Figure 1.

Combination of IGF-1 and BMP7 synergizes matrix formation by NP cells. NP cells were cultured in 1.2% alginate in serum-free medium with mini-ITS (control) or the control medium plus 100 ng/ml IGF-1, 100 ng/ml of BMP7, cocktail of IGF-1 and BMP7, and 1 ng/ml IL-1α. A, NP cells were stimulated for 21 days in indicated treatment condition. At the end of the culture period, the amount of PG in the cell-associated matrix were measured by DMMB assay and normalized to cell numbers using DNA measurement. Samples were measured in triplicate and presented as a percentage of the day 21 control cultures. B, NP cells were stimulated for 7 days by indicated treatment condition. At the end of the culture period, PG synthesis was measured during the last 4 hrs of culture using ³⁵S-sulfate incorporation and was normalized to cell numbers by DNA assay. C, NP cell pericellular matrix production after alginate culture for 21 days by indicated treatment condition was measured in an exclusion assay as described in Materials and methods. A representative cell was photographed using an inverted phase-contrast microscope. The CM can be seen excluding the erythrocytes from the cell plasma membrane (original magnification ×400). Four independent experiments in triplicates were performed.