Chondrocyte, the sole cell population in articular cartilage, is responsible for the homeostasis of the extracellular matrix in cartilage. My thesis work aimed to understand the metabolism of cartilage, chondrocyte, and their mutual interactions, with the purpose for the search of potential treatments for osteoarthritis (OA).
To study the behaviors of chondrocytes residing in their native environment, long-term in vitro culture of cartilage explants were investigated. In my first study, the effects of serum medium and serum-free chondrogenic medium for cartilage explant culture were compared. To evaluate the behaviors of in situ chondrocytes in the two culture medium, an in situ imaging approach was developed, where the spontaneous intracellular calcium ([Ca2+]i ) signaling of chondrocytes could be recorded and analyzed. We proved that the serum-free chondrogenic medium is beneficial for the mechanical integrity of cartilage tissue, as well as the viability, phenotype, and metabolic activities of chondrocytes. Aging is strongly correlated with the occurrence of OA. To understand the effect of age on chondrocyte metabolism, my second study was to analyze the correlation between aging and [Ca2+]i signaling of chondrocyte, as well as the impact of osmotic environment. We found that adult chondrocytes have more vigorous [Ca2+]i signaling than juvenile chondrocytes. In this thesis, the spontaneous [Ca2+]i signaling is employed as an important indicator of chondrocyte metabolic behaviors. Thus my third study serves as a systematic effort to understand the features and potential initiation mechanisms of the spontaneous [Ca2+]i signaling of chondrocyte. A theoretical biophysical model was built to describe the spontaneous [Ca2+]i peaks, The model can successfully explain the lognormal distribution of signaling-related temporal parameters and the “fingerprint” phenomenon. Using eight pathway antagonists, it was found that the initiation of spontaneous [Ca2+]i peaks in chondrocytes requires extracellular Ca2+ source. PLC-IP 3 pathway, purinoceptors, and TRPV4 channel on plasma membrane also play key roles in the spontaneous [Ca2+]i signaling of chondrocytes. My last study was targeting at a potential molecule for OA treatment, i.e., investigating the chondro-protective effects of resveratrol. Resveratrol is a natural polyphenol known for its anti-oxidation effects. My study revealed the protective effects of resveratrol on chondrocytes under inflammatory attack. A novel collagen association effect of resveratrol was discovered, where the resveratrol molecules are able to associate collagen fibrils via the dynamic hydrogen bonds. This is particularly important for future treamtment of OA, especially for the middle stage OA where the number of functional chondrocytes are highly limited in the degenerated cartilage.
Taken together, studies in this thesis contribute to the further understanding of the in vitro behaviors of cartilage, spontaneous [Ca2+]i signaling of chondrocytes, and the chondro-protective mechanisms of resveratrol, all of which are to serve the potential treatment of OA.
|2003||Donahue SW, Donahue HJ, Jacobs CR. Osteoblastic cells have refractory periods for fluid-flow-induced intracellular calcium oscillations for short bouts of flow and display multiple low-magnitude oscillations during long-term flow. J Biomech. January 2003;36(1):35-43.|
|2010||Goldring MB, Goldring SR. Articular cartilage and subchondral bone in the pathogenesis of osteoarthritis. Annals NY Acad Sci. March 2010;1192(1):230-237.|
|2006||Buehler MJ. Nature designs tough collagen: explaining the nanostructure of collagen fibrils. Proc Natl Acad Sci USA. August 15, 2006;103(33):12285-12290.|
|2000||Grodzinsky AJ, Levenston ME, Jin M, Frank EH. Cartilage tissue remodeling in response to mechanical forces. Annu Rev Biomed Eng. 2000;2:691-713.|
|2009||Adachi T, Aonuma Y, Tanaka M, Hojo M, Takano-Yamamoto T, Kamioka H. Calcium response in single osteocytes to locally applied mechanical stimulus: differences in cell process and cell body. J Biomech. August 25, 2009;42(12):1989-1995.|
|1980||Mow VC, Kuei SC, Lai WM, Armstrong CG. Biphasic creep and stress relaxation of articular cartilage in compression: theory and experiments. J Biomech Eng. February 1980;102(1):73-84.|
|2007||Lu X. Indentation Analysis of Articular Cartilage Using the Triphasic Mixture Theory [PhD thesis]. Columbia University; 2007.|
|1991||Lai WM, Hou JS, Mow VC. A triphasic theory for the swelling and deformation behaviors of articular cartilage. J Biomech Eng. August 1991;113(3):245-258.|
|1992||Mow VC, Ratcliffe A, Robin Poole A. Cartilage and diarthrodial joints as paradigms for hierarchical materials and structures. Biomaterials. 1992;13(22):67-97.|
|2006||Engler AJ, Sen S, Sweeney HL, Discher DE. Matrix elasticity directs stem cell lineage specification. Cell. August 25, 2006;126(4):P677-P689.|
|1999||Soulhat J, Buschmann MD, Shirazi-Adl A. A fibril-network-reinforced biphasic model of cartilage in unconfined compression. J Biomech Eng. June 1999;121(3):340-347.|
|1984||Armstrong CG, Lai WM, Mow VC. An analysis of the unconfined compression of articular cartilage. J Biomech Eng. May 1984;106(2):165-173.|
|2005||Mow VC, Huiskes R, eds. Basic Orthopaedic Biomechanics & Mechano-Biology. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.|
|2012||Lu XL, Huo B, Chiang V, Guo XE. Osteocytic network is more responsive in calcium signaling than osteoblastic network under fluid flow. J Bone Miner Res. March 2012;27(3):563-574.|
|2009||Fox AJS, Bedi A, Rodeo SA. The basic science of articular cartilage: structure, composition, and function. Sports Health. November–December 2009;1(6):461-468.|
|2002||Hunziker EB. Articular cartilage repair: basic science and clinical progress. a review of the current status and prospects. Osteoarthritis Cartilage. June 2002;10(6):432-463.|