Human Reproduction vol.7 no.6 pp.773-734, 1992
EDITORIALS Why are agonadal and post-amenorrhoeic women so fertile after oocyte donation? Many reports now testify to the high fecundity of women who are agonadal or have had a premature or normal menopause, when given an oocyte from a donor. Hormone replacement therapy (HRT) with oocyte donation was initially used to establish pregnancy in an agonadal woman by Lutjen et al. (1984), and pregnancy was first established in post-menopausal women using similar methods by Serhal and Craft (1989). Excellent implantation rates per embryo can occur in these women, sometimes over 25% which is remarkably high for human conception. Agonadal and post-menopausal women are highly fertile when almost 50 (Edwards et al., 1991) and may well continue to be so after this age. These studies are certain to clarify some aspects of one of the most obtuse areas of human reproduction, i.e. the factors regulating embryo implantation. For some reason, oocyte donation with HRT restores or enhances previous fertility. An immediate response to such data is to ascribe it all to the use of oocytes from younger donors. Some factors could well impair the health of oocytes in ageing ovaries, for X-rays selectively kill primordial follicles by generating hydroxyl radicals, and peroxidative damage could gradually impair their developmental capacity with age. Curiously, though, oocytes from the same cohort implant better in amenorrhoeic women given HRT than in the younger donors (Navot et al., 1991), and some investigators have established pregnancies using donated oocytes from women over 40. The role of the uterus in the fertility of women well over 40 years old or in agonadal women could be decisive in restoring their fertility. Why should it suddenly become so effective at implantation? It almost seems as if amenorrhoea or a rest period after a period of repeated menstrual cycles enables it to recover an ability to implant typical of a very young woman. The fact that implantation is possible should not surprise us. The onset of menopause is not a uterus-dependent event: it seems to be due primarily to the exhaustion of the ovarian follicle population (Gosden, 1987). With time, the uterus will presumably become ineffective in its own right as it ages like all tissues. These processes could be delayed until the 70s, and it could retain its implantation ability in the meantime, providing a window of 10—20 years for implantation after the menopause. Uterine ageing must be clarified to explain high fertility in ageing and agonadal women. Infertility seems to strike suddenly as women age. They do not display increases in biochemical pregnancies or very early abortions or delayed implantation as far as I know; they are suddenly unable to implant their embryos. There is such a thing as secretory exhaustion in cyclic women (Dellenbach-Hellweg, 1987). The uterine epithelium displays few pinopodes under some conditions (Martel et al., 1991), and
Editorial by: R.G.Edwards, Extraordinary Fellow, Churchill College, Cambridge, UK
pinopodes could well be the secret weapon in all this work. They apparently extract uterine fluid during implantation, drawing the epithelium tightly together to trap the embryo preparatory for adhesion (Enders and Nelson, 1973). They are driven by progesterone (Martel et al., 1991). Their malfunction would leave blastocysts stranded in a mass of uterine fluid instead of tightly apposed to the endometrium. Implantation would hardly be possible, and this could well explain the situation in older women. If not pinopodes, reactive oxygen species might limit fertility in older mothers. They have devastating effects on sperm membranes, maturing oocytes and embryos (Aitken and Clarkson, 1987; Nasr-Esfahani et al., 1990; Legge and Sellens, 1991). They are produced in many tissues, including those of the reproductive tract. Superoxide dismutases are also produced widely, e.g. in follicles, oviducts and predecidual cells (Narimoto et al., 1991). They could be directly or indirectly involved in implantation. Mononuclear cells from women who fail to implant their transferred