Bolstering a type of bacteria native to the uterus reduced markers of uterine aging and improved embryo implantation in laboratory experiments and aged mice, researchers report. The study, published Aug. 6 in Cell Host & Microbe, identifies a bacterial byproduct derived from Lactobacillus as the active agent and proposes the uterine microbiome as a potential target for interventions to support reproductive function.
The team analysed endometrial samples from 149 women aged 20 to 45 undergoing fertility treatment in China and found that older participants had lower levels of beneficial Lactobacillus species, notably L. gasseri and L. crispatus. Among 93 women who proceeded with IVF, those who achieved pregnancy had higher uterine Lactobacillus abundance, although overall microbial diversity did not differ markedly across ages. Co-author Dr. Rong Li of Peking University Third Hospital noted that shifts involved specific species rather than broad diversity changes.
In laboratory experiments the investigators isolated five Lactobacillus species and identified L. gasseri as particularly effective at attaching to uterine cells, reducing inflammation and limiting oxidative stress. The bacterium produced substantial exopolysaccharides (EPS), which the researchers purified into a postbiotic they named LG-EPS. Daily vaginal application of either live L. gasseri or LG-EPS to older female mice for four weeks was associated with fewer signs of uterine aging and higher embryo implantation rates; a modified strain unable to produce EPS did not confer the same benefits.
Mechanistic studies indicated that the postbiotic modulated a signaling pathway involved in cell growth and tissue repair, and pharmacological blockade of a key protein in that pathway abolished the observed effects. Independent fertility specialist Dr. Alex Robles of Columbia University Fertility Center described the approach as promising but underlined that translation to human fertility outcomes requires validation across diverse populations and controlled clinical trials. He also cautioned against ad hoc use of over-the-counter probiotics for this purpose.
The authors and independent experts emphasise that the findings are preliminary. While postbiotics like LG-EPS could offer manufacturing advantages over live microbial therapies and might be investigated as adjuncts to IVF, clinical safety, dosing and effectiveness must be established before clinical application.
