There is clear evidence that tissues related to the intervertebral dis
c, such as articular cartilage, contain several phenotypically differe
nt chondrocytic cell populations. Histological data for the disc sugge
st the same may be true for the annulus fibrosus and nucleus pulposus,
but this has not been shown directly. For the first time, cells from
adult human nondegenerative nucleus pulposus and annulus fibrosus were
recovered after enzymatic digestion and maintained in an alginate bea
d culture system for up to 6 wk. The cells remained viable and produce
d matrix, but did not divide. Cultured cells were stained simultaneous
ly for the presence of chondroitin sulphate and keratan sulphate, or t
ypes I and II collagen. The majority of the cells from both the annulu
s fibrosus and the nucleus pulposus produced both keratan sulphate and
chondroitin sulphate (> 60%), a few only detectable levels of one or
the other, but a significant population produced neither. This is an i
ndication of a population of cells with a nonchondrocytic phenotype. I
n nondegenerative discs, the majority of the annulus fibrosus cells pr
oduced both types I and II collagen but the majority of nucleus pulpos
us cells produced only type II collagen. These observations are consis
tent with the presence of at least 2 phenotypically stable populations
of cells in the adult human intervertebral disc and with the view tha
t the phenotype of the major population of the annulus is different fr
om that of the nucleus.