# An in vivo assay for osteoclast activity using mouse calvaria

## TL;DR

This paper introduces a new in vivo method to measure osteoclast activity in mice using micro-CT scans of calvaria bone resorption.

## Contribution

A novel in vivo assay for directly measuring osteoclast activity in mouse calvaria using micro-computed tomography.

## Key findings

- Localized RANKL injection induces osteoclast-mediated bone resorption in mouse calvaria.
- Micro-CT and 3D analysis quantify resorption pits and bone loss volume effectively.
- The method was validated using zoledronic acid, a known osteoporosis drug.

## Abstract

Osteoclasts are essential for maintaining healthy bone. Pathological elevation of osteoclastogenesis or osteoclast activity can cause osteoporosis and increase the risk of bone fracture. However, a few options are available for directly measuring osteoclast activity in vivo to test interventions that may affect osteoclasts. Here, we describe an in vivo method to measure osteoclast‐mediated bone loss targeted at normal mouse calvaria. The method employs a novel procedure for measuring osteoclast resorption pits using micro‐computed tomography. The potential utility of this mouse calvaria model to assess therapies targeting osteoclasts was validated using zoledronic acid, which is a nitrogen‐containing bisphosphonate drug used to treat osteoporosis.

This study describes a novel method for measuring osteoclast‐mediated bone resorption in vivo using a mouse model. Localized injection of RANKL in a basement membrane matrix above the cranium induced osteoclast‐mediated bone resorption. Utilizing micro‐computed tomography and a semiautomated three‐dimensional analysis program, osteoclast resorption pit number, pit volume, and total resorbed bone volume were quantified to measure osteoclast activity.