title: Nucleus pulposus phenotypic markers to determine stem cell differentiation: fact or fiction?
abstract: Progress in mesenchymal stem cell (MSC) based therapies for nucleus pulposus (NP) regeneration are hampered by a lack of understanding and consensus of the normal NP cell phenotype. Despite the recent consensus paper on NP markers, there is still a need to further validate proposed markers. This study aimed to determine whether an NP phenotypic profile could be identified within a large population of mature NP samples.qRT-PCR was conducted to assess mRNA expression of 13 genes within human non-degenerate articular chondrocytes (AC) (n=10) and NP cells extracted from patients across a spectrum of histological degeneration grades (n=71). qRT-PCR results were used to select NP marker candidates for protein expression analysis.Differential expression at mRNA between AC and non-degenerate NP cells was only observed for Paired Box Protein 1 (PAX1) and Forkhead box F1 (FOXF1). In contrast no other previously suggested markers displayed differential expression between non-degenerate NP and AC at mRNA level. PAX1 and FOXF1 protein expression was significantly higher in the NP compared to annulus fibrosus (AF), cartilaginous endplate (CEP) and AC. In contrast Laminin-5 (LAM-332), Keratin-19 (KRT-19) and Hypoxia Inducible Factor 1 alpha (HIF1α) showed no differential expression in NP cells compared with AC cells.A marker which exclusively differentiates NP cells from AF and AC cells remains to be identified, raising the question: is the NP a heterogeneous population of cells? Or does the natural biological variation during IVD development, degeneration state and even the life cycle of cells make finding one definitive marker impossible?
authors.affiliation: Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK.
authors.forename: Abbey A
authors.initials: AA
authors.lastname: Thorpe
authors.affiliation: Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK.
authors.forename: Abbie L A
authors.initials: AL
authors.lastname: Binch
authors.affiliation: UMC Utrecht, Orthopaedics Department, Utrecht, Netherlands.
authors.forename: Laura B
authors.initials: LB
authors.lastname: Creemers
authors.affiliation: Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Sammon
authors.affiliation: Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Le Maitre
mesh_terms: D002358:Cartilage, Articular / Q000166:cytology*; D015815:Cell Adhesion Molecules / Q000096:biosynthesis; D002454:Cell Differentiation; D019902:Chondrocytes / Q000166:cytology*; D051858:Forkhead Transcription Factors / Q000235:genetics*; D005819:Genetic Markers / Q000235:genetics; D048091:Guided Tissue Regeneration / Q000379:methods; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis; D007403:Intervertebral Disc / Q000166:cytology*; D055959:Intervertebral Disc Degeneration / Q000628:therapy; D053539:Keratin-19 / Q000096:biosynthesis; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D051761:Paired Box Transcription Factors / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D000097794:Kalinin
chemical_list: D015815:Cell Adhesion Molecules; D051858:Forkhead Transcription Factors; D005819:Genetic Markers; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D053539:Keratin-19; D051761:Paired Box Transcription Factors; D012333:RNA, Messenger; D000097794:Kalinin; C098521:FOXF1 protein, human; C497442:HIF1A protein, human; C070835:PAX1 transcription factor
keywords: FOXF1; Pathology Section; nucleus pulposus; phenotypic markers; regeneration; stem cells PAX1