Novel explant model to study mechanotransduction and cell–cell communication

Abstract

To understand in situ behavior of osteocytes, we characterized a model of osteocytes in their native bone matrix and demonstrated real-time biologic activity of osteocytes while bending the bone matrix. Using 43 male Sprague-Dawley rats, dumbbell-shaped explants were harvested from stainless steel femoral implants after 6-12 weeks and incubated in culture medium or fixed. Sixteen specimens were used to determine bone volume density (BV/TV), volumetric bone mineral density (BMD) and histology for different implantation periods. Osteocyte viability was evaluated by L-lactate dehydrogenase (LDH) activity in 12 cultured explants. Confocal microscopy was used to assess tracer diffusion in three explants and changes in osteocyte pH of a mechanically loaded explant. From 6 to 12 weeks, explant BV/TV and volumetric BMD trended up 92.5% and 101%, respectively. They were significantly and highly correlated. Tissues were uniformly intramembranous and all bone cell types were present. Explants maintained LDH activity through culture day 8. Diffusion at 200 mM was limited to 1,209 Da. Explants appeared capable of reproducing complex bone biology. This model may be useful in understanding osteocyte mechanotransduction in the context of a physiologically relevant bone matrix. ß

Low-intensity pulsed ultrasound induces apoptosis in osteoclasts: Fish scales are a suitable model for the analysis of bone metabolism by ultrasound

“…Bone consists of osteoblasts, osteoclasts, and a bone matrix, and cell-to-cell and cell-to-matrix interactions are critical for cell response to physical stress (Harter et al, 1995;Owan et al, 1997;Hoffler et al, 2006). Consequently, coculture systems that include bone matrix and both osteoclasts and osteoblasts are required to accurately assess the effect of ultrasound stimuli on bone formation and resorption.…”

Static and Dynamic Hypergravity Responses of Osteoblasts and Osteoclasts in Medaka Scales

“…Most studies using in vitro models noted osteoblastic responses to physical strain as the determinant in bone (Tjandrawinata et al, 1997;Tanaka et al, 2003). Bone consists of osteoblasts, osteoclasts, and the bone matrix, and both cell-to-cell and cell-to-matrix interactions are critical for cell response to physical stress (Harter et al, 1995;Owan et al, 1997;Hoffler et al, 2006). It was recently reported that mechanical stretch-induced calcium efflux from bone matrix and stimulated osteoblasts, suggesting that the bone matrix acts as a reservoir for mechanochemical transducers, which convert mechanical strain into a chemical signal for the onset of calcium efflux (Sun et al, 2012).…”

<b>Effects of low-intensity pulsed ultrasound on osteoclasts: Analysis with goldfish scales as a model of </b><b>bone </b>

“…As a result, osteoblastic activity significantly increased under 2-to 4-G loading by both centrifugation and vibration (26), as it did in the present study. It is known that bone matrix plays an important role in the response to physical stress (6,14,24). As teleost scale is a calcified tissue that contains osteoclasts, osteoblasts, and bone matrix (4,12,18,27), we conclude that fish scales are a suitable model for physical stimuli, including LIPUS, to examine the interaction between osteoclasts and osteoblasts.…”

“…Using the removed regenerating scales, the influence of LIPUS on osteoclasts was examined. After LIPUS treatment (20 min), the scales were incubated at 15°C for 3,6,12, and 24 h with Leibovitz's L-15 medium (Invitrogen, Grand Island, NY, USA) containing a 1% penicillin-streptomycin mixture (ICN Biomedicals, Inc., Aurora, OH, USA) and then frozen at −80°C for mRNA analysis. The LIPUS-untreated scales were incubated in the same conditions as the experimental group and compared with LIPUS-treated scales.…”