Regional difference in the appearance of apoptotic cell death in the ligamentum flavum of the human cervical spine

Oxidative stress mediates age-related hypertrophy of ligamentum flavum by inducing inflammation, fibrosis, and apoptosis through activating Akt and MAPK pathways

The role of oxidative stress in ligamentum flavum (LF) hypertrophy has not been elucidated. We hypothesize that oxidative stress induces inflammatory responses and the subsequent fibrotic processes in LF, via activation of the Akt and MAPK pathways. Specimens of LFs were collected during surgeries for lumbar disc herniation (LDH) or lumbar spinal stenosis (LSS). Part of the LF specimens underwent analyses for ROS, fibrotic markers, and inflammatory mediators, with the remainder minced for cell cultures. The cell cultures were treated with H₂O₂, after which the cells were lysed and analyzed via western blotting. The specimens of the LSS patients showed increased infiltration of inflammatory cells and were stained positively for MMP-3, MMP-9, vimentin, and fibronectin. The LF of the LSS patients had increased oxidative stress and inflammation compared to that of the LDH patients. In vitro analyses demonstrated that oxidative stress rapidly activated the Akt and MAPK pathways. Inflammatory mediators, iNOS and NF-κB, and fibrotic markers, including TGF-β, β-catenin, α-SMA and vimentin, were significantly upregulated after induction of oxidative stress. Oxidative stress activated the intrinsic apoptotic pathway. These findings revealed that oxidative stress is one of the etiological factors of LF hypertrophy, which might provide new insights into treatment approaches.

Ossification of the Ligamentum Flavum in a Nineteenth-Century Skeletal Population Sample from Ireland: Using Bioarchaeology to Reveal a Neglected Spine Pathology

Ossification of the ligamentum flavum of the spine (OLF) is rarely reported in individuals of European ancestry. It has, however, been observed in archaeological skeletons from Europe. The aim of this study was to revisit OLF rates, utilising a mid-nineteenth-century skeletal sample from Ireland. The hypothesis was that the OLF prevalence rate was similar to studies on non-Europeans. Spines from 345 individuals were analysed, and the extent of OLF recorded on the cranial and caudal attachment sites of each vertebra using the following classification system: Grade 0 (no change); Grade 1 (<2 mm); Grade 2 (2–4 mm); Grade 3 (≥4 mm). OLF was observed at prevalence rates of 83.6%. There was no disparity in prevalence based on sex, except for individuals aged 36–45 years at death in which the male rate was higher. Advancing age was a determining factor in the OLF occurrence with an onset in young adulthood (18–25 years), and most severe grades occurring over the age of 25 years. OLF coincides with spinal osteoarthritis, spondylosis deformans and Schmorl’s nodes in both sexes, and with intervertebral osteochondrosis in females. The results of this study indicate that OLF is likely to be an understudied rather than rare condition in European populations.

Cyclic stretch enhances apoptosis in human lumbar ligamentum flavum cells via the induction of reactive oxygen species generation

OBJECTIVE

The lumbar ligamentum flavum (LF) is an important part of the spine to maintain the stability of the spine. In this study we aimed to examine whether mechanical force by cyclic stretch could induce apoptosis in human LF cells and investigate the underlying mechanism.

METHODS

LF cells were isolated from six young patients undergoing spinal surgery and then cultured in vitro. LF cells were subjected to cyclic stretch and the poptosis was detected by flow cytometry. The level of intracellular reactive oxygen species (ROS) and caspase-9 activity were measured.

RESULTS

Cyclic stretch at a frequency of 0.5 Hz with 20% elongation induced the apoptosis of human LF cells in vitro, and this was correlated with increased ROS generation and activation of caspase-9.

CONCLUSION

Our study suggests that cyclic stretch-induced apoptosis in human LF cells may be mediated by ROS generation and the activation of caspase-9.

