The growth cartilage of the cranial base, the sphenooccipital synchondrosis (SOS), is thought to be regulated solely by genetic inheritance. Our recent data demonstrate that the genetically programmed growth of the SOS in juvenile rabbits can be accelerated by dynamic forces with sinusoidal waveforms. Objectives. The objective of the present work was to determine the level of plasticity of the SOS in response to micromechanical stimulation in neonatal rabbits. Methods. 32 seven-day-old male white New Zealand rabbits were allocated to control (n = 16) and loaded groups (n = 16). After euthanasia, the cranial-base growth plate was dissected under aseptic condition. The harvested growth plate explants were placed in Dulbecco's medium (DMEM) fortified with 10% fetal bovine serum and 1% Penicillin-streptomycin-L-glutamine solution. Micromechanical stresses were applied to the experimental explants at 200 mN and 1 Hz for 1 hour. After loading, the explants were cultured for three consecutive days, followed by sample fixation or microdissection of the growth plate explants and storage at -70°C for further analysis according to the experimental protocol. Chondrocyte count, growth plate height and immunohistochemistry quantification was measured using histomorphometry. The content of sulfated proteoglycans (PGs) and Hyaluronic acid (HA) was determined using a modified DMB dye binding method and a sandwich ELISA technique respectively. DNA content was measured using bisbenzimidazole fluorescent dye (Hoechst 33258). Results. Chondrocyte count, growth plate height and antibody binding area were significantly higher in the loaded group compared to the control. Total proteoglycan, keratan and collagen synthesis did not change significantly, whereas hyaluronate increased by almost three folds in the loaded group when compared to the control. RC-PCR data showed mRNA expression of decorin, biglycan and versican genes in the normal neonatal growth plate. Upon mechanical stimulation of growth plates, biglycan gene expression was absent. Taken together, the present data suggest important roles micromechanical stresses play in growth plate metabolism in early postnatal development.
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