Characterization of commercial laminin preparations from human placenta in comparison to recombinant laminins 2 (α2β1γ1), 8 (α4β1γ1), 10 (α5β1γ1)

Laminins, a family of large heterotrimeric (αβγ) proteins, are major components of basement membranes implicated in a variety of cellular functions. Different commercial laminin preparations isolated from human placenta have been widely used in functional studies but their molecular properties are poorly known. In the present study, we characterized several of these preparations by ELISA, silver staining and Western blotting, in comparison to mouse laminin 1 (α1β1γ1), and recombinant human laminins 2 (α2β1γ1), 8 (α4β1γ1) and 10 (α5β1γ1). The cell migration-promoting activity of different batches was also tested. The placenta laminin preparations differed from one another and consisted of highly fragmented proteins, a mixture of laminin isoforms, and/or contaminating fibronectin. Major functional differences between batches were also observed, reflecting molecular heterogeneity. Previous data obtained in functional studies using these preparations need to be interpreted with caution and may require revision, and future functional studies demand prior molecular characterization of the laminins, particularly their α-chain.