Ultrastructural change of ligamentum flavum in galactosialidosis

PURPOSE

Galactosialidosis is an autosomal recessive lysosomal storage disease caused by deficiency of both α-neuraminidase and β-galactosidase due to a defect of the protective protein/cathepsin A. Three clinical subtypes have been described, depending on the age of onset and severity of the symptoms: the early infantile, late infantile and juvenile/adult form. We report an adult-type patient who underwent surgery for galactosialidosis-related spinal deformity, and showed a favorable course thereafter.

METHODS

The patient was a 50-year-old male, and he consulted our hospital with pain of the bilateral anterior thigh. Lumbar radiograph showed applanation and horn-like deformity of the L2 vertebral body, which is characteristic of this disease, narrowing of the L1/2 intervertebral space, and topical kyphosis. Fenestration between the L1/2, decompression of the L2 nerve root, and posterolateral fusion involving the T12 to L3 were performed.

RESULTS

Immediately after surgery, pain of the lower limbs disappeared. During the 2-year postoperative follow-up, bone assimilation was achieved, showing a favorable course. Histological examination of the ligamentum flavum (LF) collected during surgery showed that the elastic fibers were thin, whereas the collagen fibers were abundant and dense. The ligament cells were swollen, and there were a large number of vacuoles in the cytoplasm.

CONCLUSION

This is the first report on spinal surgery for adult-type galactosialidosis and histological examination of spinal LF.

An ultrastructural study on the ligamentum flavum of the cervical spine in patients with ossification of the posterior longitudinal ligament

Some histological analyses of the ossification of the posterior longitudinal ligament (OPLL) have been reported, but no ultrastructural studies of the ligamentum flavum (LF) in patients with OPLL have been published to date. To understand the pathology of the ossification of the spinal ligament, we examined, by electron microscopy, ultrastructural changes in the LF in cases of OPLL and made a comparison with the LF in cervical spondylotic myelopathy (CSM). Subjects were three men and two women with cervical OPLL who underwent longitudinal spinous process-splitting laminoplasty. During surgery, a small piece of the LF was collected from C2-C3 to C7-T1 and was then analyzed by light and electron microscopy. We observed atrophic elastic bundles with a two-layer structure and disarrangement, a partially torn area, the disappearance of microfibrils, and an enlarged interstitium with an irregular alignment of collagen fibrils. We observed some properties of a cell preceding its death: the initial phase may be the disappearance of the plasma-membrane, followed by the scattering of many organellae around its degenerated nucleus. Finally, many extracellular plasma membrane-invested particles that resemble matrix vesicles remain there without phagocytosis. These results suggest that ultrastructural abnormalities exist in the spinal ligament in cases of ossification of the spinal ligament.

Immunohistochemical and electron-microscopic observation of beta-cells in pancreatic islets of spontaneously diabetic Goto-Kakizaki rats

The Goto-Kakizaki (GK) rat offers a genetic model of type 2 diabetes and displays profoundly defective insulin secretion leading to basal hyperglycemia. This animal is widely used for studying type 2 diabetes. However, the morphological characteristics of the pancreatic islets of Langerhans in GK rats are not fully understood. The present study sought to clarify this issue using immunohistochemical and electron microscopic techniques. GK rats were killed at 7, 14, 21, and 35 weeks of age. Structural islet changes were not observed at 7 weeks old. At 14 and 21 weeks of age, GK rats displayed histopathological islet changes. The general shape of islets became irregular, and immunoreaction of beta-cells against antiinsulin appeared diffusely weakened. Electron microscopy revealed that the numbers of so-called beta-granules decreased and the numbers of immature granules increased. The Golgi apparatus of beta-cells was developed and the cisternae of rough endoplasmic reticulum were often dilated, indicating hyperfunction of the cells. However, at 35 weeks old, immunoreactivities of dispersed beta-cells into the exocrine portion recovered, and numbers of secretory granules increased again and features of the cell organelles did not display hyperfunction. These results suggest that insulin deficiency in GK rats is not caused by simple dysfunction and/or degeneration of beta-cells but rather by more complicated events within cells.