Fallopian tube organoids provide a new way to study pelvic host-microbe interactions

From the Fredricks Lab, Vaccine and Infectious Disease Division

Pelvic inflammatory diseases occur when pathogenic bacteria colonize areas of the female reproductive system, such as the uterus or fallopian tubes. While easily treated with antibiotics, these infections can cause scarring and lead to infertility if left untreated. Unfortunately, finding ways to study these bacterial-induced inflammatory responses and the adverse health effects these infections cause has been challenging. “There are no optimal animal models of human pelvic inflammatory disease induced by bacteria that normally inhabit the human vagina since non-human primates have different anatomy and microbiota,” stated Dr. David Fredricks, a professor in the Vaccine and Infectious Disease Division. Dr. Fredricks  and Dr. Yu (a physician-scientist in Obstetrics and Gynecology) thought a human organoid model system could provide “a unique opportunity to study how human vaginal bacteria interact with cells of the fallopian tube.” Specifically, the group is “interested in which vaginal bacteria may ascend to the upper reproductive tract and influence the inflammatory response leading to pelvic inflammatory disease and other outcomes including ovarian cancer,” Dr. Fredricks explained. To improve their ability to study host-pathogen interactions in pelvic inflammatory disease, the group developed a patient-derived fallopian tube organoid system and examined how these organoids respond to bacterial infection. Furthermore, this model provides the opportunity to facilitate future mechanistic studies investigating how these infections may contribute to infertility or ovarian cancer. This work was recently published in Reproductive Sciences.

To develop their model system, the researchers first obtained fallopian tube tissue samples from four women undergoing surgical removal of one or both fallopian tubes for benign gynecological reasons, for example for contraceptive purposes. The Fredricks group then established a protocol to construct their three-dimensional organoid system and verified that these mini in vitro fallopian tubes retained normal fallopian tube characteristics, such as containing secretory and ciliated cells. After development of the fallopian tube organoids, the authors inoculated the organoid culture with either a bacterial species present in healthy vaginal microbiota (Lactobacillus crispatus) or a pathogenic one that has been linked to pelvic inflammatory disease (Fannyhessea vaginae). After 24 hours of culture, the research team collected the fallopian tube organoids to study the inflammatory responses elicited by these microbes.

Differential gene expression between fallopian tube organoids treated with non-pathogenic Lactobacillus crispatus or pathogenic Fannyessea (A. vaginae).
Differential gene expression between fallopian tube organoids treated with non-pathogenic Lactobacillus crispatus or pathogenic Fannyessea (A. vaginae). Image provided by Dr. David Fredricks.

Using a gene expression panel to investigate changes of 250 inflammatory genes, the authors compared the transcriptional responses between organoids cultured with these two types of bacteria, in addition to ones cultured without bacteria. They found that while organoids generated from each individual had different inflammatory responses, clear trends were evident in their general response to bacteria. Here, the authors found a shared upregulation of genes in the CC-chemokine ligand (CCL) family in both L. crispatus and F. vaginae infected organoids compared to uninfected controls. Comparing differences in inflammatory responses induced by each bacterial species, the researchers found a “stark contrast in inflammatory profiles induced by Lactobacillus crispatus which is associated with vaginal health, and Fannyhessea vaginae which is associated with bacterial vaginosis. The gene expression profiles elicited by these different bacteria highlight why some bacteria may lead to more upper tract inflammation through recruitment of immune cells,” explained Dr. Fredricks. Specifically, the group found that CXCL genes (CXCL1, 2, 3, 5, 6 and 10) were highly expressed in the pathogenic F. vaginae infected organoids, which may enhance leukocyte recruitment. On the other hand, organoids infected with L. crispatus had upregulation of genes such as TGFB1 or TRADD, and downregulation of mitogen-activated protein kinase (MAPK) family genes. Furthermore, flow cytometry revealed that immune cells contributed to a small minority of the organoid composition, indicating that the inflammatory responses observed here were likely generated by the epithelial cells.

This pilot study enables a new way “of studying host-microbe interactions using tissue organoids” and “will allow investigators to answer key mechanistic questions about how genital tract bacteria cause adverse health impacts in a system that reflects human biology,” Dr. Fredricks stated. Moving forward, Fredricks explained that “there are many additional bacteria that can be investigated using this approach to better understand how the genital tract microbiota influence host cells in the reproductive tract. We plan to use this system to determine if bacteria linked to pelvic inflammatory disease in epidemiological studies impart a specific host immune response that then leads to health outcomes such as infertility and even cancer.”

This work was supported by the National Institutes of Health, the Akiko Yamazaki and Jerry Yang Faculty Scholar Fund, the Stanford Women’s Cancer Innovation Award, the Stanford Cancer Institute, and the Dunlevie Maternal-Fetal Medicine Center for Discovery, Innovation and Clinical Impact.

Fred Hutch/UW/Seattle Children’s Cancer Consortium member Dr. David Fredricks contributed to this work.

Yu B, McCartney S, Strenk S, Valint DJ, Liu C, Haggerty CL, Fredricks DN. Vaginal Bacteria Elicit Acute Inflammatory Response in Fallopian Tube Organoids. Reprod Sci. 2023 Sep 19. doi: 10.1007/s43032-023-01350-5. Epub ahead of print. PMID: 37726587.