embryos produce a burst of oxidative species in response to phorbol esters; those from women with implanted embryos do not (Maly et al., 1990). Other factors could well impose limits on implantation in particular women, e.g. infectious organisms responsive to steroid hormones, or inflammatory or other uterine changes. These theories are not difficult to test. Long-term downregulation provides a respite from the repeated cyclic exposure of the uterus to steroids. Vitamins or other anti-oxidants might control oxygen radicals. Many oocyte recipients have been acyclic for some time, and some cyclic recipients are given a long protocol with LHRH analogues before HRT. One snag arises for these theories: any form of oocyte donation introduces new embryonic antigens to challenge the mother, and her responses could include an enhanced fertility. Perhaps we have overstressed the importance of the non-polymorphic HLA-G as the major histocompatibility antigen expressed on migratory trophoblast (Ellis et al., 1990; Kovats et al., 1990) for reports of extremely high rates of pregnancy in cases of surrogacy could be explained by histoincompatibility between mother and fetus, or other interactive factors. These aspects of pregnancy might well enhance fertility in programmes of oocyte donation quite apart from any effects of young eggs or a rejuvenated uterus. Meanwhile the door is wide open to establishing pregnancies after the menopause. The social implications give room for thought. References Aitken.R.J. and ClarksooJ.S. (1987) Cellular basis of defective sperm function and its association with the genesis of reactive oxygen species by human spermatozoa. Reprott Fertil., 81, 459-469. Dellenbach-Hellweg.G. (1987) Histopathology of the Endometrium. 4th edn, Springer-Verlag, Berlin. Edwards.R.G., Morcos.S., Macnamee.M., Balmaceda^.P., Walters,D.E. and Asch.R. (1991) High fecundity of amenorrhoeic women in embryo-transfer programmes. Lancet, 338, 292-294. Hlis.S.A., Palmer,M.S. and McMichael.A.J. (1990) Human trophoblast and the choriocarcinoma cell line BeWo express a truncated HLA class I molecule. J. Immunol, 114, 731-735.
733
Editorials Enders.A.C. and Nelson,D.M. (1973) Pinocytotic activity of the uterus of the rat. Am, J. Ana., 138, 277-300.
Table I. Embryo implantation and pregnancy rates in patients with their own embryos and after oocyte or embryo donation
Gosden.R.G. (1987) Follicular status at the menopause. Hum. Reprod , 2, Patients' own embryos
617-621. Kovats.S., Main,E.K., Librach.C, Stubblebine,M., FisherJ. and De Marrs.R. (1990) A class I antigen, HLA-G, expressed in human txophoblast Science, 248, 220. Legge,M. and Sellens.M.H. (1991) Free radical scavengers ameliorate the 2-cell block in mouse embryo culture Hum. Reprod., 6, 867-871. Lutjen.P.J., Trounson,A.O., Leeton.F.J., Wood,C, Renou.P. and Chan,L.K. (1984) The establishment and maintenance of pregnancy using in vitro fertilization and embryo donation in a patient with primary ovarian failure. Nature, 307, 174-176. Maly.F.E , Sterzik.K., Henderson.D. and de Weck.A.L. (1990) Enhancement of mononuclear cell oxidative burst by early post-transfer sera from unsuccessful human embryo transfer patients. Hum. Reprod., 5, 342-344. Martel,D., Monier.M.N., Roche.D. and Psychoyos.A. (1991) Hormonal dependence of pinopode formation at the utenne luminal surface. Hum. Reprod., 6, 597-603. Narimoto.K., Noda.Y , Shiotani.M., Matsuyama,S., Mori.T , Fujimoto.K., Ogawa,K. and Kim,Y.C. (1991) Superoxide dismutase in the fallopian tube function—immunohistochemical assessment of superoxide dismutase in the fallopian tube. Ada Histochem. Cytochem., 24, 8 5 - 9 1 . Nasr-Esfahani.M.N., Aitken.J R. and Johnson,M.H. (1990) Hydrogen peroxide levels in mouse oocytes and early cleavage stage embryos developed in vitro or in vitro. Development, 109, 501-507. Navot.D., Bergh.P.A., Williams,M.A , Garrisi.G.J., Guzman,I., Sandler.B. and Grunfcld,L. (1991) Poor oocyte quality rather than implantation failure as a cause of age-related decline in female fertility. Lancet, 337, 1575-1577. Serhal.P. and Craft,I.L. (1989) Oocyte donation in 61 patients. Lancet, i, 1185-1187.
