Connective tissue growth factor and its regulation in the peritoneal cavity of peritoneal dialysis patients.
BACKGROUND
Connective tissue growth factor (CTGF) is a fibrogenic cytokine that is highly expressed in wound healing and fibrotic lesions. The role of transforming growth factor-beta (TGF-beta) in fibrosis is well documented, and the emerging understanding that its fibrogenic actions are mediated through CTGF has provided an attractive target molecule for the modulation of matrix overproduction in fibrotic disease. The involvement of CTGF in the pathogenesis of peritoneal membrane fibrosis in peritoneal dialysis (PD) patients has not been investigated, and so the aim of this study was to ascertain whether CTGF is produced in the peritoneal cavity of PD patients and to investigate its regulation by cytokines.


METHODS
Reverse transcription-polymerase chain reaction (RT-PCR), Northern blotting, and Western blotting were used to study CTGF expression by cultured human peritoneal mesothelial cells (HPMC) from peritoneal dialysis patients. Western blotting was used to detect CTGF expression in spent peritoneal dialysate from patients with and without peritonitis.


RESULTS
RT-PCR analysis demonstrated the expression of CTGF mRNA in cultured primay HPMCs isolated from spent peritoneal effluent. The production of the major 36 to 38 kD CTGF protein doublet by HPMC in addition to a 23 to 25 kD proteolytically processed form was confirmed by Western blotting. Several molecular weight forms of CTGF (18 to 38 kD) were also detected by Western blotting in peritoneal dialysate, with levels markedly elevated during episodes of peritonitis. Northern and Western blot analysis revealed that CTGF mRNA and protein production by HPMC was up-regulated by TGF-beta, with mRNA levels significantly increasing above the control (P < 0.01). In contrast, platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and tumor necrosis factor-alpha (TNF-alpha) had no measurable effects on CTGF mRNA expression.


CONCLUSIONS
These results are the first to demonstrate the production of CTGF by HPMC and its presence in the peritoneal cavity of PD patients. The marked increase in CTGF levels by factors implicated in the development of peritoneal membrane fibrosis suggests its involvement in the underlying pathophysiologic mechanism(s).
Zarrinkalam
Krystyna H
KH
Department of Renal Medicine, Royal Adelaide Hospital, Adelaide, South Australia.
Stanley
Jodie M
JM
Gray
Julia
J
Oliver
Noelynn
N
Faull
Randall J
RJ
D001483:Base Sequence / Q000235:genetics; D015152:Blotting, Northern; D015153:Blotting, Western; D016022:Case-Control Studies; D055513:Connective Tissue Growth Factor; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010530:Peritoneal Dialysis; D010537:Peritoneum / Q000378:metabolism* / Q000473:pathology; D010538:Peritonitis / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D015854:Up-Regulation
C526317:CCN2 protein, human; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor