Aberrant expression of SPARC and its impact on proliferation and apoptosis in ADPKD cyst-lining epithelia.
BACKGROUND
Autosomal dominant polycystic kidney disease (ADPKD) results from a combination of environmental and genetic factors. Secreted protein acidic and rich in cysteine (SPARC) can be expressed by many different cell types and is associated with development, remodelling, cell turnover and tissue repair. The analysis of SPARC would help evaluate the effect of the unique matricellular glycoprotein on renal disease progression in ADPKD.


METHODS
The concentration of SPARC was measured with an enzyme-linked immunosorbent assay (ELISA); distribution and expression levels were measured with in situ hybridization, immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) and western blot assays. Apoptosis was assessed by morphological observation and fluorescence-activated cell sorting (FACS) apoptosis index (AI) analysis. Cell cycle phase was examined by FACS analysis. Cell proliferation was studied using bromodeoxyuridine (BrdU) incorporation ELISA.


RESULTS
The SPARC level in the renal cyst fluid of patients with ADPKD was greater than that in patients with simple renal cyst (SRC), and also greater than that found in the plasma and urine of patients with either ADPKD or SRC and normal subjects. SPARC mRNA and protein levels in polycystic renal tissue were greater than that in normal renal tissue. Additionally, SPARC could inhibit cyst-lining epithelial cell proliferation, bring about cell cycle arrest in the G0/G1 phase and induce apoptosis in vitro. SPARC treatment resulted in decreased mRNA levels of PCNA (proliferating cell nuclear antigen), MCM2 (minichromosome maintenance protein 2), ClnD1 and Bcl-2, but an increased mRNA level of p21(Waf1) in cyst-lining epithelial cells.


CONCLUSIONS
Our findings suggest that the increased SPARC expression in ADPKD renal tissue may provide negative feedback in ADPKD patients.
Wang
Wenjing
W
Division of Nephrology, Center of Kidney Disease, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai 200003, China.
Mei
Changlin
C
Tang
Bing
B
Zhao
Haidan
H
Xu
Chenggang
C
Li
Zhanyuan
Z
Shen
Xuefei
X
Fu
Wencheng
W
Dai
Bing
B
D000293:Adolescent; D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000235:genetics; D001483:Base Sequence; D015153:Blotting, Western; D016022:Case-Control Studies; D049109:Cell Proliferation; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000166:cytology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D015676:Osteonectin / Q000235:genetics*; D016891:Polycystic Kidney, Autosomal Dominant / Q000235:genetics / Q000473:pathology*; D011336:Probability; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012494:Sampling Studies
D018076:DNA, Complementary; D015676:Osteonectin