High pregnancy rates after oocyte and embryo donation Assisted reproduction is now performed with increasing frequency in many clinics, but implantation rates per embryo after replacing oocytes or embryos in the uterus are still modest. Numerous factors could be responsible for this low success, and asynchrony between endometrial development and embryonic age is likely to be critical. Attempts to clarify the roles of endometrium and embryo have led to conflicting opinions. Embryo quality was the main fetor determining the chances of implantation in programmes of oocyte donation during hormone replacement cycles (HRT) according to some investigators (Meldrum et al., 1990; Navot et al., 1991). A better endometrial quality was postulated when implantation rates were found to be higher with oocyte donation and HRT during FVF as compared with the same therapy in matched controls using stimulated cycles (Paulson etal., 1990). Our own studies have revealed enormous effects of oocyte donation and embryo donation (gestational surrogacy) on implantation rates. Comparisons were made between three groups of patients. These were: normocyclic patients with tubal factor infertility given their own embryos during controlled stimulation with LHRH analogues, HMG-FSH and HCG (Balmaceda et al., 1988); nulligravid patients given HRT and oocyte donation during IVF (Borrero et al., 1989); and previously fertile women
Editorial by: R.H.Asch, Department of Obstetrics and Gynecology, University of California, Irvine, CA, USA
734
No. of cases 123 30.9 ± 2.4 Mean age Mean donor age Mean recipient age Embryos replaced 499 Embryos per patient 4 1 ± 0.9 64 Gestational sacs Embryo implantation 12.8 51 (41%) Pregnancies (%) Biochemical 9 3 Ectopic 9 Abortions
Oocyte donation
Embryo donation
20
17
27.9 30.3 77 3.8 ± 0.8 14 18.1
32 5 3.8 40 32.1 55 3.2 ± 1.2 17 30.91 13 (77%)b 1 0 0
12 (60%) 2 1 2
'P < 0.01. b P < 0.02.
(>para 2) given down regulation for x days and HRT with embryo donation. All subjects were 26—35 years old, 2—5 fresh embryos were replaced, all replacements were non-traumatic, and mean ages of donors did not differ from recipients. Data in Table I show high implantation rates with oocyte donation, but much higher rates with embryo donation. It is impossible to find suitable control patients to measure the effects of these procedures, but for what it is worth the implantation rates with embryo donation are significantly higher than in the other groups. Indeed, the very high implantation rates in these patients belie previous reports on the 'limits' of implantation rates in the human uterus. Embryo donation may therefore provide a further increment to implantation rates above those obtained by oocyte donation, raising the possibility of immunological or other interactions between mother and fetus. The efficiency of implantation and growth to term in women after embryo donation may be due to their previous proven fertility enabling blastocysts to implant more easily than in infertile women. Such findings previously have been made in animals (Martel et al., 1989).
References Balmaceda.J P., Gastaldi.C, Remohi.J., Borrero.C , Ord.T. and Asch.R.H (1988) Tubal embryo transfer as a treatment for infertility due to male factor Fertil. Sterii, 50, 476-479. Borrero.C., RemohiJ., Ord.T., BalmacedaJ.P , Rojas.F. and Asch,R.H (1989) A programme of oocyte donation and gamete intra-Fallopian transfer. Hum. Reprod., 4, 275-279 Martel,D , etal. (1989) Hormonal dependence of the material gland. In Yoshinaga.K. (ed), Blastocyst Implantation. Adams Publishing Group, Boston, MA, pp. 179-192. Meldrum.DR., Hamilton,F., Marr.B., Stubbs.C, Wisot.A., Hite.R. (1990) Oocyte donation (OD) increases the proportion of embryos implanting and reverses the age-related decline in infertility Pacific Coast Fertility Society. Supplement, Abstract 0 - 2 2 , p. A17. Navot.D., Bergh,P., Williams.M., Garisi.G.J., Guzman,I., Sandler.B.. FoxJ.. Schreiner-Engle,P., Hofman.G and Grunfeld.L. (1991) An insight into early reproductive process through the in vivo model of ovum donation. J. Clm. Endocrinol., 72, 408-414. Paulson,R.J., Sauer,M.V and Lobo.R.A. (1990) Embryo implantation after human in vitro fertilization. Fertil Sterii , 53, 870-874.
