PC12 cells grown on cellulosic filters differentiate in response to NGF and exhibit a polarity not seen when they are grown on solid substrata.

Studies were performed with cellulosic filters and standard culture plates to compare methods of cell culture and differentiation of the cell line PC12, a clone originating from a rat pheochromocytoma. PC12 cells respond to nerve growth factor (NGF) by flattening of the cell body and subsequent extension of neurite-like processes. When PC12 cells are cultured in dishes without NGF, they have a diameter of approximately 3 to 7 micron and exhibit short processes of no longer than 3 to 5 micron. If PC12 cells are grown on a cellulosic filter they have the same average soma diameter and similar short processes extending laterally, but in addition have branching processes which extend as far as 10 to 15 micron into the filter substrate. When dish-cultured and filter-cultured cells are incubated with 50 ng/ml NGF they both exhibit differentiation-specific ultrastructural changes by 3 d of treatment. In the case of dish-cultured cells, large cytoplasmic processes exhibit an increase in the number of chromaffin cell-like secretory granules by 3 d of treatment. This characteristic is also demonstrated by filter-cultured cells, but the processes containing these granules are found concentrated within the cellulosic meshwork. Thus the timing of the NGF-elicited differentiation program is similar to both filter-cultured and dish-cultured cells, but the ultrastructural consequences are different. The filter-cultured PC12 cells exhibit a polarity not demonstrated by dish-cultured cells. Growing PC12 cells on cellulosic filters is a technique useful for "anchoring" neurons without the complication of the addition of extracellular matrix components. Filter-culture may represent a more in vivo-like method for studying neuronal growth and differentiation.