Human platelet lysate biotherapy for traumatic brain injury: preclinical assessment

Traumatic brain injury (TBI) leads to major brain anatomopathological damages underlined by neuroinflammation, oxidative stress and progressive neurodegeneration, ultimately leading to motor and cognitive deterioration. The multiple pathological events resulting from TBI can be addressed not by a single therapeutic approach, but rather by a synergistic biotherapy capable of activating a complementary set of signalling pathways and providing synergistic neuroprotective, anti-inflammatory, antioxidative, and neurorestorative activities. Human platelet lysate might fulfil these requirements as it is composed of a plethora of biomolecules readily accessible as a TBI biotherapy. In the present study, we tested the therapeutic potential of human platelet lysate using in vitro and in vivo models of TBI. We first prepared and characterized platelet lysate from clinical-grade human platelet concentrates. Platelets were pelletized, lysed by three freeze-thaw cycles, and centrifuged. The supernatant was purified by 56°C 30 min heat treatment and spun to obtain the heat-treated platelet pellet lysate that was characterized by ELISA and proteomic analyses. Two mouse models were used to investigate platelet lysate neuroprotective potential. The injury was induced by an in-house manual controlled scratching of the animals' cortex or by controlled cortical impact injury. The platelet lysate treatment was performed by topical application of 60 µl in the lesioned area, followed by daily 60 µl intranasal administration from Day 1 to 6 post-injury. Platelet lysate proteomics identified over 1000 proteins including growth factors, neurotrophins, and antioxidants. ELISA detected several neurotrophic and angiogenic factors at ∼1-50 ng/ml levels. We demonstrate, using two mouse models of TBI, that topical application and intranasal platelet lysate consistently improved mouse motor function in the beam and rotarod tests, mitigated cortical neuroinflammation, and oxidative stress in the injury area, as revealed by downregulation of pro-inflammatory genes and the reduction in reactive oxygen species levels. Moreover, platelet lysate treatment reduced the loss of cortical synaptic proteins. Unbiased proteomic analyses revealed that heat-treated platelet pellet lysate reversed several pathways promoted by both controlled cortical impact and cortical brain scratch and related to transport, postsynaptic density, mitochondria or lipid metabolism. The present data strongly support, for the first time, that human platelet lysate is a reliable and effective therapeutic source of neurorestorative factors. Therefore, brain administration of platelet lysate is a therapeutical strategy that deserves serious and urgent consideration for universal brain trauma treatment.

Characterization and Chromatographic Isolation of Platelet Extracellular Vesicles from Human Platelet Lysates for Applications in Neuroregenerative Medicine

Human platelet lysates (HPLs) made from clinical-grade platelet concentrates are currently evaluated in the preclinical models of Parkinson's disease, Alzheimer's disease, traumatic brain injury, and others, as a new polyvalent neuroprotective biotherapy of the central nervous system. However, the presence and content of extracellular vesicles (EVs) in HPLs and their potential contribution to the neuroprotective and neurorestorative activities of HPLs are still unknown. We, therefore, characterized the EVs present in four different HPL preparations and after purification by size-exclusion chromatography. We then tested the effect of the isolated EVs on neuronal cell repair. We identified that all four HPLs contained a high and similar amount of EVs (10¹¹ to 10¹²/mL) with a mean size ranging from ca. 50 to 300 nm and a negative zeta potential as determined by nanoparticle tracking analysis and dynamic light scattering. Western blot analysis revealed that the EVs present in HPLs expressed the clusters of differentiation 41 (CD41) and 61 (CD61) characteristic of platelets. These EVs were efficiently isolated from HPL proteins by Sepharose CL-2B size-exclusion column chromatography as confirmed by total protein determination and protein profile by sodium dodecyl sulfate polyacrylamide gel electrophoresis, with 73-85% recovery and maintenance of their size, negative zeta potential, and CD41 and CD61 expression. Interestingly, the EVs purified from the four HPLs exhibited a differential capacity to promote cell growth and migration in a wound-healing assay using SH-SY5Y neuronal cells, and one EV preparation stimulated network formation in primary neuronal cultures. These data indicated that the EVs present in HPLs have different neuroregenerative capacities and that some EV preparations may have interesting applications as a stand-alone therapy for usage in neuroregenerative medicine.

Platelet Extracellular Vesicles Loaded Gelatine Hydrogels for Wound Care

Platelet extracellular vesicles (pEVs) isolated from clinical-grade human platelet concentrates are attracting attention as a promising agent for wound healing therapies. Although pEVs have shown potential for skin regeneration, their incorporation into wound bandages has remained limitedly explored. Herein, gelatine-based hydrogel (PAH-G) foams for pEVs loading and release are formulated by crosslinking gelatine with poly(allylamine) hydrochloride (PAH) in the presence of glutaraldehyde and sodium bicarbonate. The optimized PAH-G hydrogel foam, PAH0.24G37, displayed an elastic modulus G' = 8.5 kPa at 37 °C and retained a rubbery state at elevated temperatures. The excellent swelling properties of PAH0.24G37 allowed to easily absorb pEVs at high concentration (1 × 1011 particles mL-1). The therapeutic effect of pEVs was evaluated in vivo on a chronic wound rat model. These studies demonstrated full wound closure after 14 days upon treatment with PAH0.24G37@pEVs. The maintenance of a reduced-inflammatory environment from the onset of treatment promoted a quicker transition to skin remodeling. Promotion of follicle activation and angiogenesis as well as M1-M2 macrophage modulation are evidenced. Altogether, the multifunctional properties of PAH0.24G37@pEVs addressed the complex challenges associated with chronic diabetic wounds, representing a significant advance toward personalized treatment regimens for these conditions.

Platelet Extracellular Vesicles as Natural Delivery Vehicles for Mitochondrial Dysfunction Therapy?

Mitochondria are vital for energy production, metabolic regulation, and cellular signaling. Their dysfunction is strongly implicated in neurological, cardiovascular, and muscular degenerative diseases, where energy deficits and oxidative stress accelerate disease progression. Platelet extracellular vesicles (PEVs), once called "platelet dust", have emerged as promising agents for mitigating mitochondrial dysfunction. Like other extracellular vesicles (EVs), PEVs carry diverse molecular cargo and surface markers implicated in disease processes and therapeutic efficacy. Notably, they may possibly contain intact or partially functional mitochondrial components, making them tentatively attractive for targeting mitochondrial damage. Although direct research on PEVs-mediated mitochondrial rescue remains limited, current evidence suggests that PEVs can modulate diseases associated with mitochondrial dysfunction and potentially enhance mitochondrial health. This review explores the therapeutic potential of PEVs in neurodegenerative and cardiovascular disorders, highlighting their role in restoring mitochondrial health. By examining recent advancements in PEVs research, we aim to shed light on novel strategies for utilizing PEVs as therapeutic agents. Our goal is to underscore the importance of further fundamental and applied research into PEVs-based interventions, as innovative tools for combating a wide range of diseases linked to mitochondrial dysfunction.