EDITORIALS Why are agonadal and post-amenorrhoeic women so fertile after oocyte donation? Many reports now testify to the high fecundity of women who are agonadal or have had a premature or normal menopause, when given an oocyte from a donor. Hormone replacement therapy (HRT) with oocyte donation was initially used to establish pregnancy in an agonadal woman by Lutjen et al. (1984), and pregnancy was first established in post-menopausal women using similar methods by Serhal and Craft (1989). Excellent implantation rates per embryo can occur in these women, sometimes over 25% which is remarkably high for human conception. Agonadal and post-menopausal women are highly fertile when almost 50 (Edwards et al., 1991) and may well continue to be so after this age. These studies are certain to clarify some aspects of one of the most obtuse areas of human reproduction, i.e. the factors regulating embryo implantation. For some reason, oocyte donation with HRT restores or enhances previous fertility. An immediate response to such data is to ascribe it all to the use of oocytes from younger donors. Some factors could well impair the health of oocytes in ageing ovaries, for X-rays selectively kill primordial follicles by generating hydroxyl radicals, and peroxidative damage could gradually impair their developmental capacity with age. Curiously, though, oocytes from the same cohort implant better in amenorrhoeic women given HRT than in the younger donors (Navot et al., 1991), and some investigators have established pregnancies using donated oocytes from women over 40. The role of the uterus in the fertility of women well over 40 years old or in agonadal women could be decisive in restoring their fertility. Why should it suddenly become so effective at implantation? It almost seems as if amenorrhoea or a rest period after a period of repeated menstrual cycles enables it to recover an ability to implant typical of a very young woman. The fact that implantation is possible should not surprise us. The onset of menopause is not a uterus-dependent event: it seems to be due primarily to the exhaustion of the ovarian follicle population (Gosden, 1987). With time, the uterus will presumably become ineffective in its own right as it ages like all tissues. These processes could be delayed until the 70s, and it could retain its implantation ability in the meantime, providing a window of 10—20 years for implantation after the menopause. Uterine ageing must be clarified to explain high fertility in ageing and agonadal women. Infertility seems to strike suddenly as women age. They do not display increases in biochemical pregnancies or very early abortions or delayed implantation as far as I know; they are suddenly unable to implant their embryos. There is such a thing as secretory exhaustion in cyclic women (Dellenbach-Hellweg, 1987). The uterine epithelium displays few pinopodes under some conditions (Martel et al., 1991), and
Editorial by: R.G.Edwards, Extraordinary Fellow, Churchill College, Cambridge, UK
pinopodes could well be the secret weapon in all this work. They apparently extract uterine fluid during implantation, drawing the epithelium tightly together to trap the embryo preparatory for adhesion (Enders and Nelson, 1973). They are driven by progesterone (Martel et al., 1991). Their malfunction would leave blastocysts stranded in a mass of uterine fluid instead of tightly apposed to the endometrium. Implantation would hardly be possible, and this could well explain the situation in older women. If not pinopodes, reactive oxygen species might limit fertility in older mothers. They have devastating effects on sperm membranes, maturing oocytes and embryos (Aitken and Clarkson, 1987; Nasr-Esfahani et al., 1990; Legge and Sellens, 1991). They are produced in many tissues, including those of the reproductive tract. Superoxide dismutases are also produced widely, e.g. in follicles, oviducts and predecidual cells (Narimoto et al., 1991). They could be directly or indirectly involved in implantation. Mononuclear cells from women who fail to implant their transferred embryos produce a burst of