Intradiscal treatment of the cartilage endplate for improving solute transport and disc nutrition

Abstract

Poor nutrient transport through the cartilage endplate (CEP) is a key factor in the etiology of intervertebral disc degeneration and may hinder the efficacy of biologic strategies for disc regeneration. Yet, there are currently no treatments for improving nutrient transport through the CEP. In this study we tested whether intradiscal delivery of a matrix-modifying enzyme to the CEP improves solute transport into whole human and bovine discs. Ten human lumbar motion segments harvested from five fresh cadaveric spines (38–66 years old) and nine bovine coccygeal motion segments harvested from three adult steers were treated intradiscally either with collagenase enzyme or control buffer that was loaded in alginate carrier. Motion segments were then incubated for 18 h at 37 °C, the bony endplates removed, and the isolated discs were compressed under static (0.2 MPa) and cyclic (0.4–0.8 MPa, 0.2 Hz) loads while submerged in fluorescein tracer solution (376 Da; 0.1 mg/ml). Fluorescein concentrations from site-matched nucleus pulposus (NP) samples were compared between discs. CEP samples from each disc were digested and assayed for sulfated glycosaminoglycan (sGAG) and collagen contents. Results showed that enzymatic treatment of the CEP dramatically enhanced small solute transport into the disc. Discs with enzyme-treated CEPs had up to 10.8-fold (human) and 14.0-fold (bovine) higher fluorescein concentration in the NP compared to site-matched locations in discs with buffer-treated CEPs (p < 0.0001). Increases in solute transport were consistent with the effects of enzymatic treatment on CEP composition, which included reductions in sGAG content of 33.5% (human) and 40% (bovine). Whole disc biomechanical behavior—namely, creep strain and disc modulus—was similar between discs with enzyme- and buffer-treated CEPs. Taken together, these findings demonstrate the potential for matrix modification of the CEP to improve the transport of small solutes into whole intact discs.

Non‐enzymatic glycation reduces glucose transport in the human cartilage endplate independently of matrix porosity or proteoglycan content

“…Prior to spine harvest, cadavers underwent magnetic resonance imaging (GE Discovery MR 750W 3T; GE Healthcare), which consisted of a sagittal fast spin‐echo T2‐weighted sequence with the following parameters: echo‐time 61.6 ms; repetition time 2500 ms; echo train length 8; acquisition matrix 512 × 512; slice thickness 3 mm; and field‐of‐view 27 cm × 27 cm. Disc degeneration was evaluated using the Pfirrmann classification system 4,21 …”

“…Disc degeneration was evaluated using the Pfirrmann classification system. 4,21 After magnetic resonance imaging, intact CEPs from the central region of the L4-L5 and L5-S1 discs were removed from the subchondral bone and trimmed of nucleus pulposus tissue with a razor blade.…”

Emerging role and therapeutic implications of p53 in intervertebral disc degeneration

“…In a high-glucose environment, SIRT1 activation inhibits p53 acetylation, which protects NPCs from high glucose-induced apoptosis and senescence [ 112 ]. In addition, CEP degeneration plays an important role in IDD associated with nutritional disorders [ 250 ]. Under sublethal oxidative stress, SIRT1 overexpression significantly reduced p53 acetylation and alleviated oxidative stress-induced senescence in human CEP cells by inhibiting the p53/p21 pathway [ 251 ].…”