Identification of phenotypic discriminating markers for intervertebral disc cells and articular chondrocytes.

OBJECTIVE The present study was conducted to improve our knowledge of intervertebral disc (IVD) cell biology by comparing the phenotype of nucleus pulposus (NP) and annulus fibrosus (AF) cells with that of articular chondrocytes (ACs). METHODS Rabbit cells from NP and AF were isolated and their phenotype was compared with that of AC by real-time PCR analysis of type I (COL1A1), II (COL2A1) and V (COL5A1) collagens, aggrecan transcript (AGC1), matrix Gla protein (MGP) and Htra serine peptidase 1 (Htra1). RESULTS Transcript analysis indicated that despite certain similarities, IVD cells exhibit distinct COL2A1/COL1A1 and COL2A1/AGC1 ratios as compared with AC. The expression pattern of COL5A1, MGP and Htra1 makes it possible to define a phenotypic signature for NP and AF cells. CONCLUSIONS Our study shows that NP and AF cells exhibit a clearly distinguishable phenotype from that of AC. Type V collagen, MGP and HtrA1 could greatly help to discriminate among NP, AF and AC cells.