II.

No abstract

II.

It is commonly accepted that bone marrow-derived stem cells (BMSCs) have to be expanded in vitro, but a prolonged time in culture decreases their multilineage potential. Mechanical and biological stimuli have been used to improve their osteogenic potential. While long-term stimulation has been shown to improve osteogenic differentiation, it remains to be seen whether short-term stimulation is also sufficient.We investigated the influence of 24 hours' cyclic loading (0.05Hz, 4kPa) on gene expression of human BMSCs in three-dimensional fibrin-DMEM constructs (n=7) in a compression bioreactor using DNA-array technology. Expression of the following genes showed a significant increase after mechanical stimulation: 2.6-fold osteopontin (OPN) and integrin-β1 (ITGB1), 2.2-fold transforming growth factor-β-receptor 1 (TGF-β-R1) and 2.4-fold SMAD5 expression, compared to controls without mechanical stimulation (p<0.05 each). Platelet-derived growth factor-α (PDGF-α ) and annexin-V were also significantly overexpressed, the mechanical stimulation resulting in a 1.8-fold and 1.6-fold expression (p<0.05).Cells were identified as osteoblast precursors with a high proliferative capacity. Given the identical in-vitro environment for both groups, the increase in gene expression has been interpreted as a direct influence of cyclic mechanical stimulation on osteogenic differentiation. It may be postulated that short-term mechanical stimulation results in an improved osseous integration of tissue engineered grafts in bone defect healing.

It increased significantly in all patients without being different between the groups (AL, 48.2→83.6; TG, 50.8→85.9). Patients in the TG group had a higher sTnI than those in the AL group 24 h postoperatively (21.6 vs. 10.9 nmol/ml, p = 0.022). The AL approach results in a reduced muscle traumatization compared with the TG approach, without this being revealed by the HHS.