Engineering the follicle microenvironment

Abstract

In vitro ovarian follicle culture provides a tool to investigate folliculogenesis, and may one day provide women with fertility-preservation options. The application of tissue engineering principles to ovarian follicle maturation may enable the creation of controllable microenvironments that will coordinate the growth of the multiple cellular compartments within the follicle. Three-dimensional culture systems can preserve follicle architecture, thereby maintaining critical cell-cell and cell-matrix signaling lost in traditional two-dimensional attached follicle culture systems. Maintaining the follicular structure while manipulating the biochemical and mechanical environment will enable the development of controllable systems to investigate the fundamental biological principles underlying follicle maturation. This review describes recent advances in ovarian follicle culture, and highlights the tissue engineering principles that may be applied to follicle culture, with the ultimate objective of germline preservation for females facing premature infertility.

Figure 1

Follicle development is regulated by (A) interactions between granulosa cells, (B) communication between the oocyte and its surrounding granulosa cells, (C) signaling between the theca and granulosa cells, (D) factors that arrive at the ovary via the bloodstream, and (E) the extracellular matrix within the follicle. oo, oocyte; gc, granulosa cells; tc, theca cells; bm, basement membrane.

Figure 2

(A) Follicle architecture in a two-dimensional culture system. On a two-dimensional substrate, proliferating follicle cells spread onto the surface (red arrows). (B) In a three-dimensional culture system, the follicle grows radially from the oocyte (red arrows). If a matrix surrounds the follicle, it will produce an opposing force on the follicle (blue arrows). This is demonstrated in (C) and (D). (C) Follicles cultured on a two-dimensional substrate lose their structure as they spread onto the surface, whereas (D) follicles maintain their morphology in an alginate matrix. Follicles in (C) and (D) are labeled with dextran (red) to demonstrate active uptake of compounds from the culture media and phalloidin (green) to visualize the distribution of the actin cytoskeleton of follicular cells. oo, oocyte; gc, granulosa cells; tc, theca cells. Scale bar =30 μm. (Figures 2C and 2D are reprinted from Kreeger, PK, Deck, JW, Woodruff, TK, Shea, LD. The in vitro regulation of ovarian follicle development using alginate-extracellular matrix gels. Biomaterials 2006;27:714–723, with permission from Elsevier.)