Stimulation of transforming growth factor-beta-1 and contact with type I collagen cooperatively facilitate irreversible transdifferentiation in proximal tubular cells.
BACKGROUND
By transdifferentiation, proximal tubular cells (PTC) have been considered as a source of interstitial myofibroblasts. We examined the combined effect of transforming growth factor-beta-1 (TGF-β1) stimulation and contact with type I collagen on PTC transdifferentiation.


METHODS
Human kidney-2 cells were grown on type I substratum with the concurrent stimulation of TGF-β1.


RESULTS
Following addition of TGF-β1, cells acquired an elongated fibroblastic appearance and an increase in α-smooth muscle actin (α-SMA) expression, a myofibroblastic marker. Upon addition of TGF-β1, E-cadherin expression, an epithelial marker, was reduced, while cytokeratin expression, another epithelial marker, remained unaltered. Following removal of TGF-β1, PTC regained an epithelial appearance and E-cadherin expression reverted to the unstimulated level, suggesting incomplete and reversible transdifferentiation. Addition of TGF-β1 to cells grown on type I collagen demonstrated a cooperatively increased α-SMA expression and decreased E-cadherin and cytokeratin expressions, suggesting more complete transdifferentiation. Co-stimulation of TGF-β1 and contact with type I collagen led to a stable cell phenotype and persistently decreased E-cadherin, which was not reversed upon removal of TGF-β1, indicating irreversible transdifferentiation. Addition of TGF-β1 or type I collagen caused a 4-fold increase in migratory cell number as compared to the control, whereas addition of both TGF-β1 and type I collagen led to an 11-fold increase.


CONCLUSIONS
TGF-β1 alone results in a reversible and incomplete transdifferentiation. The combination of TGF-β1 and exposure to type I collagen leads to an irreversible and complete PTC transdifferentiation.
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Chieh-Li
CL
Yen
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Yi-Jung
YJ
Li
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Hsin-Hsu
HH
Wu
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Cheng-Hao
CH
Weng
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Cheng-Chia
CC
Lee
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Yung-Chang
YC
Chen
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Ming-Yang
MY
Chang
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Tzung-Hai
TH
Yen
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Hsiang-Hao
HH
Hsu
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Cheng-Chieh
CC
Hung
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Chih-Wei
CW
Yang
Department of Nephrology, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan. Electronic address: dryctian@adm.cgmh.org.tw.
Ya-Chung
YC
Tian
D015820:Cadherins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D002460:Cell Line; D054338:Cell Transdifferentiation / Q000187:drug effects* / Q000502:physiology; D024042:Collagen Type I / Q000378:metabolism / Q000494:pharmacology*; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects*; D006801:Humans; D053773:Transforming Growth Factor beta1 / Q000378:metabolism / Q000494:pharmacology*
D015820:Cadherins; D024042:Collagen Type I; D053773:Transforming Growth Factor beta1
E-cadherin; Transdifferentiation; Transforming growth factor-beta-1; Type I collagen; α-Smooth muscle actin