Microbial Reconstitution Improves Aging-Driven Lacrimal Gland Circadian Dysfunction

Lacrimal glands are highly susceptible to aging and exhibit age-related structural and functional alterations. However, the mechanisms by which aging affects the lacrimal glands are not well-established. The current study explores the crosstalk between the aging process, gut microbiota, and circadian rhythm in age-associated lacrimal gland dysfunction. C57BL/6J mice were divided into young, old, and fecal microbiota transplant (FMT)-treated old groups. The gut bacterial community diversity was analyzed by 16S rRNA sequencing. Exorbital lacrimal glands (ELGs) were collected at 3-hour intervals over a 24-hour circadian cycle, and total RNA was subjected to high-throughput sequencing. Rhythmic transcriptional data were analyzed using the Jonckheere-Terpstra-Kendall algorithm and bioinformatics analysis technology. Immunostaining was used to identify lymphocytic infiltration, lipid deposition, and nerve innervation in the ELGs. Compared with young mice, old mice underwent a significant gut microbial community shift. The rhythmically transcriptomic profile was significantly reprogrammed over a 24-hour cycle in the old ELG group. Intervention with serial FMT from young donors for 1 month rejuvinated the gut microbial community of the old mice. Most alterations in rhythmic transcriptomic profiling were improved. Furthermore, chronic inflammation, lipid deposition, and aberrant neural response of the aging lacrimal glands were significantly reduced. Thus, the study shows that reconstitution of age-associated gut dysbiosis with FMTs from young donors improves aging-driven lacrimal gland circadian dysfunction.