Department of Obstetrics and Gynaecology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China.
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China.
Clin Chem. 2018 Dec;64(12):1743-1752. doi: 10.1373/clinchem.2018.289306. Epub 2018 Sep 20.
A recent study has reported that the microbiota in endometrial fluid of patients receiving in vitro fertilization and embryo transfer (IVF-ET) may predict implantation and pregnancy rates. However, studies are lacking that simultaneously compare the microbiota between endometrial fluid and tissue samples. Whether the microbiota composition in endometrial fluid reflects that in the endometrial tissue remains unclear.
We systematically profiled the microbiota in endometrial fluid and tissue samples of IVF-ET patients using massively parallel sequencing. The bacterial 16S ribosomal RNA gene (V4 region) was PCR-amplified. Sequencing reads with >98% nucleotide identity were clustered as a bacterial taxon. To account for the different number of reads per sample, we normalized the read counts of each taxon before comparing its relative abundances across samples.
Thirteen taxa, including Verrucomicrobiaceae, , , , and , were consistently detected only in endometrial tissue samples but not fluid samples. Eight taxa were detected in fluid but not tissue. Twenty-two taxa were differentially abundant between fluid and tissue samples (adjusted values, 4.1 × 10 to 0.025). The numbers of taxa identified per 1000 sequencing reads, diversity, and evenness in fluid samples were smaller than those in tissue samples.
Our data suggest that the microbiota composition in endometrial fluid does not fully reflect that in endometrial tissue. Sampling from both endometrial fluid and biopsy allows a more comprehensive view of microbial colonization. Further efforts are needed to identify the preanalytical effects, including sampling sites, methods, and sequencing depth, on profiling endometrial microbiota.
最近的一项研究报告称，接受体外受精和胚胎移植（IVF-ET）的患者的子宫内膜液中的微生物群可能预测着床和妊娠率。然而，缺乏同时比较子宫内膜液和组织样本中微生物群的研究。子宫内膜液中的微生物群组成是否反映了子宫内膜组织中的情况尚不清楚。
我们使用大规模平行测序系统地对 IVF-ET 患者的子宫内膜液和组织样本中的微生物群进行了分析。扩增细菌 16S 核糖体 RNA 基因（V4 区）。将具有 >98%核苷酸同一性的测序读长聚类为细菌分类群。为了考虑每个样本中读取数的不同，我们在比较样本之间相对丰度之前，对每个分类群的读取计数进行了归一化。
包括韦荣球菌科、、、、和在内的 13 个分类群仅在子宫内膜组织样本中而不在液体样本中一致检测到。8 个分类群仅在液体样本中检测到。22 个分类群在液体和组织样本之间的丰度存在差异（调整后 值，4.1×10 至 0.025）。液体样本中每个 1000 个测序读取鉴定的分类群数量、多样性和均匀度均小于组织样本。
我们的数据表明，子宫内膜液中的微生物群组成不能完全反映子宫内膜组织中的情况。从子宫内膜液和活检中采样可以更全面地了解微生物定植情况。需要进一步努力来识别包括采样部位、方法和测序深度在内的对子宫内膜微生物组进行分析的预分析影响。
