Challenges and strategies in the repair of ruptured annulus fibrosus

Abstract

Lumbar discectomy is the surgical procedure most frequently performed for patients suffering from low back pain and sciatica. Disc herniation as a consequence of degenerative or traumatic processes is commonly encountered as the underlying cause for the painful condition. While discectomy provides favourable outcome in a majority of cases, there are conditions where unmet requirements exist in terms of treatment, such as large disc protrusions with minimal disc degeneration; in these cases, the high rate of recurrent disc herniation after discectomy is a prevalent problem. An effective biological annular repair could improve the surgical outcome in patients with contained disc herniations but otherwise minor degenerative changes. An attractive approach is a tissue-engineered implant that will enable/stimulate the repair of the ruptured annulus. The strategy is to develop three-dimensional scaffolds and activate them by seeding cells or by incorporating molecular signals that enable new matrix synthesis at the defect site, while the biomaterial provides immediate closure of the defect and maintains the mechanical properties of the disc. This review is structured into (1) introduction, (2) clinical problems, current treatment options and needs, (3) biomechanical demands, (4) cellular and extracellular components, (5) biomaterials for delivery, scaffolding and support, (6) pre-clinical models for evaluation of newly developed cell-and material-based therapies, and (7) conclusions. This article highlights that an interdisciplinary approach is necessary for successful development of new clinical methods for annulus fibrosus repair. This will benefit from a close collaboration between research groups with expertise in all areas addressed in this review.

Enhancing cell migration in shape-memory alginate–collagen composite scaffolds: In vitro and ex vivo assessment for intervertebral disc repair

“…In this context, research into biomaterial and cell based approaches has intensified over the last decade to treat both nucleus pulposus (NP) and annulus fibrosus (AF) tissues. (6)(7)(8)(9) Recent attempts to close AF defects and promote tissue repair in an ovine model using partially degradable pre-formed composite implant made of polyglycolic acid and polyvinylidene have been reported. (10) These implants were capable of successfully retaining the NP within the central region of the IVD impeding disc herniation and also supported cell infiltration and matrix deposition after 12 weeks.…”

Effects of Initial Boost with TGF-Beta 1 and Grade of Intervertebral Disc Degeneration on 3D Culture of Human Annulus Fibrosus Cells

“…In conjunction with the observation of low AF protein deposition, deduced from the weak staining results of characteristic matrix molecules, it is unclear, whether this construct would be biomechanically stable enough to facilitate AF repair in a clinical application. Several biomaterials have been suggested for AF repair that, in general, showed good biocompatibility with AF cells in vitro [10]. With regard to absorbable biomaterials, however, optimal absorption time with associated biomaterial stability has not been investigated systematically.…”

“…These changes result in a catabolic metabolic state with increasing fibrous transformation, impaired biomechanical function, and the incidence of AF defects. For biological annular repair techniques, the choice of a biocompatible and biomechanically suitable material is crucial [10]. But the additional enhancement of tissue generation with bioactive factors might be another important component [11], regardless of whether a cell-free [12] or a cell-based approach [13,14] is applied.…”

Association between the Number of Chondrocytes of Lumbar Intervertebral Discs and Age, Abdominal Aorta Atherosclerosis and Lumbar Artery Arteriosclerosis Descriptive Cross Sectional Study

“…The nucleus pulposus is highly pressurized and the annulus fibrosus prevents radial disc bulge which resists large tensile and compressive strains. The cartilaginous endplate is an interface tissue connecting the disc to the adjacent vertebral bodies, and functions to distribute stresses between the disc and the vertebrae and to act as a gateway for nutritional transport in the avascular disc [6]. Chondrocytes are the dominant cell type found in the disc and these cells are responsible for the synthesis, maintenance, and gradual turnover of the extracellular matrix.…”

“…[9]. During intervertebral disc degeneration (IVD), chondrocytes respond to early degeneration by increasing their biosynthetic processes [6]. Certain scientists believe that reimplantation of in vitro-activated autologous chondrocytes may be useful in reversing the disc degeneration process [10].…”