Relationship to Muscle
Skeletal interactions with muscle are also worth noting. A close functional and developmental relationship between bone and muscle has been appreciated for decades, which is not too surprising given their physical proximity and common cell origin and function (osteoblasts, adipocytes, myocytes, and chondrocytes are all derived from the same mesenchymal cell precursors).
The muscle-bone relationship is largely mechanical—driven by contractile muscle forces on bone—and important for maintaining bone health. However, there is evidence that muscle tissue itself acts as an endocrine organ, secreting a wide variety of growth factors and cytokines that may have the potential to alter bone metabolism.
Integrating muscle and bone biology to provide a multidisciplinary approach to research facilitates our understanding of the mechanism of action of emerging new targets in drug development, especially those designed to treat age-related muscle-wasting disorders and devastating childhood diseases such as Duchenne muscular dystrophy. Regulatory agencies are requesting comprehensive testing of new therapeutics intended for juvenile or young adult populations in order to evaluate the effects of a compound on the growing skeleton and ensure its safety.
Finally, there is a growing appreciation for the fact that many bone cell-signaling pathways are common to other cell types, and therefore therapeutics targeting a specific pathway may have off-target or downstream effects on bone, adding to the complexity of drug development and safety testing.
We lose weight: we lose bone; we build muscle: we build bone; we become diabetic: bones become fragile. Bone fragility and treating the consequences of fracture is a major public health concern costing millions of annual tax dollars, underscoring the need to ensure that nutraceuticals and pharmaceuticals are safe or beneficial for the skeleton.