Perspective of Bioartificial Uterus as Gynecological Regenerative ...

Tissue Engineering and Regenerative Medicine, Vol. 9, No. 5, pp 233-239 (2012) DOI 10.1007/s13770-012-0360-6

｜Feature Article｜

Perspective of Bioartificial Uterus as Gynecological Regenerative Medicine Yul Huh1, Yoon Young Kim1, and Seung-Yup Ku1,2* 1

Institute of Reproductive Medicine and Population, Medical Research Center, Seoul National University, Seoul, Korea 2 Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea (Received: July 6th, 2012; Revision: August 21st, 2012; Accepted: August 23rd, 2012)

Abstract : The fields of gynecology, organ transplantation, tissue engineering and regenerative medicine are in the process of convergence, promising the development of novel treatments for infertility highlighted by the advent of the bioartificial uterus. The advances made with in vitro fertilization, immunology, and stem cell biology have reopened dialogue regarding utilizing tissue engineering to create replacement reproductive organs for patients who do not have the ability to conceive naturally on their own. In this review, the possibility of creating a bioartificial uterus that can sustain gestation will be addressed with regards to the progenitor cells, various types of stem cells, the organ’s scaffolding and vasculature engineering, issues pertaining to the development of bioartificial uterus transplantation experimental model, as well as the long-term ethical implications that the bioartificial uterus poses for individuals and society as a whole. Key words: bioartificial uterus, endometrial stem cell, organ engineering, transplantation, uterine stem cell

medicine across its various specialties and disciplines as the 21st century ushers in the age of regenerative medicine. One of the fields that will benefit greatly from the development of stem cell biology and regenerative medicine is obstetrics and gynecology, and a particular technology whose advancement may be dramatically furthered is the bioartificial uterus. With the advent of the artificial placenta in 1998 utilizing a novel fetal arterovenousextracorporeal membrane oxygenation (AVECMO) system that fully externalized fetal oxygenation for the first time (Fig 1),3 along with the development of bioartificial organs, the increasing influence of stem cell biology and regenerative medicine will enhance the discovery of novel treatments for infertility and fetal disease, the field of gynecology and obstetrics is pointing towards a future promising the diversification and enhanced efficacy of clinical treatment with the development of the bioartificial uterus.

1. Introduction The field of obstetrics and gynecology developed several new technologies during the 20th century to treat the problems associated with the distal ends of pregnancy, namely in vitro fertilization for assisted reproduction and the advent of neonatal intensive care units to care for and aid the development of premature and ill newborns. Concurrently, researches in developmental biology furthered the understanding about the changes the embryo experiences in the womb as it grows into the fetus and eventually an infant. Thus, much progress occurred in gaining knowledge of the development of a pregnancy from conception to birth. The intrinsic relationship between the fields of developmental biology and obstetrics and gynecology led to one of contemporary science’s most exciting topics, namely stem cell researches. Thomson et al discovered in 1998 a method to isolate and culture human embryonic stem cells opened the door to harnessing the pluripotency of the ultimate progenitor cell of humans.1 With research in embryonic stem cell biology, the recent discovery of induced pluripotent stem cells by Shinya Yamanaka,2 and the continuing research of adult stem cells, the field of stem cell biology is poised to change the face of

2. Uterine Stem Cells Adult stem cells are identified by high proliferative activity, the ability to robustly self-renew, and the characteristic of differentiating into at least one mature cell type.4 In the case of the uterus, the human endometrium is a tissue of dynamic change with an estimated 400 cycles of regeneration, differentiation, and sloughing during menses over the course of

*Tel: +82-2-2072-1971; Fax: +82-2-762-3599 e-mail: [email protected] (Seung-Yup Ku)

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Yul Huh, Yoon Young Kim, and Seung-Yup Ku

Figure 2. The location of endometrial stem cells within the uterine lining is situated predominantly in the endometrial basalis towards the basement membrane with the myometrium.6

