Development of a Perfusion Reactor for Intervertebral Disk Regeneration

Abstract

A tissue-engineered biological disk replacement has been proposed as a promising approach for the treatment of degenerative disk disease. A perfusion bioreactor would be a logical consideration to facilitate this scale-up as such reactors have been shown to improve nutrient delivery and provide beneficial mechanical forces that support the cultivation of large three-dimensional constructs. It was hypothesized that perfusion culture of tissue-engineered intervertebral disk (IVD) tissues would be capable of generating outer annulus fibrosus (oAF) and nucleus pulposus (NP) tissues comparable with established spinner reactor or static cultures, respectively, without compromising cellular viability, nutrient delivery, and tissue formation. In this study, the perfusion grown oAF and NP tissues did not show a significant difference in extracellular matrix (ECM) quantity or cellular phenotype when compared with their control conditions. In addition, they maintained cellular viability at the center core of the tissues and received enhanced diffusion of medium throughout the tissue when compared with static conditions. This study lays the groundwork for future studies to grow an entire IVD tissue to a physiologically relevant size.

Impact statement

Degenerative disk disease is associated with back pain and loss of disk function. Bioengineering a replacement intervertebral disk (IVD) is a promising solution, and a perfusion bioreactor may offer the necessary culture conditions to support formation of such tissues. This study demonstrated that in vitro generated components of the disk, the nucleus fibrosus, and annulus fibrosus, grown in perfusion culture, yielded promising improvements to nutrient delivery and cellular viability. This outcome lays the groundwork for constructing IVD constructs that are closer to physiological size and composition, leading us closer to bioengineering a fully functional disk.