Collagendependent neurite outgrowth and response to dynamic deformation in three-dimensional neuronal cultures

Abstract—In vitro models of brain injury that use thick 3-D cultures and control extracellular matrix constituents allow evaluation of cell–matrix interactions in a more physiolog-ically relevant configuration than traditional 2-D cultures. We have developed a 3-D cell culture system consisting of primary rat cortical neurons distributed throughout thick (>500 lm) gels consisting of type IV collagen (Col) conju-gated to agarose. Neuronal viability and neurite outgrowth were examined for a range of agarose (AG) percentages (1.0– 3.0%) and initial collagen concentrations ([Col]i; 0–600 lg/ mL). In unmodified AG, 1.5 % gels supported viable cultures with significant neurite outgrowth, which was not found at lower (£1.0%) concentrations. Varying [Col]i in 1.25 % AG revealed the formation of dense, 3-D neurite networks at [Col]i of 300 lg/mL, while neurons in unmodified AG and at higher [Col]i (600 lg/mL) exhibited significantly less neurite outgrowth; although, neuronal survival did not vary with [Col]i. The effect of [Col]i on acute neuronal response following high magnitude, high rate shear deformation (0.50 strain, 30 s)1 strain rate) was evaluated in 1.5 % AG for [Col]i of 30, 150, and 300 lg/mL, which supported cultures with similar baseline viability and neurite outgrowth. Conjugation of Col to AG also increased the complex modulus of the hydrogel. Following high rate deformation, neuronal viability significantly decreased with increasing [Col]i, implicating cell–matrix adhesions in acute mechano-transduction events associated with traumatic loading. These results suggest interrelated roles for matrix mechanical properties and receptor-mediated cell–matrix interactions in neuronal viability, neurite outgrowth, and transduction of high rate deformation. This model system may be further exploited for the elucidation of mechanotransduction mech-anisms and cellular pathology following mechanical insult