Nanostructure and mechanical properties of the osteocyte lacunar-canalicular network-associated bone matrix revealed by quantitative nanomechanical mapping

Osteocytes are the main bone cells embedded in the bone matrix where they form a large surface-area network called the lacunar-canalicular network (LCN), interconnecting their resident spaces with the lacunae by the canaliculi. Increasing evidence points toward osteocytes playing a pivotal role in maintaining bone quality. On the one hand, osteocytes transmit mechanical strain and microenvironmental signals through the LCN to regulate the activity of osteoblasts and osteoclasts; on the other hand, osteocytes are suggested to be able to remodel the LCN-associated bone matrix. However, due to the challenges involved in the assessment and characterization of the LCN-associated bone matrix, little is known about its structure and the corresponding mechanical properties. In this work, we used quantitative nanomechanical mapping, backscattered electron imaging, and nanoindentation to characterize the LCN-associated bone matrix. The results show that the techniques can be used to probe the LCN-associated bone matrix. Nanoindentation and quantitative mechanical mapping reveal spatially inhomogeneous mechanical properties of the bone matrix associated with the osteocyte lacunae and canaliculi. The obtained nano-topography and corresponding nano-mechanical maps reveal altered mechanical properties in the immediate vicinity of the osteocyte lacunae and canaliculi, which cannot be explained solely by the topographic change.