Aggrecan, versican and type VI collagen are components of annular translamellar crossbridges in the intervertebral disc

Abstract

The aim of this study was to undertake a detailed analysis of the structure of the inter and intralamellar regions of the annulus fibrosus. A total of 30 newborn to 6 year-old lumbar ovine intervertebral discs (IVDs) were fixed and decalcified en-bloc to avoid differential swelling artifacts during processing and vertical midsagittal, and horizontal 4 lm sections were cut. These were stained with toluidine blue to visualise anionic proteoglycan (PG) species, H & E for cellular morphology and picrosirius red (viewed under polarized light) to examine collagenous organization. Immunolocalisations were also undertaken using anti-PG core-protein and glycosaminoglycan (GAG) side chain antibodies to native chondroitin sulphate (CS), D C-4-S and C-6-S unsaturated stubs generated by chondroitinase ABC digestion of CS, keratan sulphate (KS), and with antibodies to type I, II, VI, IX and X collagens. Trans-lamellar cross bridges (TLCBs), discontinuities in annular lamellae's which provide transverse interconnections, stained prominently with toluidine blue in the adult IVDs but less so in the newborn IVDs. In adult discs TLCBs were evident in both the posterior and anterior AF where they extended from the outermost annular lamellae almost to the transitional zone extending across as many as eight lamellar layers displaying a characteristic circuitous, meandering, serpentine type course. There were significantly fewer TLCBs in 2 week-old compared with skeletally mature sheep and there was a further increase from 2 to 6 years. Immunolocalisation of perlecan delineated blood vessels in the TLBs of the newborn but not adult IVDs extending into the mid AF. In contrast adult but not 2 week-old TLCBs were immunpositive for C-4-S, C-6-S, KS, aggrecan, versican and type VI collagen. The change in number and matrix components of the translamellar cross bridges with skeletal maturity and ageing suggest that they represent an adaptation to the complex biomechanical forces occurring in the annulus fibrosus.

The elastic fibre network of the human lumbar anulus fibrosus: architecture, mechanical function and potential role in the progression of intervertebral disc degeneration

“…The existence of trans-lamellar 'cross-bridges' in the anulus, and their chemical composition, has been described [40,57,73,74]. Observed in both the transverse and sagittal planes, these structures appear to form connections between collagen bundles in non-consecutive lamellae.…”

“…through inter-bundle spaces [38], enabling them to function without interrupting the intralamellar structure. In addition to containing aggrecan, versican and type VI collagen [40], these cross-bridges contain densely arranged elastic fibres [73,74].…”

“…With respect to trans-lamellar cross-bridges, the presence of elastic fibres in these structures [73,74] suggests they may be capable of extending to, and recovering from, significant tensile strains, while the presence of collagen VI [40] suggests they also possess some intrinsic tensile strength. Evidence of such a composite mechanical capability may indicate the potential importance of anular cross-bridges in restoring the hierarchical lamellar structure following the complex normal and shear strains experienced by the anulus during physiological deformation.…”

Intervertebral Disc Characteristic on Progressive Neurological Deficit

“…Therefore, early diagnosis of disc degeneration is critical for the success of any modality of treatment strategy. 8,9 The etiologic factors of nocioceptive and disability caused by pathological disc is still currently debatable. 2,10 A common belief is that changes the diffusion of water will result in structural changes in nucleus pulposus, annulus and end plate that are altered the internal disc stability.…”

Avaliacão da placa vertebral terminal na coluna cervical em diferentes faixas etárias e sua correlação com a espessura do disco intervertebral

“…O disco intervertebral (DI) é estrutura avascular e composta de fibras colágenas, água e proteoglicanos (1) . A nutrição do disco intervertebral ocorre por meio de difusão dos nutrientes através da placa vertebral terminal (2) .…”