M.Sc Thesis

M.Sc StudentPreiss-Bloom Orahn
SubjectMechanical Stimulation of Tissue Engineered Cartilage
DepartmentDepartment of Biomedical Engineering
Supervisors PROFESSOR EMERITUS Joseph Mizrahi
Full Thesis textFull thesis text - English Version


Mechanical stimulation improves tissue engineered cartilage development both in terms of biochemical composition and structural properties. However, the link between the compositional changes attributed to mechanical stimulation and the changing structural properties of the engineered cartilage is poorly understood. We hypothesize that transient events associated with construct stiffening can be documented and used to understand milestones in construct development. To do this we designed and built a mechanical stimulation bioreactor that can continuously record the force response of the engineered construct in real-time. This study documents the transient changes of the stiffness of tissue engineered cartilage constructs over the first 14 days of their development under cyclic loading. Compressive strain stimulation (15%, 1-Hz) was applied to poly(ethylene-glycol) (PEG) hydrogels seeded with primary articular chondrocytes. The average compressive modulus of strain stimulated constructs was 12.7 ± 1.45 kPa after 2 weeks, significantly greater (p<0.01) than the average compressive moduli of both unstimulated constructs (10.7 ± 0.94 kPa) and non-viable stimulated constructs (11.2 ± 0.91 kPa).  The system was able to document that nearly all of the stiffness increase occurred over the last two days of the experiment, where live-cell constructs demonstrated a rapid 20% increase in force response.  The systems ability to track significant increases in stiffness over time was also confirmed by Instron® testing. These results present a novel view of the early mechanical development of tissue engineering cartilage constructs and suggests that the real-time monitoring of force response may be used to non-invasively track the development of engineered tissue.