Figure 4. Schematic of cell and matrix reciprocity under macromolecular crowding.

(A) Adherent mesenchymal stromal cell (MSC) under typical in vitro culture conditions. (B) Upon the addition of macromolecular crowders, excluded volume effects promote bundling and alignment of extracellular matrix (ECM) fibers. (C) In response to the aligned ECM, the intracellular actin cytoskeleton reorganizes to align with the ECM. In addition, the cell secretes more matrix proteins, which are deposited to and further enhance the alignment of the ECM. We find that these reciprocal changes in the matrix material and intracellular cytoskeletal organization correlate with an increase in proliferation and a decrease in motility of MSCs.