Fibroblast growth factor-2 maintains the differentiation potential of nucleus pulposus cells in vitro: implications for cell-based transplantation therapy.
METHODS
To investigate effects of FGF-2 on nucleus pulposus cell growth and differentiation.


OBJECTIVE
To elucidate the phenotypic changes that occur during expansion of nucleus pulposus cells in monolayer culture, and to investigate the effects of fibroblast growth factor (FGF)-2 on cell growth and differentiation.


BACKGROUND
Nucleus pulposus cells would have a limited application for autologous cell transplantation if phenotypic dedifferentiation takes place during culture expansion. FGF-2 has been shown to retain the differentiation potential of monolayer expanded chondrocytic cells. However, its effect on nucleus pulposus cells is not known.


METHODS
Bovine nucleus pulposus cells were serially passaged in the presence or absence of FGF-2 (1 and 10 ng/mL). After passage numbers 1 and 7, cells were immobilized in alginate beads and treated with transforming growth factor (TGF)-beta1 for 1 week to assess their differentiation.


RESULTS
During culture expansion in monolayer, nucleus pulposus cells maintained the expression of aggrecan messenger ribonucleic acid (mRNA). However, mRNA levels of collagen type I, collagen type II, Sox-9, and versican decreased with increasing passage number for both control (untreated) cells and FGF-2 treated cells. When grown in alginate with TFG-beta1, passage 7 cells that received FGF-2 during culture expansion restored the mRNA expression of type II collagen, Sox-9, COMP, chondroadherin, and fibromodulin. Moreover, FGF-2 treatment resulted in increased sulfated proteoglycan synthesis and lower aggrecan turnover compared to untreated controls under identical culture conditions. FGF-2 treated cells continued to express HIF-1alpha protein till passage 7, while MMP-2 expression was evident in cells treated with TGF-beta1. In addition, cells pretreated with FGF-2 showed higher induction of phospho ERK1/2 after treatment with TGF-beta1. Also, FGF-2 maintained smad 2/smad 3 mediated signaling in cells after TGF-beta treatment. FGF-2 action resulted in reduced actin stress fiber formation and migratory cell morphology, with no effect on cell proliferation.


CONCLUSIONS
The presence of FGF-2 during culture expansion of nucleus pulposus cells in monolayer can sustain a differentiated cell phenotype by maintaining responsiveness to TGF-beta1. Our results suggest that FGF-2 should be tested for its ability to maintain the reactivity of the nucleus pulposus cells to other morphogenic factors that may be used for cell-based transplantation therapy.
Tsai
Tsung-Ting
TT
Department of Orthopaedic Surgery and Graduate Program in Tissue Engineering and Regenerative Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Guttapalli
Asha
A
Oguz
Erbil
E
Chen
Lih-Huei
LH
Vaccaro
Alexander R
AR
Albert
Todd J
TJ
Shapiro
Irving M
IM
Risbud
Makarand V
MV
D008841:Actin Cytoskeleton / Q000378:metabolism; D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D048430:Cell Shape; D017690:Cell Transplantation / Q000379:methods; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism* / Q000494:pharmacology; D005786:Gene Expression Regulation; D006609:High Mobility Group Proteins / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D007403:Intervertebral Disc / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D010641:Phenotype; D011509:Proteoglycans / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D055758:SOX9 Transcription Factor; D051785:Smad Proteins / Q000378:metabolism; D013122:Spinal Diseases / Q000601:surgery; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D014182:Transplantation, Autologous
D053674:Aggrecans; D016326:Extracellular Matrix Proteins; D006609:High Mobility Group Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011509:Proteoglycans; D012333:RNA, Messenger; D055758:SOX9 Transcription Factor; D051785:Smad Proteins; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; D016222:Fibroblast Growth Factor 2; D048049:Extracellular Signal-Regulated MAP Kinases; D020778:Matrix Metalloproteinase 2