[Effects of hydrostatic pressure on proliferation and expression of the differentiated phenotype of cultured chondrocytes derived from rabbit craniofacial complex].

Abstract

To investigate the effects of mechanical forces on the growth of cartilages of the craniofacial complex, chondrocytes isolated from nasal septal cartilage (NSC), spheno-occipital synchondrosis (SOS), and mandibular condylar cartilage (MCC) were cultured and exposed to hydrostatic pressure in vitro. Following results were obtained. 1. By application of the pressure, DNA synthesis increased in NSC and SOS (150% of control by 50 g/cm2, 1 min), but not so much in MCC in the medium containing 10% fetal calf serum (FCS). On the other hand, GAG synthesis increased in SOS (140% of control by 50 g/cm2, 2 min.) and MCC (160% of control by 100 g/cm2, 5 min), but decreased slightly in NSC in the same condition. The stimulations in DNA and GAG syntheses reached maxima 20-22 hr and 24-27 hr respectively after the application of the pressure. These stimulatory effects of the hydrostatic pressure on DNA and GAG syntheses could be found when cultured chondrocytes were in a multilayer stage. 2. It has been reported that addition of FCS at a concentration of 10% increases DNA synthesis in these chondrocytes preincubated in medium containing 0.3% FCS. The application of the pressure 2 min before the addition of 10% FCS potentiated the increase by FCS of DNA synthesis in NSC (130% of control), but not so much that in SOS and little that in MCC. 3. When the pressure was applied on these cells 2 min before addition of parathyroid hormone (PTH; 10(-7) M), this mechanical stimulation potentiated the increase by PTH of GAG synthesis in MCC (130% of control), but not so much that in SOS, and little that in NSC. Moreover, the intracellular cAMP level which was increased just after the addition of PTH also became higher by the application of the pressure. 4. These potentiation by the hydrostatic pressure in the cases of the addition of FCS and PTH diminished when intervals between application of pressure and addition of these factors were more than 10 min. These findings suggested that mechanical forces have influences on the growth of cartilages in craniofacial complex and that these effects are mediated by factors contained in serum.