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Transillumination increases oocyte recovery from ovaries collected at slaughter. A new technique report
1Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. Arav@agri.huji.ac.il
Abstract:
An inexpensive and convenient method of collecting large number of oocytes for in vitro procedures is by aspiration of follicles visible on the surface of isolated ovary. This method yielded only moderate numbers of oocytes per ovary, and it was found that the yield could be improved by slicing the tissue to reach deep, cortical follicles. However, slicing was time consuming and increased chances for sepsis. We developed a new technique that allows direct viewing of cortical follicles for aspiration of oocytes by transillumination of the ovarian medulla and cortex with a Plexiglas rod inserted through a small incision at the hilus. The technique, called "Transillumination-Aspiration Ovary" (TAO), increased the oocyte yield by 50% per ovary. The oocytes are probably recovered from deeper follicles which are difficult to identify during regular oocyte aspiration. The oocytes had a normal grading and exhibited normal in vitro development efficiency. Using the "TAO" technique we recovered 777 oocytes from 2160 follicles in 106 ovaries, a recovery rate of 36% from follicles and a mean of 7.3 oocytes/ovary. When we aspirated only surface follicles, we obtained 523 oocytes in 1384 visible follicles in 107 ovaries, for a recovery rates of 37% but a mean yield of 4.9 oocytes per ovary. Mean number of follicles were 20.5% with TAO and 12.8% without, thus recovery rates of oocytes per follicle were similar with both methods, but yield of oocytes per ovary was higher with TAO, thus showing that the difference between the two methods lies in higher numbers of visible follicles with TAO. Moreover, with the TAO technique 71% of the total oocytes we recovered (n=551) were grade I or II oocytes, in which 52% cleaved to the 2 to 4-cell stage and 26% had reached the blastocyst stage. We conclude that the method is effective for accurately locating cortical and peripheral follicles that contain oocytes suitable for IVF and in vitro embryo production (IVP).