P.I. Responsible: Hortensia Ferrero
Technician: Alicia Quiñonero
Uterine fibroids are the most common benign tumor in women of reproductive age, affecting 25% of them [1, 2]. They are composed of smooth muscle cells derived from myometrium and extracellular matrix, which consists in collagen, fibronectin and proteoglycans that contribute to tumor growth, resulting in well-defined fascicular capsule within myometrium. A striking feature of uterine fibroids is their dependency on the estrogen and progesterone, an increase of these hormones is associated with fibroid growth. Although the main uterine fibroids treatment is surgery, either myomectomy or hysterectomy, inhibition of estrogen and progesterone secretion by GnRH agonist (GnRHa) is widely used [3, 4] because it reduces significantly the fibroids size (35-65%).
It has been observed that deregulation in Wnt/β-Catenin pathway is a common denominator in a wide variety of tumors [5-7], including uterine fibroids. Several studies suggest that inhibition of this pathway in fibroid cells decreases the proliferation and differentiation in these cells , so Wnt/β-Catenin pathway could be a promising target for new therapies in uterine fibroids treatment. In this regard, it has been observe that estrogen and progesterone activated Wnt/β-Catenin pathway in fibroid cells, causing increases in tumor proliferation and differentiation . It could explain the reason because estrogen and progesterone trigger the uterine fibroids growth. Based on these findings, we suggest that inhibition of estrogen and progesterone by GnRHa inhibits Wnt/β-Catenin pathway and thereby, fibroids size. However, GnRHa cannot be used more than 3-6 months due to the side effects that they produce, such as osteoporosis [10, 11]. Although GnRHa use produces a 47% reduction in fibroids size , the 100% of fibroids have reverted to its original size 6 months after treatment ends . For this reason, a new strategy for long-term treatment should be developed.
Recently, it has been shown a negative correlation between Vitamin D deficiency and fibroids presence, thereby lower serum Vitamin D levels are related with greater risk of uterine fibroids [15, 16], suggesting that Vitamin D could play an important role in fibroids development. Besides, Vitamin D, specifically the active metabolite 1,25-dihidroxivitamina D3 (1,25[OH]2D3), not only contributes to calcium homeostasis but also regulates cell proliferation and differentiation inhibiting the Wnt/β-Catenin pathway in cancer cells  and fibroids cells  in vitro and causes a reduction of fibroids size in vivo . These findings suggests that Vitamin D might be inhibiting proliferation and differentiation of fibroid cells by Wnt/β-Catenin pathway. Hence, Vitamin D might be used alone or as a co-treatment method in therapies that cannot be applied more than 6 months due to its side effects, such as GnRHa and thereby, we could control the fibroid size and associated symptoms at long-term.
In order to determine effects of Vitamin D treatment alone or in combination with GnRHa on fibroid growth, we isolate normal myometrium cells from myometrium and myoma cells from fibroid tissue and cultivate them in vitro with different treatments, alone or in combination: Vitamin D, GnRHa, Wnt inhibitor (sFRP1). Subsequently, in order to determine whether Vitamin D acts by Wnt/β-Catenin pathway, we evaluate apoptosis, cell proliferation and differentiation. Furthermore, we will determine in vivo whether Vitamin D, alone or in combination with GnRHa, inhibits cell proliferation and differentiation by Wnt/β-Catenin pathway and thereby, decreases the uterine fibroid size in rats that present fibroids and mice to which fibroid is implanted.
Figure 1: Schematic representation of the mechanism of Wnt/β-Catenin pathway repression by Vitamin D in fibroid cells. Vitamin D activated its cellular receptor, Vitamin D receptor (VDR), which binds to β-Catenin inhibiting its union with the transcription factor TCF and thereby, inhibiting the target genes expression involved in proliferation, metabolism, migration and differentiation.
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