound-healing and tissue-repair mechanisms. Platelets contain mitochondria, lysosomes, dense granules, and alpha-granules, which collectively are a remarkable reservoir of multiple trophic factors, enzymes, and signaling molecules. In addition, platelets are prone to release in the blood circulation a unique set of extracellular vesicles (p-EVs), which carry a rich biomolecular cargo influential in cell–cell communications. The exceptional functional roles played by platelets and p-EVs explain the recent interest in exploring the use of allogeneic PCs as source material to develop new biotherapies that could address needs in cell therapy, regenerative medicine, and targeted drug delivery. Pooled human platelet lysates (HPLs) can be produced from allogeneic PCs that have reached their expiration date and are no longer suitable for transfusion but remain valuable source materials for other applications. These HPLs can substitute for fetal bovine serum as a clinical grade xeno-free supplement of growth media used in the in vitro expansion of human cells for transplantation purposes. The use of expired allogeneic platelet concentrates has opened the way for small-pool or large-pool allogeneic HPLs and HPL-derived p-EVs as biotherapy for ocular surface disorders, wound care and, potentially, neurodegenerative diseases, osteoarthritis, and others. Additionally, allogeneic platelets are now seen as a readily available source of cells and EVs that can be exploited for targeted drug delivery vehicles. This article aims to offer an in-depth update on emerging translational applications of allogeneic platelet biotherapies while also highlighting their advantages and limitations as a clinical modality in regenerative medicine and cell therapies.

Background The burgeoning field of regenerative medicine has significantly advanced with recent findings on biotherapies using human platelet lysates (HPLs), derived from clinical-grade platelet concentrates (PCs), for treating brain disorders. These developments have opened new translational research avenues to explore the neuroprotective effects of platelet-extracellular vesicles (PEVs). Their potential in managing neurodegenerative conditions like traumatic brain injury (TBI) and Parkinson’s disease (PD) warrants further exploration. We aimed here to characterize the composition of a PEV preparation isolated from platelet concentrate (PC) supernatant, and determine its neuroprotective potential and neurorestorative effects in cellular and animal models of TBI and PD. Methods We isolated PEVs from the supernatant of clinical-grade PC collected from healthy blood donors utilizing high-speed centrifugation. PEVs were characterized by biophysical, biochemical, microscopic, and LC–MS/MS proteomics methods to unveil biological functions. Their functionality was assessed in vitro using SH-SY5Y neuronal cells, LUHMES dopaminergic neurons, and BV-2 microglial cells, and in vivo by intranasal administration in a controlled cortical impact (CCI)-TBI model using 8-weeks-old male C57/BL6 mice, and in a PD model induced by MPTP in 5-month-old male C57/BL6 mice. Results PEVs varied in size from 50 to 350 nm, predominantly around 200 nm, with concentrations ranging between 10 10 and 10 11 /mL. They expressed specific platelet membrane markers, exhibited a lipid bilayer by cryo-electron microscopy and, importantly, showed low expression of pro-coagulant phosphatidylserine. LC–MS/MS indicated a rich composition of trophic factors, including neurotrophins, anti-inflammatory agents, neurotransmitters, and antioxidants, unveiling their multifaceted biological functions. PEVs aided in the restoration of neuronal functions in SH-SY5Y cells and demonstrated remarkable neuroprotective capabilities against erastin-induced ferroptosis in dopaminergic neurons. In microglial cells, they promoted anti-inflammatory responses, particularly under inflammatory conditions. In vivo , intranasally delivered PEVs showed strong anti-inflammatory effects in a TBI mouse model and conserved tyrosine hydroxylase expression of dopaminergic neurons of the substantia nigra in a PD model, leading to improved motor function. Conclusions The potential of PEV-based therapies in neuroprotection opens new therapeutic avenues for neurodegenerative disorders. The study advocates for clinical trials to establish the efficacy of PEV-based biotherapies in neuroregenerative medicine. Graphical Abstract

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 ex vivo expansion of corneal endothelium cells. These findings open a new paradigm for ex vivo propagation protocols of corneal endothelium cells in compliance with good tissue culture practices and regulatory recommendations to limit the use of xenogenic materials.

