Expression of Integrin Subunits in the Herniated Intervertebral Disc

Abstract

Integrins are a class of cell adhesion molecules that regulate interactions between cells and their extracellular matrix (ECM). Several specific integrin receptors have been indentified in intervertebral discs, including the fibronectin-binding integrin receptors α₅ β₁, α_v β₃ and the collagen-binding integrin receptors α₁ β₁, α₂ β₁, and, α_v β₁. But the integrins expressions in degenerated intervertebral discs are still unknown. In our study, the expressions of α₁, α₂, α₅, α_v, β₁, β₃ integrin subunits, collagens, and fibronectin in normal and herniated intervertebral discs of human were determined. Specimens of human lumbar intervertebral discs were divided into 3 groups: normal discs (n = 10), protrusion (n = 15), and extrusion (n = 15). Real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunoprecipitation were used to evaluate the α₁, α₂, α₅,α_v, β₁, and β₃ integrin subunits messenger ribonucleic acid (mRNA) and protein expressions. RT-PCR was also performed to measure the mRNA level of collagen I, collagen II, and fibronectin. The expressions of α₅ and β₁ subunits were increased in herniated discs, especially in the discs of extrusion. But as to α₁, α₂, α_v and β₃, their expressions had no difference among the discs. Fibronectin, whose binding integrin receptor was α₅ β₁ was also increased. And in herniated discs, the collagen I was increased, but the collagen II was decreased. The expressions of some integrin subunits were increased in herniated discs. These results may be attributed to the interaction between cells and the ECM in the process of degeneration.

Keywords:

• Integrin
• Intervertebral Disc
• Collagen
• Fibronectin