Introduction
Chronic endometritis (CE) is a persistent inflammatory condition characterized by the infiltration of plasma cells into the uterine endometrial stroma (1). Particularly, it is believed that CE is a contributing factor to repeated implantation failure (RIF) or recurrent pregnancy loss (RPL) in women undergoing assisted reproductive technology treatments. It is anticipated that successful treatment of CE could lead to improved implantation rates in RIF patients and increased ongoing pregnancy rates in RPL patients (2-6). Regarding the treatment of CE, the standard approach has traditionally involved the administration of oral antibiotics (3, 4, 6, 7). Doxycycline, a broad-spectrum antibiotic, is the standard first-line treatment for CE (3, 6, 7). In cases where doxycycline treatment fails, a combination of metronidazole along with either ciprofloxacin or ofloxacin is often selected (2, 8). This second-line regimen resulted in a cure rate of 95% among women with CE (2). Despite the well-discussed and established treatment protocols for CE, it remains uncertain how the inflammatory condition in the uterine cavity arises.
A recent report indicated that peritoneal microorganisms originating from the gastrointestinal tract could potentially traverse the fallopian tubes and reach the uterine endometrium in humans, leading to endometritis (9). Additionally, recent research has demonstrated that regulating intestinal flora can reduce endometritis in mice (10). These findings collectively suggest that medical interventions aimed at maintaining a healthy intestinal environment could potentially serve as an efficient strategy for CE treatment. ImmuBalanceTM (IMB) (Nichimo Biotics, Japan) is a fermentation product derived from defatted soybeans using Aspergillus oryzae and lactic acid bacteria through proprietary fermentation technology (11, 12). A previous study demonstrated that IMB could improve chronic kidney disease by exerting anti-inflammatory effects and modulating gut microbiota (13). Based on this evidence, oral supplementation of IMB is anticipated to positively influence gut microbiota, thereby potentially improving the uterine endometrial environment. Consequently, daily intake of IMB could emerge as a promising treatment approach for CE.
In the present study, the effectiveness of oral administration of IMB in improving CE was evaluated.
Methods
Study population: This retrospective observational study was conducted at Sugiyama Clinic Shinjuku between April 2021 and August 2022. The study received ethical approval from the Ethics Committee of Sugiyama Clinic (Approval No. 22-010). During the study period, a total of 819 women were diagnosed with CE.
The flowchart of the classification of the participants is shown in figure 1. Among the 819 women diagnosed with CE, 809 received treatment with antibiotics (doxycycline, antibiotics-1), while the remaining 10 women received IMB (Group 1). One or two weeks following the first-line treatment, all women underwent evaluation of treatment effectiveness through endometrial biopsy. Out of the 819 women, 610 were determined to be cured after the initial treatment, while the remaining 209 women required further intervention. Of the 209 women, four received doxycycline, 190 received a combination of amoxicillin, azithromycin, and metronidazole (antobiotics-2), and 15 received IMB (Group 2). After one or two weeks from the second-line treatment, the treatment effectiveness was reassessed through endometrial biopsy. Out of the 209 women, 162 were determined to be cured, while the remaining 47 women underwent additional treatment with either IMB (n=4, Group 3) or curettage (14). Overall, 29 women received IMB as the treatment for CE.
Endometrial biopsies for CD138 immunohistochemistry: To evaluate the intrauterine environment and diagnose CE, endometrial sampling was performed between the late follicular and luteal phases of the menstrual cycle using an endometrial suction curette. The specimens collected were fixed in 10% formaldehyde. Pathologists stained the specimens using an anti-CD138 antibody and counted CD138-positive plasma cells in 10 non-overlapping random stromal areas visualized at 400-fold magnification. CE was diagnosed in cases where five or more CD138-positive cells were present (2).
Treatment of chronic endometritis: The first-line antibiotic treatment included the administration of 100 mg of oral doxycycline (Vibramycin®), twice a day for 14 days (2). The second-line antibiotic treatment consisted of a combination of 250 mg of amoxicillin (Sawacillin®), 250 mg of azithromycin (Azithromycin®), and 250 mg of metronidazole (Flagyl®), along with 6 mg of antibiotic-resistant lactic acid bacteria (Biofermin-R®), administrated twice a day for 14 days. For the treatment of CE with IMB, supplementation involved the administration of IMB (ImmuBalanceTM) at a dose of 9 tablets daily for 14 days.
The definitions of the variables and the statistical analysis: The following data were extracted from medical records: age, pregnancy history, treatment for CE, and the number of CD138-positive cells before and after treatment. Statistical analysis of the number of CD138-positive cells before and after the treatment was conducted using Fisher’s exact test.
