[Mechanism of P38 Mitogen Activated Protein Kinase Signaling Pathway on Promoting the Hypertrophy of Human Lumbar Ligamentum Flavum Via Transforming Growth Factor β /connective Tissue Growth Factor]

Objective: To investigate the mechanism of p38 mitogen activated protein kinase (MAPK) signaling pathway in regulating the hyperplasia and hypertrophy of human lumbar ligamentum flavum via transforming growth factor β (TGF-β )/connective tissue growth factor (CTGF).

Methods: The lumbar ligamentum flavum tissue taken from patient with lumbar intervertebral disc herniation was isolated by collagenase-predigested explant cultures. The ligamentum flavum cells were treated with the extracellular regulated protein kinase pathway blocker PD98059, c-Jun N-terminal kinase pathway blocker SP600125, and p38 pathway blocker SB203580, and then the mRNA expressions of CTGF, collagen type Ⅰ, and collagen type Ⅲ were detected by real-time fluorescence quantitative PCR (qRT-PCR). The ligamentum flavum cells were divided into 4 groups, and transfected with small interfering RNA (siRNA), p38 siRNA, siRNA+3 ng/mL TGF-β , and p38 siRNA+3 ng/mL TGF-β in groups A, B, C, and D, respectively. After 24 hours of transfection, immunofluorescence staining was performed to observe the expressions of p38 and phosphorylation p38 (p-p38); the relative mRNA expressions of CTGF, collagen type Ⅰ, and collagen type Ⅲ in each group were detected by qRT-PCR; the protein expression of CTGF in each group was detected by Western blot.

Results: p38 pathway blocker SB203580 could significantly reduce the relative mRNA expressions of CTGF, collagen type Ⅰ, and collagen type Ⅲ ( <0.05). After 24 hours of transfection, immunofluorescence staining showed positive staining with p38 and p-p38 expressions in groups A, C, and D and negative staining in group B. Compared with group A, the relative mRNA expressions of CTGF, collagen type Ⅰ, and collagen type Ⅲ and relative protein expression of CTGF in group B decreased significantly ( <0.05), while those in groups C and D increased significantly ( <0.05); and those indicators significantly increased in group C than in group D ( <0.05).

Conclusion: TGF-β /CTGF based on the p38 MAPK signaling pathway play an important role in the occurance and development of hypertrophy of human lumbar ligamentum flavum.