Search

Once prostate cancer cells metastasize to bone, they perceive approximately 2 kPa compression. We hypothesize that 2 kPa compression stimulates the epithelial-to-mesenchymal transition (EMT) of prostate cancer cells and alters their production of paracrine signals to affect osteoclast and osteoblast behavior. Human DU145 prostate cancer cells were subjected to 2 kPa compression for 2 days. Compression decreased expression of 2 epithelial genes, 5 out of 13 mesenchymal genes, and increased 2 mesenchymal genes by DU145 cells, as quantified by qPCR. Conditioned medium (CM) of DU145 cells was added to human monocytes that were stimulated to differentiate into osteoclasts for 21 days. CM from compressed DU145 cells decreased osteoclast resorptive activity by 38% but did not affect osteoclast size and number compared to CM from non-compressed cells. CM was also added to human adipose stromal cells, grown in osteogenic medium. CM of compressed DU145 cells increased bone nodule production (Alizarin Red) by osteoblasts from four out of six donors. Compression did not affect IL6 or TNF-alpha production by PC DU145 cells. Our data suggest that compression affects EMT-related gene expression in DU145 cells, and alters their production of paracrine signals to decrease osteoclast resorptive activity while increasing mineralization by osteoblasts is donor dependent. This observation gives further insight in the altered behavior of PC cells upon mechanical stimuli, which could provide novel leads for therapies, preventing bone metastases., Funding Agencies|MechanoCHIP

Muscle stem cells (MuSCs) are involved in muscle maintenance and regeneration. Mechanically loaded MuSCs within their native niche undergo tensile and shear deformations, but how MuSCs sense mechanical stimuli and translate these into biochemical signals regulating function and fate is still poorly understood. We aimed to investigate whether the glycocalyx is involved in the MuSC mechanoresponse, and whether MuSC morphology affects mechanical loading-induced pressure, shear stress, and fluid velocity distribution. FSS-induced deformation of active proliferating MuSCs (myoblasts) with intact or degraded glycocalyx was assessed by live-cell imaging. Glycocalyx-degradation did not significantly affect nitric oxide production, but reduced FSS-induced myoblast deformation and modulated gene expression. Finite-element analysis revealed that the distribution of FSS-induced pressure, shear stress, and fluid velocity on myoblasts was non-uniform, and the magnitude depended on myoblast morphology and apex-height. In conclusion, our results suggest that the glycocalyx does not play a role in NO production in myoblasts but might impact mechanotransduction and gene expression, which needs further investigation. Future studies will unravel the underlying mechanism by which the glycocalyx affects FSS-induced myoblast deformation, which might be related to increased drag forces. Moreover, MuSCs with varying apex-height experience different levels of FSS-induced pressure, shear stress, and fluid velocity, suggesting differential responsiveness to fluid shear forces.

To date, it is unclear how fluid dynamics stimulate mechanosensory cells to induce an osteoprotective or osteodestructive response. We investigated how murine hematopoietic progenitor cells respond to 2 minutes of dynamic fluid flow stimulation with a precisely controlled sequence of fluid shear stresses. The response was quantified by measuring extracellular adenosine triphosphate (ATP), immunocytochemistry of Piezo1, and sarcoplasmic/endoplasmic Ca2+ reticulum ATPase 2 (SERCA2), and by the ability of soluble factors produced by mechanically stimulated cells to modulate osteoclast differentiation. We rejected our initial hypothesis that peak wall shear stress rate determines the response of hematopoietic progenitor cells to dynamic fluid shear stress, as it had only a minor correlation with the abovementioned parameters. Low stimulus amplitudes corresponded to activation of Piezo1, SERCA2, low concentrations of extracellular ATP, and inhibition of osteoclastogenesis and resorption area, while high amplitudes generally corresponded to osteodestructive responses. At a given amplitude (3 Pa) and waveform (square), the duration of individual stimuli (duty cycle) showed a strong correlation with the release of ATP and osteoclast number and resorption area. Collectively, our data suggest that hematopoietic progenitor cells respond in a viscoelastic manner to loading, since a combination of high shear stress amplitude and prolonged duty cycle is needed to trigger an osteodestructive response. Plain Language Summary In case of painful joints or missing teeth, the current intervention is to replace them with an implant to keep a high-quality lifestyle. When exercising or chewing, the cells in the bone around the implant experience mechanical loading. This loading generally supports bone formation to strengthen the bone and prevent breaking, but can also stimulate bone loss when the mechanical loading becomes too high around orthopedic and dental implants. We still do not fu, Funding Agencies|Vetenskapsradet (Swedish Research Council Formas) [2016-01822, 2016-06097, 521-20132593]; VINNOVA (Swedish Governmental Agency for Innovation Systems)Vinnova [2012-04409]