Introduction: Mechanical loading, which can regulate longitudinal bone growth, has clinical implications in progressive skeletal deformities. Nevertheless, the mechanisms underlying this process, occurring in growth plates with structurally distinct zones, are not well understood.
Objective: This study aims at documenting the relationship between the biochemical composition and the morphological changes following compression of growth plates in its three zones.
Method: Growth plates were dissected from ulnae of immature swine (N=13). Six of the specimens were tested under 15% compressive strain and confocal microscopy was used to image fluorescently labeled chondrocytes. Quantitative morphological analyses at both tissue (cell/matrix volume ratio) and cell levels (volume, surface area, and sphericity) were performed using IMARIS software. Seven of the samples were processed to evaluate water, collagen (Hydroxyproline assay) and GAG (Dimethylmethylene blue assay) contents within the three zones.
Result: Both deformational state and biochemical composition results showed heterogeneity among the zones. Lower volume changes were mainly found in the reserve zone where higher collagen content was measured, whereas higher volume changes were observed in the proliferative and hypertrophic zones where lower collagen content was detected. All three zones contained a similar GAG and water content.
Conclusion: Growth plate compressive behaviour was related to its collagen content. The reserve zone might play a more significant role of mechanical support relative to the proliferative and hypertrophic zones, which have an anabolic role in the growth process.
Significance: Study of growth plate mechanobiology is essential to establish a scientific basis to improve treatment approaches of progressive skeletal deformities.