Stimulation of 3D osteogenesis by mesenchymal stem cells using a nanovibrational bioreactor.

Bone grafts are one of the most commonly transplanted tissues. However, autologous grafts are in short supply, and can be associated with pain and donor-site morbidity. The creation of tissue-engineered bone grafts could help to fulfil clinical demand and provide a crucial resource for drug screening. Here, we show that vibrations of nanoscale amplitude provided by a newly developed bioreactor can differentiate a potential autologous cell source, mesenchymal stem cells (MSCs), into mineralized tissue in 3D. We demonstrate that nanoscale mechanotransduction can stimulate osteogenesis independently of other environmental factors, such as matrix rigidity. We show this by generating mineralized matrix from MSCs seeded in collagen gels with stiffness an order of magnitude below the stiffness of gels needed to induce bone formation in vitro. Our approach is scalable and can be compatible with 3D scaffolds.

Publisher Correction: Stimulation of 3D osteogenesis by mesenchymal stem cells using a nanovibrational bioreactor.

In the version of this Article originally published, in Fig. 4f, the asterisk was missing; in Fig. 6a-c, the labels 'Wnt/ß-catenin signalling', 'Wnt/Ca+ pathway' and 'ERK' and their associated lines/arrows were missing; and in Fig. 6d and in the sentence beginning "In MSCs that were...", 'myosin' and 'nanostimulated', respectively, were spelt incorrectly. These errors have now been corrected in all versions of the Article.

Use of nanoscale mechanical stimulation for control and manipulation of cell behaviour.

The ability to control cell behaviour, cell fate and simulate reliable tissue models in vitro remains a significant challenge yet is crucial for various applications of high throughput screening e.g. drug discovery. Mechanotransduction (the ability of cells to convert mechanical forces in their environment to biochemical signalling) represents an alternative mechanism to attain this control with such studies developing techniques to reproducibly control the mechanical environment in techniques which have potential to be scaled. In this review, the use of techniques such as finite element modelling and precision interferometric measurement are examined to provide context for a novel technique based on nanoscale vibration, also known as "nanokicking". Studies have shown this stimulus to alter cellular responses in both endothelial and mesenchymal stem cells (MSCs), particularly in increased proliferation rate and induced osteogenesis respectively. Endothelial cell lines were exposed to nanoscale vibration amplitudes across a frequency range of 1-100 Hz, and MSCs primarily at 1 kHz. This technique provides significant potential benefits over existing technologies, as cellular responses can be initiated without the use of expensive engineering techniques and/or chemical induction factors. Due to the reproducible and scalable nature of the apparatus it is conceivable that nanokicking could be used for controlling cell behaviour within a wide array of high throughput procedures in the research environment, within drug discovery, and for clinical/therapeutic applications. STATEMENT OF SIGNIFICANCE: The results discussed within this article summarise the potential benefits of using nanoscale vibration protocols for controlling cell behaviour. There is a significant need for reliable tissue models within the clinical and pharma industries, and the control of cell behaviour and stem cell differentiation would be highly beneficial. The full potential of this method of controlling cell behaviour has not yet been realised.

Nanoscale stimulation of osteoblastogenesis from mesenchymal stem cells: nanotopography and nanokicking.

AIM: Mesenchymal stem cells (MSCs) have large regenerative potential to replace damaged cells from several tissues along the mesodermal lineage. The potency of these cells promises to change the longer term prognosis for many degenerative conditions currently suffered by our aging population. We have endeavored to demonstrate our ability to induce osteoblatogenesis in MSCs using high-frequency (1000-5000 Hz) piezo-driven nanodisplacements (16-30 nm displacements) in a vertical direction. MATERIALS & METHODS: Osteoblastogenesis has been determined by the upregulation of osteoblasic genes such as osteonectin (ONN), RUNX2 and Osterix, assessed via quantitative real-time PCR; the increase of osteocalcin (OCN) and osteopontin (OPN) at the protein level and the deposition of calcium phosphate determined by histological staining. RESULTS: Intriguingly, we have observed a relationship between nanotopography and piezo-stimulated mechanotransduction and possibly see evidence of two differing osteogenic mechanisms at work. These data provide confidence in nanomechanotransduction for stem cell differentiation without dependence on soluble factors and complex chemistries. CONCLUSION: In the future it is envisaged that this technology may have beneficial therapeutic applications in the healthcare industry, for conditions whose overall phenotype maybe characterized by weak or damaged bones (e.g., osteoporosis and bone fractures), and which can benefit from having an increased number of osteoblastic cells in vivo.