Trafficking in Fetal Tissue: Regulatory and Policy Considerations

 

In the summer of 2015, young pro-life activists at the Center for Medical Progress (CMP) released a video showing Planned Parenthood employees and an undercover “broker” negotiating fees that would be paid to the abortion clinic in return for collecting fetal tissue specimens. For many in the pro-life community, the videos revealed a cavalier attitude toward fetal remains and the immoral, and possibly illegal, commodification of human life. For abortion activists, the videos were merely another salvo in the longstanding “war on women” waged by pro-life activists and a backdoor attempt to limit access to abortion.[1] Though the videos did little to change the hardened positions of either abortion supporters or opponents, the episode has elevated the issue of fetal tissue procurement, research, and transplantation into our national political conversation.

At one level, the ethics of fetal tissue procurement are unavoidably linked with the ethics of abortion itself. For those of us in the pro-life community, post-abortive fetal tissue “donation” adds egregious insult to the already injurious assault on human dignity inherent in the intentional termination of a human life. For this reason alone, many favor legal restrictions on the practice, and indeed this was the tenor of the arguments made by pro-life ethicists in the early 1990s, when current laws for fetal tissue procurement were being established.[2] Nonetheless, abortion remains legal in the United States, and the country is deeply divided over the issue. Rather than allow the issue of fetal tissue procurement to remain stuck in the larger debate over abortion, common good arguments for restrictions on fetal tissue procurement can be made. When assessed by analogy to organ donation and its abuses, potential harms associated with current policies and practices regulating fetal tissue donation should become clear for all who care about protecting vulnerable women, including those who favor abortion rights.

Organ Donation Laws

Organ donation is an apt frame within which to consider fetal tissue procurement. In fact, U.S. law has historically viewed human fetal tissue transfer as a type of organ donation due to the ethical issues shared by both. A broad, nationwide framework for regulating organ donation was first established in 1968, when the Uniform Anatomical Gift Act was passed and subsequently adopted with minor variations by all 50 states and the District of Columbia by 1971.[3] This framework outlined processes for guaranteeing consent on behalf of deceased organ donors, including stillborn babies and aborted fetuses. Medical ethicists were concerned that the demand for donated organs and tissue would create perverse incentives for potential donors and their family members, so the act prohibits the sale of organs or tissue for profit and restricts their use. When Roe v. Wade made abortion legal nationwide in 1973, the potential emerged for the exploitation of pregnant women who might be coerced into abortion because of the demand for fetal tissue. This fear was underscored by the gruesome accounts of experimentation on still-living but aborted fetuses in Europe published that same year.[4]

In 1984, the National Organ Transplant Act made profiting from organ donation a federal crime, prohibiting anyone from making “valuable consideration” for organ donation. Under the law, “valuable consideration” refers to any economic or other gain resulting from the transfer of the organ from the donor to the recipient. Almost identical language was then used in the 1993 law that governs fetal tissue procurement for transplantation. In both cases, the law explicitly clarifies that “valuable consideration” does not include “reasonable payments associated with the transportation, implantation, processing, preservation, quality control, or storage” of the organ or tissue.[5] In prohibiting profiteering from the donation of human organs and tissue, including fetal tissue, U.S. law acknowledges the vulnerability of potential donors and seeks to set parameters to minimize exploitation. In so doing, the law criminalizes the commodification of human organs and fetal tissue.

Commodification of human life is not the only risk associated with organ transplantation and human fetal tissue procurement. In both cases, because of the demand for their life-saving organs or tissue, a potential donor’s death might be hastened or even caused when the donor might otherwise have lived. To guard against this possibility—at least in the case of organ donation—ethical norms (often referred to as the dead donor rule) and statutory guidelines adopted in the Uniform Declaration of Death Act together have formalized definitions of death in an attempt to ensure that no one is ever killed for their organs.[6] Similarly, for fetal tissue, federal law requires that the decision to have the abortion be made separately from the decision to donate fetal tissue to avoid undue influence over an already tragic choice.

