Bioengineering the ovary to preserve and reestablish female fertility

Abstract

Different bioengineering strategies can be presently adopted and have been shown to have great potential in the treatment of female infertility and ovarian dysfunction deriving from chemotherapy, congenital malformations, massive adhesions as well as aging and lifestyle. One option is transplantation of fresh or cryopreserved organs/fragments into the patient. A further possibility uses tissue engineering approaches that involve a combination of cells, biomaterials and factors that stimulate local ability to regenerate/ repair the reproductive organ. Organ transplant has shown promising results in large animal models. However, the source of the organ needs to be identified and the immunogenic effects of allografts remain still to be solved before the technology may enter the clinical practice. Decellularization/ repopulation of ovary with autologous cells or follicles could represent an interesting, still very experimental alternative. Here we summarize the recent advancements in the bioengineering strategies applied to the ovary, we present the principles for these systems and discuss the advantages of these emerging opportunities to preserve or improve female fertility.

Keywords: 3D printing; cryopreservation; decellularization; female infertility; ovary; tissue engineering.

Figure 1. Different strategies presently used to restore ovarian function.

Figure 2. Perfusion systems allow to maintain functional whole sheep ovaries for several days, preserving functional activity of both fresh and cryopreserved organs, with identical hormonal secretion levels and comparable estradiol and progesterone production.

Figure 3. In directional freezing, the freezing rate is determined by the combination of temperature gradient and speed of the sample along the track. If the velocity of the sample is slower than the speed at which the heat is removed from the center of the sample towards its periphery, heat transfer is quickly removed in the direction opposite to that of the sample movement. All this results in a uniform cooling rate throughout the sample. The 3 thermal blocks are generally set at 4°, -10° and -70°C respectively, thereby imposing a temperature gradient around the tubes. Freezing tubes are pushed lengthwise, along the thermal gradient, and the speed is set at 0.01 mm/s, resulting in a cooling rate of 0.3°C/min down to -70°C. At the end of the procedure, samples are plunged into liquid nitrogen.

Figure 4. Schematic study plan to obtain a decellularized extracellular matrix from ovary. From the fresh ovary to the ECM material, the tissue is passed through the thermic treatment to obtain cell rupture. Effective cell removal is achieved thanks to the use of different ionic and non-ionic detergents, such as Triton X100, SDS and Deoxycolic acid and combining them to basic compounds such as ammonium hydroxide.