The disease activity of SLE was assessed clinically by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)17 on the day of kidney biopsy. Baseline serum creatinine, urine protein, complement levels (C3 MK-2206 molecular weight and C4) and anti-double strand (ds) DNA antibody titre were also measured. Glomerular filtration rate (GFR) was estimated by a standard equation.18 Kidney biopsy specimen was evaluated according to the International Society of Nephrology (ISN) classification of lupus nephritis.19 The activity index (AI) and chronicity index (CI) of each biopsy specimen were scored by standard methods.19 The method of laser micro-dissection has
been described in our previous studies.16,20,21 Briefly, cryosections of 10 µm thickness were prepared on a cryostat (Leica Microsystems, Wetzlar, Germany) using disposable RG7204 mw microtome blades (Leica Microsystem) in RNase-free conditions and were mounted on MembraneSlide 0.17 PEN slides (Carl Zeiss PALM Microlaser Technologies, Bernried, Germany). Immediately after taking the slides out of the cryostat, the sections were fixed in 70% ethanol and dehydrated in 100% ethanol. Sections were air-dried at room temperature. Laser micro-dissection of the snap-frozen kidney biopsy specimens was performed using the PALM Microlaser System
(PALM Microlaser Technologies), which is equipped with a pulsed high-quality laser beam, computer-controlled microscope stage and micromanipulator. Under direct
visual control, areas of interest in the histological specimens were selected through the PALM RoboSoftware (PALM Microlaser Technologies) by moving the computer mouse and micro-dissected by cutting the contour of the selected areas with the adjusted laser beam. The isolated tissue was then laser-catapulted into a microcentrifuge tube filled with guanidine thiocyanate containing lysis buffer for the subsequent RNA isolation. Approximately 20–30 glomerulus and 20 randomly selected tubulointerstitial areas were isolated from each specimen. The tissue lysate of glomerulus and tubulointerstitium were kept learn more at −80°C until RNA extraction was performed with the RNAqueous-Micro Kit (Applied Biosystems, Foster City, CA, USA), following manufacturer’s instruction. The RNAqueous-Micro Kit (Applied Biosystems) was used for the extraction of total RNA. TaqMan microRNA Reverse Transcription kit (Applied Biosystems) and High Capacity cDNA Reverse Transcription Kit (Applied Biosystems) were used for reverse transcription. Intrarenal expression of miR-146a, miR-155, miR-198 miR-638 and miR-663 were quantified by reverse transcription-quantitative polymerase chain reaction (RT-QPCR) with the ABI Prism 7900 Sequence Detection System (Applied Biosystems). These targets were selected because previous studies on PBMC or urine showed that they were differentially expressed between lupus nephritis patients and normal controls.