|M.Sc Student||Reshef Bankay Ella|
|Subject||The Signal Transduction Pathway Involved in the Effect of|
Metabolic Acidosis on the Development of
Chondrocytes in Growth Centers
|Department||Department of Medicine||Supervisors||Professor Raymond Coleman|
|Dr. Gila Maor|
|Mr. Jacob Green (Deceased)|
An experimental study examined the effects of chronic metabolic acidosis on skeletal growth retardation in models of endochondral ossification. These models included mandibular condyles of newborn ICR mice in organ culture and also mandibular condyle-derived primary tissue culture (MCDC) and an ATDC5 cell line (clonal mouse embryonal carcinoma cells). The study included histology, morphometric analysis, TUNEL, immunohistochemistry, in situ hybridization and Western blot analysis. In order to focus on the cAMP/PKA signal transduction pathway, we used cAMP-inducing factors (cAMP-IFs) to amplify this track by increasing cAMP levels. Results showed that cAMP-IFs mimicked the effects of acidosis on morphological and biochemical functions of the mandibular condyle. cAMP-IFs mimicked acidosis effects by inhibiting early proliferation (PCNA), inhibiting early differentiation (decreased type II collagen and proteoglycans), interfering with local growth factors (reduced IGF-1 system and uncoupled Ihh/PTHrP axis), increasing apoptotic levels and late differentiation (increased osteocalcin mRNA levels). Furthermore, study of the cAMP/PKA axis components showed that acidosis activates this cellular pathway by increasing Gsa levels, increasing levels of cAMP, activating PKA that phosphorylates CREB to pCREB, which probably modulates genes transcription that may be involved in regulation of differentiation processes of the chondrocytes. Inhibition of this specific track by GDPbS, a Gs protein inhibitor, ameliorates the morphological effects of acidosis.
This research showed that acidosis induces its adverse effects on skeletal growth through the cAMP/PKA axis.