The role of CTGF in the diabetic rat retina and its relationship with VEGF and TGF-β(2) , elucidated by treatment with CTGFsiRNA.
OBJECTIVE
The critical association of connective tissue growth factor (CTGF) with diabetic retinopathy (DR) remains to be clarified. We detected alterations in the gene and protein expression of CTGF and related cytokines, including vascular endothelial growth factor (VEGF) and transforming growth factor-β(2) (TGF-β(2) ), and their response to small interfering RNA (siRNA) targeting the CTGF (CTGFsiRNA) in the retina of diabetic rats. The relationships between CTGF, VEGF and TGF-β(2) levels, as well as the degree of apoptosis in the diabetic retina, were also investigated.


METHODS
Diabetes was induced in rats by the β-cell toxin streptozotocin (STZ). Retinas were obtained from control and diabetic rats and similar animals treated with CTGFsiRNA by intravitreal injection. mRNA level and protein expression of CTGF, VEGF and TGF-β(2) were measured by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, and located by immunohistochemistry. Retinal apoptosis was detected by TUNEL staining.


RESULTS
The levels of CTGF, VEGF and TGF-β(2) and the number of TUNEL-positive nuclei were significantly higher in diabetic retinas than in control retinas (p<0.01). The level of CTGF rose at 8weeks, earlier than levels of VEGF and TGF-β(2) , which rose at 12weeks after the onset of diabetes. The difference was significant (p<0.05). siRNA-mediated inhibition of CTGF mRNA inhibited retinal VEGF and TGF-β(2) and also resulted in a significant decrease in apoptosis. Significant correlations were found between CTGF and VEGF (p=0.009), CTGF and TGF-β(2) (p=0.01), and apoptosis and these three cytokines (p<0.01) in the rat retina early in diabetes.


CONCLUSIONS
These results suggest that the diabetes-mediated increase in CTGF upregulates VEGF and TGF-β(2) expression and induces apoptosis in the retina. This elevation may be inhibited by treatment with CTGFsiRNA. Connective tissue growth factor may serve as a potential target for the prevention and treatment of DR.
Yang
Hongwei
H
Department of Ophthalmology, Shengjing Affiliated Hospital, China Medical University, Shenyang, China.
Huang
Yonggang
Y
Chen
Xiaolong
X
Liu
Jie
J
Lu
Yan
Y
Bu
Limin
L
Xia
Likun
L
Xiao
Wei
W
Chen
Ming
M
Nie
Qingzhu
Q
Liu
Zheli
Z
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D055513:Connective Tissue Growth Factor / Q000235:genetics* / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D003930:Diabetic Retinopathy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000502:physiology*; D020868:Gene Silencing / Q000502:physiology; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D058449:Intravitreal Injections; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics*; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053781:Transforming Growth Factor beta2 / Q000235:genetics* / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics* / Q000378:metabolism
C526316:CCN2 protein, rat; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053781:Transforming Growth Factor beta2; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D055513:Connective Tissue Growth Factor