INTRODUCTION: Galectin‐1 (Gal‐1), an endogenous β‐galactoside‐binding protein, is known to bind to various extracellular matrix proteins including laminins. Previously, higher laminin‐10 (LM‐511) expression was found in nucleus pulposus (NP) as compared to anulus fibrosus (AF) tissues of intervertebral disc (IVD), which may differentially contribute to Gal‐1 interactions with extracellular matrix. In addition, we also identified higher levels of Gal‐1 mRNA in immature rat NP tissues as compared to AF, further suggesting that the interactions between Gal‐1 and laminins may be unique for NP cells. The objective of this study was to evaluate protein expression of Gal‐1 in IVD tissues and to test for an effect of Gal‐1 to mediate IVD cell adhesion to laminins through cell attachment and magnetic activated cell sorting (MACS) studies.
METHODS: NP and AF tissues were harvested from IVDs of rats, pigs and patients (scoliosis or disc degeneration). Frozen tissue sections were immunostained with a polyclonal antibody to human Gal‐1. Attachment of isolated NP and AF cells from pig and human IVDs on laminins (LM‐111 and LM‐511) were compared with/without preincubation with Gal‐1. A biotinylated Gal‐1(B‐Gal‐1) recombinant protein was used to evaluate its affinity binding to IVD cells and to select IVD cells by MACS with streptavidin.
RESULTS: Similar staining patterns for Gal‐1 and LM‐511 in IVD tissue suggests that Gal‐1 may serve as an adhesion molecule to interact with both cells and laminin matrix. However, Gal‐1 increased both NP and AF cell attachment (more than 100% as compared to control) to laminins and exhibited a similar binding affinity to both cell types in vitro. Incubation with B‐Gal‐1 was also able to promote retention of more than 50% of NP and AF cells by MACS. These results suggest that a MACS protocol based on IVD cell attachment to B‐Gal‐1 may be useful for enriching healthy IVD cells from mixed cell populations for autologous cell delivery.