Table 3.

Examples of evidence of human platelet trophic factors contributions to central nervous system (CNS) repair

Pathology	Platelet preparations	Model	Biological outcomes	References
Stroke	Human platelets isolated from platelet-rich plasma, resuspended in PBS, and subjected to three freeze–thaw cycles	• In vivo: focal ischaemia in focal Male spontaneously hypertensive rats produced by permanent distal middle cerebral artery occlusion (PMCAO) • Injection to the lateral ventricle	• Increases eNSC proliferation and angiogenesis in the SVZ and in the peri-lesion cortex • Improved behavioral deficits	[69]
	Human platelet microparticles and exosomes prepared from thrombin-activated human platelets and isolated by ultracentrifugation (100′000 × g)	• In vivo PMCAO model in adult spontaneously hypertensive rats • Topical application by biodegradable polymer	• Triggers neurogenesis and angiogenesis at the infarct boundary zone • Improves behavioral deficits	[151]
Alzheimer’s disease	Human plasma rich in growth factors obtained by calcium chloride treatment in glass tubes and centrifuged	• In vitro: Primary cortical and hippocampal neurons • In vivo: intranasal delivery to double-transgenic APP/PS1 mouse model	• Enhances proliferation of and survival of primary neuronal cultures • Enhances hippocampal neurogenesis and reduces Aβ-induced neurodegeneration	[65, 66]
Parkinson’s disease	Human plasma rich in growth factors obtained by calcium chloride treatment in glass tubes and centrifuged [65]	• In vitro: human dopaminergic neuroblastoma cell line (SH-SY5Y) treated with MPP +  • In vivo: MPTP mice model. Intranasal administration	• Protects dopaminergic neurons from MPP + toxicity • Prevents striatal dopaminergic neurons and dopamine depletion from MPTP toxicity; diminishes the inflammatory responses and improves motor performance, associated with reduction in NF-κB activation, and inflammatory markers expression in the substantia nigra	[67]
	Human platelets isolated from clinical-grade platelet concentrates and heat-treated (56 °C, 30 min) (HPPL)	• In vitro: dopaminergic LUHMES cells exposed to MPP + ; BV2 microglial cells with/without LPS stimulation • In vivo: MPTP mice model. Intranasal administration	• Protects dopaminergic LUHMES neurons against MPP + neurotoxin; protects BV2 cells against inflammation • Diffuses in the striatum and cortex; protects the substantia nigra and striatum against MPTP intoxication; no neuroinflammation	[49]
	HPPL preparation [49]	• In vitro: LUHMES cells exposed to various specific pro-oxidants and regulated cell death inducers: MPP + , menadione, elastin, staurosporine, and rapamycin	• Protects LUHMES cells against erastin, menadione and MPP + in part through an activation of the Akt and MEK pathways	[64]
	HPPL preparation [49] made from outdated pathogen-reduced (Intercept) clinical-grade platelet concentrates	• In vitro: dopaminergic Lund human mesencephalic (LUHMES) cells; primary cortical/hippocampal neurons	• Non-toxic to LUHMES cells nor primary neurons • Enhances the expression of tyrosine hydroxylase and neuron-specific enolase in LUHMES cells, and protects against ferroptosis induced by erastin • No detrimental impact on synaptic protein expression in primary neurons • No inflammation of BV2 microglial cells	[53]
Brain injuries	Human platelet microparticles and exosomes preparation [151]	• In vitro assay of neural stem cell (NSC) proliferation, survival and differentiation	• Increases NSC proliferation survival, and differentiation, partially through ERK and Akt signalling	[224]
	Pooled HPL prepared from  outdated platelet concentrates by two freeze–thaw cycles and centrifugation at 4000 × g	• In vitro: Effect on proliferating subependymal zone (SEZ), derived NSPCs	• Increases the numbers of in vitro proliferating adult rat SEZ-derived NPCs and reduces apoptosis without affecting proliferative or lineage-differentiation capacity	[217]
	HPPL preparation [49] made from outdated pathogen-reduced (Intercept) clinical-grade platelet concentrates	• In vitro: non-differentiated SH-SY5Y neuroblastoma cells; EA-hy926 human endothelial cell; BV2 microglial cells stimulated or not with LPS	• Non-toxic to SH-SY5Y, BV-2 and EA-hy926 cells • Stimulates wound healing and neuronal differentiation of SH-SY5Y into neurons • Does not trigger TNF or COX-2 inflammatory markers by BV-2 microglia, and decreases inflammation after LPS stimulation	[50]
	HPPL preparation [49]	• In vitro: scratch assay performed using differentiated SH-SY5Y neuroblastoma cell cultures • In vivo: two mouse models of TBI (controlled cortical impact and in-house cortical brain scratch) injury. One topical administration in the lesioned area followed by daily intranasal administration for 6 days	• Stimulates wound healing of differentiated SH-SY5Y neuroblastoma • Improves mouse motor function • Mitigates cortical neuroinflammation, and oxidative stress in the injured area • Reduces loss of cortical synaptic proteins • Reverses several pathways promoted by the TBI models related to transport, postsynaptic density, mitochondria or lipid metabolism	[51]
	EVs isolated from four HPL using size-exclusion chromatography	• In vitro: wound healing assay of SH-SY5Y neuroblastoma cells; mice primary neuronal cells	• Non-toxic to SH-SY5Y neuronal cells • Differentially promotes cell growth and migration in a wound healing model of SH-SY5Y cells • Stimulates network formation in primary neuronal cultures	[235]
Amyotrophic lateral sclerosis	HPPL preparation 49	• In vitro: NSC34 motoneurons exposed to various specific pro-oxidants and regulated cell death inducers: MPP + , menadione, elastin, staurosporine, and rapamycin	• Protects NSC34 motoneurons against STS and menadione toxicity in part through activation of the Akt and MEK pathways	[64]
	HPL prepared from pooled human platelet concentrates, sero-converted and heat-treated (HHPL) and its sub-fractions	• In vitro: motoneuron cultures isolated from E12.5 spinal cord of Hb9:: GFP or C57BL/6 embryos and exposed to erastin, STS or menadione) or glutamate • In vivo: FVB Tg(Sod1*G86R)M1Jwg/J mice; intracerebroventricular administration of HHPL; intranasal administration of < 3 kDa fraction	• HPPL and sub-fractions exerts Akt-dependent neuroprotection, strong anti-apoptotic and anti-ferroptotic actions on neuronal cells • The < 3 kDa fraction has GPX4 dependent anti-ferroptotic properties • Intracerebral delivery of HHPL or intranasal administration of < 3 kDa fraction increases the lifespan of SOD1G86R mice	[236]

APP/PS1 Amyloid precursor protein/presenilin-1, eNSC embryonic neural stem cells, MPP + 1-methyl-4-phenylpyridinium, MPTP 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, LPS lipopolysaccharides, LUHMES Lund human mesencephalic, NF-κB nuclear transcription factor-κB, PMCAO permanent distal middle cerebral artery occlusion