Why is feeder cells not required for primary cell culture?
Feeder cell layers usually consist of adherent growth-arrested but viable and bioactive cells (primary cells or continuous cell lines) that have been incapacitated, for example by irradiation. These cells are used as a substratum on which other cells are grown in a co-culture system. Some cells can be grown in culture dishes, coated, for example, with collagen, fibronectin, or a mixture of the extracellular matrix components (Matrigel). Many cell types, however, are completely dependent on physical contact with a feeder layer for survival and expansion. Feeder cell layers provide an intact and functional extracellular matrix and matrix-associated factors (see also: juxtacrine) and still secrete known and unknown cytokines into the conditioned medium. As such feeder cells have the capacity to support in vitro survival and growth of some fastidious cells that would require, for example, the presence of a variety of known or unknown soluble or membrane-bound growth factors and receptors.
