Animals
The female Wistar rats (n=80) at the age of 7 weeks were purchased from Jinan Pengyue experimental animal breeding Co, Ltd (Shandong, China). The rats were housed in cage under reference atmospheres and free access to food and water. All the experimental procedures have been approved by the Institutional Animal Care and Use Committee at Binzhou Medical University. The study was conducted in accordance with the National Research Council Guidance for Care and Use of Laboratory Animals.
Chemicals
Cisplatin (CDDP) (Meilunbio, China) was dissolved in warmed distilled water (DW) at a stock concentration of 3.33 mM and added to stromal cells cultures at a final concentration of 0 - 60 µM. The TGF-β1 inhibitor, SB431542 (Selleck, USA), was dissolved in DMSO at a stock concentration of 10mM and added to stromal cells cultures at a final concentration of 10 μM.
Group and treatment
According to reports in the literature, CDDP as a common anticancer drug can lead to POI [12, 25]. This study was conducted on the successful establishment of a CDDP - induced POI rat model. The rats were randomly assigned to four groups: control, POI + hUMSCs, POI and POI + PBS group. In the control group, normal rats were injected intraperitoneally with physiological saline for 7 days; in the POI + hUMSCs group, seven days after the injection of CDDP, 200 µl phosphate buffered saline (PBS) containing 2x106 hUMSCs were injected into the tail vein of POI rats; in the POI group, the rats were injected intraperitoneally with CDDP for 7 days; in the POI + PBS group, the POI rats were injected with 200 µl PBS via the tail vein. After 1 - week treatment, four rats were randomly selected from each group for fertility testing. The remaining rats were necropsied for the study.
Isolation and culture of hUCMSCs
The umbilical cords were collected from healthy donors who received cesarean section and signed a written informed consent. The collected umbilical cord was washed twice with PBS, mechanically minced, and then cultured with low - glucose Dulbecco’ s modified Eagle’ s Medium containing (Gibco) supplemented with 10% fetal bovine serum (FBS), 1% 100 U/mL streptomycin sulfate, and 100 U/mL penicillin G in a humidified atmosphere with 5% CO2 at 37℃. To confirm the phenotype of hUMSCs, cell morphology was observed under light microscope. The differentiation ability to adipocytes and osteoblast was examined by alizarin red staining and oil red O staining. The cell surface and intracellular markers such as CD44, CD73, CD90, CD34, HLA - DR, and CD45 were examined using flow cytometry (FCM). The cells at the third to fifth generation were selected for the experiments.
Isolation,culture and identification of Ovarian Stromal Cells
Ovarian stromal cells were isolated from the ovarian cortex of normal immature 3 - to 4 - week - old rats. Briefly, the surface epithelium and ovarian medulla was removed by using forceps and, the granulosa cells (GCs) and oocytes were released by puncturing the follicles with a sterile needle. The remaining ovary tissues were cut into 1 mm3 fragments using scissors and washed with PBS for three times. The tissues were digested with type II collagenase that was dissolved in McCoy’ s 5A (Modified) Medium at 37℃ for 60 min. After digestion, the dispersed cells were washed with McCoy’ s 5A medium and centrifuged at 1000 rpm at 37℃ for 5 minutes. The pellet was suspended in McCoy’ s 5A medium containing 10% FBS, 1% 100 U/mL streptomycin sulfate, and 100 U/mL penicillin G and cultured in a 37℃ humidified incubator with 5% CO2.
Fertility examination
Four rats were randomly selected from each group including control, POI + hUMSCs, POI and POI + PBS group. The rats were mated at 2:1 ratio with sexually mature male rats and euthanized 9 days after the appearance of vaginal plugs. The uterus was collected and examined for the number of developed fetuses.
Enzyme-linked immunosorbent assay (ELISA)
The serum of each rat was collected and stored at −80 ℃ after centrifuge for analysis. The serum levels of estradiol (E2), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were measured using ELISA kit following the manufacturer’ s instructions (Mlbio, China).
Hematoxylin and eosin (H&E) staining
Ovaries were collected from the rats of each group and fixed in 4% paraformaldehyde for 24h. Then, the tissues were processed by paraffin embedding, sectioning (5 µm), and hematoxylin and eosin (H&E) staining. To analyze the ovarian morphology and count the numbers of ovarian follicles, the slides were examined under light microscope. The follicles were categorized as primordial follicles, primary follicles, secondary follicles, and atresia follicles according to the previous report [24].
Masson trichrome staining and Sirius red staining
Ovaries were collected from the rats of each group and fixed in 4% paraformaldehyde for 24h. Following the paraffin embedding and sectioning (5 µm) process, the tissues were stained with Masson trichrome and Sirius red. To evaluate the fibrosis of ovary tissues in each group, the slides were analyzed and photographed under light microscope. Five fields in each staining image were randomly selected for examination. Image J software was used to quantitate the degree of interstitial fibrosis in the ovary tissue.
