Transforming growth factor-beta1 modulates insulin-like growth factor binding protein-4 expression and proteolysis in cultured periosteal explants.
OBJECTIVE
Periosteum is involved in bone growth and fracture healing and has been used as a cell source and tissue graft for tissue engineering and orthopedic reconstruction including joint resurfacing. Periosteum can be induced by transforming growth factor beta (TGF-beta) or insulin-like growth factor-I (IGF-I) alone or in combination to form cartilage. However, little is known about the interaction between IGF and TGF-beta signaling during periosteal chondrogenesis. The purpose of this study was to determine the effect of TGF-beta1 on IGF binding protein-4 (IGFBP-4) and the IGFBP-4 protease pregnancy-associated plasma protein-A (PAPP-A) expression in cultured periosteal explants.


METHODS
Periosteal explants from rabbits were cultured with or without TGF-beta1. IGFBP-4 and PAPP-A mRNA levels were determined by real-time quantitative PCR. Conditioned medium was analyzed for IGFBP-4 and PAPP-A protein levels and IGFBP-4 protease activity.


RESULTS
TGF-beta1-treated explants contained lower IGFBP-4 mRNA levels throughout the culture period with a maximum reduction of 70% on day 5 of culture. Lower levels of IGFBP-4 protein were also detected in the conditioned medium from TGF-beta1-treated explants. PAPP-A mRNA levels were increased 1.6-fold, PAPP-A protein levels were increased threefold, and IGFBP-4 protease activity was increased 8.5-fold between 7 and 10days of culture (the onset of cartilage formation in this model) in conditioned medium from TGF-beta1-treated explants.


CONCLUSIONS
This study demonstrates that TGF-beta1 modulates the expression of IGFBP-4 and PAPP-A in cultured periosteal explants.
Gonzalez
Carlos
C
Cartilage and Connective Tissue Research Laboratory, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
Auw Yang
Kiem G
KG
Schwab
Joseph H
JH
Fitzsimmons
James S
JS
Reinholz
Monica M
MM
Resch
Zachary T
ZT
Bale
Laurie K
LK
Clemens
Victoria R
VR
Conover
Cheryl A
CA
O'Driscoll
Shawn W
SW
Reinholz
Gregory G
GG
D000818:Animals; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics* / Q000378:metabolism*; D009924:Organ Culture Techniques; D010521:Periosteum / Q000187:drug effects* / Q000378:metabolism*; D011266:Pregnancy-Associated Plasma Protein-A / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D011817:Rabbits; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology* / Q000502:physiology
D018974:Insulin-Like Growth Factor Binding Protein 4; D012333:RNA, Messenger; D053773:Transforming Growth Factor beta1; D011266:Pregnancy-Associated Plasma Protein-A