Figure 1. This is a diagram of the fetal arteriovenousextracorporeal membrane oxygenation (AV-ECMO) system, otherwise known as the artificial placenta, which connects to fetal circulation through umbilical catheterization and serves the dual function of filtration and oxygenation of mechanically pumped blood. Ao, Aorta; PA, pulmonary artery; UA, umbilical artery; UV, umbilical vein; DA, ductus arteriosus; DV, ductus venosus, IVC, inferior vena cava; SVC, superior vena cava; RV, right ventricle; LV, left ventricle; LA, left atrium; RA, right atrium; FO, foramen ovale.3

Figure 3. Human endometrial side population cells, which comprise endometrial stem cells expel. Hoechst staining and are doubly positive for hCD31 and ABCG2, marked by the yellow arrowheads in the figure.7

a woman’s lifetime. The human endometrium’s two component regions that include the functionalis, which is the upper twothirds shed during menses, and the lower basalis, which contains the basal region and glands with dense stroma and large vasculature serving as the source of growth for the functionalis in each menstrual cycle, work in concert through the activity of endometrial adult stem and progenitor cells.5 Interestingly, the cycle of growth and regeneration in the endometrium resembles the regenerative processes found in the epidermis and bone marrow, which are also instigated by the activities of adult stem cells. Thus, the endometrial basalis is the source of the endometrium’s regenerative stem cell population (Fig 2). From an endometrial biopsy, a subpopulation of endometrial cells can be isolated through fluorescence activated cell sorting (FACS) by taking advantage of the fact that there is a side population (SP) of cells which expel Hoechst dye, while non SP cells incorporate the dye. Furthermore, SP cells in the endometrium possess distinctive markers including hCD31 and ABCG2, allowing for characterization through confocal microscopy and isolation through flow cytometry (Fig 3). This side population of cells has been discovered to demonstrate the capacity to differentiate into several types of tissue. Hence, these cells have been designated as endometrial stem cells. In order to appreciate the developmental complexity of the human endometrium, one may survey the various stem cell and

progenitor cell types which differentiate into the uterus’s epithelial and stromal cells. These cells include clonogenic human endometrial epithelial cells, clonogenic human endometrial stromal cells, human CD146 + PDGF-Rβ + endometrial mesencymal stem cells (MSC)-like cells (eMSC), human endometrial tissue-reconstituting cells, endometrial stromal cells, human endometrial SP cells, bone marrowdervied cells, and menstrual blood cells in particular menstrual blood mesenchymal stem cells (mbMSC).5 With regards to regenerative medicine bone marrow-derived mesenchymal stem cells (MSC) have been of particular interest due to their broad applicability in studies of treatment for heart disease, stroke, cartilage repair and spinal cord injury, which is a result of MSCs’ ability to migrate to regions of tissue damage and promote tissue repair factors without engrafting onto the tissue itself. With the discovery of eMSC, there is further interest into the possible homologous functionality of these cell types with regards to regenerative medical applications as they pertain to the uterus.5 Intriguingly, the regenerative abilities of eMSCs have been demonstrated in studies using menstrual blood MSCs where they demonstrated to not cause immunological

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Perspective of Bioartificial Uterus as Gynecological Regenerative Medicine

Figure 4. The bladder, being a hollow organ, can serve as a suitable model from which to develop the bioartificial uterus. Construction of the scaffold would be followed by cell-seeding and connection of anastomses to the recipient during transplantation.8

strong amount of focus on producing a variety of suitable transplantable organs. Although uterus engineering has not been a focal point of current bioartificial organ engineering research, the results of projects in bladder, heart, and lung engineering can be conveyed towards developing the production of the bioartificial uterus by combining the knowledge of cadaver harvesting, scaffold construction, cell-seeding, and organ development with the uterine-specific knowledge related to uterine stem cell biology and endometrial development (Fig 4). A variety of candidate biomaterials are available per use in the design and fabrication of bioartificial scaffolds. The function of these materials is to serve as an analgous structure to the natural extracellular matrix found in human tissues by providing a three-dimensional substrate onto which organ specific cells can be seeded and subsequently treated with appropriate bioactive factors for organ differentiation and development.8 The current available materials include three traditional classes of substrates which are 1) naturally derived materials including collagen and alginate, 2) acellular tissue matrices derived from de-cellularized (via physical enzymatic or chemical means) submucosa from for instance the bladder and small-intestine,9 and 3) synthetic polymers which include polyglycolic acid (PGA), poly-lactic acid (PLA), and poly(lactic-co-glycolic acid) (PLGA).8 Whereas natural materials are biologically recognized, synthetic materials can be reproduced on a large scale and controlled for physical properties such as tensile strength, degradation rate, and threedimensional design.8 With an underlying scaffold base, composed from either a natural source or designed and fabricated from artificial materials, the next choice that needs to be made involves the candidate cells for seeding the bioartificial organ. The interdependent relationship between the three-dimensional matrix of the scaffold and the types and source of cells that will repopulate the organ to be fabricated makes cell selection a

reactions or adverse effects in clinical trials in patients with multiple sclerosis, while in another study mbMSCs led to muscle repair in atrophied skeletal muscle in immunodeficient mdx mouse models of Duchenne muscular dystrophy. Thus, with a variety of sources of MSCs, a promising application of these cells in regerative medicine would be to utilize these cells in structural scaffolds for bioartificial organs such as the uterus. MSCs have multipotent potential. Thus, when seeded these cells with bioartificial uterus, in addition to benefiting from MSC differention into soft tissue lining characteristic of the endometrium, are also poised to experience enhanced differentiation. Development as MSCs also lead to angiogenesis promotion through VEGF promoter signaling and extracellular matrix regeneration through the secretion of various factors.5 Further researches into the various progenitor and stem cell types of the endometrium will elucidate the roles played by these cells in the development of the tissue, and a strong knowledge base of the composition of the uterine’s progenitor cell population will enhance the efficacy of cellseeding preparations in the generation of bioartificial uterus.

2.1 3-D Culture and Bioartificial Organ Engineering Prior to developing full-scale bioartificial tissue and organ level uterine transplants, an intermediary in vitro scale model must be established in order to verify the physiological integrity of the cellular model under investigation. This threedimensional culture of human endometrium must be fully characterized, including finding the optimal substrate for cell seeding, appropriate medium conditions, and measuring genetic and morphological development of the endometrial stem cell cultures to ensure normal development. A suitable three-dimensional culture model can be expanded to generate larger scaled constructs as an extrapolation of the success of the smaller scaled initial in vitro culture system. Researches in the field of organ engineering have invested a

