Platelet Rich Plasma and Culture Configuration Affect the Matrix Forming Phenotype of Bone Marrow Stromal Cells

We aim to examine the influence of platelet rich plasma (PRP) and spatial cues in cartilage/bone matrix forming proteins, and to evaluate the mitotic and chemotactic potential of PRP on human mesenchymal stem cells (hMSCs). Directed cell migration towards PRP gradients was assessed in chemotactic chambers, and recorded by time-lapse microscopy. hMSCs cultured in three-dimensional (3D) scaffolds were visualized by scanning electron microscopy; Hoechst dye was used to confirm cell confluence in 3D-constructs and monolayers before experimental treatment. MSCs were treated with 10% PRP lysate or 10% PRP lysate supplemented with TGF-β-based differentiation medium. The expression of cartilage (COL2A1, Sox9, ACAN, COMP), and bone (COL1A1, VEGF, COL10A1, Runx2) fundamental genes was assessed by real time PCR in monolayers and 3D-constructs. PRP had mitotic (p < 0.001), and chemotactic effect on hMSCs, Ralyleigh test p = 1.02E - 10. Two and three-week exposure of MSCs to PRP secretome in 3D-constructs or monolayers decreased Sox9 expression (p < 0.001 and p = 0.050) and COL2A1, (p = 0.011 and p = 0.019). MSCs in monolayers exposed to PRP showed increased ACAN (p = 0.050) and COMP (p < 0.001). Adding TGF-β-based differentiation medium to PRP increased COMP, and COL2A1 expression at gene and protein level, but merely in 3D-constructs, p < 0.001. TGF-β addition to monolayers reduced Sox9 (p < 0.001), aggrecan (p = 0.004), and VEGF (p = 0.004). Cells exposed to PRP showed no changes in hypertrophy associated genes in either monolayers or 3D-constructs. Our study suggests hMSCs have high-degree of plasticity having the potential to change their matrix-forming phenotype when exposed to PRP and according to spatial configuration.