Frozen-thawed cumulus-granulosa cells support bovine embryo development during coculture *†*Supported by a grant from the Hillcrest Medical Center Foundation, Tulsa, Oklahoma.†Presented in part at the Conjoint Meeting of The American Fertility Society and the Canadian Fertility and Andrology Society, Montreal, Quebec, Canada, October 11 to 14, 1993

Effect of cryopreservation on human granulosa cell viability and responsiveness to gonadotropin

In human, the use of freshly recovered granulosa cells for experiments remains difficult. Because of the single use of human cells, the experiments cannot be repeated, and no additional conditions can be tested afterwards with the cells of the same patient. Therefore, granulosa cell cryopreservation could be a good alternative to keep part of these cells for later controls or experiments. The aim of this study is to compare the responsiveness to FSH of fresh and frozen-thawed human primary granulosa-lutein cells (hGLC) and determine if cryopreserved granulosa cells can be used in place of fresh cells. Two cryopreservation methods were also compared: a conventional versus a simplified freezing method. This experimental study was undertaken at Igyxos S.A., Nouzilly, France. Seventy women undergoing oocyte retrieval at the IVF Unit from Bretonneau University Hospital (Tours, France) were recruited in 2016. Fresh and frozen-thawed hGLC were cultured for 7 days and then stimulated by r-FSH for 48 h. To assess r-FSH efficacy and potency, extracellular cAMP accumulated in the supernatant for each stimulation point was measured. We demonstrated that hGLC remain responsive to FSH stimulation after freezing-thawing and 7 days of pre-culture. They are able to secrete cAMP with a similar EC50 value as fresh hGLC, but FSH efficacy is lowered. As our study did not show any significant difference between the two freezing methods concerning the sensitivity of hGLC to FSH, hGLC could be cryopreserved with the simplified freezing method without taking up too much time for IVF laboratories.

Mammalian embryo co-culture: Trials and tribulations of a misunderstood method

Embryo-somatic cell co-culture was devised over 40 years ago in an attempt to improve the development and viability of mammalian preimplantation embryos generated and cultured in vitro. While initial endeavours were successful in this respect, other studies soon highlighted a number of significant long-term detrimental impacts of this approach. Surprisingly little is known about the mechanisms underlying the beneficial effects of co-culture, although the production of embryotrophic compounds, modulation of nutrient profile, protection against culture-induced stress and/or toxin clearance are all contenders. The extent to which the inadvertent exposure of embryos to serum accounts for many of these effects remains open to question. Although the popularity of somatic cell co-culture has recently declined in favour of the use of sequential media due to concerns associated with its risk of disease transmission and long-term sequelae, we argue that complete dismissal of this technique is ill advised, given that our limited understanding of basic somatic cell interactions has prevented us from fully exploiting its potential. In this respect, there is some merit in focussing future research strategies based on reconstructed maternal tract tissue. Although the use of co-culture in clinical practice is unacceptable and its implementation in domestic species for commercial purposes should be viewed with diffidence, this technique can still provide a wealth of information on the development of novel, more physiological embryo in vitro culture systems. The proviso for acquiring such information is to gain a fuller understanding of the culture requirements/biochemistry of somatic cells and their interaction with the early conceptus.

Protective effect of vascular endothelial growth factor (VEGF) in frozen-thawed granulosa cells is mediated by inhibition of apoptosis

OBJECTIVES

This study was conducted to evaluate the involvement of apoptosis in the freeze-thaw process and to investigate the anti-apoptotic effect of vascular endothelial growth factor (VEGF) in the frozen-thawed granulosa cells.

STUDY DESIGN

Isolated rat granulosa cells were cultured, frozen-thawed, and were cultured for 24h. Cell viabilities (by Trypan blue exclusion test) and apoptotic patterns (by Annexin-V/propidium iodide (PI) Double-Staining) were determined at each step. Apoptotic cell death was confirmed by following DNA degradation and caspase-3 activity.

RESULTS

After freeze-thaw process and 24h of culture, reductions in the cellular viabilities and increases in the number of cells containing degraded DNA were lower in the VEGF pretreated group than in the control group (p<0.05). In the VEGF pretreated group, increases in the proportions of late apoptotic cells [Annexin-V (+)/PI (+)] were significantly lower and caspase-3 expression was prevented immediate after thawing (p<0.05). Furthermore, increases in the proportions of early apoptotic cells [Annexin-V (+)/PI (-)] and reductions in the proportions of viable cells [Annexin-V (-)/PI (-)] were significantly lower in the VEGF pretreated group after culture for 24h (p<0.05). Of the different doses of VEGF pretreated, 50ng/ml was found to be most effective with respect to protecting frozen-thawed granulosa cells from cryoinjury.

CONCLUSION

Granulosa cell damage induced by cryopreservation is mediated, at least in part, by an apoptotic process. Our preliminary results suggest that VEGF treatment before freeze-thaw process reduces rat ovarian granulosa cell damage by inhibiting apoptosis.

Embryo production by ovum pick up from live donors

Embryo production by in vitro techniques has increased steadily over the years. For cattle where this technology is more advanced and is applied more, the number of in vitro produced embryos transferred to final recipients was over 30,000 in 1998. An increasing proportion of in vitro produced embryos are coming from oocytes collected from live donors by ultrasound-guided follicular aspiration (ovum pick up, OPU). This procedure allows the repeated production of embryos from live donors of particular value and is a serious alternative to superovulation. Ovum pick up is a very flexible technique. It can be performed twice a week for many weeks without side effects on the donor's reproductive career. The donor can be in almost any physiological status and still be suitable for oocyte recovery. A scanner with a sectorial or convex probe and a vacuum pump are required. Collection is performed with minimal stress to the donor. An average of 8 to 10 oocytes are collected per OPU with an average production of 2 transferable embryos. The laboratory production of embryos from such oocytes does not differ from that of oocytes harvested at slaughter as the results after transfer to final recipients. For other species such as buffalo and horses OPU has been attempted similarly to cattle and data will be presented and reviewed. For small ruminants, laparotomy or laparoscopy seems the only reliable route so far to collect oocytes from live donors.

Potential use of embryo coculture with human in vitro fertilization procedures

PURPOSE

This review was designed to outline potential uses of an embryo co-culture system in human assisted reproduction programs to improve embryo quality and pregnancy rates.

RESULTS

The various cell types used in embryo co-culture were reviewed in addition to the use of co-culture for both animal and human embryos. Co-culture provides a method to enhance embryo development in an inadequate in vitro environment without compromising embryo quality. Human IVF laboratories have used various types of "helper cells" to improve rate of development, reduce cell fragmentation rate and in some instances increases pregnancy and implantation rates.

CONCLUSION

In conjunction with several assisted reproduction procedures such as IVF, microsurgical fertilization, cryopreservation and genetic evaluation, co-culture may increase the number of viable embryos for replacement and improve pregnancy rates.