THE AFFECT OF 3D MATRIX MECHANICS ON STEM CELL DIFFERENTIATION
Sapun H. Parekh1, Kaushik Chatterjee1,2, Sheng Lin-Gibson1, Marcus T. Cicerone1, Marian F. Young2, and Carl G. Simon Jr.1
1Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD
2National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD
Deterministically controlling cell fate is paramount to success of tissue engineered systems as clinical therapies. Several groups have shown that the extracellular matrix modulates human bone marrow stromal cell (hBMSC) cell behavior, gene expression, and ultimately cell fate in two dimensional (2D) culture. We have developed a three dimensional (3D) culture system using non-degradable (poly)ethylene glycol (PEG) hydrogels to investigate the role of matrix mechanics on stem cell proliferation and cell fate in 3D. Our results show that hBMSC in 3D culture differentiate into bone-like cells in both soft (~ 300 Pa compressive modulus) and stiff (~ 59 kPa compressive modulus) hydrogels and produce calcium deposits by 10 days. Furthermore, we show upregulation of Runx2, a protein involved in bone signaling pathways, and demonstrate that cytoskeletal integrity is not required for differentiation in 3D PEG hydrogels. In contrast to 2D culture on tissue culture plastic (infinitely stiff substrate) where cells are quiescent and do not acquire a late-stage bone phenotype for more than 30 days, cells in 3D PEG hydrogels are sufficiently stimulated to differentiate into bone-like cells on a faster timescale. These results raise questions regarding the importance of cytoskeletal function, matrix rigidity, and dimensionality in control hBMSC fate.