A comparison of three cell types as potential candidates for intervertebral disc therapy: annulus fibrosus cells, chondrocytes, and bone marrow derived cells.

OBJECTIVES: Candidate cell types for disc cell transplantation therapy include anulus fibrosus (AF) cells, chondrocytes, and bone marrow derived cells (BMDCs). We compared the disc matrix production in these three types of cells, before and after stimulation with rhBMP-2. There is no study extant that compares these three cell types to determine the best candidate for the disc cell therapy.
METHODS: AF cells, chondrocytes, and BMDCs (iliac crest and femur) were isolated and grown in monolayer. They were treated for 3 days with rhBMP-2. After 3 days, proteoglycan (sGAG) content in the media was quantified. The results were normalized by cell numbers. The mRNA expression of aggrecan, type I collagen, and type II collagen was measured using real-time PCR. Each cell type was also cultured in chamber slides and immunostained for aggrecan, type I collagen, and type II collagen after 3 days of treatment with rhBMP-2.
RESULTS: (1) Without rhBMP-2 the chondrocytes produced more proteoglycan (sGAG) as compared to the other two cell types (AF cells and BMDCs). After stimulation with rhBMP-2 the chondrocytes produce even more proteoglycan than the other two cell types. (2) As compared to the other two cell types, in terms of mRNA expression, the chondrocytes expressed more aggrecan, type I collagen, and type II collagen before stimulation with rhBMP-2. After rhBMP-2 stimulation, the chondrocytes expressed even more aggrecan, type I collagen, and type II collagen in proportion to the concentration of rhBMP-2. For the BMDCs there were no changes in type I and II collagen. (3) rhBMP-2 stimulation produced increases in the protein levels of aggrecan, type I and II collagen in all three types of cells.
CONCLUSIONS: On balance, according to these results, it would seem that chondrocytes are the best candidate for the disc cell therapy.