Some fish have healthy bones despite missing the specific brain cells that every other vertebrate needs to build and repair them.
In humans and most other animals, cells called osteocytes are the essential managers that tell the body when to strengthen or break down bone. Medaka fish are anosteocytic, meaning they lack these cells entirely, yet their skeletons remain perfectly strong. Researchers discovered that their bone-building osteoblast cells have evolved to take over these mechanical sensing and regulatory duties. This proves that the brain of the bone is not a universal requirement in nature and can be replaced by other cell types. Understanding how these fish manage their skeletons could lead to new treatments for human bone diseases like osteoporosis.
Maintenance of bone health by osteoblasts in the absence of osteocytes: comparative analysis of gene expression in medaka and zebrafish vertebrae
SSRN · 6730166
Osteocytes are regarded as the strain-sensing bone cells, their capacity to sense and convert mechanical loads into biological signals underpins our current understanding of how bone is (re)modelled to normalise local strains. However, most extant fish are anosteocytic and lack osteocytes, yet their bone structure and (re)modelling abilities remain unimpeded, sitting uncomfortably with this paradigm. We propose that alternative, non-osteocytic, mechano-sensing mechanisms are present in anosteocy