The physiological importance of apoptosis in the development and function of the growth plate is of major import. Without some mechanisms for removing terminally differentiated cells from cartilage, the plate would expand uncontrollably and there would be impaired bone formation. Accordingly, apoptosis provides a physiological mechanism for the rapid and controlled removal of terminally differentiated cells from epiphyseal tissue. Based on current studies, we now propose that apoptosis is regulated at two separate levels: a powerful late acting system that is dependent on release of specific components of the extracellular matrix and an early maturation-dependent system that prepares and sensitizes chondrocytes to apoptotic stimuli. Herein, we focus on early events in the induction of the apoptotic process. Experiments are described that explore the role of metabolic factors in the initiation of apoptosis, focusing on mitochondrial function and cellular metabolism. A second area of study that impacts on apoptosis is the control of survival responses. Accordingly, we will examine regulation of a key survival pathway and determine its relationship to metabolic factors that are common to both systems. There are three Specific Aims:
The first aim i s to determine at what maturation stage chondrocytes exhibit a decrease in the mitochondrial transmembrane potential and exhibit evidence of apoptosome formation and caspase activation; to ascertain if a change in transmembrane potential causes an alteration in caspase-3 activity; to learn if a low transmembrane potential increases susceptibility of chondrocytes to apoptosis.
The second aim i s in two parts: (A) to examine ROS/NO generation and GSH levels in relationship to transmembrane potential; to determine the role of ROS, NO and GSH in the activation of caspase-3, and/or non-cytochrome c dependent caspase systems and apoptosis; (B) to learn if Uncoupling Protein (UCP) is expressed by maturing chondrocytes: to ascertain if UCP expression is related to loss of transmembrane potential, thiol depletion, ROS generation and caspase activation. The last aim of the investigation is to examine survival pathways in maturing chondrocytes; to relate changes in transmembrane potential and ROS generation to activation of PI 3 kinase; to determine if Akt is a major target of PI 3 kinase; to relate inhibition of Akt to caspase activation and chondrocyte apoptosis.
| Davidson, Helen; Poon, Martin; Saunders, Ray et al. (2015) Tetracycline tethered to titanium inhibits colonization by Gram-negative bacteria. J Biomed Mater Res B Appl Biomater 103:1381-9 |
| Hickok, Noreen J; Shapiro, Irving M (2012) Immobilized antibiotics to prevent orthopaedic implant infections. Adv Drug Deliv Rev 64:1165-76 |
| Shapiro, I M; Hickok, N J; Parvizi, J et al. (2012) Molecular engineering of an orthopaedic implant: from bench to bedside. Eur Cell Mater 23:362-70 |
| Ketonis, Constantinos; Barr, Stephanie; Shapiro, Irving M et al. (2011) Antibacterial activity of bone allografts: comparison of a new vancomycin-tethered allograft with allograft loaded with adsorbed vancomycin. Bone 48:631-8 |
| Zahm, Adam M; Bohensky, Jolene; Adams, Christopher S et al. (2011) Bone cell autophagy is regulated by environmental factors. Cells Tissues Organs 194:274-8 |
| Ketonis, Constantinos; Barr, Stephanie; Adams, Christopher S et al. (2011) Vancomycin bonded to bone grafts prevents bacterial colonization. Antimicrob Agents Chemother 55:487-94 |
| Ketonis, Constantinos; Barr, Stephanie; Adams, Christopher S et al. (2010) Bacterial colonization of bone allografts: establishment and effects of antibiotics. Clin Orthop Relat Res 468:2113-21 |
| Bohensky, Jolene; Leshinsky, Serge; Srinivas, Vickram et al. (2010) Chondrocyte autophagy is stimulated by HIF-1 dependent AMPK activation and mTOR suppression. Pediatr Nephrol 25:633-42 |
| Zahm, Adam M; Bucaro, Michael A; Ayyaswamy, Portonovo S et al. (2010) Numerical modeling of oxygen distributions in cortical and cancellous bone: oxygen availability governs osteonal and trabecular dimensions. Am J Physiol Cell Physiol 299:C922-9 |
| Ketonis, Constantinos; Adams, Christopher S; Barr, Stephanie et al. (2010) Antibiotic modification of native grafts: improving upon nature's scaffolds. Tissue Eng Part A 16:2041-9 |
Showing the most recent 10 out of 65 publications