Organ and fetal tissue donation also share a third, serious ethical concern: the rise of black markets in human organs and tissue associated with human trafficking. As techniques and survival rates for organ transplantation have improved, the demand for intact organs has skyrocketed. Waitlists for organs are long, and patients routinely die before they can access a life-saving organ. Where there is high demand and limited supply, there is always the potential for the development of a black market, and such is the case with organ transplantation. Organ trafficking is an international problem that “holds a critical place with transnational organized crime groups due to high demand and relatively low rates of law enforcement.”[7] Conservative estimates of the volume of the illegal organ trade range from $480 million to $1.7 billion annually.[8] International watchdogs have noted that “cases are emerging where an organ donor may have been a victim of sex trafficking and/or labor trafficking.”[9] Indeed, a Canadian organization founded to combat sex trafficking recently expanded its scope to include organ trafficking.[10] Though tragic and appalling, the evil logic is clear: once a person is considered a commodity, all of their prospective “goods” and “services” are available for exploitation and sale.

Trafficking rings and black markets of any kind pose the greatest risk for the most vulnerable in society, and this holds true for both organ donation and fetal tissue procurement. In both cases, underage minors and the poor are particularly vulnerable to exploitation. The global poor are documented targets of organ trafficking,[11] and, sadly, low-income women in the United States are the primary source for fetal tissue procurement. As many as 75% of abortions in the United States are performed on women whose incomes are at or below 200% of the federal poverty level,[12] meaning that an overwhelming majority of women who have the option to donate fetal tissue are socioeconomically vulnerable. Even though most states have clear guidelines and age limits for donating organs, minors undergoing an abortion procedure may designate their fetal tissue for donation. Though these women may not be directly offered money in return for fetal tissue (as is often the case for living donors of kidneys and other organs around the world), their economic vulnerability and—in the case of minors, their age—compounds a decision that is already fraught with emotional stress and mental health risk.[13]

Inconsistent Regulations and Lack of Oversight

Trafficking and other abuses associated with black markets are more prevalent in countries that lack robust legal and regulatory protections for donors, highlighting the need for strong enforcement mechanisms to protect the vulnerable. Even in the United States, where organ donation is regulated extensively by the Centers for Medicare and Medicaid Services (CMS) and by the Joint Commission responsible for accrediting hospitals, cases of conflicts of interest, medical error, and financial mishandling have been documented.[14] Nonetheless, in the case of organ donation, several key factors keep these abuses in check. First, though more oversight may be needed, CMS regularly audits the organizations (called organ procurement organizations or OPOs) that are responsible for matching donors with transplant patients. Second, these OPOs are part of a national network with common standards and are required to operate as non-profit organizations. Though cases of financial mismanagement have been cited, profit is prohibited. Third, ethical norms maintained through physician licensure and the pressures of a robust medical malpractice system also serve to limit malfeasance. Fourth, both organ retrieval and transplantation are performed in hospitals that are highly regulated by the federal government, accreditation bodies, and, increasingly, quality assessments and patient reviews. This network of regulatory oversight creates strong incentives for hospitals, which are under intense financial pressures to maintain high-quality services. Finally, human organs are only viable for transplantation for a narrow window of time post-retrieval. The heart, lungs, and liver must be transplanted within 12 hours or less after retrieval, and kidneys only remain viable for 36 hours.[15] This short retrieval window narrows the scope of responsibility for OPOs, who act primarily to recruit potential donors and talk to families facing the tragic, unexpected death of a loved one about the possibility of organ donation.

