A papain-induced disc degeneration model for the assessment of thermo-reversible hydrogel-cells therapeutic approach

Abstract

Nucleus pulposus (NP) regeneration by the application of injectable cell-embedded hydrogels is an appealing approach for tissue engineering. We investigated a thermo-reversible hydrogel (TR-HG), based on a modified polysaccharide with a thermo-reversible polyamide [poly(N-isopropylacrylamide), pNIPAM], which is made to behave as a liquid at room temperature and hardens at > 32 °C. In order to test the hydrogel, a papain-induced bovine caudal disc degeneration model (PDDM), creating a cavity in the NP, was employed. Human mesenchymal stem cells (hMSCs) or autologous bovine NP cells (bNPCs) were seeded in TR-HG; hMSCs were additionally preconditioned with rhGDF-5 for 7 days. Then, TR-HG was reversed to a fluid and the cell suspension injected into the PDDM and kept under static loading for 7 days. Experimental design was: (D1) fresh disc control + PBS injection; (D2) PDDM + PBS injection; (D3) PDDM + TR-HG (material control); (D4) PDDM + TR-HG + bNPCs; (D5) PDDM + TR-HG + hMSCs. Magnetic resonance imaging performed before and after loading, on days 9 and 16, allowed imaging of the hydrogel-filled PDDM and assessment of disc height and volume changes. In gel-injected discs the NP region showed a major drop in volume and disc height during culture under static load. The RT-PCR results of injected hMSCs showed significant upregulation of ACAN, COL2A1, VCAN and SOX9 during culture in the disc cavity, whereas the gene expression profile of NP cells remained unchanged. The cell viability of injected cells (NPCs or hMSCs) was maintained at over 86% in 3D culture and dropped to ~72% after organ culture. Our results underline the need for load-bearing hydrogels that are also cyto-compatible.

Fibrin-genipin adhesive hydrogel for annulus fibrosus repair: performance evaluation with large animal organ culture, in situ biomechanics, and in vivo degradation tests

“…Bovine caudal IVDs were used because of their large size and similarities with human lumbar IVDs (Demers et al ., 2004; Oshima et al ., 1993). In addition, bovine and other large animal IVDs are readily available and have been thoroughly characterised biomechanically and in organ culture studies (Chan et al ., 2011; Gantenbein et al ., 2006; Haglund et al ., 2011; Illien-Junger et al ., 2012; Junger et al ., 2009; Korecki et al ., 2008a; Korecki et al ., 2008b; Lee et al ., 2006; Malonzo et al ., 2013; Michalek and Iatridis, 2012; Ohshima et al ., 1995; Paul et al ., 2012; Walter et al ., 2011). …”

Chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells in a simulated osteochondral environment is hydrogel dependent

“…This specific gel has been developed for future minimally invasive treatments allowing injection of the material followed by in situ gelation. So far, the HA-pNIPAM gel has been studied for possible use in nucleus pulposus tissue regeneration (Peroglio et al, 2012;Malonzo et al, 2013).…”

Mechanical Loading Promoted Discogenic Differentiation of Human Mesenchymal Stem Cells Incorporated in 3D-PEG Scaffolds with rhGDF5 and RGD

“…The presence of GDF-5 seems to increase cell activity (Figure 2) and the rate of PEG hydrogel degradation as shown by reduced amount of PEG hydrogel in histological evaluation (Figure 4). In recent findings by our group we could demonstrate that the IVD environment along with mechanical loading represents a major "discogenic" differentiation stimulus for hMSC; this stimulus being much stronger than the pre-conditioning in presence of 100ng/ Ml GDF5 added to the media [35]. Several studies have shown that mechanical loading applied on stem cells might improve the outcome of chondrogenesis of stem cells [18,19,36].…”