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The increased clinical interest in uterine transplantation has been a recent phenomenon. Literature in the reproductive sciences between the 1960s and 1980s broadly studied the female reproductive tract as a whole, rather than a strong focus on the uterus specifically. With the advent of in vitro fertilization (IVF) in 1978 and the increased practice of surrogate pregnancies in reproductive medicine, there was not a critical push within the field to develop the practice of uterine transplantation despite the significant advances made in the understanding of immunology in the 1990s.10 In 2000, the one and only human uterine transplant procedure was conducted in Saudi Arabia, and although the graft needed to be removed 99 days post operation, 14 the event generated renewed interest in uterine transplantation. Since the year 2000, the study about uterine transplantation has developed significantly, with the development of uterine transplantation models in the mouse, rat, pig, sheep, and non-human primates13,14 including cases of first pregnancies in animal models receiving syngeneic uterine transplantations in 2002 and 2003, and the first pregnancy from an allogeneic uterine transplant in 2010.12 As is the case with other solid-organ transplants, sufficient blood supply to the donor organ is of utmost importance for the success of the procedure and long-term functioning within the recipient. As a matter of fact the first human uterus transplantation performed in 2000 failed after 99 days due to necrosis because of insufficient vascular blood supply.14 The vessels that supply the uterus with blood are the bilateral uterine arteries and veins, the deep uterine veins, and the ovarian arteries and veins.13 Evidenced by the resulting necrosis of the first attempt at a human uterine transplantation, many researches were necessary regarding the development of a transplantation protocol to account for the proper methodology and procedure to ensure an effective and safe transplantation. The most recent studies in uterine transplantation have taken place in non-human primates to better understand the pelvic vascular anatomy. A group in Sweden led by Enskog et al published a methodology for uterine auto-transplantation in the baboon.13 The procedure was composed of two phases, these being uterine retrieval and uterine auto-transplantation. At retrieval, ovarian veins and uterine arteries along with the anterior branches of the internal iliacs were isolated to enable the harvesting of the utero-tubal-ovarian specimen.13 As the specimen was flushed and kept ex vivo for a 2 hour period, the two uterine arterial ends and the two uterine venous ends were anastamosed to form a singular arterial end and a singular venous end. At auto-transplantation the single combined arterial end and the combined venous end were then attached respectively to the external iliacs of the host; the total time of

strongly important step of the process. Potential stem and progenitor cell sources include embryonic stem cells, fetal cells, adult and umbilical cord-derived stem and progenitor cells, and induced pluripotent stem cells derived from adult tissue. Additionally, parenchymal and supportive cells such as fibroblasts and endothelial cells that form vasculature can also be included in the construction of the cellular seeding of the organ scaffold.9 With these various cell types available for seeding, the concurrent decision that needs to be made is whether to utilize autologous versus allogenic cells and whether to use adult cells versus embryonic stem cells and progenitor cells. Autologous cells are the safest to use for transplantation as they do not pose a major problem for immunologic rejection, however the number of autologous cells that can be harvested is far lower than the potential number of cells which can be collected from allogenic sources in individuals who are younger and healthier in certain cases compared with the patient. 9 A further consideration is the timeframe demanded by the transplantation. Allogenic cells can be readily available if collected en masse and prepared in vitro in a commercial environment, whereas autologous cells require a longer waiting period, as a biopsy from the patient followed by in vitro growth could take weeks or months, thus an immediate need for transplantation would indicate the use of an allogenic source while a less timedependent transplantation can be developed using autologous cells.9 Regardless of the choices made for scaffolding materials and cell sources for seeding, the vasculature of the bioartificial organ must allow for proficient oxygen delivery, as this issue has proved to be a major obstacle thus far in the generation of successful highly metabolically active, transplantable organs.9 Simple diffusion cannot provide the oxygen necessary for organ function, thus the construction of 3D microvascular networks will serve as a means towards alleviating the obstacle posed by this organ engineering challenge. Wu et al devised a method to print omnidirectional microvascular networks in hydrogel-based scaffolds.11

2.2 Uterine Transplantation Organ transplantation has been an important component of medicine for the past several decades. Numerous lives have been saved through transplantation of various organs of the human body. These procedures used organs from a variety of sources, including other living patients in the case of kidney, liver and bone marrow transplants, cadavers in the case of heart, lung and arthroscopic tissues among others, as well as artificial devices such as the Jarvik heart.