In contrast, such a robust regulatory regime is practically non-existent in the case of fetal tissue procurement. Though similar ethical concerns exist for the transfer of fetal tissue as for the transplantation of human organs, the regulatory landscape is vastly different. Indeed, in the case of post-abortive fetal tissue transfer, additional concerns emerge, including unnecessary medical risk for the mother. Federal law mandates that the medical techniques used for the abortion procedure should not be altered in an effort to obtain “better” fetal tissue specimens. Yet, there is almost no effort by the federal government to ensure that these important protections are maintained. Indeed, in 2000, an investigation by ABC News “20/20” found employees of fetal tissue procurement firms who alleged that abortion procedures had been altered in order to obtain intact fetal organs or tissue.[16] Similar allegations were raised in the wake of the 2015 CMP videos and the subsequent inquiries of the Select Investigative Panel of the Committee on Energy and Commerce of the U.S. House of Representatives.[17]

The federal law that governs fetal tissue donation, enacted in 1993, envisioned regular oversight of the practice by the Department of Health and Human Services. Sadly, these regulatory mechanisms designed by Congress are rarely utilized. The law states, “The Secretary shall annually submit to [Congress] a report . . . including a description of whether or to what extent research . . . has been conducted in accordance with this [law].”[18] Yet in 2000, at a Congressional hearing on the practice, Rep. Thomas Bliley (R-VA) said:

Congress’ objectives in this [law] were threefold: to ensure that fetal tissue could be made available for valuable research purposes, while at the same time preventing the development of a market for such tissue and ensuring that the health of women undergoing abortions would not be put at risk simply to acquire the tissue. Yet, over the last 7 years, since this bill became law of the land, there has been no government oversight of any type concerning whether this important law is being followed.

We contacted the National Institutes of Health, and it informed us that since the law was passed the agency has not reviewed at all whether the law is being complied with.

We contacted the Department of Justice, and their representatives told us the same thing, even though the 1993 law is a criminal statute with criminal enforcement provisions.[19]

This hearing was prompted in part by an ABC News “20/20” undercover investigation of potential profiteering by fetal tissue recovery and processing companies. As the press release accompanying the broadcast stated, “‘20/20’ has investigated one businessman whose company issued a price list charging what many call exorbitant prices for fetal tissue.”[20] The appearance of profiteering was so clear that bioethicist Arthur Caplan said to “20/20,” “That’s trading in body parts. There’s no doubt about it.”[21]

Yet, in the twenty years since those hearings were held, none of the companies exposed by “20/20’s” investigation has been charged with wrongdoing, and very few reports have been sent to Congress detailing government oversight of fetal tissue transfer. An internet search of reports issued by the Federal Government Accountability Office (GAO) yields only one audit of fetal tissue donation since 1993, conducted around the time of the Congressional hearings and the “20/20” broadcast in 2000. Most other audits conducted of Planned Parenthood by federal agencies have focused on their use of federal funds and not the protocols and fees related to fetal tissue transfer.

The absence of legal action surrounding the procurement of fetal tissue is in large part due to textual ambiguity in the federal statute regarding fetal tissue donation and lacunae in the regulations implementing that statute, both of which contribute to lax enforcement. The statute expressly permits women to donate fetal tissue after an elective abortion. Furthermore, though federal law prohibits the sale of human organs or tissue (including fetal tissue) for a profit, the law allows “reasonable” payments to be made to cover the costs of collection, shipping, storing, and processing tissue samples.[22] In the controversial CMP videos, the Planned Parenthood employees discussed fees in the range of $100 per sample, an amount that many experts view as “reasonable.” This is in contrast to the “20/20” investigation which uncovered fees as high as $999 for fetal tissue specimens.[23]

Notably, the term “reasonable” has never been defined by regulators for fetal tissue procurement. As Arthur Caplan said in response to the 2015 CMP videos, “It appears to be legal no matter how much you charge.”[24] Further complicating matters, federal law does not account for or envision middlemen, brokers who use highly trained “procurement technicians to obtain fetal tissue.”[25] These companies often send technicians to the abortion clinic to obtain tissue directly. The desired cell types might then be isolated, concentrated, and cultured. The final fetal tissue specimen is then sold to a research lab for amounts ranging from $300 to $24,000 or more. As reported in The New York Times, two of the tissue procurement and processing companies used most often by researchers, StemExpress and Advanced Bioscience Resources, Inc. (ABR), have annual revenues ranging between $1 to 2 million.[26] In a brochure made by StemExpress to advertise its procurement services, abortion clinics are told that in partnering with StemExpress, “you will also be contributing to the fiscal growth of your own clinic,” a statement that seems at odds with the idea that fees paid by brokerage companies to abortion clinics merely cover the costs of collection.[27] These issues and the associated negative publicity were concerning enough that Planned Parenthood decided that its affiliates would no longer accept fees from fetal tissue procurement middlemen in return for donated fetal tissue.[28] Despite these concerns and the subsequent investigations of lawmakers and prosecutors around the country, no charges or lawsuits have been filed against StemExpress or ABR.

