| Low-magnitude high-frequency (LMHF) vibrations show anabolic effects On bone when applied to the whole body in both animal and human studies. As such, it is being explored as a treatment for osteoporosis and osteopenia in vulnerable populations. In humans, whole-body vibrations have shown modest increases in the bone mineral density of postmenopausal women, children and adolescents, though it had no effect in young adults. These conflicting results prompted long term studies to establish the optimal frequency, magnitude and duration of the vibration. In vitro cellular studies have been carried out to study the physical and biologic mechanisms underlining these outcomes. But there are conflicting results of LMHF vibrations when applied to cell culture as well, with some studies showing no effect when cells are cultured in 2D monolayer as opposed to other studies reporting increased differentiation of progenitor cells towards an osteogenic lineage when cells are cultured in 3D scaffolds. It is worthy of note that the majority of scaffolds used in these studies are from natural sources, which in and of themselves may promote differentiation due to biochemical and microarchitectural cues. This master thesis seeks to explore the effect of Low magnitude high frequency vibrations on human mesenchymal stem cells (hMSCs) encapsulated within a 3D microsphere structure composed of synthetic polymer polyethylene glycol diacrylate (PEGDA). Synthetic PEGDA has no inherent cues and can serve as a "blank slate" to the entrapped cells. In this study, three different intensity vibrations of 0.3g, 3g and 6g at 100Hz were applied for 24 hours to the encapsulated hMSCs by means of a vibration unit. These cells were subsequently tested for adipocyte, chondrocyte and osteoblast differentiation over a period of 21 days. There was early onset of osteogenic differentiation in 0.3 g and 3 g test samples compared to control samples, while there was no osteogenic differentiation at all observed in 6g test samples. In addition, as the magnitude of acceleration applied increased, the osteogenic differentiation of the encapsulated hMSCs decreased. Thus, LMHF vibrations with low accelerations accelerated the osteogenic differentiation of encapsulated hMSCs, indicating that hydrogel-encapsulated hMSCs may mimic the whole body response to vibration, which paves the way for further in vitro LMHF experiments with encapsulated cells. |
