Effect of nucleus pulposus cells having different phenotypes on chondrogenic differentiation of adipose-derived stromal cells in a coculture system using porous membranes

In this study, adipose-derived stem cells (ASCs) were cocultured with nucleus pulposus (NP) cells using a porous membrane to investigate the effect of NP cell phenotype on ASC chondrogenic differentiation. Human NP cells were collected from 14 patients and classified into two groups (normal vs. degenerative) depending on the level of type II collagen, aggrecan (AGG), type I collagen, and bax gene expression. Human ASCs were then cocultured with each group of NP cells on porous membranes in the absence of chondrogenic supplements. After 2 weeks, real-time-polymerase chain reaction results showed that ASCs cocultured with normal NP cells had much higher type II collagen and AGG gene expression than ASCs cocultured with degenerative NP cells. The production of AGG was also observed only in the group cocultured with normal NP cells. Additionally, coculture of ASC pellets with normal NP cells promoted the production of AGG as compared to coculture of ASC monolayer with normal NP cells. These data demonstrate that a coculture system using porous membranes can induce ASC differentiation into NP cells without chondrogenic supplements. Further, the phenotype of cocultured NP cells significantly influences the extent of ASC differentiation.