Induction of adenomyosis by mechanical stimulation of the mouse uterus
All procedures described in this study were conducted in accordance with the guidelines and regulations of the Animal Care and Use of the University of Tokyo Committee. Six-week-old BALB/c female mice were purchased from Japan SLC, Inc. (Tokyo, Japan). The mice were fed a mouse diet and water and maintained on a light/dark cycle (12 h/12 h) under controlled living conditions. The adenomyosis mouse model was established as follows. First, a midline incision was made in the abdomen to expose the uterine horns. Using a 30 G (½ inch) needle, the entire uterine wall of one horn was mechanically punctured at a frequency of 100 times/1 cm (adenomyosishorn). The other horn was left unpunctured (control horn). The puncture penetrated through the entire uterine wall, as shown in Fig. 1A. The mice were sacrificed 14 (D14) and 65 days (D65)after the operation, and uteri were collected (n=3 for each timepoint).
Tissue preparation for hematoxylin and eosin staining (H&E staining)
Uterine tissues were sectioned, fixed in 10% formalin, dehydrated gradually in ethanol, and embedded in paraffin at 60°C. For hematoxylin and eosin staining (H&E staining), sections were cut horizontally at a thickness of 6 μm and mounted on slides for analysis.
Immunohistochemistry (IHC)
We investigatedthe extent of the adenomyosis lesions by cutting through the entire horn and quantitatively analyzing the number and volume of lesions. To confirm the presence of lesions, we prepared serial sections and performed immunohistochemistry.One section was stained with cytokeratin 8 (CK8) to detect epithelial cells and the other section with alpha smooth muscle actin (αSMA) to detect smooth muscle cells. When epithelial cellswere found within a smooth muscle layer, the area was considered an adenomyosis lesion.IHC was conducted as follows.All sections were deparaffinized in xylene and hydrated in a series of graded alcohols (100%, 100%, 100%, 90%, 80%, and 70%). Antigen retrieval was performed by boiling the samples in an ethylenediaminetetraacetic acid(EDTA) antigen retrieval solution (pH 9) (DAKO, Cat. No. K8004, Glostrup, Denmark) for 45 min at 98°C. The samples were then incubated at room temperature for 30 min. The samples were washed three times in phosphate-buffered saline (PBS) and incubated with a peroxidase blocking agent (DAKO, Cat. No. S2023) for 10 min. The samples were washed again and incubated overnight with the diluted primary antibodies listed in Table 1 at 4 °C. The samples were then washed with PBS and incubated with the secondary antibody from the REAL EnVision Detection System (DAKO, Cat. No. K5007) at room temperature for 30 min. Afterward, the samples were visualized using 3,3'-
diaminobenzidine (DAB) chromogen from the REAL EnVision Detection System (DAKO, Cat. No. K5007). Samples were counterstained with hematoxylin, graduallydehydratedusing graded alcohol and xylene, and then mounted with mounting medium.
Table 1. The list of the primary antibodies for immunohistochemistry
Molecule
|
Dilution
|
Origin
|
Supplier (catalog no,)
|
CK8
|
1/1000 (IHC)
1/100 (IF)
|
Rabbit monoclonal (EP1628Y)
|
ABCAM (Cat. #ab53280)
|
Alpha SMA
|
1/1000 (IHC)
|
Rabbit monoclonal (EPR5368)
|
ABCAM (Cat. #ab124964)
|
Alpha SMA
|
1/100 (IF)
|
Goat polyclonal
|
ABCAM (Cat. #ab21027)
|
Ki67
|
1/500 (IHC)
|
Rabbit monoclonal (Clone SP6)
|
Funakoshi (Cat. #RM-9106-S1)
|
CD31
|
1/300 (IHC)
|
Rabbit monoclonal (D8V9E)
|
Cell Signaling (Cat. #77699)
|
Immunofluorescent staining
Paraffin-embedded samples were sliced at a thickness of 5 μm, deparaffinized in xylene, and rehydrated in a graded alcohol sequence. Antigen retrieval was performed as previously described. Sections were then co-incubated with rabbit anti-CK8 and goat anti-αSMA antibodies (Table 1). Immunofluorescence detection was performed using secondary Alexa Fluor 488 goat anti-rabbit IgG (H+L) pAb (1:200; A-11034; RRID: AB_2576217; Thermo Fisher Scientific,Waltham, MA) and secondary Alexa 568 donkey anti-goat IgG (H+L) pAb (1:200; A-11057; RRID: AB_2534104; Thermo Fisher Scientific) before incubation for 120 min at room temperature. The samples were counterstained with 4′,6-diamidino-2-phenylindole (DAPI). Fluorescent images were obtained using a Zeiss LSM 700 confocal microscope (Carl Zeiss, Germany).