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the procedure was timed at 6 hours.14 Five out of nine animals resumed cyclicity, and two of these five cyclic animals resumed menstruation, signaling the re-establishment of ovarian and uterine function.13 This baboon model, being the first nonhuman primate uterine transplantation vascular study demonstrated the capacity for uterine transplantation to restore uterine functionality. To characterize a transplantation model that more closely resembles the human uterine vascular system and the issues pertaining to its microsurgery in transplantation, a group from Japan composed of Mihara et al developed an uterine autotransplantation model in cynomologous macaque.14 Whereas the ovarian vein was used in the baboon uterus transplantation model by Enskog et al, because it is the thickest among uterine veins,13 Mihara et al noted that the use of the ovarian vein in the transplantation is not realistic for use in uterus transplantation in humans, as this would lead to decreased ovarian functionality.14 In humans, therefore, the deep uterine vein would need to be used, and in their macaque study, Mihara et al chose to develop an anastamoses procedure using the deep uterine vein to most closely mimic a future uterus transplantation procedure for humans (Fig 5).14 Following their revised transplantation procedure Mihara et al used ICG fluorescence angiography to confirm the resumption of favorable blood flow to the autotransplanted uterus. Currently, in the field of transplantation a high number of procedures involve the donation of allograft tissue to a recipient. Granted the replacement tissue provides restored organ functionality to the patient, one of the main issues that must be dealt with for a prolonged period following the

transplantation procedure is the use of immunosuppressants such as cyclosporine in the case of allogenic transplantations in order to prevent the activation of the recipient’s immune response and the development of graft versus host disease, which would nullify the benefits of the transplantation as well as pose potential threats to the health of the recipient in the form of increased inflammation and other hyper-immune response. Through designing bioartificial organs with stem cells derived from the recipient’s own body, for instance the endometrial stem cells of the host will compose the graft in order to seed the bioartificial organ, the artificial organ will not pose as a foreign body to the host immune system, alleviating the necessity for immunesuppression and increasing the safety and efficiency of the transplantation.

2.3 Ethics of Ectogenesis The development of the bioartificial uterus will open the opportunity for the medical field to close the current gap between a pregnancy’s 16th and 23rd week where medicine does not have ability to support the embryo outside of the maternal womb.15 In doing so, the reproductive sciences will in turn be able to link the process of artificial conception of in vitro fertilization with the artificial gestation of the human fetus through neonatal care technology, effectively creating a fullyfunctioning stand-alone apparatus for ectogenesis. 15 Advocates for ectogenesis have historically cited three main reasons in support of the technology, which include giving access to control of gestation’s processes at any stage of the pregnancy, leading to improved prenatal diagnostics and treatment, scientific observation, and human developmental research, freeing women from the role as “clever incubators” and the pain and associated health risks characteristic of human pregnancy, and increased social liberties for women in making lifestyle and career choices.15 Within even the best medical settings, premature newborns in neonatal intensive care units are at a high risk of death or suffering brain damage and developmental abnormalities. The artificial uterus could be a more physiologically correct and protective environment in comparison to the current incubators used in hospitals. The use of the artificial uterus can also save the life of the mother in the case of preeclampsia, which normally poses a difficult situation for obstetricians as the toxic environment of the maternal womb forces a c-section delivery that places the life of the mother and fetus at risk. The bioartificial uterus can thus help physicians circumvent the risks to the fetus and mother by initiating an early delivery and placing the premature newborn into the protective confines of the bioartificial uterus.16 Furthermore, the artificial uterus can

Figure 5. A very important aspect of transplantation is the correct and sufficient connection of anastomoses to ensure blood supply to the organ. In the case of the uterus, this strategy which connects the external iliac arteries and veins to the uterine arteries and deep uterine veins via end-to-side anastomoses was developed by Mihara et al on macaque monkeys. FT, fallopian tube; OAV, ovarian artery and vein; UV, uterus vein; UA, uterus artery; DUV, deep uterus vein.14

