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 identified in intervertebral discs, including the fibronectin-binding integrin receptors alpha(5) beta(1), alpha(v) beta(3) and the collagen-binding integrin receptors alpha(1) beta(1), alpha(2) beta(1), and, alpha(v) beta(1). But the integrins expressions in degenerated intervertebral discs are still unknown. In our study, the expressions of alpha(1), alpha(2), alpha(5), alpha(v), beta(1), beta(3) 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 alpha(1), alpha(2), alpha(5),alpha(v), beta(1), and beta(3) 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 alpha(5) and beta(1) subunits were increased in herniated discs, especially in the discs of extrusion. But as to alpha(1), alpha(2), alpha(v) and beta(3), their expressions had no difference among the discs. Fibronectin, whose binding integrin receptor was alpha(5) beta(1) 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.

Integrin – Dependent Mechanotransduction in Mechanically Stimulated Human Annulus Fibrosus Cells: Evidence for an Alternative Mechanotransduction Pathway Operating with Degeneration

“…Taken together, this study and that by Le Maitre and colleagues suggest a role for RGD-integrins as mechano-receptors in mechanically stimulated AF and NP cells. Interestingly however, involvement of these RGD-integrins in both cell types appears to then be lost with degeneration, suggesting that RGD integrin mediated mechanotransduction may not be operational in cells derived from degenerate IVDs, although they have been shown to express integrin subunits [36], [37], [38].…”

“…IVD cells have been shown to express many of the integrin subunits expressed by chondrocytes [36], [37], [38] and a role for integrins in the mechano-response of IVD cells has been suggested [30].…”

CCN2 Suppresses Catabolic Effects of Interleukin-1β through α5β1 and αVβ3 Integrins in Nucleus Pulposus Cells

“…These studies show that the ␤1 integrin, especially the ␣5␤1 heterodimer, is essential for NP cell attachment to fibronectin, collagen II, and lamin isoforms (LM-111 and LM-511), with additional contribution from ␣1, ␣2, and ␣3 integrin subunits (43)(44)(45). In the context of the disc degeneration, one study reported an increase in ␣5␤1 integrin expression in herniated disc tissue; it was speculated that the measured increase in fibronectin and collagen I was a result of altered cell-matrix interactions (46). Further evidence of altered expression came from our own studies that showed a trend of increasing expression of ␤1, ␣5, and ␣V integrin subunits in severely degenerated human disc samples (grade 4 and 5) compared with moderately degenerated discs (grade 2 and 3).…”

Fibronectin fragment activation of ERK increasing integrin α5 and β1 subunit expression to degenerate nucleus pulposus cells

“…For the determination of the mRNA expression of integrin α 5 , integrin β 1 , MMP9, MMP13, and collagen II, real‐time quantitative polymerase chain reaction (RT‐PCR) was performed as previously described 10. After releasing the cells from the beads as described above, the cell pellet was washed and suspended in Trizol for RNA extraction 10. Forward and reverse primer sequences are listed in Table 1 and synthesized by TaKaRa Biotechnology (Dalian, China).…”

“…The protein level of MMP9, MMP13, collagen II, ERK 1/2 , and phosphorylated ERK 1/2 was measured by immunoblotting, and the protein expression of integrin α 5 and β 1 was determined by immunoprecipitation and Western blotting as previously described 10. The cells were also released from the alginate beads.…”