Correlational Analysis of the Vaginal Microecology and Pelvic Organ Prolapse

There were no significant differences in age, BMI, number of deliveries, diabetes mellitus or hypertension between the POP group and non-POP group (see Appendix Table 7 and Table 8). Compared with the non-POP group, the POP group exhibited significantly higher levels of vaginal PH, H2O2 positivity and LE positivity. However, there was no significant difference in salivary acid glycosidase positivity between the two groups (p = 0.754, Table 2). Further stratification of the POP group was performed, with 13 cases classified as POP-Q stage III and 17 cases classified as POP-Q stage IV, and results indicated that patients with POP-Q stage IV had higher rates of vaginal pH, H2O2 positivity, and LE positivity than those with POP-Q stage III (Table 3).

Table 2 Comparison of vaginal microecological function outcomes between two patient cohortsTable 3 Comparison of vaginal microecological function outcomes between two patient cohortsThe mRNA Expression Levels of DCN, TGF-β1, MMP-3, Collagen I, and Collagen III were Quantified by qPCR in the POP and Non-POP Groups

The findings revealed that the mRNA expression levels of DCN, TGF-β1, and MMP-3 were significantly higher in the POP group than those in the non-POP group (Fig. 1A–C), Conversely, the mRNA expression levels of collagen I and III were markedly lower in the POP group than those in the non-POP group (Fig. 1D, E).

Fig. 1

The mRNA expression levels of A decorin (DCN), B transforming growth factor beta 1 (TGF-β1), C matrix metalloproteinase-3 (MMP-3), D collagen I, and E collagen III in tissue samples from the uterosacral ligament were quantified using quantitative polymerase chain reaction in patients with pelvic organ prolapse (POP) and non-POP. Statistical analysis revealed significant differences between the two groups (*p < 0.05, ***p < 0.001)

Protein Expression of MMP-3, Collagen I, and Collagen III was Evaluated by IHC in the POP and Non-POP Groups

The findings indicated that the positive expression of MMP-3 in uterosacral ligament tissue was significantly upregulated in the POP group compared with the non-POP group (p = 0.035, Fig. 2). However, the positive expression of collagen I and collagen III in uterosacral ligament tissue was significantly downregulated in the POP group compared with the non-POP group (p = 0.004, Fig. 3; p = 0.019, Fig. 4).

Fig. 2

Matrix metalloproteinase-3 (MMP-3) is significantly upregulated in pelvic organ prolapse (POP). Tissue sections were subjected to A hematoxylin and eosin (HE) staining and B immunohistochemistry analysis for MMP-3 expression in both POP and non-POP tissues (bar, 50 μm). *p < 0.05

Fig. 3

Collagen I expression is significantly lower in pelvic organ prolapse (POP) than in non-POP. Tissue samples were A stained with hematoxylin and eosin (HE) and B subjected to immunohistochemistry analysis for collagen I expression. (bar, 50 μm). **p < 0.01

Fig. 4

Collagen III expression is significantly lower in pelvic organ prolapse (POP) than in non-POP. Tissue samples were A stained with hematoxylin and eosin (HE) and B subjected to immunohistochemistry analysis for collagen III expression. (bar, 50 μm). *p < 0.05

Correlation Analysis between Vaginal Microecology and Collagen Metabolism in Patients with POP

There was a significant positive correlation between vaginal pH and MMP-3 expression (p = 0.033, r = 0.331). However, no significant correlation was observed between pH and collagen I or collagen III (all p > 0.05). H2O2 positivity demonstrated a significant positive correlation with MMP-3 (p = 0.013, r = 0.384), as well as a negative correlation with collagen I (p = 0.014, r = −0.381) and collagen III (p = 0.013, r = −0.395). LE positivity also showed a positive correlation with MMP-3 (p = 0.023, r = 0.352), whereas no significant correlations were observed between LE positivity and collagen I or collagen III (all p > 0.05).

The MMP-3 exhibited a negative correlation with both collagen I and collagen III (Fig. 5A. p = 0.002, r = −0.533; Fig. 5B; p = 0.002, r = −0.534), whereas collagen I demonstrated a positive correlation with collagen III (Fig. 5C. p = 0.001, r = 0.578) based on the results of IHC staining and interpretation criteria.

Fig. 5

A–C Correlation of matrix metalloproteinase-3 (MMP-3), collagen I, and collagen III with clinical characteristics in patients with pelvic organ prolapse

Correlation of MMP-3, Collagen I, and Collagen III with Clinical Characteristics in Patients with POP

The protein expression levels of MMP-3, collagen I, and collagen III were analyzed in relation to clinical parameters (age, menopause, BMI, and POP-Q stage) of patients with POP (n = 30), using IHC staining results and interpretation criteria scores combined with clinicopathological tissue sample information.

Based on the IHC staining results and interpretation criteria, MMP-3 expression was classified as high expression (≥ 5 points) and low expression (< 5 points), with a median interpretation result of 5 points. The findings indicated that there were 15 patients with high expression of MMP-3 and 15 patients with low expression among 30 samples of POP tissue. Notably, elevated levels of MMP-3 were significantly associated with menopause (p = 0.021) and the severity of POP (p = 0.003, Table 4).

Table 4 Clinical relevance of matrix metalloproteinase-3 (MMP-3) in pelvic organ prolapse

Similarly, collagen I expression was classified as high expression (≥ 4 points) and low expression (< 4 points), with a median interpretation result of 4 points. The findings indicated that there were 16 patients with high expression of collagen I and 14 cases with low expression among 30 samples of POP tissue. Notably, low expression of collagen I was significantly associated with menopause (p = 0.026) and the severity of POP (p = 0.004, Table 5).

Table 5 Clinical relevance of collagen I in pelvic organ prolapse

Additionally, collagen III expression was classified as high expression (≥ 4 points) and low expression (< 4 points), with a median interpretation result of 4 points. The findings indicated that there were 16 patients with high expression of collagen III and 14 patients with low expression among 30 samples of POP tissue. Notably, low expression of collagen III was significantly associated with menopause (p = 0.026) and the severity of POP (p = 0.033, Table 6).

Table 6 Clinical relevance of collagen III in pelvic organ prolapse