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circles, lead to the increased demeaning and controlling of women. New legal issues may also arise with the development of ectogenesis. In the course of natural pregnancy, the mother has sole authority regarding the legal right of the pregnancy's outcome, as she has the entitlement to require the termination of the fetus or to request a procedure to avoid undergoing a natural delivery. In the case of an artificial, external pregnancy, the power of ownership over the developing fetus may be divided equally between the mother and father, as both parties contribute equally to the pregnancy by donation of egg and sperm. The legal body will need to decide for instance in the case of conflicting desires between partners to continue the gestation or another scenario where both partners decide to abort the pregnancy what the rights of the partners and the developing fetus are in relation to the novel situation of childbirth outside of the mother's body.16 Finally, the biological development of the fetus itself needs to be taken into consideration, as the artificial uterus will introduce a number of dramatic differences to its gestation in comparison to a natural birth. The embryo and fetus are known to respond to stimuli from the mother, for example the mother's heart beat. And in late stages of natural gestation, the fetus is influenced by its mother's character which affects learning abilities and the development of language.16 The intimate bond between mother and the developing fetus in a natural pregnancy also has important effects on creating a strong bond between mother and child, and it has been shown in premature infants isolated in incubators for extended periods of time that these conditions lead to later problems in their psychological development.17 Thus, although the practice of ectogenesis may give rise to increased equality between men and women reproductive roles, the children and their health must not be tabled as an afterthought. The notion of a fully-supported external gestation and birth is still far from being a reality. However, with the development of technologies that bring the vision of ectogenesis closer to fruition, the ethics and moral issues surrounding the possibility of the introduction of such technology needs to be preemptively addressed. Ectogenesis can increase the freedom of men and women from their biological roles, bringing the process of reproduction up to speed with the profound social evolution that has occurred as society has continued to quell the haste of human instinct and formulate law and order to increase equality and justice for all members of society. The increasingly intertwining relationship between technology and gestation will have profound effects on society, and it will be the responsibility of the people to preserve and enhance humanity with the introduction and practice of these technologies to

allow for prenatal surgery to treat physical abnormalities such as spina bifida, isolate 3rd trimester fetuses from the womb in the case of severe maternofoetal blood group immune reactions namely RhD or viral infections, and also allow for ex utero stem cell therapy to treat inherited disorders during the early stages of pregnancy.16 Thus, the benefits of the artificial uterus are numerous from a strictly medical standpoint. The question surrounding ectogenesis then should become ectogenesis be used, and if so, in what capacity? Perhaps the foremost apparent application of the artificial uterus would be to assist women who are not capable of giving natural birth. However, the artificial uterus’s implication in the development full ectogenesis raises the notion that this technology can be used to separate women from their intrinsic biological ties to the process of childbirth, a notion that has released the floodgates of ethical debate. On one side of the argument, proponents of ectogenesis proclaim there will be an increase in the sexual and reproductive liberties of women, a yearning for which is suggested by the strong adoption of the contraceptive pill as well as the fact that 25% of pregnant women choose to avoid natural birth by opting to undergo caesarian sections.16 Furthermore, ectogenesis will provide means for transgender, people born with ambiguous genitalia, and gay and lesbian couples to have children, thus expanding the options for couples interested in childbearing.16 And this is not to mention the attractive prospect for women in demanding careers, as they will be able to continue to work without the physical constraints placed on their work schedules.16 However with the increased control that the medical sciences will afford over the process of gestation, a number of concerns arise. Although proponents of ectogenesis cite the expanded freedom for women to make choices regarding reproduction and its relationship to their bodies, the technology may lead to difficult ethical situations where women's choices are compromised. One particular scenario involves the issue of women's right to abortion, as the development of bioartificial uterus that are capable of sustaining smaller premature babies ex utero could save the lives of a greater number of aborted fetuses, thus in theory eliminating the biological need for an abortion.18 Thus, in strictly legal rights regarding abortion, there will be problems in justifying a woman's decision to allow a fetus that could otherwise live instead die. This development could reduce the freedom of women regarding their reproductive choices, as an abortion would change from a decision based perhaps partly on medical reasoning to a predominantly moral decision, which place more ethical pressure on the woman's decision-making process and according to certain feminist

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avoid the pitfalls of their misuse.