oxidative species in response to phorbol esters; those from women with implanted embryos do not (Maly et al., 1990). Other factors could well impose limits on implantation in particular women, e.g. infectious organisms responsive to steroid hormones, or inflammatory or other uterine changes. These theories are not difficult to test. Long-term downregulation provides a respite from the repeated cyclic exposure of the uterus to steroids. Vitamins or other anti-oxidants might control oxygen radicals. Many oocyte recipients have been acyclic for some time, and some cyclic recipients are given a long protocol with LHRH analogues before HRT. One snag arises for these theories: any form of oocyte donation introduces new embryonic antigens to challenge the mother, and her responses could include an enhanced fertility. Perhaps we have overstressed the importance of the non-polymorphic HLA-G as the major histocompatibility antigen expressed on migratory trophoblast (Ellis et al., 1990; Kovats et al., 1990) for reports of extremely high rates of pregnancy in cases of surrogacy could be explained by histoincompatibility between mother and fetus, or other interactive factors. These aspects of pregnancy might well enhance fertility in programmes of oocyte donation quite apart from any effects of young eggs or a rejuvenated uterus. Meanwhile the door is wide open to establishing pregnancies after the menopause. The social implications give room for thought. References Aitken.R.J. and ClarksooJ.S. (1987) Cellular basis of defective sperm function and its association with the genesis of reactive oxygen species by human spermatozoa. Reprott Fertil., 81, 459-469. Dellenbach-Hellweg.G. (1987) Histopathology of the Endometrium. 4th edn, Springer-Verlag, Berlin. Edwards.R.G., Morcos.S., Macnamee.M., Balmaceda^.P., Walters,D.E. and Asch.R. (1991) High fecundity of amenorrhoeic women in embryo-transfer programmes. Lancet, 338, 292-294. Hlis.S.A., Palmer,M.S. and McMichael.A.J. (1990) Human trophoblast and the choriocarcinoma cell line BeWo express a truncated HLA class I molecule. J. Immunol, 114, 731-735.
733
Editorials Enders.A.C. and Nelson,D.M. (1973) Pinocytotic activity of the uterus of the rat. Am, J. Ana., 138, 277-300.
Table I. Embryo implantation and pregnancy rates in patients with their own embryos and after oocyte or embryo donation
Gosden.R.G. (1987) Follicular status at the menopause. Hum. Reprod , 2, Patients' own embryos
617-621. Kovats.S., Main,E.K., Librach.C, Stubblebine,M., FisherJ. and De Marrs.R. (1990) A class I antigen, HLA-G, expressed in human txophoblast Science, 248, 220. Legge,M. and Sellens.M.H. (1991) Free radical scavengers ameliorate the 2-cell block in mouse embryo culture Hum. Reprod., 6, 867-871. Lutjen.P.J., Trounson,A.O., Leeton.F.J., Wood,C, Renou.P. and Chan,L.K. (1984) The establishment and maintenance of pregnancy using in vitro fertilization and embryo donation in a patient with primary ovarian failure. Nature, 307, 174-176. Maly.F.E , Sterzik.K., Henderson.D. and de Weck.A.L. (1990) Enhancement of mononuclear cell oxidative burst by early post-transfer sera from unsuccessful human embryo transfer patients. Hum. Reprod., 5, 342-344. Martel,D., Monier.M.N., Roche.D. and Psychoyos.A. (1991) Hormonal dependence of pinopode formation at the utenne luminal surface. Hum. Reprod., 6, 597-603. Narimoto.K., Noda.Y , Shiotani.M., Matsuyama,S., Mori.T , Fujimoto.K., Ogawa,K. and Kim,Y.C. (1991) Superoxide dismutase in the fallopian tube function—immunohistochemical assessment of superoxide dismutase in the fallopian tube. Ada Histochem. Cytochem., 24, 8 5 - 9 1 . Nasr-Esfahani.M.N., Aitken.J R. and Johnson,M.H. (1990) Hydrogen peroxide levels in mouse oocytes and early cleavage stage embryos developed in vitro or in vitro. Development, 109, 501-507. Navot.D., Bergh.P.A., Williams,M.A , Garrisi.G.J., Guzman,I., Sandler.B. and Grunfcld,L. (1991) Poor oocyte quality rather than implantation failure as a cause of age-related decline in female fertility. Lancet, 337, 1575-1577. Serhal.P. and Craft,I.L. (1989) Oocyte donation in 61 patients. Lancet, i, 1185-1187.
