Recent research has addressed menopause-related molecular processes that impact the high prevalence of knee osteoarthritis in post-menopausal women. Restoration of female sex hormones in a post-menopausal mouse model improved joint health [1].
A centuries-old observation
The authors start the article with a quote from the English physician John Haygarth from 1805:
the nodosities [irregularities] of the joint are almost peculiar to women and begin when the menses naturally cease.
While this 200-year-old observation has been confirmed by contemporary medicine, an inadequate amount of attention is still given to knee osteoarthritis in post-menopausal females, even though age and sex are risk factors for this condition and knee osteoarthritis is more prevalent and severe in post-menopausal women than men [2, 3, 4]. The researchers of this study aimed to fill this gap and focused explicitly on post-menopausal models.
Mimicking human menopause
The researchers mention a few ways to mimic menopause in mice, which do not have the same menopausal transition as humans. One of them is the surgical removal of the ovaries (ovariectomy), although this model has many drawbacks. Human females normally transition into menopause through a period of perimenopause, during which regular cycles become irregular and finally cease. However, ovariectomy results in a sharp cessation of cycles and the abrupt disruption of ovarian sex hormones, including those that do not change during normal menopause.
Due to those shortcomings, ovariectomy is not the best model for investigating the effects of the menopause transition on the trajectory of knee osteoarthritis. Therefore, the researchers used a different model that chemically induced menopause. They injected mice with the ovarian toxin 4-vinylcyclohexene diepoxide (VCD). This approach is not an exact representation of menopause and might cause some unwanted changes in biology. However, it seems to have more benefits than ovariectomy; for example, the animals undergo perimenopause and have intact ovaries.
The authors modified previous protocols and treated 14- to 16-month-old female C57BL/6N mice with VCD. These middle-aged mice roughly correspond to 47- to 52-year-old humans, an average perimenopause age.
As expected, animals treated with VCD experienced perimenopause and the menopausal transition, including body temperature, weight, and hormonal changes that mirrored that of humans. The researchers called the VCD-treated group the ‘menopause group’ and control mice the ‘non-menopause group.’
Declining joint health
The researchers assessed the impact of menopause on cartilage, the layer of bone below the cartilage in a joint (subchondral bone), and the membranous structure located on the inner surface of joint capsules (synovium). Cartilage, subchondral bone, and synovium health didn’t differ between these groups early in the experiment, 11 days after VCD injections.
However, when cartilage integrity was scored in the menopausal group during perimenopause and the menopausal transition, the researchers noted “progressively increased degeneration,” which was not observed in the non-menopause group. Synovium health worsened in both the menopause and non-menopause groups, but the menopause group had worse scores compared to the non-menopause group. The impact of menopause on subchondral bone depended on the bone region, with some areas showing no differences between groups and others showing a decrease in bone volume and density in the menopause group.
Modeling the molecular changes
The researchers aimed to understand the molecular mechanisms behind their observation. They used mass spectrometry to identify proteins present in cartilage samples of mice at mid-perimenopause, the start of menopause, and late menopause. After identifying what proteins changed, the researchers identified pathways impacted by the menopausal transition and integrated them into a network to identify changes in pathways over time.
Their analysis revealed cellular signaling changes followed by extracellular matrix (ECM) changes, such as changes in collagen expression, in the menopause group. Conducted experiments also suggested an increased susceptibility to collagen degradation caused by menopause.
Further analysis of menopause-associated protein changes showed that, besides changes to the ECM, cellular senescence and actin cytoskeleton stress were also impacted by the menopausal transition.
Then, the researchers used a simulation system to estimate how altering sex hormone levels and administering senolytics would impact health. In this simulation, administering 17β-estradiol plus progesterone eliminated ‘cellular senescence’ and ‘ECM disassembly’ processes and improved other measurements. A senolytic, dasatinib, had a similar effect.
Testing the predictions
The researchers tested their simulation’s results in vivo. They induced menopause in mice and treated them daily from mid-perimenopause to the start of menopause with either 17β-estradiol, progesterone, 17β-estradiol plus progesterone, or dasatinib.
Cartilage integrity was improved in mice treated with 17β-estradiol and 17β-estradiol plus progesterone compared to controls. However, synovium and subchondral bone tissue were not affected by the treatments.
While analyzing a few mice from the groups for side effects, the researchers noticed abnormalities and excessive growth of tissues in the intestine of some of the animals treated with either 17β-estradiol or progesterone, but further research is needed to confirm that it was indeed caused by the treatment since the sample size was too small to be conclusive.
To learn about the functionally relevant impact of the treatments, the researchers tested behavioral outcomes. The differences were seen only in step length (increased in menopausal mice) and stride length (decreased in menopausal mice). Both progesterone and 17β-estradiol plus progesterone treatments restored those measurements to non-menopausal levels.
Improved chondrocytes health
Encouraging results in mouse models led the researchers to further experimentation on available human material. They isolated cells responsible for cartilage formation (chondrocytes) from post-menopausal patients undergoing knee surgery.
Culturing human-derived chondrocytes with 17β-estradiol, progesterone,17β-estradiol plus progesterone, and dasatinib resulted in a decreased proportion of cells expressing senescence markers, an increase in the cells expressing proliferation markers, and a reduction in the senescence-associated secretory phenotype (SASP).
Additionally, progesterone, 17β-estradiol plus progesterone, and dasatinib led to a modest increase in the expression of transcription factors essential in regulating key genes related to cartilage formation and development (chondrogenicity). 17β-estradiol plus progesterone improved the health of chondrocytes and positively regulated the expression of different types of collagen.
The researchers concluded that “these findings support our network medicine analyses suggesting that restoration of progesterone signaling alters the senescent phenotype of aged, post-menopausal chondrocytes.”
Restoring health with hormones
This study suggests a link between changes in sex hormone signaling during the menopausal transition and knee osteoarthritis development in post-menopausal females. Restoration of those hormones improves cartilage and chondrocyte health. Future studies are required to address whether such a therapy could help women with knee osteoarthritis.
Literature
[1] Gilmer, G., Iijima, H., Hettinger, Z. R., Jackson, N., Bergmann, J., Bean, A. C., Shahshahan, N., Creed, E., Kopchak, R., Wang, K., Houston, H., Franks, J. M., Calderon, M. J., St Croix, C., Thurston, R. C., Evans, C. H., & Ambrosio, F. (2025). Menopause-induced 17β-estradiol and progesterone loss increases senescence markers, matrix disassembly and degeneration in mouse cartilage. Nature aging, 5(1), 65–86.
[2] Prieto-Alhambra, D., Judge, A., Javaid, M. K., Cooper, C., Diez-Perez, A., & Arden, N. K. (2014). Incidence and risk factors for clinically diagnosed knee, hip and hand osteoarthritis: influences of age, gender and osteoarthritis affecting other joints. Annals of the rheumatic diseases, 73(9), 1659–1664.
[3] Hame, S. L., & Alexander, R. A. (2013). Knee osteoarthritis in women. Current reviews in musculoskeletal medicine, 6(2), 182–187.
[4] Srikanth, V. K., Fryer, J. L., Zhai, G., Winzenberg, T. M., Hosmer, D., & Jones, G. (2005). A meta-analysis of sex differences prevalence, incidence and severity of osteoarthritis. Osteoarthritis and cartilage, 13(9), 769–781.
