Tendon healing in vivo: gene expression and production of multiple growth factors in early tendon healing period.
OBJECTIVE
The actions of growth factors during healing of injured flexor tendons are not well characterized, although information pertinent to some individual growth factors is available. We studied gene expression and protein production of a number of growth factors at several time points during the early healing period in a chicken model.


METHODS
Seventy-four long toes of 37 white Leghorn chickens were used. The flexor digitorum profundus tendons of 60 toes were surgically repaired after complete transection and were harvested for analysis 3, 5, 7, 9, 14, and 21 days after surgery. The expression of 6 growth factors was studied at 4 time points after surgery with real-time quantitative polymerase chain reactions, and production and distribution of 3 growth factors at all 6 time points were studied by immunohistochemical staining with antibodies. Fourteen tendons that had no surgery served as day 0 controls. Tendon healing status was also assessed histologically.


RESULTS
Throughout the early tendon healing period, connective tissue growth factor (CTGF) and transforming growth factor beta (TGF-beta) showed high levels of gene expression. Levels of gene expression of vascular endothelial growth factor (VEGF) and insulin-like growth factor 1 (IGF-1) were high or moderately high. Expression of the TGF-beta gene was upregulated after injury, whereas the basic fibroblast growth factor (bFGF) gene was downregulated at all postsurgical time points and expressed at the lowest levels among 6 growth factor genes 2 to 3 weeks after surgery. The platelet-derived growth factor B (PDGF-B) gene was also minimally expressed. Findings of immunohistochemistry corresponded to TGF-beta, bFGF, and IGF-1 gene expression.


CONCLUSIONS
In this model, up to 3 weeks after surgery, gene expression and production of TGF-beta are high and are upregulated in this healing period. However, expression of the bFGF gene and protein is low and decreases in the healing tendon. The CTGF, VEGF, and IGF-1 genes are expressed at high or moderately high levels, but PDGF-B is minimally expressed.
Chen
Chuan Hao
CH
Department of Hand Surgery, Hand Surgery Research Center, Affiliated Hospital of Nantong University, Nantong, Jiangsu, China.
Cao
Yi
Y
Wu
Ya Fang
YF
Bais
Anthony J
AJ
Gao
Jing Song
JS
Tang
Jin Bo
JB
D000818:Animals; D002645:Chickens; D055513:Connective Tissue Growth Factor / Q000235:genetics / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000235:genetics / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D020574:Proto-Oncogene Proteins c-sis / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013708:Tendon Injuries / Q000235:genetics* / Q000378:metabolism* / Q000628:therapy; D013997:Time Factors; D014034:Toes; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D014945:Wound Healing / Q000502:physiology*
D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D055513:Connective Tissue Growth Factor; D007334:Insulin-Like Growth Factor I