Home » Key Drug Discovery Articles » Concanavalin-A induces granulosa cell death and inhibits FSH-mediated follicular growth and ovarian maturation in female rats

Concanavalin-A induces granulosa cell death and inhibits FSH-mediated follicular growth and ovarian maturation in female rats

Significance Statement

Significant interest exists to understand the molecular mechanism conducting to normal fertility which will also bring light about the causes of infertility and potential targets for diagnosis or treatment. In the female, a delicate balance between follicular maturation and atresia is critical to the success of reproductive function. Although a substantial knowledge about factors and cellular pathways contributing to control follicular maturation has been achieved in the last decades, the precise mechanism determining the balance between follicular growth and atresia is not fully understood.

Follicular growth and maturation towards a pre-ovulatory state are mainly under the guidance of Follicle Stimulating Hormone (FSH). It acts on granulosa cells to promote survival, proliferation, endocrine activity and cell differentiation through several molecular mechanisms. Furthermore, Follicle Stimulating Hormone modulates the ovarian angiogenesis by regulating gene expression and protein levels of angiogenic related factors. Currently, follicle stimulating hormone in natural and recombinant forms is widely used in clinic for the treatment of both women and men during assisted reproductive procedures.

In this article, we report for the first time a fraction of recombinant follicle stimulating hormone that promotes granulosa cell death. Using ex-vivo and in-vivo experiments we confirmed that this fraction is also capable of preventing follicular maturation and increasing atresia. Additional analysis by mass spectrometry to dissect FSH fraction composition confirmed the presence of follicle stimulating hormone but also revealed the presence of the lectin Concanavalin-A (Con-A). Lectins are characterized by their sugar-binding ability and Concanavalin-A is the most common lectin used for purification of glycoproteins as recombinant gonadotropins. To determine if Concanavalin-A is the “active molecule” in the follicle stimulating hormone fraction which causes cell death, it was essential to ascertain if former results obtained with the follicle stimulating hormone fraction can be replicated by the lectin alone. As it was previously observed, Concanavalin-A may induce cell death in primary cultured granulosa cells, preventing maturation of small antral follicles and increasing atresia in an animal model. Interestingly, our results showed that cell death induced by Concanavalin-A brought about the demise of the ovarian follicle in a manner that looks indistinguishable to the physiological process of atresia. Furthermore, we demonstrate that follicle stimulating hormone promotes changes in the ovarian glycosylation pattern and these events may allow interaction with a carbohydrate-binding lectin to conduct different cell responses as live or death. These results suggest a key role of glycosylation in the process of follicular selection and atresia, and also a potential use of this knowledge for ovarian cancer treatment.

Concanavalin-A induces granulosa cell death and inhibits FSH-mediated follicular growth and ovarian maturation

Journal Reference

Velasquez EV, Rios M, Ortiz ME, Lizama C, Nunez E, Abramovich D, Orge F, Oliva B, Orellana R, Villalon M, Moreno RD, Tesone M, Rokka A, Corthals G,Croxatto HB, Parborell F, Owen GI.

Endocrinology. 2013 May;154(5):1885-96.

 

Pontificia Universidad Católica de Chile, Alameda 340, Santiago, Chile. [email protected]

 

Abstract

Reproductive success stems from a finely regulated balance between follicular maturation and atresia, in which the role of carbohydrate structure is poorly understood. Here, we describe for the first time a fraction of purified recombinant human FSH that is capable of bringing about the cell death ofgranulosa cells and preventing follicular maturation in a rat model. Further analysis by mass spectrometry revealed the presence of the lectin Concanavalin-A (Con-A) within this fraction of recombinant follicle stimulating hormone. Using both the fractionated follicle stimulating hormone and Concanavalin-A, the observed cell death was predominantly located to the granulosa cells. Ex vivo culture of rat follicles demonstrated that follicle degeneration occurred and resulted in the release of a denuded and deteriorated oocyte. Moreover, in vivo experiments confirmed an increase in atresia and a corresponding reduction confined to follicle in early antral stage. As a mechanism of action, Concanavalin-A reduces ovarian proliferation, Von Willebrand staining, and angiogenesis. Based on the observation that Concanavalin-A may induce granulosa cell death followed by follicle death, our results further demonstrate that follicular carbohydrate moiety is changing under the influence of follicle stimulating hormone, which may allow a carbohydrate-binding lectin to increase  granulosa cell death. The physiological consequences of circulating lectin-like molecules remain to be determined. However, our results suggest a potential exploitation of carbohydrate binding in fertility and ovarian cancer treatment. This work may shed light on a key role of carbohydrates in the still obscure physiological process of follicular selection and atresia.

 

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