Low temperature storage and grafting of human ovarian tissue

A finite stockpile of germ cells forms in the human ovary before birth and is progressively utilised until it is almost exhausted at menopause in mid- life. Currently, there is no proven method for preventing wastage of this i rreplaceable store, although cryopreservation provides an opportunity for l ong-term preservation of oocytes. This technology can potentially be used t o conserve fertility in patients undergoing sterilising treatment or otherw ise at risk of an early menopause. The structure of the ovary is well-suite d to tissue storage because primordial follicles are abundant, developmenta lly dormant and located peripherally. Thin cortical slices of tissue can be prepared either from biopsies collected laparoscopically or by dissecting the cortex from the whole ovary. To test survival after freezing and thawin g, tissues donated from women undergoing Caesarian section or gynaecologica l surgery were cooled slowly to liquid nitrogen temperatures in various cry oprotectant solutions and thawed rapidly. Three weeks after grafting under the renal capsule of immunodeficient SCID mice the majority of follicles we re still viable. To test the procedure in human volunteers, small discs of ovarian tissue were autografted to the anterior uterus. After 3-4 months th e tissues still contained follicles, including growing stages with PCNA-pos itive granulosa cells, but only about a quarter of the original follicle po pulation had survived. In another study using either human xenografts or mu rine isografts, follicle survival rates were improved by administration of antioxidants to counteract ischaemia-reperfusion injury. Ovarian tissue ban king should still be regarded as an experimental procedure, though recent r esults indicate that it has clinical potential. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.