Morphological Alteration and TGF-β1 Expression in Multifidus with Lumbar Disc Herniation

Abstract

Background: Lumbar disc herniation (LDH) can cause lumbar nerve root compression, which can lead to denervated atrophy of paraspinal muscles theoretically, however, the conclusions of morphological alteration in multifidus with LDH remain controversial. Transforming growth factor-beta 1 (TGF-β1) plays an essential role in the development of tissue fibrosis and is a molecular marker in the study of muscle fibrosis, but no relevant studies on TGF-β1 expression in multifidus have been reported so far. This study is to observe altered morphology of multifidus in patients with LDH, and to explore the correlation between multifidus fibrosis and TGF-β1 expression.

Materials and methods: 46 LDH patients with low back pain combined with unilateral leg radiation pain and/or numbness were selected. Patients were divided into four groups according to their medical histories. Group 1: medical history less than 6 months (15 cases); group 2: a medical history of 6-12 months (10 cases); group 3: a medical history of 12-24 months (13 cases); and group 4: medical history > 24 months (8 cases). Bilateral multifidus specimens were taken from compressed nerve root segments, and morphological changes in multifidus were determined. Multi-parameter changes in TGF-β1 expression in multifidus were observed by immunohistochemistry and immunofluorescence.

Results: HE staining showed that the cross-sectional area (CSA) of multifidus in the involved sides decreased and muscle fibers atrophied. Masson's trichrome staining showed a decrease in the sectional area ratio of myofibers to collagen fibers in the involved side. In groups 1 and 2, there were no significant differences in the aforementioned parameters. In groups 3 and 4, statistically significant differences in the sectional area ratio of myofibers to collagen fibers in both sides were seen (P < 0.05). TGF-β1 expression was significantly enhanced in both muscle cells and the matrix of the involved side, while no expression or a little expression was found in the matrix in the uninvolved side. In group 1, there was no statistically significant difference in TGF-β1 expression in both sides. In the remaining three groups, TGF-β1 expression in the involved sides was higher than were found in the uninvolved sides.

Conclusions: Nerve root compression by LDH leads to multifidus atrophy, fibrosis, and increased TGF-β1 expression, which might promote multifidus fibrosis.Trials registration All Clinical Trials done in India should preferably be registered with the Clinical Trials Registry of India, set up by the Indian Council of Medical Research (website: http://ctri.nic.in). Authors should provide the CTRI number along with the manuscript.

Keywords: Fibrosis; Intervertebral disc degeneration; Lumbar disc herniation; Lumbar vertebrae; Microscopic findings; Morphological; Multifidus; Paraspinal muscles; Transforming growth factor beta 1.

Fig. 1

Typical case: male, 53-years of age, with a history of complaining about low back pain accompanied by radiative pain and numbness in the left lower extremity for 9 months. MRI sagittal image showed L4–L5 disc prolapse and dissociation (a). Cross-sectional imaging showed that the L4–L5 left posterior disc had herniated and the left L5 nerve root was compressed significantly

Fig. 2

HE staining of the multifidus: uninvolved side (a), group 1 (b), group 2 (c), group 3 (d), and group 4 (e). Masson’s trichrome staining: uninvolved side (f), group 1 (g), group 2 (h), group 3 (i), and group 4 (j)

Fig. 3

Immunohistochemical results of the multifidus: uninvolved side (a), group 1 (b), group 2 (c), group 3 (d), and group 4 (e). The expression of TGF-β1 was stained brown and the nuclei were stained blue

Fig. 4

Results of immunofluorescence staining of the multifidus: uninvolved side (a), group 1 (b), group 2 (c), group 3 (d), and group 4 (e). Expression of TGF-β1 was detected as a red staining pattern, and the nuclei were detected as blue staining by immunofluorescence