In other words, not much has changed in the twenty years since “20/20” ran its broadcast. As law and bioethics professor George Annas noted: “It remains legal for a company to obtain fetal tissue from aborted fetuses, for the clinic to recover its out-of-pocket costs, and for the company that gets the fetal tissue to process it and sell it for a profit.”[29] Note the contrast with our national system for organ donation, where the “middlemen” are not-for-profit organizations that participate in a national, regulated network.

Adding to the regulatory confusion, the federal law that applies to fetal tissue donation specifically applies to “research on the transplantation of human fetal tissue for therapeutic purposes.”[30] This phrase specifically refers to the transfer of fetal tissue, or cells directly derived from such tissue, into a human patient for the purpose of improving a patient’s prognosis. Many other uses of fetal tissue, including the isolation of fetal cell lines for vaccine research, the screening of drug candidates using fetal liver tissue, or studies of early embryonic and fetal development, would not be considered “transplantation . . . for therapeutic purposes.” In a letter to National Institutes of Health (NIH) Director Francis Collins, Planned Parenthood signaled its own narrow interpretation of the law’s applicability, stating, “Although we are not legally required to follow the provisions in the 1993 law applicable to fetal tissue transplantation, we are doing so voluntarily.”[31] If authorities were ever to bring charges against Planned Parenthood for violations of the federal laws governing fetal tissue donation, the organization will likely claim that these laws are largely inapplicable to their practices because the fetal tissue donated at their clinics is not directly used in human patients. Though this loophole has never been tested in court, these legal ambiguities—both in the application of the law to the wider practice of fetal tissue research and in the regulation of the fees that exchange hands—leave federal and state authorities few tools for ensuring that current fetal tissue transfer practices satisfy the intent of Congress when it passed laws regulating fetal tissue donation in 1993.

Even if “reasonable” was defined more clearly in the law, or if it could be proven that amounts charged, either by Planned Parenthood or by the tissue collection and preparation companies themselves, exceeded the costs incurred by those organizations, enforcement of federal and state law regarding fetal tissue research has been limited and relies on the resources and priorities of applicable state and federal enforcement agencies. The divisive nature of the abortion debate often means that enforcement shifts with the political winds.

In 2016, Republican District Attorney Tony Rackauckas filed a civil lawsuit against two related companies identified in the CMP videos as tissue procurement organizations, alleging that the two companies charged fees for processing, shipping, and handling that vastly exceeded their costs. The two companies (DaVinci Biosciences and DV Biologics) settled out of court, admitting unlawful activity and agreeing to close their businesses.[32] In the end, this case is an exception that proves the rule. Though these companies are no longer in the business of fetal tissue procurement, justice is best served when enforcement is viewed as impartial.

Because of the lax and politically fraught oversight of fetal tissue procurement, the ethical considerations that both pro-life and pro-choice policymakers sought to remedy in the 1993 law remain unaddressed, leaving women exposed to potential exploitation and harm. Even those who are in favor of permissive abortion laws should be able to agree that these risks ought to be minimized wherever possible. Yet—as history has demonstrated—efforts to increase oversight of fetal tissue procurement will likely remain caught in our cycle of abortion politics, with abortion advocates viewing efforts to regulate fetal tissue procurement as merely a shrewd attempt to close down abortion clinics.

