BoneKEy Reports | BoneKEy Watch
Bisphosphonates: bone mineral affinity affects skeletal distribution
DOI:10.1038/bonekey.2012.130
Bisphosphonates (BPs) are able to restrict osteoclast activity because they have a strong affinity for bone mineral. To investigate how different BPs localize in bone due to their different affinities for bone mineral, researchers in this study looked at how fluorescently labeled risedronate (high affinity) bound to bone mineral surfaces in growing rats compared with two lower-affinity analogues.
One day after the BPs were administered, all were detected on the endocortical (forming) surfaces as opposed to the periosteal (resorbing) surfaces. The lower affinity analogues bound preferentially to resorption lacunae, whereas risedronate was distributed more generally on the resorbing surface.
Differences were also seen at the forming surfaces, where the ability of the BP to penetrate the mineralizing osteoid was inversely correlated with its affinity for bone mineral. The lower-affinity analogues, in particular, targeted lacunae deep within the cortical bone, including the osteocyte lacunar walls, which suggests that these BPs penetrate the osteocyte canalicular network more effectively. These differences persisted at 7 days after drug administration, by which time fluorescent compounds had become incorporated into newly formed bone.
Editor's comment: This study suggests that the affinity of BPs for bone mineral relates to their distribution and redistribution. These effects may be of clinical relevance and may explain why BPs show differences in longevity of action between individual patients.
Subject terms: Bisphosphonates; osteoclasts; bone remodeling
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