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ligands on osteoblastic cells, we evaluated celi survival in the MC3T3-E1 celi linę following a 96 h incubation with increasing amounts of each agent. As shown in Figurę 3.4A and B, both hexarelin (from 10'⁹ to 10'⁷ M) and TSP-1 (at 500 and 600 ng/mL) increased MC3T3-E1 celi proliferation by about 50% compared to untreated control. After treatment with TSP-1 at 600 ng/mL and hexarelin at 10'⁹ M, a marked enhancement of proliferation was observed in WT but not in Cd36-nuli MSCs (Fig. 3.4C, D). Since both ligands are known to induce the expression and/or activity of the PPARy transcription factor through binding to CD36 (Demers et al., 2008), we investigated whether the expression of this factor was affected in the nuli cells.

It was found that Ppary is overexpressed in Cd36-nuli MSCs (Fig. 3.5A); moreover, Gli-I, a member of SHH signaling pathway implicated in angiogenic differentiation of bonę marrow derived cells (Renault et al., 2010) was also upregulated in Cd36-null MSCs (Fig. 3.5B). Another possible important transcription factor in the regulation of celi cycle is forkhead-Ol (FOX01) which is implicated in a wide rangę of cellular and developmental processes (van der Vos et Coffer, 2008). Foxol was over-expressed by 2.5 fold in Cd36-nu\\ MSCs compared to WT cells counterpart (Fig. 3.5C). Interestingly, both GLI-I and FOX01 have been reported to interact with the Wnt signaling pathway (Iyer et al., 2013; Nakamura et al., 2013); considering the importance of Wnt signaling in bonę metabolism, we explored whether this pathway was affected by CD36 deficiency.

3.6.4 Wnt signaling pathway

Since Wnt signaling has been identified as a major pathway in MSCs commitment and differentiation into the osteoblastic lineage (Gordon et Nusse, 2006), we analysed this pathway in WT and Cd36-nuli MSCs. As shown in Fig. 3.6A, gene expression of Wnt receptor Lrp5/6 and Wnt secreted ligand Rspo-2, was comparable in both