CELL-AGGREGATION AND NEURITE GROWTH IN GELS OF EXTRACELLULAR-MATRIX MOLECULES

Components of the extracellular matrix are believed to guide both nerv e cells and neurites to their targets during embryogenesis and, theref ore, might be useful for controlling regeneration of nervous tissue in adults. To study the influence of extracellular conditions on neurite outgrowth and cell motility, PC12 cells were suspended in three-dimen sional gels containing (i) collagen (0.4 to 2 mg/mL), (ii) collagen (1 mg/mL) with added fibronectin or laminin(l to 100 mu g/mL), and (iii) agarose (7 mg/mL) with added collagen (0.001 to 1 mg/mL). Neurite out growth was stimulated with nerve growth factor (NGF) and both the exte nt of neurite outgrowth and cell aggregation were quantitated over 10 to 12 days in culture. The extent of neurite outgrowth was greatest at the lowest collagen concentration tested (0.4 mg/mL) and decreased wi th increasing concentration. The addition of laminin or fibronectin al tered the extent of neurite outgrowth in collagen gels, but the differ ences were small. Although no neurite growth was observed in pure agar ose gels, considerable neurite outgrowth occurred with the addition of small amounts (greater than or equal to 0.01 mg/mL) of collagen. Mean aggregate size increased more quickly in gels with lower concentratio ns of collagen. For cells in 1.0 mg/mL collagen, a four- to fivefold i ncrease in aggregate volume was seen between days 2 and 10 of the cult ure period, whereas the increase in DNA content during this same perio d was less than twofold, suggesting that the cells were aggregating, n ot multiplying. These results suggest that the composition of the matr ix supporting nerve cells has a significant effect on both neurite out growth and cell motility. (C) 1994 John Wiley and Sons, Inc.