Genetic enhancement of matrix synthesis by articular chondrocytes: comparison of different growth factor genes in the presence and absence of interleukin-1.
OBJECTIVE
To determine whether articular chondrocytes express growth factor genes delivered by adenoviral vectors and whether expression of these genes influences matrix synthesis in the presence and absence of interleukin-1 (IL-1).


METHODS
Monolayer cultures of rabbit articular chondrocytes were infected with recombinant adenovirus carrying genes encoding the following growth factors: insulin-like growth factor 1 (IGF-1), transforming growth factor beta1 (TGFbeta1), and bone morphogenetic protein 2 (BMP-2). As a control, cells were transduced with the lac Z gene. Cultures were also treated with each growth factor supplied as a protein. Levels of gene expression were noted, and the synthesis of proteoglycan, collagen, and noncollagenous proteins was measured by radiolabeling. Collagen was typed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The effects of growth factor gene transfer on proteoglycan synthesis in the presence of IL-1 were also measured.


RESULTS
The expression of all transgenes was high following adenoviral transduction. Proteoglycan synthesis was stimulated approximately 8-fold by the BMP-2 gene and 2-3-fold by the IGF-1 gene. The effects of BMP-2 and IGF-1 genes were additive upon cotransduction. Synthesis of collagen and noncollagenous proteins, in contrast, was most strongly stimulated by the IGF-1 gene. In each case, collagen typing confirmed the synthesis of type II collagen. IL-1 suppressed proteoglycan synthesis by 50-60%. IGF-1 and TGFbeta genes restored proteoglycan synthesis to control levels in the presence of IL-1. The BMP-2 gene, in contrast, elevated proteoglycan synthesis beyond control levels in the presence of IL-1.


CONCLUSIONS
Transfer of growth factor genes to articular chondrocytes can greatly increase matrix synthesis in vitro, even in the presence of the inflammatory cytokine IL-1. This result encourages the further development of gene therapy for the repair of damaged cartilage.
Smith
P
P
University of Pittsburgh School of Medicine, Pennsylvania, USA.
Shuler
F D
FD
Georgescu
H I
HI
Ghivizzani
S C
SC
Johnstone
B
B
Niyibizi
C
C
Robbins
P D
PD
Evans
C H
CH
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000235:genetics; D002358:Cartilage, Articular / Q000166:cytology* / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis* / Q000235:genetics; D015870:Gene Expression; D005822:Genetic Vectors / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000235:genetics; D007375:Interleukin-1 / Q000494:pharmacology; D011817:Rabbits; D016212:Transforming Growth Factor beta / Q000235:genetics
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D016326:Extracellular Matrix Proteins; D007375:Interleukin-1; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I