Semester

Fall

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Ming Pei

Committee Co-Chair

Jacky Prucz

Committee Member

Nianqiang Wu

Abstract

Intervertebral disc degeneration begins early in life, increases with age, and can ultimately result in disc failure. At the center of the disc, the nucleus pulposus (NP) resides in a hypoxic environment where degeneration is thought to begin. Initially, nucleus pulposus cells (NPCs) display altered morphology and function, along with increased rates of cellular senescence and apoptosis. Though no widely accepted treatment exists, autologous NP implantation techniques have shown promise. However, the process is flawed as a result of the long in vitro expansion required to obtain sufficient numbers of cells. Prolonged expansion on plastic produces negative changes such as loss of the NP phenotype and reduced redifferentiation ability. Because cell based tissue engineering techniques require a metabolically active population of cells, stem cells have attracted attention for regenerative NP strategies due to their self-renewal ability and multipotent differentiation capacity. Specifically, synovium derived stem cells (SDSCs) have a higher chondrogenic capacity compared to stem cells derived from other tissues. Another advantage and potential use of SDSCs is that they can produce decellularized extracellular matrix (DECM); expansion of SDSCs or NPCs on this substrate can dramatically increase the rates of proliferation, delay senescence associated changes, and support chondrogenic activity upon induction. In this study, it was determined that NPCs alone and NPCs in co-culture with SDSCs can produce their own unique DECM. It was determined that DECM properties may be modulated by varying oxygen tension during DECM deposition. While the DECM deposited by NPCs along with SDSCs improved proliferation and guided SDSC differentiation towards the NP lineage, the effect was greater than NPC derived DECM and comparable to SDSC derived DECM. Normoxic conditions during DECM preparation were more beneficial to cell proliferation, but hypoxic conditions promoted differentiation towards the NP lineage. Finally, hypoxic conditions during pellet culture promoted NPC viability and redifferentiation. Low oxygen combined with DECM can facilitate cell-based NP regeneration.

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