Human platelet lysate biotherapy for traumatic brain injury: preclinical assessment

Traumatic brain injury 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 traumatic brain injury can be addressed not by a single therapeutic approach, but rather by a synergistic biotherapy capable of activating a complementary set of signaling pathways and providing synergistic neuroprotective, anti-inflammatory, antioxidative, and neurorestorative activities. Human platelet lysate might fulfill these requirements as it is comprised of a plethora of biomolecules readily accessible as a traumatic brain injury biotherapy. In the present study, we have tested the therapeutic potential of human platelet lysate using in vitro and in vivo models of traumatic brain injury. 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 minutes 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 ca. 1-50 ng/mL levels. We demonstrate, using the two mouse models of traumatic brain injury that topical application and intranasal platelet lysate consistently improved mice 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 HPPL reversed several pathways promoted by both CCI and CBS and related to transport, post-synaptic 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.