All the statistical analyses were conducted using EZR software. The p<0.05 were considered statistically significant.<>
Results
A total of 29 women received IMB as the treatment for CE. The median age of the participants was 36 years, with an age range between 31 and 41 years. Among them, 21 women had a history of pregnancy, 11 had a history of labor, and 17 had a history of miscarriage.
In Group 1, consisting of women who received IMB as the first-line treatment, six out of ten participants (60%) achieved a clinical cure with IMB alone. The remaining four women, who were not treated with IMB, attained a successful outcome following the administration of oral doxycycline (antibiotics-1). The median CD138-positive plasma cell counts before and after taking IMB were 9.5 (range: 6-19) and 3.5 (range: 0-20) per 10 high power fields (HPF), respectively. However, this reduction was not statistically significant (p=0.13, table 1). In Group 2, consisting of 15 women who were not treated by antibiotics-1, only IMB was administered as the second-line treatment. All participants in this group achieved clinical cure following the administration of IMB. The median CD138-positive plasma cell count was 15 (range: 5-89) per 10 HPF before CE treatment. After the first-line treatment with antibiotics-1, this count slightly increased to 16 (range: 6-94) per 10 HPF, with no statistically significant difference (p=1.0). However, there was a significant decrease in CD138-positive plasma cell counts to a median of 1 (range: 0–7) per 10 HPF after IMB treatment compared to the counts following antibiotics-1 administration (p<0.01 ) (table 2). in group 3, four women who were not treated by both antibiotics-1 and antibiotics-2 received imb, and all four were confirmed to have attained clinical cure. the median of cd138-positive plasma cell count before ce treatment was 6.5 (range of 5-13) per 10 hpf. after the first- and second-line treatments with antibiotics-1 and antibiotics-2, these values increased to 9.5 (range: 8-13) per 10 hpf and 10.5 (range: 7-15) per 10 hpf, respectively. the median of cd138-positive plasma cell counts after receiving imb decreased to 1 (range: 0-3) per 10 hpf, representing a significant decrease compared to that after the second-line treatment (p="0.04," table 3).<>
Discussion
CE is widely believed to be potentially caused by microorganisms in the uterine cavity, although its exact origin remains unclear and not fully understood. Recent research has suggested that microorganisms from the gastrointestinal tract can migrate to the uterine cavity via the fallopian tube (9). Moreover, another study indicated that regulating intestinal flora can improve the condition of uterine tissues and reduce the prevalence of CE (10). Based on these findings, it is plausible to speculate that the improvement of CE following the administration of oral antibiotics may be attributed to the destruction of intestinal microflora, which could lead to a reduction in the presence of microorganisms associated with the condition. Moreover, these two studies strongly suggest that the dysbiosis of the intestinal microflora may contribute to the development of CE. Considering our hypothesis and the aforementioned research findings, it can be concluded that administering a product capable of improving intestinal microflora could be a viable treatment option for CE. Therefore, the effectiveness of administering IMB, a product that aligns with our hypothesis, was investigated as a potential treatment for CE.
ImmuBalanceTM contains koji polysaccharide as its main ingredient, which is derived from fermenting defatted soybeans with Aspergillus oryzae and lactic acid bacteria (11). This fermentation process results in a product rich in both probiotics (lactic acid bacteria) and prebiotics (dietary fiber and soybean oligosaccharides). The synergistic action of these probiotics and prebiotics is believed to improve intestinal microflora. To the best of our knowledge, this is the first study to demonstrate that IMB can serve as a viable treatment option for CE. In this study, the administration of IMB led to a significant decrease in the CD138-positive plasma cells in CE cases, particularly for the patients who experienced antibiotic-resistant CE (Tables 1-3). Kadogami et al. suggested that a combination of prebiotics and probiotics, administered after antibiotic treatment, can improve the intrauterine microbiome (15). This finding aligns closely with the results of our study. Our overall hypothesis posits that while antibiotics create a bacteriostatic environment in the intestinal tract, subsequent administration of IMB helps normalize gut microbiota. This normalization process may explain why CE was effectively treated with IMB, especially after antibiotic administration.
The present study has limitations that warrant consideration. The retrospective nature of our study and the relatively small study population may introduce inherent biases. Future studies with larger sample sizes are needed to validate our results.
Conclusion
Based on the findings of the study, it can be concluded that IMB can emerge as a promising supplementation material for treatment of CE. Moreover, IMB may represent a viable treatment option for cases of antibiotic resistance in CE.
Acknowledgement
The authors would like to thank Editage (www.editage.jp) for editing the English language in this paper.
Funding: This study was conducted without any external financial sources of support.
Conflict of Interest
Fumio Suyama, Koji Nakagawa, Keisuke Shiobara, Takashi Horikawa, Keiji Kuroda, Hisayo Kataoka, Yuko Ojiro, Satoru Takamizawa, and Rikikazu Sugiyama declared no conflicts of interest that could appear to influence the results from this study.