טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBomzon Ze'ev
SubjectComputational Methods for Studying Cytoplasmic Mechanics
in Isolated Chondrocytes Seeded in Agarose
Constructs
DepartmentDepartment of Agricultural Engineering
Supervisors Professor Emeritus Eitan Kimmel
Professor Dror Seliktar


Abstract

Mechanical loading alters the function and metabolism of chondrocytes. This process, known as mechanotransduction, is essential to the maintenance of healthy cartilage. The modes by which mechanotransduction occurs remain unclear. Thus, it is important to understand how mechanical loads are distributed within chondrocytes.  In this thesis we present a study on the intracellular mechanical properties of Chondrocytes.

Articular chondrocytes isolated from mature-bovine metacarpal-phalangeal joints were seeded into agarose constructs. The mitochondria within the cells were labeled with Mitotracker. Constructs were placed on a specially designed compression rig mounted on a confocal microscope, and individual cells within constructs were imaged at varying levels of strain. Displacements of the mitochondria and the resulting strains were mapped from the images using Digital Image Correlation. . In a separate study the mitochondria in unstrained cells were imaged for periods of up to half an hour, and the motion of the mitochondria was characterized by calculating the MSD.

The results showed that the cytoplasm is a heterogeneous viscoelastic material. It provides evidence to that the cytoplasm is a biphasic material. Consequently. a  model describing the behavior of heterogeneous viscoelastic materials was derived using Functional Perturbation Method. Analysis of the inherent motion of mitochondria showed that the cytoplasm behaves like a fluid on large time-scales. This effect is probably due to the dynamic instability of the cytoskeleton. This study provides insight into the mechanics of Chondrocytes. It sheds light on the mechanical nature of the cytoplasm. This insight could help to understand mechanotransduction.