title: 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.
authors.affiliation: Tissue and Organ Mechano Biology, Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Malonzo
authors.affiliation: Tissue and Organ Mechano Biology, Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland.
authors.forename: S C W
authors.initials: SC
authors.lastname: Chan
authors.affiliation: Tissue and Organ Mechano Biology, Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Kabiri
authors.affiliation: AO Research Institute, Davos, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Eglin
authors.affiliation: AO Research Institute, Davos, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Grad
authors.affiliation: Institute for Diagnostic, Pediatric and Interventional Radiology, Inselspital, University of Bern, Switzerland.
authors.forename: H M
authors.initials: HM
authors.lastname: Bonél
authors.affiliation: Orthopaedic Department, Inselspital, University of Bern, Switzerland.
authors.forename: L M
authors.initials: LM
authors.lastname: Benneker
authors.affiliation: Tissue and Organ Mechano Biology, Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Gantenbein-Ritter
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D000943:Antigens, Differentiation / Q000096:biosynthesis; D002417:Cattle; D006801:Humans; D020100:Hydrogels / Q000737:chemistry / Q000494:pharmacology; D055959:Intervertebral Disc Degeneration / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D059630:Mesenchymal Stem Cells / Q000378:metabolism / Q000473:pathology; D008954:Models, Biological; D009924:Organ Culture Techniques; D010206:Papain / Q000633:toxicity*
chemical_list: D000180:Acrylic Resins; D000943:Antigens, Differentiation; D020100:Hydrogels; C052970:poly-N-isopropylacrylamide; D010206:Papain
keywords: intervertebral disc; mesenchymal stem cells; nucleus pulposus replacement; organ culture; relative gene expression; thermo-reversible hydrogel