![]() Type II collagen is also present in the AF but to a far lesser extent, the NP however is rich in type II collagen where type II fibrillar networks entrap the hyaluronan (HA)-aggrecan-link ternary complexes which are so important for discal biomechanical function. Type I collagen is the major fibrillar collagen of the AF with its concentration maximal in the outer annular lamellae. Furthermore, bulging of the NP upon axial spinal loading results in load transfer to the annular lamellae which bulge and generate radial hoop stresses which dissipate shear stresses generated during axial loading of the spine. Hyaluronan forms massive link-protein stabilized aggregates with aggrecan which have impressive water regain properties the high concentration of aggrecan in the NP generate an internal hydrostatic pressure in the IVD which counters axial spinal loading. The major proteoglycan of the NP is a large chondroitin sulphate (CS)and keratan sulphate (KS)rich proteoglycan of the Hyalectan family called aggrecan. The hydration provided by the hydrophilic proteoglycans of the NP afford viscoelastic and hydrodynamic properties which equip the IVD with its ability to act as a weight bearing cushion. Collectively, this arrangement of connective tissues equips the IVD with unique weight-bearing capability. Superior and inferior endplates of hyaline cartilage, the cartilaginous endplates (CEPs), enclose the NP where it borders the spinal vertebrae. The outer regions of the IVD, the annulus fibrosus (AF), is composed of collagen rich annular lamellae, which are arranged around a central proteoglycan rich region called the nucleus pulposus (NP). The IVD achieves these remarkable properties through the interplay of a number of connective tissues of disparate structure and function that collectively endow the composite IVD with its unique mechanical properties. The intervertebral disc (IVD) is a tough but intricately organized connective tissue which resists tension and weight bearing during axial and torsional spinal loading but also provides spinal stability and flexibility. MSCs induced a strong recovery in discal pathology with a reduction in cumulative histopathology degeneracy score from 15.2 to 2.7 ( p = 0.001) over a three-month recovery period but no recovery in carrier injected discs. Similar features in 6 × 20 mm lesions occurred over a 3–6-month post operative period. Focal proteoglycan depletion was associated with 5 × 5 mm annular rim lesions, bifurcations, annular delamellation, concentric and radial annular tears and an early influx of blood vessels and cells around remodeling lesions but the inner lesion did not heal. Lumbar intervertebral discs (IVDs) were scored under categories (i–vi) to provide a cumulative score, which underwent statistical analysis using STATA software. Three study groups were examined: 5 × 5 mm lesion 6 × 20 mm lesion and 6 × 20 mm lesion plus mesenchymal stem cell (MSC) treatment. Toluidine blue and Haematoxylin and Eosin (H&E) staining were used to evaluate cellular morphology: (i) disc structure/lesion morphology (ii) proteoglycan depletion (iii) cellular morphology (iv) blood vessel in-growth (v) cell influx into lesion and (vi) cystic degeneration/chondroid metaplasia. The purpose of this study was to develop a quantitative histopathological scoring scheme to evaluate disc degeneration and regeneration using an ovine annular lesion model of experimental disc degeneration.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |