Study of Correlation Between the Level of Intradiscal Periostin Expression and Pfirrmann Grading.

Intervertebral disc degeneration (IVDD) is a well-recognized musculoskeletal condition that imposes a substantial socioeconomic burden and is an important cause of low back pain. IVDD can result from a variety of factors, including aging, obesity, genetic predisposition, degeneration of the multifidus and psoas muscles, osteoporosis, inflammation, and oxidative stress. The intervertebral disc (IVD) within the spine is composed of a gel-like nucleus pulposus (NP) at its center, a surrounding annulus fibrosus (AF), and cartilaginous endplates above and below. The NP and AF produce a water-rich extracellular matrix (ECM), which contributes to normal functioning of the spinal column.

Various internal and external stimuli cause dysfunction of the NP and AF, and excessive metabolic activity of the endplates leads to endplate degeneration and calcification, ultimately resulting in disc degeneration. In addition to aging and mechanical overload, increased oxidative stress and inflammatory cytokine release further accelerate IVDD (1,2).

Periostin is a component of the ECM that is associated with mechanical stress, inflammation, and aging, and has been closely linked to the development and progression of IVDD. Periostin binds to ECM molecules within the IVD and is involved in disc maintenance and repair; however, excessive ECM turnover induces and accelerates disc degeneration. Periostin affects IVD degeneration through pathways related to mechanical stress and inflammation, and serum periostin levels have been reported to be elevated in patients with more advanced disc degeneration. A recent study demonstrated a strong correlation between serum periostin concentration and the Pfirrmann grading system (3). However, measuring periostin concentration through blood sampling has limitations, as serum periostin levels can also increase similarly in patients with a history of head and neck cancer or allergic disease. Therefore, it is necessary to directly assess the degree of periostin expression within the intervertebral disc itself and to determine whether it shows a meaningful correlation with the Pfirrmann grading system. In addition, periostin is known to be more abundant in the AF than in the NP, but this has not previously been demonstrated through actual staining of disc tissue; this study therefore aims to compare the degree of periostin expression between the NP and AF using immunohistochemical staining.

Pfirrmann et al. developed a reliable, MRI-based grading system that is the most commonly used method for evaluating IVDD. The Pfirrmann grading system is based on analysis of T2-weighted MR sagittal images of the IVD, incorporating disc homogeneity, morphology, the distinction between the AF and NP boundary, T2 signal intensity, and disc height (2).