Cellular Fluid Mechanics in Osteochondral Tissue Engineering

UoM administered thesis: Phd

  • Authors:
  • Ruikang Xue

Abstract

As an alternative treatment to bone and cartilage injuries, tissue engineering uses cells, scaffolds and mechanical stimulation to produce cell-laden constructs in vitro. Fluid-induced shear stress (FSS) is able to facilitate desired tissue formation and it has been shown to change cellular behaviour of both 2 dimensional (2D) and 3D cultured cells inside a porous scaffold. Mechanotransduction is the study of translating mechanical stimuli to cellular behaviour. 2D mechanotransduction studies often employ a parallel-plate flow chamber (PFC) to induce FSS of which the magnitude can be calculated analytically. However, the disturbance of the seeded cells to local flow field in real-time needs to be elucidated. FSS up to 4 Pa is normally used in 2D studies whereas significant lower FSS (up to 0.015 Pa) is applied to 3D cultured cells to induce the same cellular response. The geometrical cues introduced from a 3D porous scaffold has been shown to influence cellular behaviour. Limited tools and in vitro models are a major hurdle to 3D mechanotransduction study due to the inaccessibility of 3D scaffolds. Because of the distinct difference between bone and cartilage, osteochondral tissue engineering (OCTE) employs bi-layered scaffolds and co-culture bioreactors to create tissue-specific micro-environment. Additive manufactured scaffolds from computer-aided designs (CAD) with tunable properties are ideal candidates for OCTE. Firstly, this project used a novel particle tracking technique to study the real-time effect of local flow field on cellular behaviour of human mesenchymal stem cells (hMSC) and mouse MC3T3-E1 cells during 1 h perfusion. It showed that the local flow field is dependent on cell morphology, which can lead to cellular behaviour change during the perfusion in real-time. Secondly, this project developed a simple in vitro 2.5D model using glass capillary tubes which mimics the 3D cell culture environment with a curved surface. Compared to the 2D culture, cells in the 2.5D model led to significant higher osteogenesis under low levels of FSS. Moreover, a morphometric analysis has been developed to quantify actin network reorganisation during hMSC osteogenesis. Lastly, this project developed an osteochondral culture system using a novel additive manufactured scaffold and a co-culture perfusion bioreactor. It was shown to support cell survival, proliferation and distribution, which was comparable to a commercial acellular scaffold. The finite element analysis (FEA) revealed that the culture system provided an optimal osteochondral culture environment. Compared to the CAD, the FEA showed that the actual produced scaffold geometry led to significant different flow velocity, FSS and differentiation media mixing.

Details

Original languageEnglish
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Supervisors/Advisors
Award date1 Aug 2019