Speaker
Description
Bone is a fascinating material fulfilling mechanical, hematopoiesis, mineral storage and hormonal functions. A constant supply of nutrients and mineralization precursors is fundamental to its physiological function with the osteocyte lacuno-canalicular network (LCN) as one of the key players [1]. The osteocytes are embedded in the bone matrix with the cell body housed in lacunae and their dendritic cell processes extending in canaliculi and connecting to other osteocytes via gap junctions. The canaliculi are long canals over several $\mu$m with diameters around 300 nm. In humans the total canalicular length adds up to 2x10$^5$ km (corresponding to a density of 74 km/cm$^3$) leading to an enormous inner surface estimated at 215 m$^2$ [2,3]. In this presentation, I will show how the LCN can be measured and reconstructed in 3D using fluorescent rhodamine staining and confocal laser scanning microscopy. Measurement of human iliac crest autopsy samples from donors aged between 50 and 95 years showed that the local network density depends on tissue age, rather than on donor age [4]. Interestingly, all donors of our cohort showed local network defects, like engorged and distorted canaliculi or large overstained regions. These defects can be further characterized using high-resolution techniques. Focused ion beam-SEM investigations showed a 4-fold increase in the amount of non-mineralized tissue in defective compared to typical regions [4]. X-ray nano-holotomography measurements at the ESRF, Grenoble, confirmed these results showing that non-mineralized regions can be frequently found close to normally mineralized ones. While in the investigated cohort such mineralization defects could be found in donors of all ages, their size increased with age. This might be a contributor to the loss of bone material quality in the elderly.
[1] Raguin et al., Adv. Sci. 10, 2301231 (2023)
[2] Buenzli & Sims, Bone 75, 144 (2015)
[3] Repp et al., Bone Rep. 6, 101 (2017)
[4] Jones et al., Acta Biomater. 209, 493 (2026)