Differential effect of serum on laminin-dependent outgrowth of embryonic and adult mouse optic axons in vitro.

Laminin is an extracellular matrix molecule which promotes neurite outgrowth from a variety of neurons in culture. However, the reported effectiveness of laminin on neurite outgrowth from retinal ganglion cells in rat and that from chick have been contradictory. In chick, embryonic retinal ganglion cells show strong laminin-dependent neurite outgrowth which is lost during development. In contrast, in rat, laminin promotes neurite outgrowth from adult, but not embryonic retinal ganglion cells. We have reexamined the response of adult and embryonic mouse retinal ganglion cells to laminin in culture. We found, first, that both adult and embryonic retinal neurites respond to laminin with neurite outgrowth in serum-free medium. Second, we found that the addition of serum to the medium greatly inhibits the outgrowth of neurites from embryonic, but not adult, retinal explants. This inhibition appears specific for neurite outgrowth involving laminin receptors, since embryonic explants showed extensive neurite outgrowth in the presence of serum when astrocytes were used as a substrate. These developmental differences in the effect of serum on laminin-dependent neurite outgrowth may indicate maturational changes in surface molecules on optic fibers related to regenerative failure in the adult CNS.