Platelet derivatives: from bench to bedside. Molecular characterization of the effect of platelet derivatives on cells and their use for skin chronic ulcer treatment

The present paper is related to the field of cell culture medium supplements. In particular, it refers to (i) an heparin-free human Platelet Lysate devoid of serum or plasma components (v-PL) and (ii) an heparin-free human serum devoid of platelet lysate components (Pl-s), and to their use as single components or in combination in primary or cell line cultures. Human Mesenchymal Stem Cells (MSC) primary cultures were obtained from adipose, bonemarrow and umbilical cord. The cumulative cell doubling number in the presence of the different culture medium supplements was determined at different culture times. In general, MSC expanded in the presence of Pl-s alone showed a low or no proliferation in comparison to cells grown with the combination of Pl-s and v-PL. Confluent, growth arrested cells, either human MSC or human articular chondrocytes, treated with v-PL resumed proliferation, whereas control cultures, not supplemented with v-PL, remained quiescent and did not proliferate. Interestingly, signal transduction pathways distinctive of proliferation were activated also in cells treated with v-PL in the absence of serum, when cell proliferation did not occur, indicating that v-PL could induce the cell re-entry in the cell cycle (cell commitment), but the presence of serum proteins was an indispensable requirement for cell proliferation to happen. Indeed, Pl-s alone supported cell growth in constitutively activated cell lines (U-937, HeLa, HaCaT, V-79) regardless the co-presence of v- PL. Plasma and plasma-derived serum were equally able to sustain cell proliferation although, for cells cultured in adhesion, the Pl-s was more efficient than the plasma from which it was derived. Moreover, cell expanded in the presence of the new additives maintained their differentiation potential and did not show alterations in their karyotype. In a different work we showed how Platelet Lysate (PL) derived from Platelet Rich Plasma (PRP) was capable to support growth and isolation of MSC (Mesenchymal Stromal Cell). However, the molecular mechanisms involved in these processes were still unknown. We focused our attention on a family of highly conserved proteins involved in different cellular mechanisms such as cell growth, proliferation and apoptosis, MYC's family. In particular, MYC is a transcription factor that activates or inhibits the transcription of several genes by interacting with other proteins. The three proteins of C-MYC gene have the same c-terminal part, differing in the N-terminal region due to an alternative translation at the start site. The three forms are C-MYC1, C-MYC2 and CMYCS, differently expressed during cell growth.