Biological characteristics of adult degenerative nucleus pulposus cells in a three-dimensional microcarrier stirring culture system

Abstract

A major problem in reconstructing degenerative intervertebral discs is to obtain sufficient nucleus pulposus (NP) seeding cells with normal physiologic functions. The current study adopted a three-dimensional microcarrier culture system for massive cell expansion and evaluated the biological characteristics and physiological functions of the propagated adult degenerative NP cells. Isolated adult NP cells were cultured in either microcarrier stirring culturing system or traditional monolayer cultivation. The growth characteristics, proliferation, extracellular matrix secretion, and apoptosis potential were examined to evaluate the different features of the two cultivation methods. Compared to the monolayer cultivation system, the adhesion time of NP cells in the three-dimensional microcarrier culture system appeared longer with relatively transient stable growth period. MTT and 3H-TdR assays suggested significantly elevated proliferation and higher thymidine incorporation rates in cells from microcarrier system compare to cells in the monolayer system at the exponential growth phase (p < 0.05). Western blot data complimented the immunostaining results that the NP cells in the microcarrier system expressed significantly more protein levels of both type collagens at the exponential growth phase than that in the monolayer system (p < 0.05). Further, significantly more 35S labeled proteoglycan incorporation was noticed in the cells on the microcarriers at both the stable growth and the exponential growth phases (p < 0.05 and p < 0.01). In conclusion, the three-dimensional microcarrier stirring culture system provides a means of fast and massive propagation of NP seeding cells which maintain their normal physiological characteristics and functions.