Bone ageing and the role of osteocytes

The article provides an overview of physiological and pathophysiological processes of human ageing with special respect to bone age­ ing. Ageing is characterized by changes in the proportion of osteoblasts, responsible for bone formation, and osteoclasts, responsible for bone resorption. Among other things, this results in impaired mineralization, osteoporosis and a higher risk of fractures. In recent years, studies on bone ageing have focused mainly on osteocytes, osteoblasts within bones. Until recently, osteocytes were considered mechanosensors maintaining elasticity of bone under pressure. Osteocytes, with their extensions (canals) have been shown to be metabolically very active cells. When compared to osteoblasts and osteoclasts, osteocytes are most abundant and have the longest lifes­ pan. Impaired osteocyte function has a major impact on both mineral and organic bone homeostasis. In particular, this may be due to oxidative stress and its metabolic effects, impacts on the autophagic activity of lysosomes, nucleoporins and the GHRH-GH-IGF-1-insulin axis and, probably, also on telomere shortening, lamin A gene expressions and the Klotho gene. From the above genes, especially those potentially beneficial in the prevention and treatment of osteopathies, in particular osteoporo­ sis, are searched for.

Keywords: bone ageing, osteocytes, oxidative stress, lysosome autophagy, nucleoporins, GHRH-GH -IGF-1, in­ sulin, telomeres, lamin A, Klotho gene