References 1. J Thomson, J Itskovitz-Eldor, SS Shapiro, et al., Embryonic

3. Summary

stem cell lines derived from human blastocysts, Science, 282, 1145 (1998). 2. K Takahashi, S Yamanaka, Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors, Cell, 126, 663 (2006). 3. M Sakata, K Hisano, M Okada, et al., A new artificial placenta with a centrifugal pump: long-term total extrauterine support of goat fetuses, J Thoracic Cardiov Sur, 115, 1023 (1998). 4. CE Gargett, Uterine stem cells: what is the evidence? Hum Reprod Update, 13, 87 (2006). 5. CE Gargett, H Masuda, Adult stem cells in the endometrium, Mol Hum Reprod, 16, 818 (2010). 6. CE Gargett, RW Chan, KE Schwab, Hormone and growth factor signaling in endometrial renewal: role of stem/progenitor cells, Mol Cell Endocrinol, 288, 22 (2008). 7. H Masuda, Y Matsuzaki, E Hiratsu, et al., Stem cell-like properties of the endometrial side population: implication in endometrial regeneration, PLoS One, 5, e10387 (2010). 8. A Atala, Engineering organs, Curr Opinion Biotech, 20, 575 (2009). 9. SF Badylak, D Taylor, K Uygun, Whole-organ tissue engineering: decellularization and recellularization of threedimensional matrix scaffolds, Annu Rev Biomed Engin, 13, 27 (2011). 10. JJ Song, HC Ott, Bioartificial lung engineering, Am J Transplant, 12, 283 (2012). 11. W Wu, A DeConinck, JA Lewis, Omnidirectional printing of 3D microvascular networks, Adv Mater, 23, H178 (2011). 12. S Saso, SK Logan, Y Abdallah, et al., Use of cyclosporine in uterine transplantation, J Transplant, 2012, 134936 (2012). 13. A Enskog, L Johannesson, DC Chai, et al., Uterus transplantation in the baboon: methodology and long-term function after autotransplantation, Hum Reprod, 25, 1980 (2010). 14. M Mihara, I Kisu, H Hara, et al., Uterus autotransplantation in cynomolgus macaques: intraoperative evaluation of uterine blood flow using indocyanine green, Hum Reprod, 26, 3019 (2011). 15. I Aristarkhova, Ectogenesis and mother as machine, Body Soc, 11, 43 (2005). 16. M Adinolfi, The artificial uterus, Prenat Diag, 24, 570 (2004). 17. T Takala, Human Before Sex? Ectogenesis as a way to equality, In Reprogen-ethics and the Future of Gender, F Simonstein, ed, (Dordrecht: Springer Netherlands), 187 (2009).

At the moment, the components of a bioartificial uterus have been characterized, these being the scaffold structure, which will serve as the frame of the organ and its basement membrane, and the endometrial stem cell population which will serve as the cell source utilized to seed to scaffolding with biologically active multipotent cells leading to the development and differentiation of the bioartificial uterus. Parameters that need to be determined in the development of the bioartificial uterus include seeding efficiency of stem cells, their resulting differentiation, and the functioning of the bioartificial organ as a whole in the context of physiological processes for instance menstruation and gestation. Endometrial stem cells, bone marrow stem cells, and other candidate cells that will form the basis of the cell-seeded scaffolding will need to be further investigated to determine the ratio and seeding pattern that will result in proper development and functioning of the organ. These processes will be verified in pre-clinical animal models to verify the transplantation and subsequent in vivo functionality of the bioartificial uterus. Furthermore, continued discussion into the ethics of the use of bioartificial uterus will be necessary to address the proper practice and delineate guidelines, laws, and oversight into using this technology as a means to address the healthcare needs of patients who will require the use of the artificial uterus in order to give natural birth in a situation where else they would lack the means to do so without the use of this technology. Acknowledgements: This study was supported by a grant of the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (A111539) and by grant of the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012-0004131). The authors appreciate the assistance of Jun Beom Ku for his proofreading.

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