Injectable decellularized nucleus pulposus tissue maintains neuroinhibitory properties

Authors: PIENING, LOGAN - University Of Nebraska; LILLYMAN, DAVID - University Of Nebraska; LEE, FEI - University Of Nebraska; LOZANO, ALVARO - University Of Nebraska; Miles, Jeremy; WACHS, REBECCA - University Of Nebraska

Submitted to: Journal of Orthopaedic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Development of chronic low back pain affects a significant proportion of the human population throughout the world. A major contributing factor to chronic low back pain is the degeneration of the intervertebral disc of the spine and loss of the gelatinous nucleus pulposus core allowing for nerve growth into the inner core of the disc and resulting in pain due to loss of neuroinhibitory sulfated glycosaminoglycans within the nucleus pulposus. Decellularized nucleus pulposus tissue has promise to restore sulfated glycosaminoglycans and reintroduce neuroinhibitory properties and serve as an alternative treatment to alleviate pain. Therefore, the objective of this study was to develop a decellularization method from porcine nucleus pulposus tissue that removes cells and maintains sulfated glycosaminoglycans and neuroinhibitory properties. The decellularized nucleus pulposus was then modified into a thermally forming gel and regelled nucleus pulposus was tested for cytotoxicity and neuroinhibitory properties. The regelled nucleus pulposus created a suitable environment for nucleus pulposus cells to grow and remodel the matrix, while inhibiting growth of neurites. These results suggest that a decellularized nucleus pulposus gel may be used as treatment to prevent nerve growth in a degenerate disc and prevent pain progression.

Technical Abstract: Chronic low back pain (LBP) is a leading cause of disability but treatments for LBP are limited. Degeneration of the intervertebral disc (IVD) allows nerves from the DRG to grow into the inner core of the disc and cause pain, due to loss of neuroinhibitory sulfated glycosaminoglycans (sGAGs). Treatment with a decellularized tissue hydrogel that contains sGAGs may inhibit nerve growth and prevent LBP. A protocol to decellularize porcine nucleus pulposus (NP) was adapted from previous methods. The content of DNA, sGAG, alpha-gal antigen and collagen were analyzed. The decellularized tissue was then modified to be injectable and form a gel at 37 °C. Following this, the mechanical properties, cytotoxicity, and neuroinhibitory properties were analyzed. The decellularization process removed 99% of DNA, and maintained 74% of sGAG and 154% of collagen compared to the original mass. Rheology demonstrated that regelled NP exhibited properties similar to collagen. Culture of NP cells in the regelled NP demonstrated an increase in metabolic activity and DNA content over 7 days. The collagen content of the regelled NP stayed relatively constant over 7 days. Analysis of the neuroinhibitory properties demonstrated regelled NP inhibited significantly more neuronal growth than collagen controls. The decellularization process developed here for porcine NP tissue was able to remove the antigenic material while maintaining most of the extracellular matrix proteins. This decellularized tissue was then able to be modified into a thermally forming that maintained the viability of cells cultured and demonstrated robust neuroinhibitory properties. This material holds promise to prevent nerve growth into the native disc and NP in vivo.