Quantitative and reliable in vitro method combining scanning electron microscopy and image analysis for the screening of osteotropic modulators
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Updated: Aug 8, 2026
Multimodal Approach to Assess Bone Regeneration and Scaffold Performance
Published on: February 13, 2026
Gaël Grimandi1, Assem Soueidan, Abed Aktam Anjrini
1Inserm, UMRS 791, Laboratoire d'ingénierie Ostéo-articulaire et dentaire (LIOAD), Univ Nantes, Faculté de chirurgie dentaire, F-44042 Nantes, France.
Abstract:
The increased generation and up-regulated activity of bone resorbing cells (osteoclasts) play a part in the impairment of bone remodeling in many bone diseases. Numerous drugs (bisphosphonates, calcitonin, selective estrogen receptor modulators) have been proposed to inhibit this increased osteoclastic activity. In this report, we describe a pit resorption assay quantified by scanning electron microscopy coupled with image analysis. Total rabbit bone cells with large numbers of osteoclasts were cultured on dentin slices. The whole surface of the dentin slice was scanned and both the number of resorption pits and the total resorbed surface area were measured. Resorption pits appeared at 48 h and increased gradually up to 96 h. Despite the observation of a strong correlation between the total resorption area and the number of pits, we suggest that area measurement is the most relevant marker for osteoclastic activity. Osteotropic factors stimulating or inhibiting osteoclastic activity were used to test the variations in resorption activity as measured with our method. This reproducible and sensitive quantitative method is a valuable tool for screening for osteoclastic inhibitors and, more generally, for investigating bone modulators.
Insights
A new pit resorption assay quantifies osteoclast activity in bone diseases. Measuring resorbed surface area is the most relevant marker for assessing bone resorption, aiding in the development of new bone disease treatments.
Area of Science:
- Bone biology and disease
- Cellular and molecular mechanisms of bone remodeling
Background:
- Increased osteoclast activity impairs bone remodeling in various bone diseases.
- Existing drugs like bisphosphonates aim to inhibit osteoclast activity.
- A sensitive assay is needed to quantify osteoclast function.
Purpose of the Study:
- To develop and validate a quantitative pit resorption assay for measuring osteoclast activity.
- To determine the most relevant metric for osteoclast activity: pit number or resorbed area.
- To assess the assay's utility for screening bone modulators.
Main Methods:
- Culturing rabbit bone cells rich in osteoclasts on dentin slices.
- Quantifying resorption pits using scanning electron microscopy and image analysis.
- Measuring both the number of resorption pits and the total resorbed surface area.
Main Results:
- Resorption pits formed by 48 hours and increased up to 96 hours.
- A strong correlation was observed between total resorbed area and pit number.
- Resorbed surface area was identified as the most relevant marker of osteoclast activity.
Conclusions:
- The developed pit resorption assay is reproducible and sensitive.
- This quantitative method is valuable for screening osteoclast inhibitors.
- The assay can be broadly applied to investigate bone modulators and bone disease mechanisms.
