Uterine fibroids affect up to 77% of women by menopause, yet researchers struggle to develop effective treatments due to the lack of reliable animal models that accurately replicate human disease. The Massachusetts General Hospital at Harvard Medical School conducted comprehensive research revealing that current animal models fail to capture the complexity of human uterine fibroid pathophysiology. Uterine fibroids, also called leiomyomas or myomas, are non-cancerous growths in the muscle wall of the uterus (the myometrium) that can cause heavy bleeding, pain, and fertility problems.
Despite being the most common benign tumors in women worldwide, there is a lack of appropriate pharmacotherapeutic agents and preventive measures for uterine fibroids, mainly because of the lack of reliable in vivo models. In vivo research refers to studies conducted in living organisms, while in vitro studies occur in laboratory environments outside the body. Animal models are laboratory animals used to study human diseases, but they must accurately represent the biological processes seen in humans to be useful for developing treatments.
Seventy percent of women will present with uterine fibroids at some point in their lives, making this one of the most significant women’s health challenges, yet the etiology and pathophysiology are not properly understood. Etiology refers to the cause of a disease, while pathophysiology describes how the disease develops and progresses in the body. This knowledge gap has contributed to limited treatment options beyond surgical removal.
Eker Rat Model Shows Critical Limitations
The Eker rat model is the most widely used in vivo animal model to study uterine fibroids, but this animal model has some limitations that make it unsuitable for human disease research. The Eker rat carries a genetic mutation in the tuberous sclerosis complex-2 (TSC2) tumor suppressor gene, which is a gene that normally prevents tumor formation. The Eker rat develops uterine fibroids with a frequency of about 65% by 16 months of age, making it appear useful for research at first glance.
Dr. Arno Commandeur from Massachusetts General Hospital explains that “mutations in the TSC gene have not been linked to the disease in humans”, meaning the genetic cause of fibroids in these rats is completely different from what causes fibroids in women. This fundamental difference makes any treatments developed using this model potentially irrelevant for human patients. Additionally, the developing uterine fibroids in Eker rats show relatively small amounts of collagenous connective tissue stroma, unlike human uterine fibroids, which present a high amount of abnormally formed cross-linked collagen.
Finally, Eker rats develop both benign and malignant smooth muscle tumors, while human uterine fibroids are almost always benign (non-cancerous). This difference creates confusion about which research findings apply to typical human fibroid cases versus rare cancerous forms.
Alternative Models Show Similar Inadequacies
Several novel models of leiomyomas have been proposed lately for a variety of animal species, including guinea pig models, potbellied pig models, and rabbit VX2 tumor models. Guinea pigs naturally develop fibroids in 8.4% of guinea pigs until 4 years of age, but this low rate makes research difficult and expensive. The guinea pig model requires hormone treatments to increase fibroid development, creating an artificial disease state that may not reflect natural human fibroid formation.
These approaches are useful for studying tumor formation in vivo but lack myometrial controls, as the matched human myometrial cells do not form xenografts easily in this system. Xenografts involve transplanting human tissue into animals with suppressed immune systems. Without proper control tissue for comparison, researchers cannot determine which changes are due to the disease versus normal tissue responses to the experimental environment.
Emerging Three-Dimensional Cell Culture Solutions
Due to some limitations using animal models, the use of three-dimensional (3D) models has attracted more attention in uterine fibroid research, particularly using myometrial stem cells instead of differentiated myometrial cells. Three-dimensional cell culture refers to growing cells in laboratory conditions that allow them to form structures similar to natural tissues, rather than growing them flat on plastic surfaces. The 3D model provides a more biomimetic cell culture environment than 2D substrates, with the advantage of more closely mimicking in vivo tissue architecture.
Professor José Teixeira from Massachusetts General Hospital notes that “MMSC-material interactions in 3D with topographical cues may provide an effective means to regulate many fibroid-related biological events, including differentiation, epigenetic state, or cell reprogramming”. Myometrial stem cells (MMSCs) are the original cells that can develop into different types of uterine muscle cells. Epigenetic changes refer to modifications in gene activity that don’t change the DNA sequence itself but affect how genes are expressed.
These models bridge traditional 2D cell cultures and animal models, offering a cost-effective, scalable, and ethical alternative for preclinical research. Preclinical research refers to laboratory studies conducted before testing treatments in human patients, making this an essential step in drug development.
Research Advancement Through Better Models
Little is known about fibroid pathophysiology or genetic risk factors beyond what has been learned from cell culture studies and tumor biology, with barriers including lack of imaging, limited racial diversity in cohorts, and availability of DNA samples. Cohorts refer to groups of study participants followed over time to understand disease patterns. The lack of diverse study populations means treatments may not work equally well for all women, particularly concerning since African-American women are three times more likely to develop fibroids.
3D cell culture models can help bridge the gap between in vitro cell cultures and in vivo responses by more accurately simulating the natural in vivo environment, shape, tissue stiffness, stressors, gradients and cellular response while avoiding the costs and ethical concerns associated with animal models. This technology allows researchers to study human fibroid cells in conditions that better represent the actual uterine environment.
A systematized review was performed analyzing all reported in vivo models of uterine fibroids, conducted by researchers from multiple institutions and published in leading reproductive biology journals between 2021-2022, consolidating current understanding of 918 scientific articles to guide further research development
Key Takeaways
- Current animal models fail to replicate human fibroid genetics, tissue structure, and disease progression patterns accurately.
- The widely-used Eker rat model has genetic mutations and tissue characteristics completely different from human fibroids.
- Three-dimensional cell culture technology offers promising alternatives that better mimic human uterine tissue for treatment development.
Related Content
- 3D Cell Culture for Uterine Fibroid Drug Research and Development – Discover how three-dimensional cell culture technology is replacing animal testing in pharmaceutical research and drug development.
- Why Women’s Health Remains Understudied – Learn why women’s health conditions remain understudied and how new research approaches are addressing these gaps.