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 administration of human platelet lysates (HPL) is a potential emerging biotherapy of neurodegenerative and traumatic diseases of the central nervous system. HPLs being prepared from pooled platelet concentrates, thereby increasing viral risks, manufacturing processes should incorporate robust virus‐reduction treatments. We evaluated a 19 ± 2‐nm virus removal nanofiltration process using hydrophilic regenerated cellulose hollow fibers on the properties of a neuroprotective heat‐treated HPL (HPPL). Spiking experiments demonstrated >5.30 log removal of 20–22‐nm non‐enveloped minute virus of mice‐mock particles using an immuno‐quantitative polymerase chain reaction assay. The nanofiltered HPPL (NHPPL) contained a range of neurotrophic factors like HPPL. There was >2 log removal of extracellular vesicles (EVs), associated with decreased expression of pro‐thrombogenic phosphatidylserine and procoagulant activity. LC‐MS/MS proteomics showed that ca. 80% of HPPL proteins, including neurotrophins, cytokines, and antioxidants, were still found in NHPPL, whereas proteins associated with some infections and cancer‐associated pathways, pro‐coagulation and EVs, were removed. NHPPL maintained intact neuroprotective activity in Lund human mesencephalic dopaminergic neuron model of Parkinson's disease (PD), stimulated the differentiation of SH‐SY5Y neuronal cells and showed preserved anti‐inflammatory function upon intranasal administration in a mouse model of traumatic brain injury (TBI). Therefore, nanofiltration of HPL is feasible, lowers the viral, prothrombotic and procoagulant risks, and preserves the neuroprotective and anti‐inflammatory properties in neuronal pre‐clinical models of PD and TBI.

Risk of transmission of hepatitis C virus (HCV) by clinical plasma remains high in countries with a high prevalence of hepatitis C, justifying the implementation of viral inactivation treatments. In this study, we assessed the extent of inactivation of HCV during minipool solvent/detergent (SD; 1% TnBP / 1% Triton X-45) treatment of human plasma. Luciferase-tagged infectious cell culture-derived HCV (HCVcc) particles were used to spike human plasma prior to treatment by SD at 31 ± 0.5°C for 30 min. Samples were taken before and after SD treatment and filtered on a Sep-Pak Plus C18 cartridge to remove the SD agents. Risk of cytotoxicity was assessed by XTT cell viability assay. Viral infectivity was analyzed based on the luciferase signals, 50% tissue culture infectious dose viral titer, and immunofluorescence staining for HCV NS5A protein. Total protein, cholesterol, and triglyceride contents were determined before and after SD treatment and C18 cartridge filtration. Binding analysis, using patient-derived HCV clinical isolates, was also examined to validate the efficacy of the inactivation by SD. SD treatment effectively inactivated HCVcc within 30 min, as demonstrated by the baseline level of reporter signals, total loss of viral infectivity, and absence of viral protein NS5A. SD specifically targeted HCV particles to render them inactive, with essentially no effect on plasma protein content and hemostatic function. More importantly, the efficacy of the SD inactivation method was confirmed against various genotypes of patient-derived HCV clinical isolates and against HCVcc infection of primary human hepatocytes. Therefore, treatment by 1% TnBP / 1% Triton X-45 at 31°C is highly efficient to inactivate HCV in plasma for transfusion, showing its capacity to enhance the safety of therapeutic plasma products. We propose that the methodology used here to study HCV infectivity can be valuable in the validation of viral inactivation and removal processes of human plasma-derived products.

Cases of variant Creutzfeldt-Jakob disease in people who had consumed contaminated meat products from cattle with bovine spongiform encephalopathy emphasize the need for measures aimed at preventing the transmission of the pathogenic prion protein (PrPSc) from materials derived from cattle. Highly stringent scrutiny is required for fetal bovine serum (FBS), a growth-medium supplement used in the production of parenteral vaccines and therapeutic recombinant proteins and in the ex vivo expansion of stem cells for transplantation. One such approach is the implementation of manufacturing steps dedicated to removing PrPSc from materials containing FBS. We evaluated the use of the QyuSpeed D (QSD) adsorbent hollow-fiber anion-exchange chromatographic column (Asahi Kasei Medical, Tokyo, Japan) for the removal of PrPSc from cell culture media supplemented with FBS. We first established that QSD filtration had no adverse effect on the chemical composition of various types of culture media supplemented with 10% FBS or the growth and viability characteristics of human embryonic kidney (HEK293) cells, baby hamster kidney (BHK-21) cells, African green monkey kidney (Vero) cells, and Chinese hamster ovary (CHO-k1) cells propagated in the various culture-medium filtrates. We used a 0.6-mL QSD column for removing PrPSc from up to 1000 mL of Dulbecco's modified Eagle's medium containing 10% FBS previously spiked with the 263K strain of hamster-adapted scrapie. The Western blot analysis, validated alongside an infectivity assay, revealed that the level of PrPSc in the initial 200mL flow-through was reduced by 2.5 to > 3 log10, compared with that of the starting material. These results indicate that QSD filtration removes PrPSc from cell culture media containing 10% FBS, and demonstrate the ease with which QSD filtration can be implemented in at industrial-scale to improve the safety of vaccines, therapeutic recombinant proteins, and ex vivo expanded stem cells produced using growth media supplemented with FBS.

