Modulatory effect of aquaporin 5 on estrogen-induced epithelial-mesenchymal transition in prostate epithelial cells
Benign prostatic hyperplasia (BPH)—the non-cancerous enlargement of the prostate—is a ubiquitous health concern for older men. By age 50, half of men experience BPH symptoms like frequent urination or weak urine flow, and that number jumps to 90% by 80. While androgens (male hormones) have long been linked to BPH, emerging research highlights estrogen as a critical player. A 2021 study from West China Hospital of Sichuan University reveals a new piece of the puzzle: aquaporin 5 (AQP5), a water channel protein, may be the bridge between estrogen and a cellular process that drives BPH growth.
What Is EMT—and Why Does It Matter for BPH?
Epithelial-mesenchymal transition (EMT) is a normal process in embryonic development where specialized “sticky” epithelial cells (which line organs like the prostate) transform into mobile, proliferative mesenchymal cells. But when EMT goes haywire in adulthood, it fuels diseases like BPH. Mesenchymal cells multiply faster and lose their structure, contributing to prostate enlargement and symptoms.
Scientists have long known estrogen can trigger EMT in other tissues, but until now, no one had linked this to AQP5—a protein estrogen directly activates—in the prostate. The West China team hypothesized that estrogen boosts AQP5 levels, which in turn drives EMT and BPH.
How the Study Was Done
The researchers analyzed 3 normal prostate (NP) tissues (from patients with bladder cancer, no prostate abnormalities) and 5 BPH tissues (confirmed by pathology). They also used a benign prostate cell line (RWPE-1) to create an EMT model:
- Cells were treated with estradiol (E2), a natural estrogen, to mimic high estrogen levels.
- They used genetic tools (small interfering RNAs, or siRNAs) to “knock down” (reduce) AQP5 levels in cells.
- Tests like staining (to see protein location), Western blot (to measure protein levels), and cell proliferation assays tracked changes in EMT, AQP5, and estrogen receptors (ERa and ERb).
Key Findings
The results were clear: AQP5 is a linchpin in estrogen-driven BPH.
1. BPH Tissues Have More EMT—and Higher AQP5
Compared to normal prostate tissue, BPH tissues showed:
- Increased EMT: Higher levels of vimentin (a mesenchymal cell marker) and TGF-b1 (a signal that promotes EMT), plus lower E-cadherin (an epithelial cell “sticky” protein).
- Higher AQP5 and ERa: AQP5 levels were 5x higher in BPH tissues. ERa—an estrogen receptor that drives cell growth—was also elevated, while ERb (which promotes cell death) was lower.
2. Estrogen Stimulates AQP5, Proliferation, and EMT
When RWPE-1 cells were treated with E2:
- AQP5 levels rose: Cells had 20% more AQP5 than untreated controls.
- Cells multiplied faster: E2-treated cells grew 50% more than controls after 72 hours.
- EMT increased: Vimentin levels doubled, while E-cadherin dropped by 65%.
3. Knocking Down AQP5 Stops Estrogen-Induced EMT
The most compelling finding? Reducing AQP5 levels reversed the effects of estrogen:
- EMT markers dropped: Vimentin levels fell by 59%, and E-cadherin rose by 112% compared to E2-treated cells with normal AQP5.
- Cell growth slowed: AQP5-knockdown cells grew 18% less than E2-treated controls.
Why This Matters for BPH Treatment
This is the first study to link AQP5 to EMT in benign prostate cells. Here’s why it’s a game-changer:
- AQP5 as a Target: Since AQP5 is essential for estrogen-driven EMT, blocking it could slow or stop BPH growth. Existing AQP inhibitors (used in other diseases like glaucoma) could be repurposed for prostate health.
- Estrogen Receptor Balance: BPH tissues had more ERa (growth) and less ERb (death). This imbalance, combined with AQP5, may be a key driver of enlargement.
- Beyond Androgens: Most BPH treatments target androgens (e.g., finasteride). This study opens the door to estrogen/AQP5-focused therapies—critical for men where androgen blockers don’t work.
Limitations to Consider
The study had small sample sizes (3 normal, 5 BPH tissues) and didn’t test effects in animals (in vivo). More research is needed to confirm these findings in larger groups and living organisms. But the results are a strong first step.
Conclusion
The West China team’s work reveals a new pathway in BPH: estrogen → AQP5 → EMT → prostate enlargement. For the millions of men living with BPH, this could mean a future where AQP5 inhibitors offer a safe, effective alternative to current treatments.
As the population ages, BPH will only become more common. Targeting AQP5— a protein now linked to the very cells that drive enlargement—could be the key to turning the tide.
This study was published in the Chinese Medical Journal (2021) by Yu Fan, Tu-Run Song, Qiang Wei, and colleagues from the Department of Urology at West China Hospital of Sichuan University. The full paper is available at doi.org/10.1097/CM9.0000000000001132.
Was this helpful?
0 / 0