Measurement of the number and volume of the adenomyosis lesions
This study developed a novel method to quantitatively analyze the number and volume of adenomyosis lesions. Once the uterine horn was obtained, the tissues were fixed and embedded in paraffin blocks. The entire uterus was sliced into 6-μm-thick serial sections. On average, 2500 sections were prepared from onehorn. AllH&E-stained sectionswereobserved, and the number of adenomyosis lesions was counted. The length was calculated by multiplying the total number of slices containing a single lesion (from top to bottom) by 6 μm. The cross-sectional area of the lesion was measured using ImageJ(version 1.53c, National Institutes of Health), by tracing the innermost line of the smooth muscle that was identified by positive staining with αSMA and using it as the outermost line of the lesion (Fig. 2A). The cross-sectional area of the epithelial part of the lesion was measured by identifying regions of epithelium within the adenomyosis lesion with positive CK8 staining (Fig. 2A). The cross-sectional area of the stromal part of the lesion was calculated by subtracting the area of the epithelial part from the area of the entire lesion.The volumes of the lesions were calculated as the sum of the cross-sectional areas multiplied by the inter-slide spacing. The equation used to calculate this is as follows:
Volume (mm3) = ∑ cross-sectional area (mm2) × 0.006 (mm).
Evaluation of cell proliferation
Cell proliferation was evaluated by Ki67 IHC. Cells with Ki67-positive nuclei in the epithelial and stromal parts of adenomyosis lesions were counted, and the percentage of cells that were Ki67-positive was calculated.
Evaluation of vascular density
For vascular density evaluation, CD31, a marker for endothelial cells, was used to detect blood vessels. Blood vessels within the lesions were identified, the cross-sectional area of blood vessels was measured, and this was divided by the cross-sectional area of the adenomyosis lesion to calculate the vascular density.
Evaluation of fibrosis
Fibrotic regions were identifiedusing Masson’s trichrome staining. The uterine sections were deparaffinized, rehydrated, and transferred to Bouin’s solution at 56°C for 15 min. Sections were stained using Masson’s Trichrome Staining kit (Sigma-Aldrich Inc., St. Louis, MO) following the manufacturer’s instructions. Images of adenomyosis lesions were randomly taken at a magnification of 40×. The cross-sectional areaof fibrotic regions (areas where collagen deposition had occurred) was determined using image analysis software ImageJ (version 1.53c, National Institutes of Health, Bethesda, MD) with the plugin “color deconvolution” for stain separation (MTS1,2). Regions that stained bluer than the automatically calculated threshold were identified as fibrotic, and the cross-sectional areas of these regions were calculated. The percentage of the lesion that was fibroticwas calculated by dividing the area of the fibrotic region by the area of the entire lesion.
Establishment and evaluation of mouse pregnancy model
To investigate the prognosis of pregnancy in this mouse model and whether the lesions persisted after pregnancy, seven mice were used to model pregnancy. Six-week-old male BALB/c mice were used for mating. Mating was started 7 days after the establishment of adenomyosis and continued for up to 10 consecutive days until the plug was confirmed. Female mice were then kept in a separate cage until delivery, and the date of delivery was recorded. The pups were separated from the dams on the first day after delivery, and litter size was recorded. The dams were sacrificed on the third day after delivery, and the uteri were collected. The number of implantation sites in both horns was determined and recorded. The number and volume of adenomyosis lesions were evaluated as described above and compared with those of non-pregnant mice.
Statistical analysis
All data analysis were conducted using JMP Pro 15 software (SAS Institute Inc., Cary, NC). All non-parametric data were compared using Wilcoxon rank sum test. p < 0.05 was considered significant.