Analysis of sGAG production by BM and AD-MSCs in response to growth-factor stimulation. BM and AD-MSCs were seeded in type I collagen hydrogels and cultured in the absence or presence of TGF-β, GDF5, or GDF6. (A) DMMB quantification of sGAG retained within gel constructs, normalized to DNA content within the construct. (B) DMMB quantification of sGAG released cumulatively into the media throughout the culture period. (C) Quantification of total sGAG content in the construct and media normalized to DNA content within the construct at day 14. N = 3, data represent mean ± SEM. *P < 0.05. (D) Safranin O staining of MSC-seeded collagen gels demonstrating deposition of sGAG throughout the constructs, with AD-MSCs stimulated with GDF6 having the highest and most homogeneous sGAG deposition. Scale bars, 500 μm.