Module 3 Proposal

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Overview

Many times, to observe the behavior of certain cells, it is important to study them in an environment very similar to their natural one. This applies particularly to cells whose behavior is governed by many intracellular and biomechanical signals. For example, chondrocytes are cells that help maintain the cartilage, and therefore play a structural role. These cells interact extensively with surrounding cells so as to achieve the ideal cartilaginous matrix.

We believe that chondrocytes' behavior can be better studied if we simulate their natural environment to a larger extent. Specifically, we hope to simulate the dynamic nature of their natural environment. As structural cells, chondrocytes are responsible for absorbing and deflecting forces in the form of movement,friction, etc. We believe their reactions to these forces include appropriate changes in stiffness of the individual cells as well as the cartilaginous matrix. We hope to propose an experiment to measure the stiffness and other reactions of chondrocyte cells in a environment where they experience forces and perturbations that are present in their natural environment.

Background/Purpose

Chondrocytes are the cells that are found in the cartilage, and are known to contribute greatly to the production as well as the maintenance of the cartilaginous matrix. Chondrocytes also play a part as a connected tissues, implying a necessity for extensive intracellular communication. The effectiveness of the cartilaginous matrix in avoiding damage is paramount as cartilage repair occurs extremely slowly. Hence, a possible topic of investigation is the behaviour of chondrocytes associated with the damage-prevention aspect of cartilages.

Past research have been performed investigating the above topic, but the necessity of growing and observing chondrocytes in close-to-natural conditions have been mostly overlooked. A key part of chondrocytes, for example, is their ability to react to changes in biomechanical forces, which were non-existent in past studies. Recent research have claimed that such forces results in significant changes in cells, including changes in morphology, stiffness, and permeability. Hence a comprehensive and accurate characterisation of chondrocyte behavior cannot be performed without a thorough consideration of integrating key perturbations into culturing and maintenance of chondrocytic cells.

With regards to experimental design, we hope to expose chondrocytes to several conditions that are physiologically possible, and to characterise (and hopefully quantify) changes in properties listed above. The aforementioned conditions can be simulated through such methods as dynamic loading and perfusion culture environments. Also, to understand the effects of osteoarthritis, hydrostatic stress, tensile stress, and fluid flow will be induced in vitro. The cellular response can be collected such forms as collagen production, stiffness (potentially via atomic force microscopy), and permeability to cytokines. Through such methods, we hope to gain a better idea of chondrocytic reaction under a more physiologically accurate condition.

References

Garcia Cruz DM, Salmeron-Sanchez M, Gomez-Ribelles JL. Stirred flow bioreactor modulates chondrocyte growth and extracellular matrix biosynthesis in chitosan scaffolds. J Biomed Mater Res A. 2012 Apr 24 (not published yet)

Grad S, Loparic M, Peter R, Stolz M, Aebi U, Alini M. Sliding motion modulates stiffness and friction coefficient at the surface of tissue engineered cartilage. Osteoarthritis Cartilage. 2012 Apr 20(4):288-95

Zhao X, Bichara DA, Ballyns FP, Yoo JJ, Ong W, Randolph MA, Bonassar LJ, Gill T.Properties of Cartilage Engineered from Elderly Human Chondrocytes for Articular Surface Repair.Tissue Eng Part A. 2012 Mar 22.

Wang P, Zhu F, Tong Z, Konstantopoulos K.Response of chondrocytes to shear stress: antagonistic effects of the binding partners Toll-like receptor 4 and caveolin-1.FASEB J. 2011 Oct;25(10):3401-15.

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