CCK-8 cell viability assay
The effect of CDDP at different concentrations on the viability of stromal cells was measured using CCK-8 kit (Meilong Bio, China). The cells (5000 stromal cells / well) were seeded in 96-well plates and incubated overnight. After cell adhesion, the medium is replaced with media containing CDDP (0-60 µm). CCK-8 cells (10 µl) were added to the cell medium for 1 h. The absorbance was measured at 450nm using an ELISA assay kit. according to the manufacturer's instructions.
Inhibitor experiment
After achieving 80% confluence, stromal cells were seeded in 6 - well plates (1×105 cells / well). Cells were divided into four groups according the different treatments for 20 hours: 1) Control group - untreated medium, 2) CDDP group - CDDP (20 µM) alone, 3) CDDP + hUMSCs group - CDDP + hUMSCs supernatants, 4) CDDP + SB431542 group - CDDP + SB431542 (10 µM).
Immunofluorescence staining
The expression of vimentin, Factor Ⅷ, Cytokeratin, Cyp17a1 and α-SMA proteins was detected by Immunofluorescence staining. Ovarian stromal cells were washed three times with PBS, fixed in 4% paraformaldehyde for 20minutes. After washing, the cells were blocked for 30 minutes in PBS containing 5% donkey serum (Santa Cruz Biotechnology). To identify the mesenchymal, epithelial, endothelial cells, TCs and MFB, the cells were incubated with the primary antibody of anti - vimentin (1:100, Proteintech, China) , anti - cytokeratin (1:100, Proteintech, China), anti - Factor VIII (1:100, Proteintech, China), and the mixture of anti - Cyp17a1 (1:100, abcam, UK) and anti - α - SMA (1:100, abcam, UK) at 4℃ overnight , respectively. After rinsing, the stromal cells were incubated with the second antibody of goat anti - Rabbite IgG, Alexa Fluor 488 (Invitrogen, USA), goat anti - Rabbite IgG, goat anti - Rabbite IgG, Alexa Fluor 596 (Invitrogen, USA) and the mixture of goat anti - Rabbite IgG, Alexa Fluor 488 and goat anti - mouse IgG, Alexa Fluor 596 (Invitrogen, USA) respectively at 37℃ for 1h with DAPI (Solarbio, China) staining solution. The staining of the cells were visualized using a fluorescent microscope (Leica, Germany).
Quantitative reverse-transcription polymerase chain reaction (qRT - PCR)
Total RNA was isolated from ovarian stromal cells using Trizol reagent (ambion,USA) and reversed transcribed into cDNA using Transcriptor HiFi cDNA Synth (Roche, Germany). The primers for quantitative real - time polymerase chain reaction were listed as follows: transforming growth factor-β1 (TGF-β1 ) forward primer: CATTGCTGTCCCGTCAGA and reverse primer: AGGTAACGCCAGGAATTGTTGCTA; Smad3 forward primer: GCACAGCAAGTTCCCAGTGTGTA and reverse primer: GCCATGCATCCACTGTTCC; Glyceraldehyde - 3 - phosphate dehydrogenase (GAPDH) forward primer: GGCACAGTCAAGGCTGAGAATG and reverse primer: ATGGTGGTGAAGACGCCAGTA. The housekeeping gene GAPDH was used for to normalize the gene expression. The testing in each group was repeated in triplicate.
Western blot
Proteins were isolated from ovary tissues and cultured stromal cells. The samples were electrophoresed on sodium dodecyl sulfatepolyacrylamide gels, and transferred to a PVDF membrane. After blocking with 5%~7% skim milk, the membranes were incubated with anti - TGF-β1 (1:1000, abcam, UK), anti - Smad3 (1:1000, abcam, UK) , anti - p - Smad3 (1:1000, Proteintech, China), anti - Cyp17a1 (1:4000, abcam, UK), anti - α - SMA (1:1000, abcam, UK), anti - Collagen Ⅰ (1:400, Proteintech, China)), anti - Collagen Ⅲ (1:400, Proteintech, China)) and anti - GAPDH (1:20000, Proteintech, China) polyclonal antibodies for overnight. After incubation, the membranes were washed with TBS and Tween 20 (TBST) three times and then immunoblotted with HRP - conjugated secondary antibodies (Proteintech) for 1 h at room temperature. The expression of each protein was measured by an enhanced chemiluminescence reagent ( ECL) kit. The density of protein expression bands was measured using Image J software.
Data analysis
All data were expressed as mean ± SD. and analyzed by SPSS 22.0 software. Differences between two groups were determined using one-way analysis of variance (ANOVA) with post hoc Bonferroni test. A value of P< 0.05 is considered significant difference.