Developing bones are differentially affected by compromised skeletal muscle formation

Abstract

Mechanical forces are essential for normal adult bone function and repair, but the impact of prenatal muscle contractions on bone development remains to be explored in depth in mammalian model systems. In this study, we analyze skeletogenesis in two ‘muscleless’ mouse mutant models in which the formation of skeletal muscle development is disrupted; Myf5nlacZ/nlacZ:MyoD−/− and Pax3Sp/Sp (Splotch). Ossification centers were found to be differentially affected in the muscleless limbs, with significant decreases in bone formation in the scapula, humerus, ulna and femur, but not in the tibia. In the scapula and humerus, the morphologies of ossification centers were abnormal in muscleless limbs. Histology of the humerus revealed a decreased extent of the hypertrophic zone in mutant limbs but no change in the shape of this region. The elbow joint was also found to be clearly affected with a dramatic reduction in the joint line, while no abnormalities were evident in the knee. The humeral deltoid tuberosity was significantly reduced in size in the Myf5nlacZ/nlacZ:MyoD−/− mutants while a change in shape but not in size was found in the humeral tuberosities of the Pax3Sp/Sp mutants. We also examined skeletal development in a ‘reduced muscle’ model, the Myf5nlacZ/+:MyoD−/− mutant, in which skeletal muscle forms but with reduced muscle mass. The reduced muscle phenotype appeared to have an intermediate effect on skeletal development, with reduced bone formation in the scapula and humerus compared to controls, but not in other rudiments. In summary, we have demonstrated that skeletal development is differentially affected by the lack of skeletal muscle, with certain rudiments and joints being more severely affected than others. These findings indicate that the response of skeletal progenitor cells to biophysical stimuli may depend upon their location in the embryonic limb, implying a complex interaction between mechanical forces and location-specific regulatory factors affecting bone and joint development.

Life in the Slow Lane: The Effect of Reduced Mobility on Tadpole Limb Development

“…Thus, our data support the findings of other authors indicating that immobilization inhibits joint cavity formation without affecting earlier joint specifications (Pitsillides, 2006). The response of mesenchymal stem cells in the embryonic limb to biophysical stimuli may depend upon the location of the cells, suggesting that a complex interaction exists between mechanical forces and location-specific regulatory factors affecting bone and joint development (Nowland et al, 2010).…”

“…Thus, it could be argued that formation of the anlage of the sesamoid is genetically controlled, but extrinsic stimuli drive its differentiation (see also Sarin and Carter, 2000). Muscular movement is thought to stimulate bone formation (e.g., Palacios et al, 1992;Nowland et al, 2010), yet muscle maturation is delayed in experimental tadpoles. According to the sequence proposed by Muntz (1975), tadpoles in Stage 42 should have fully functional and fully differentiated limbs.…”

Bone and Cartilage from Stem Cells: Growth Optimalization and Stabilization of Cell Phenotypes

“…However, the "mechanostat" principle was launched several decades ago by Frost and colleagues (Frost 2003;Skerry 2006;Mulvihill and Prendergast 2008). Genetic lesions or immobilization (surgical or drug-induced) lead to muscle less limbs, reduced muscle fibre size/number, or non-contractile muscles, and to underdeveloped joints and bones, mostly due to a lack of mechano-stimulation (Gomez, David et al 2007;Kahn, Shwartz et al 2009;Nowlan, Bourdon et al 2010;Nowlan, Sharpe et al 2010). Several humoral factors, growth factors and receptors/ECM-protein/anchoring proteins share important signalling pathways, thus eventually leading to osteochondral differentiation of progenitor cells, for review, see (Gordeladze, Reseland et al 2009;Kelly and Jacobs 2010;Potier, Noailly et al 2010).…”

Validating a Noninvasive Technique for Monitoring Embryo Movement In Ovo

“…There is abundant evidence that musculoskeletal development is impaired, blood flow altered, and gene expression modified in the absence of normal movement (Hosseini and Hogg 1991;Pitsillides 2006;Nowlan et al 2010;Rolfe et al 2014). Moreover, embryo movement can be influenced by many factors, including pharmacological agents (Fanconi et al 1995;Heywood et al 2005;Jensen et al 2014) and external cues such as temperature and circadian rhythms (Hammond et al 2007;Ozkaya et al 2012).…”