Thermoreversible hyaluronan-hydrogel and autologous nucleus pulposus cell delivery regenerates human intervertebral discs in an ex vivo, physiological organ culture model

Abstract

Numerous studies show promise for cell-based tissue engineering strategies aiming to repair painful intervertebral disc (IVD) degeneration. However, clinical translation to human IVD repair is slow. In the present study, the regenerative potential of an autologous nucleus pulposus (NP)-cell-seeded thermoresponsive hyaluronic acid hydrogel in human lumbar IVDs was assessed under physiological conditions. First, agaroseencased in vitro constructs were developed, showing greater than 90 % NP cell viability and high proteoglycan deposition within HA-pNIPAM hydrogels following 3 weeks of dynamic loading. Second, a bovine-induced IVD degeneration model was used to optimise and validate T1ρ magnetic resonance imaging (MRI) for detection of changes in proteoglycan content in isolated intact IVDs. Finally, isolated intact human lumbar IVDs were pre-scanned using the established MRI sequence. Then, IVDs were injected with HA-pNIPAM hydrogel alone or autologous NP-cell-seeded. Next, the treated IVDs were cultured under cyclic dynamic loading for 5 weeks. Post-treatment T1ρ values were significantly higher as compared to pre-treatment scans within the same IVD and region of interest. Histological evaluation of treated human IVDs showed that the implanted hydrogel alone accumulated proteoglycans, while those that contained NP cells also displayed neo-matrix-surrounded cells within the gel. The study indicated a clinical potential for repairing early degenerative human IVDs using autologous cells/hydrogel suspensions. This unique IVD culture setup, combined with the long-term physiological culture of intact human IVDs, allowed for a more clinically relevant evaluation of human tissue repair and regeneration, which otherwise could not be replicated using the available in vitro and in vivo models.

Senotherapeutic drugs for human intervertebral disc degeneration and low back pain

“…The IVDs were treated with a single injection of vehicle, o-Vanillin, or RG-7112, delivered to the centre of the NP and were cultured for another 28 days as outlined in Figure 4A . An adapted MRI protocol ( Rosenzweig et al, 2018 ) was used to assess T1ρ-weighted MRI signal that directly correlates with proteoglycan content ( Rosenzweig et al, 2018 ; Mulligan, 2015 ). The method used to assess uniform NP regions of interest is shown in ( Figure 2—figure supplement 1B-D ).…”

“…Isolated discs were scanned by MRI before and after treatment at day 28 as described by Rosenzweig et al, 2018 . Images were obtained on a 7T Bruker BioSpec 70/30 USR (Bruker Biospin, Milton, ON, Canada) with the high-performance mini-imaging kit gradient upgrade AVIII electronics (Bruker) and a Bruker-issued T1ρ-RARE pulse sequence, as previously established ( Rosenzweig et al, 2018 ; Mulligan, 2015 ). Briefly, 3D images were acquired and T1ρ values were quantified using the MIPAV software (NIH Center for Information Technology, Bethesda, MD, USA).…”

Injectable Hydrogel Combined with Nucleus Pulposus-Derived Mesenchymal Stem Cells for the Treatment of Degenerative Intervertebral Disc in Rats

“…Cell transplantation-based biological therapy may be more beneficial to repair and restore the biomechanical function of IVD. Although implanted, autologous NP cells could remain viable, produce ECM, and retain disc height in the degenerative human IVD in an ex vivo study [31]. However, several studies showed that the NP cell lost its ability to differentiate and synthesize ECM [32] and thus has limited application.…”

Biomaterials-Induced Stem Cells Specific Differentiation Into Intervertebral Disc Lineage Cells

“…Among all these temperature response materials, poly (N-isopropylacrylamide) (pNIPAM) is most promising for biological applications because of its well defined structure and appropriate thermodynamic property. pNIPAM could be prepared into smart hydrogel which is negatively thermosensitive (Rosenzweig et al, 2018). In other words, pNIPAM could contract upon increase in temperature beyond their critical temperature and then forms a gel.…”