Suggested Solutions

To protect women, the best way forward is to ban fetal tissue procurement from abortion all together. In cases where fetal tissue is truly optimal for certain research applications, tissue can be obtained from miscarriages and stillbirths where there is less risk of exploitation of the mother (and analogous to organ donation of the unborn child). When the 1993 law was being debated in Congress and in the public square, advocates for fetal tissue procurement argued that tissue from spontaneous abortions and miscarriages was unsuitable for the applications being envisioned because the tissue contained genetic abnormalities or was otherwise compromised.[33] Almost 30 years later, direct fetal tissue transplantation is not envisioned by most in the medical community as a viable therapeutic intervention, though a few small clinical trials are ongoing.[34] Instead, fetal tissue is primarily used in basic biomedical research as a means of “humanizing” animal models of human disease. To improve the similarities between mouse models and humans, scientists use fetal tissue to create mice with human-like immune systems or lung tissue, for example.[35] These animal models are then used to test potential drugs and biologics and to understand mechanisms used by human pathogens such as HIV or Sars-Cov-2.[36] In FY2020, NIH funded $82 million of research using fetal tissue, much of it using these humanized animal models.[37] Fetal tissue from spontaneous abortions and miscarriages could be used for many of these applications, which due to technological advances can be easily screened for genetic abnormalities, pathogens, or other defects. Other forms of tissue, including tissue from neonatal cardiac surgeries, have been used to create similar humanized animal models without the use of any fetal tissue.[38]

Prohibiting fetal tissue donation after elective abortions would constrain any black-market supply chains for fetal tissue by bringing the process of acquiring fetal tissue under more stringent regulatory oversight in medical centers and hospitals where protocols governing organ donation are already in place. Many academic research institutions in the United States are affiliated with research hospitals, facilitating processing and transport of such tissue. Though alternative fetal tissue sources may be more limited and difficult to process in some cases, these obstacles are not insurmountable. The ethics, logistics, and supply chain for these sources of tissue have not been fully explored and developed because it has simply been easier for researchers to source tissue from companies with established relationships with abortion clinics.

In both organ donation and fetal tissue donation, ethicists have long recognized that the life-saving potential of the organs and tissues could easily obscure the risks for organ donors and women considering abortion and have enacted laws intended to act as fences to protect the vulnerable from exploitation. Yet our culture’s quixotic quest for health, beauty and immortality consistently presses against these limits. The short argument is—and has always been—that patients will suffer, and many will die, if we do not allow “promising” research to proceed. In the face of such enormous pressure to find cures at any costs, we have a shared responsibility to protect the vulnerable from harm. Though imperfect—and constantly under pressure to supply more organs—the regulatory framework governing organ donation in the United States is working to protect donors. Because the same cannot be said for fetal tissue procurement from elective abortion, such “donations” should be banned and alternative sources of tissue used instead.

 

References


[1] Heather D. Boonstra, “Fetal Tissue Research: A Weapon and a Casualty in the War against Abortion,” Guttmacher Policy Review 19 (2016): https://www.guttmacher.org/gpr/2016/fetal-tissue-research-weapon-and-casualty-war-against-abortion.

[2] A. F. Shorr, “Abortion and Fetal Tissue Research: Some Ethical Concerns,” Fetal Diagnosis and Therapy 9, no. 3 (1994): https://doi.org/10.1159/000263931.

[4] For a helpful summary of these cases, see O. Carter Snead, What It Means to Be Human: The Case for the Body in Public Bioethics (Cambridge, MA: Harvard University Press, 2020), 24–27.

[6] Robert M. Sade, “Brain Death, Cardiac Death, and the Dead Donor Rule,” The Journal of the South Carolina Medical Association 107, no. 4 (2011): 146–49, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3372912/.

[7] Christina Bain and Joseph Mari, “Organ Trafficking: The Unseen Form of Human Trafficking,” ACAMS Today, June 26, 2018, https://www.acamstoday.org/organ-trafficking-the-unseen-form-of-human-trafficking/.

