BackgroundOne of the characteristics of lumbar spinal stenosis (LSS) is elastin degradation and fibrosis in the ligamentum flavum (LF). However, the biochemical factors that cause these histologic changes is unclear. P16 and S100 participate in scar formation and collagen development in wound healing and fibrosis diseases. In this study, we investigate the association between P16 and S100 expression and the fibrosis of the hypertrophic LF in LSS.MethodsThe LF specimens were surgically obtained from 30 patients with single-segment LSS (SLSS), 30 patients with double-segment LSS (DLSS) and 30 patients with L4/5 lumbar disc herniation (LDH). The LF thickness was measured by axial T1-weighted MRI. The extent of LF elastin degradation and fibrosis were graded based on hematoxylin-eosin (HE) and Verhoff’s Van Gieson’s (VVG) stain, respectively. The localization of P16 and S100 was determined by immunohistochemistry.ResultsThe Absolute and relative LF thickness were greater in the DLSS group compared with the SLSS and LDH groups (p <  0.05). The elastic tissue from the dorsal aspect to the dural aspect in SLSS and DLSS groups was significantly increased. The amount of collagen deposition and elastic tissue is significantly higher in the DLSS group compared with the SLSS and LDH groups (p <  0.05). The specimens in the DLSS group showed positive staining of P16, especially in the dorsal layer. Almost all samples in the SLSS group were partially positive for P16. The LDH group showed negative staining of P16 in both the dural and dorsal layers. All the three groups were stained with S100 in the dorsal layer of the LF. On the contrary, S100 staining was absent in the dural layer of the LF in the three groups.ConclusionsElastin degradation and fibrosis of the LF in the DLSS patients is more severe compared with the SLSS and LDH patients. Increased expression of P16 associated with LF fibrosis and thickness, suggested that the expression of P16 may related to LF hypertrophy in the patients who suffer with LSS. LF hypertrophy process may not be associated with high expression of S100.

Background: Lumbar spinal stenosis (LSS) is a common degenerative disease, which can lead to neurological dysfunction and requires surgical treatment. In the previous study, we used H&E staining and immunohistochemistry to qualitatively analyze the expression of S100 and P16 in the pathological process of ligamentum flavum (LF) hypertrophy in patients with LSS. To further explore the relationship between P16, S100 and LF hypertrophy in patients with LSS, we quantitatively detected S100 and P16 and their expressed products based on molecular biology techniques, and analyzed their imaging correlation. Methods: Before posterior lumbar surgery, LF thickness was measured by Magnetic Resonance Imaging (MRI). Through the operation, we obtained the specimens of LF from 120 patients, all of whom were L4/5 LF. They were designated: simple lumbar disc herniation (LDH), single-segment spinal stenosis (SLSS), and double-segment LSS (DLSS). The detection of each side of LF was assessed. S100 and P16 and their expression products were detected by western blot and quantitative polymerase chain reaction (qPCR). Results: The dorsal mRNA expression of P16 in DLSS group was significantly higher than that in SLSS group. On the dorsal and dural side of LF, the expression of P16 mRNA and proteins in the LDH group was significantly lower than that in SLSS and DLSS groups. We found a correlation between the thickness of LF and the expression of P16. However, there was no significant difference in the expression of S100 mRNA and S100 protein on both sides of the ligament and among the three groups, and no significant correlation between the expression of S100 and the thickness of LF. Conclusions: P16 is involved in the process of LF hypertrophy in patients with LSS, and the imaging thickness of LF is related to the expression of P16. No obvious evidence proves that S100 may be related to the hypertrophy of LF in patients with LSS.