The postpartum period is when a host of changes occur at molecular, cellular, physiological and behavioral levels to prepare female humans for the challenge of maternity. Alteration or prevention of these normal adaptions is thought to contribute to disruptions of emotion regulation, motivation and cognitive abilities that underlie postpartum mental disorders, such as postpartum depression. Despite the high incidence of this disorder, and the detrimental consequences for both mother and child, its etiology and related neurobiological mechanisms remain poorly understood, partially due to the lack of appropriate animal models. In recent decades, there have been a number of attempts to model postpartum depression disorder in rats. In the present review, we first describe clinical symptoms of postpartum depression and discuss known risk factors, including both genetic and environmental factors. Thereafter, we discuss various rat models that have been developed to capture various aspects of this disorder and knowledge gained from such attempts. In doing so, we focus on the theories behind each attempt and the methods used to achieve their goals. Finally, we point out several understudied areas in this field and make suggestions for future directions.

Cases of variant Creutzfeldt-Jakob disease in people who had consumed contaminated meat products from cattle with bovine spongiform encephalopathy emphasize the need for measures aimed at preventing the transmission of the pathogenic prion protein (PrPSc) from materials derived from cattle. Highly stringent scrutiny is required for fetal bovine serum (FBS), a growth-medium supplement used in the production of parenteral vaccines and therapeutic recombinant proteins and in the ex vivo expansion of stem cells for transplantation. One such approach is the implementation of manufacturing steps dedicated to removing PrPSc from materials containing FBS. We evaluated the use of the QyuSpeed D (QSD) adsorbent hollow-fiber anion-exchange chromatographic column (Asahi Kasei Medical, Tokyo, Japan) for the removal of PrPSc from cell culture media supplemented with FBS. We first established that QSD filtration had no adverse effect on the chemical composition of various types of culture media supplemented with 10% FBS or the growth and viability characteristics of human embryonic kidney (HEK293) cells, baby hamster kidney (BHK-21) cells, African green monkey kidney (Vero) cells, and Chinese hamster ovary (CHO-k1) cells propagated in the various culture-medium filtrates. We used a 0.6-mL QSD column for removing PrPSc from up to 1000 mL of Dulbecco's modified Eagle's medium containing 10% FBS previously spiked with the 263K strain of hamster-adapted scrapie. The Western blot analysis, validated alongside an infectivity assay, revealed that the level of PrPSc in the initial 200mL flow-through was reduced by 2.5 to > 3 log10, compared with that of the starting material. These results indicate that QSD filtration removes PrPSc from cell culture media containing 10% FBS, and demonstrate the ease with which QSD filtration can be implemented in at industrial-scale to improve the safety of vaccines, therapeutic recombinant proteins, and ex vivo expanded stem cells produced using growth media supplemented with FBS.

Risk of transmission of hepatitis C virus (HCV) by clinical plasma remains high in countries with a high prevalence of hepatitis C, justifying the implementation of viral inactivation treatments. In this study, we assessed the extent of inactivation of HCV during minipool solvent/detergent (SD; 1% TnBP / 1% Triton X-45) treatment of human plasma. Luciferase-tagged infectious cell culture-derived HCV (HCVcc) particles were used to spike human plasma prior to treatment by SD at 31 plus or minus 0.5 degree C for 30 min. Samples were taken before and after SD treatment and filtered on a Sep-Pak Plus C18 cartridge to remove the SD agents. Risk of cytotoxicity was assessed by XTT cell viability assay. Viral infectivity was analyzed based on the luciferase signals, 50% tissue culture infectious dose viral titer, and immunofluorescence staining for HCV NS5A protein. Total protein, cholesterol, and triglyceride contents were determined before and after SD treatment and C18 cartridge filtration. Binding analysis, using patient-derived HCV clinical isolates, was also examined to validate the efficacy of the inactivation by SD. SD treatment effectively inactivated HCVcc within 30 min, as demonstrated by the baseline level of reporter signals, total loss of viral infectivity, and absence of viral protein NS5A. SD specifically targeted HCV particles to render them inactive, with essentially no effect on plasma protein content and hemostatic function. More importantly, the efficacy of the SD inactivation method was confirmed against various genotypes of patient-derived HCV clinical isolates and against HCVcc infection of primary human hepatocytes. Therefore, treatment by 1% TnBP / 1% Triton X-45 at 31 degree C is highly efficient to inactivate HCV in plasma for transfusion, showing its capacity to enhance the safety of therapeutic plasma products. We propose that the methodology used here to study HCV infectivity can be valuable in the validation of viral inactivation and removal processes of human plasma-derived products.