[8] Channing May, Transnational Crime and the Developing World (Global Financial Integrity, March 2017), 29, http://www.gfintegrity.org/wp-content/uploads/2017/03/Transnational_Crime-final.pdf.

[9] Bain and Mari, “Organ Trafficking.”

[10] Persons against the Crime of Trafficking in Humans, “First National Roundtable on the Topic of Human Trafficking for the Purpose of Organ Removal,” PACT-Ottawa, 2015, https://www.pact-ottawa.org/organ-trafficking-roundtable.html.

[11] Paige Comstock Cunningham and Michael J. Sleasman, “Exploitation in the Global Medical Enterprise: Bioethics & Social Injustice,” in Social Injustice: What Evangelicals Need to Know about the World, ed. Michael Cooper and William Moulder (Timothy Center Press, 2011), 105–7, https://cbhd.org/content/exploitation-global-medical-enterprise-pdf-version.

[12] Jenna Jerman, Rachel K. Jones, and Tsuyoshi Onda, Characteristics of U.S. Abortion Patients in 2014 and Changes since 2008 (Guttmacher Institute, May 2016), https://www.guttmacher.org/report/characteristics-us-abortion-patients-2014.

[13] David C. Reardon, “The Abortion and Mental Health Controversy: A Comprehensive Literature Review of Common Ground Agreements, Disagreements, Actionable Recommendations, and Research Opportunities,” SAGE Open Medicine 6 (2018): 1–38, https://doi.org/10.1177/2050312118807624.

[14] Todd Park et al., The Costly Effects of an Outdated Organ Donation System (Arnold Ventures, Schmidt Futures, Organize, and Federation of American Scientists, October 2020), Chapter 7, https://bloomworks.digital/organdonationreform/Oversight/.

[15] “What Is the Time Frame for Transplanting Organs?” Donor Alliance, August 25, 2021, https://www.donoralliance.org/newsroom/donation-essentials/what-is-the-time-frame-for-transplanting-organs/.

[16] “20/20 Baby Body Parts Investigation Shown in Court,” Liberty Counsel, October 28, 2019, https://www.lc.org/newsroom/details/102319-baby-body-parts-investigation-shown-in-court-1.

[17] Compilation of Activities of the Select Investigative Panel of the Committee on Energy and Commerce, H.R. Rep. 114-A (2017), https://www.govinfo.gov/content/pkg/CPRT-114HPRT24553/pdf/CPRT-114HPRT24553.pdf.

[19] Fetal Tissue: Is It Being Sold in Violation of Federal Law? Hearing before the Subcommittee on Health and Environment of the Committee on Commerce, 106th Cong. (2000) (statement of Tom Bliley, Congressman), https://www.govinfo.gov/content/pkg/CHRG-106hhrg63102/html/CHRG-106hhrg63102.htm.

[20] ABC News “20/20” in New York, “ABC News ‘20/20’ Investigation into Alleged Trafficking in Fetal Tissue Finds Companies That Appear to Be Profiting from Selling Human Tissue,” National Right to Life, March 6, 2000, https://www.nrlc.org/archive/Baby_Parts/20_20_Press_Release.html.

[21] ABC News “20/20” in New York, “ABC News ‘20/20’ Investigation into Alleged Trafficking in Fetal Tissue.”

[22] Prohibition of Organ Purchases, 42 U.S.C. § 274e, https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title42-section274e&num=0&edition=prelim; Research on Transplantation of Fetal Tissue, 42 U.S.C. § 289g-1.

[23] ABC News “20/20” in New York, “ABC News ‘20/20’ Investigation into Alleged Trafficking in Fetal Tissue.”

[24] Denise Grady and Nicholas St. Fleur, “Fetal Tissue from Abortions for Research Is Traded in a Gray Zone,” The New York Times, July 27, 2015, https://www.nytimes.com/2015/07/28/health/fetal-tissue-from-abortions-for-research-is-traded-in-a-gray-zone.html.

