Characterization of chondroitinase‐induced lumbar intervertebral disc degeneration in a sheep model intended for assessing biomaterials

Abstract

Intervertebral disc (IVD) degeneration (IVDD) leads to structural and functional changes.Biomaterials for restoring IVD function and promoting regeneration are currently being investigated; however, such approaches require validation using animal models that recapitulate clinical, biochemical, and biomechanical hallmarks of the human pathology. Herein, we comprehensively characterized a sheep model of chondroitinase-ABC (C-ABC) induced IVDD.Briefly, C-ABC (1U) was injected into the L1/2, L2/3, and L3/4 IVDs. Degeneration was assessed via longitudinal magnetic resonance (MR) and radiographic imaging. Additionally, kinematic, Statement of SignificanceSelecting the appropriate model for assessing biomaterials to repair and/or support regeneration of the intervertebral disc (IVD) has been controversial, leading to the use of many methods of simulating IVD degeneration (IVDD) in multiple species. Many of these models lack thorough characterization of their fidelity to human IVDD, which could hinder the translation of novel biomaterials and therapies due to unknown confounding factors. Herein, further investigation of one such model was performed using the matrix-degrading enzyme chondroitinase-ABC to induce degeneration in sheep lumbar IVDs. Degenerative changes were quantified using outcome measures relevant to human IVDD, and this dosage and method induces an aggressive degeneration environment that could be used to assess biomaterials that mimic the structure and function of the entire composite IVD. These findings may aid investigators in their selection of an appropriate animal model for preclinical testing of biomaterials and other therapeutics.

Preclinical in vivo animal models of intervertebral disc degeneration. Part 1: A systematic review

“…Surgical induced injury was the most common (168/259, 64.86%), followed by chemical injury (46/259, 17.76%) genetically modified (28/259, 10.81%) and spontaneous (28/259, 10.81%) models. For chemically induced degeneration, the two most common substances used were enzymes, via intradiscal, subchondral or systemic injection, 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 and poly (methyl methacrylate) (PMMA), via intradiscal PMMA particle injection or into the vertebral body parallel to the adjacent vertebral endplate 43 , 44 , 45 , 46 , 47 (Figure 4B ). Of the 28 (10.81%) papers that reported genetic modification to induce IVDD, 20 different genes were targeted for either gene knock‐out, 23 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ,…”

A bovine nucleus pulposus explant culture model

“…This reduced weight‐bearing capacity would lead in vivo to decreased disc height, a hallmark of IVDD. Increased creep and height loss in chABC‐injected discs were found in a sheep model 33 . Interestingly, Paul et al 37 reported an immediate change (initial creep) in chABC‐treated and sham‐injected goat discs ex vivo.…”

“…Increased creep and height loss in chABC-injected discs were found in a sheep model. 33 Interestingly, Paul et al 37 reported an immediate change (initial creep) in chABC-treated and sham-injected goat discs ex vivo. As such, it is more plausible that ECM damage occurred due to injection a large volume (100 µl), as enzymatic degradation might not have an immediate effect.…”

In Vitro Studies for Investigating Creep of Intervertebral Discs under Axial Compression: A Review of Testing Environment and Results

“…Secondly, the testing environment should be set as close as possible to in vivo conditions, notably with regard to the temperature (e.g., 37 °C for the human body, 39 °C for cows) and the osmotic pressure (immersed in PBS or saline). Based on these settings, several studies have established optimal experimental models [ 8 , 37 , 46 , 60 , 66 , 75 , 76 , 81 , 82 , 83 , 104 , 105 , 109 ]. Thirdly, the preload of 10–50 N for 30 min or three cycles is appropriate and a data-followed preload can be used for mechanical parameter calculation and mathematical model fitting.…”