Date of Award
Master of Science (MS)
The importance of understanding how costal cartilage chondrocytes respond to stimuli such as oxidative stress and low pH has been largely overlooked in studies involving tissue culturing due to major differences between oxygen and pH levels during incubation and the natural environment of hyaline cartilage. Hyaline cartilage is avascular and naturally hypoxic which subsequently leads to increased glycolytic metabolism and ultimately causes a decrease in extracellular pH. To examine how healthy costal cartilage responds to these extreme growth conditions, we examined responses in three hyaline cartilage diseases. Our ability to identify the disease mechanisms responsible for pectus excavatum, pectus carinatum, and chondrosarcoma are limited by our understanding of how these mechanisms operate. This study aimed to determine the roles of hypoxia and extracellular acidosis on the expression of genes related to the hypoxia response pathway in costal cartilage chondrocytes, two pectus chest wall deformities, and the hyaline cartilage producing cancer, chondrosarcoma. Cells isolated from costal cartilage were incubated under four experimental conditions, where cultures were subjected to 24 hours of either hypoxia (5% oxygen) or normoxia, and 60 seconds of acidic media (pH5.5) or kept at neutral pH (pH 7.2) just prior to RNA extraction. Expression levels for 84 genes were tested by RT-qPCR to determine genes of interest within the hypoxia response pathway. Two genes, factor 3 F3 and lysyl oxidase LOX, were chosen based on high fold change within the preliminary study; two replicate experiments were repeated for a total of 12 patient samples. Our analysis showed no significant change in any cell type compared to the control. However, the control and PC sample groups showed significant upregulation of both F3 (Control, p=0.0001, PC, p=0.0026) and LOX (Control, p=0.0009, PC, p=0.0047) within the cell type in response to hypoxia, but PE and JJ012 samples showed no significant response. Low pH had no significant effect on expression levels in any cell type. Further study of how cellular response mechanisms to hypoxia and acidosis in healthy and diseased hyaline cartilage is required to fill knowledge gaps and create understanding for new therapies to treat pectus chest wall deformities or chondrosarcoma cancer.
Durbin, Jamie L.. "Differential Gene Expression in Response to Hypoxia and Acidosis in Chest Wall Deformities and Chondrosarcoma" (2018). Master of Science (MS), thesis, Biological Sciences, Old Dominion University, https://digitalcommons.odu.edu/biology_etds/27