[25] Grady and St. Fleur, “Fetal Tissue from Abortions for Research.”

[26] Grady and St. Fleur, “Fetal Tissue from Abortions for Research.”

[27] Grady and St. Fleur, “Fetal Tissue from Abortions for Research.”

[28] “Taking Away Basis for Discredited Smear Campaign, Planned Parenthood Declines Any Reimbursement for Fetal Tissue Donation,” Planned Parenthood, October 13, 2015, https://www.plannedparenthood.org/about-us/newsroom/press-releases/taking-away-basis-for-discredited-smear-campaign-planned-parenthood-declines-any-reimbursement-for-fetal-tissue-donation.

[29] Tony Pugh, “Secret Videos in Abortion Wars Are Nothing New,” The News & Observer, August 21, 2015, https://www.newsobserver.com/article31678286.html.

[31] “Planned Parenthood Commends HHS for Tissue Donation Audit,” Planned Parenthood, December 28, 2015, https://www.plannedparenthood.org/about-us/newsroom/press-releases/planned-parenthood-commends-hhs-for-tissue-donation-audit.

[32]Orange County, California District Attorney, “OCDA Obtains $7.8 MILLION Settlement and Admission of Liability in Lawsuit against Companies Who Unlawfully Sold Fetal Tissue and Cells for Profit,” Operation Rescue, December 8, 2017, http://www.operationrescue.org/wp-content/uploads/2017/12/ORANGE-COUNTY-DISTRICT-ATTORNEY-Press-Release-12082017.pdf.

[33] Bryan E. Hainline et al., “Fetal Tissue Derived from Spontaneous Pregnancy Losses Is Insufficient for Human Transplantation,” Obstetrics & Gynecology 85, no. 4 (1995): 619–24, https://doi.org/10.1016/0029-7844(95)00003-A.

[34] Roger Barker et al., “Are Stem Cell-Based Therapies for Parkinson’s Disease Ready for the Clinic in 2016?” Journal of Parkinson’s Disease 6, no. 1 (2016): 57–63, https://dx.doi.org/10.3233%2FJPD-160798; Malin Parmar, Shane Grealish, and Claire Henchcliffe, The Future of Stem Cell Therapies for Parkinson Disease,” Nature Reviews Neuroscience 21 (2020): 103–15, https://doi.org/10.1038/s41583-019-0257-7; Paul E. Green et al., “Persistent Dyskinesias in Patients with Fetal Tissue Transplantation for Parkinson Disease,” npj Parkinson’s Disease 7, no. 38 (2021): https://doi.org/10.1038/s41531-021-00183-w.

[35] Louis Gonzalez, Natasa Strbo, and Eckhard R. Podack, “Humanized Mice: Novel Model for Studying Mechanisms of Human Immune-Based Therapies,” Immunologic Research 57 (2013): 326–34, https://doi.org/10.1007/s12026-013-8471-2; Hergen Spits and Julien Villaudy, “Modeling Human Lung Infections in Mice,” Nature Biotechnology 37 (2019): 1129–30, https://doi.org/10.1038/s41587-019-0269-x.

[36] Lunzhi Yuan et al., “Animal Models for Emerging Coronavirus: Progress and New Insights,” Emerging Microbes & Infections 9, no. 1 (2020): 949–61, https://doi.org/10.1080/22221751.2020.1764871.

[37] NIH, “Estimates of Funding for Various Research, Condition, and Disease Categories (RCDC),” NIH.gov, June 25, 2021, https://report.nih.gov/funding/categorical-spending#/; Kavya Sekar et al., “Human Fetal Tissue Research: Frequently Asked Questions” (Congressional Research Service, August 8, 2019), https://crsreports.congress.gov/product/pdf/R/R44129/9.

[38] Matthew E. Brown et al., “A Humanized Mouse Model Generated Using Surplus Neonatal Tissue,” Stem Cell Reports 10, no. 4 (2018): 1175–83, https://doi.org/10.1016/j.stemcr.2018.02.011.