Non-coding RNA modulation in osteoclasts and its implications for osteoblast lineage cell behavior in a co-culture system.

The interplay between osteoblasts and osteoclasts (OCs) is a highly regulated and coordinated process essential for maintaining bone skeletal integrity and health. Disruption of this balance marks the onset of various bone disorders, such as osteoporosis. In our previous study, we demonstrated that non-coding RNAs (ncRNAs) were able to regulate OC behaviour.

Cathepsin K inhibitors promote osteoclast-osteoblast communication and engagement of osteogenesis.

Cathepsin K inhibitors are well known for their inhibitory activity against bone resorption but were also reported to preserve bone formation in clinical trials, in contrast with other bone resorption antagonists. Here, we show cathepsin K inhibitors favor the crosstalk between osteoclasts and osteoblasts and help engaging the osteogenic process required for proper bone remodeling. Therefore, we used a novel approach, co-culturing human osteoclasts and osteoblast lineage cells on bone slices and monitoring through time-lapse their response to an active site (odanacatib) or an ectosteric (T06) cathepsin K inhibitor.

Isolation and Generation of Osteoclasts.

This chapter describes the isolation, expansion, staining, and imaging of osteoclasts from murine (MKS, BKD, and MMM) and human (NS, JBO, and KS) sources. We cover in detail both traditional and more modern methods of assessing osteoclast formation and function in vitro including advances in image acquisition and automated analyses. Importantly, we provide in-depth methods for human osteoclast culture systems, methods to assess human osteoclast function, and highlight potential methodological pitfalls and ways to overcome them.

CXCR4 is a response gene for parathyroid hormone which affects osteoblast and osteoclast function in vitro.

Aims: To investigate the role of CXCR4 in response to teriparatide (TPTD) treatment in osteoblasts and osteoclasts.

Methods: Primary murine and human osteoblasts and osteoclasts, MC3T3 cell lines, and hMSC-TERT4 cell lines were treated with TPTD and/or AMD3100, a pharmacological inhibitor of CXCR4. Changes in gene expression, osteoblast viability, mobility, mineralization capacity, and alkaline phosphatase activity were investigated.

Stage-specific modulation of multinucleation, fusion, and resorption by the long non-coding RNA DLEU1 and miR-16 in human primary osteoclasts.

Osteoclasts are the only cells able to resorb all the constituents of the bone matrix. While the modulation of osteoclast activity is well established for preventing bone-related diseases, there is an increasing demand for novel classes of anti-resorption agents. Herein, we investigated non-coding RNA molecules and proposed DLEU1 and miR-16 as potential candidates for modulating osteoclast functions.

Real-time analysis of osteoclast resorption and fusion dynamics in response to bone resorption inhibitors.

Cathepsin K (CatK), an essential collagenase in osteoclasts (OCs), is a potential therapeutic target for the treatment of osteoporosis. Using live-cell imaging, we monitored the bone resorptive behaviour of OCs during dose-dependent inhibition of CatK by an ectosteric (Tanshinone IIA sulfonate) and an active site inhibitor (odanacatib). CatK inhibition caused drastic reductions in the overall resorption speed of OCs.

Aging and menopause reprogram osteoclast precursors for aggressive bone resorption.

Women gradually lose bone from the age of ~35 years, but around menopause, the rate of bone loss escalates due to increasing bone resorption and decreasing bone formation levels, rendering these individuals more prone to developing osteoporosis. The increased osteoclast activity has been linked to a reduced estrogen level and other hormonal changes. However, it is unclear whether intrinsic changes in osteoclast precursors around menopause can also explain the increased osteoclast activity.

Catabolic activity of osteoblast lineage cells contributes to osteoclastic bone resorption .

Osteoblast lineage cells in human bone were recently shown to colonize eroded bone surfaces and to closely interact with osteoclasts. They proved to be identical to reversal cells and are believed to differentiate into bone-forming osteoblasts thereby coupling resorption and formation. However, they also exert catabolic activity that contributes to osteoclastic bone resorption, but this has not received much attention.