High pregnancy rates after oocyte and embryo donation Assisted reproduction is now performed with increasing frequency in many clinics, but implantation rates per embryo after replacing oocytes or embryos in the uterus are still modest. Numerous factors could be responsible for this low success, and asynchrony between endometrial development and embryonic age is likely to be critical. Attempts to clarify the roles of endometrium and embryo have led to conflicting opinions. Embryo quality was the main fetor determining the chances of implantation in programmes of oocyte donation during hormone replacement cycles (HRT) according to some investigators (Meldrum et al., 1990; Navot et al., 1991). A better endometrial quality was postulated when implantation rates were found to be higher with oocyte donation and HRT during FVF as compared with the same therapy in matched controls using stimulated cycles (Paulson etal., 1990). Our own studies have revealed enormous effects of oocyte donation and embryo donation (gestational surrogacy) on implantation rates. Comparisons were made between three groups of patients. These were: normocyclic patients with tubal factor infertility given their own embryos during controlled stimulation with LHRH analogues, HMG-FSH and HCG (Balmaceda et al., 1988); nulligravid patients given HRT and oocyte donation during IVF (Borrero et al., 1989); and previously fertile women
Editorial by: R.H.Asch, Department of Obstetrics and Gynecology, University of California, Irvine, CA, USA
734
No. of cases 123 30.9 ± 2.4 Mean age Mean donor age Mean recipient age Embryos replaced 499 Embryos per patient 4 1 ± 0.9 64 Gestational sacs Embryo implantation 12.8 51 (41%) Pregnancies (%) Biochemical 9 3 Ectopic 9 Abortions
Oocyte donation
Embryo donation
20
17
27.9 30.3 77 3.8 ± 0.8 14 18.1
32 5 3.8 40 32.1 55 3.2 ± 1.2 17 30.91 13 (77%)b 1 0 0
12 (60%) 2 1 2
'P < 0.01. b P < 0.02.
(>para 2) given down regulation for x days and HRT with embryo donation. All subjects were 26—35 years old, 2—5 fresh embryos were replaced, all replacements were non-traumatic, and mean ages of donors did not differ from recipients. Data in Table I show high implantation rates with oocyte donation, but much higher rates with embryo donation. It is impossible to find suitable control patients to measure the effects of these procedures, but for what it is worth the implantation rates with embryo donation are significantly higher than in the other groups. Indeed, the very high implantation rates in these patients belie previous reports on the 'limits' of implantation rates in the human uterus. Embryo donation may therefore provide a further increment to implantation rates above those obtained by oocyte donation, raising the possibility of immunological or other interactions between mother and fetus. The efficiency of implantation and growth to term in women after embryo donation may be due to their previous proven fertility enabling blastocysts to implant more easily than in infertile women. Such findings previously have been made in animals (Martel et al., 1989).
References Balmaceda.J P., Gastaldi.C, Remohi.J., Borrero.C , Ord.T. and Asch.R.H (1988) Tubal embryo transfer as a treatment for infertility due to male factor Fertil. Sterii, 50, 476-479. Borrero.C., RemohiJ., Ord.T., BalmacedaJ.P , Rojas.F. and Asch,R.H (1989) A programme of oocyte donation and gamete intra-Fallopian transfer. Hum. Reprod., 4, 275-279 Martel,D , etal. (1989) Hormonal dependence of the material gland. In Yoshinaga.K. (ed), Blastocyst Implantation. Adams Publishing Group, Boston, MA, pp. 179-192. Meldrum.DR., Hamilton,F., Marr.B., Stubbs.C, Wisot.A., Hite.R. (1990) Oocyte donation (OD) increases the proportion of embryos implanting and reverses the age-related decline in infertility Pacific Coast Fertility Society. Supplement, Abstract 0 - 2 2 , p. A17. Navot.D., Bergh,P., Williams.M., Garisi.G.J., Guzman,I., Sandler.B.. FoxJ.. Schreiner-Engle,P., Hofman.G and Grunfeld.L. (1991) An insight into early reproductive process through the in vivo model of ovum donation. J. Clm. Endocrinol., 72, 408-414. Paulson,R.J., Sauer,M.V and Lobo.R.A. (1990) Embryo implantation after human in vitro fertilization. Fertil Sterii , 53, 870-874.
