Hepatocytes direct the formation of a pro-metastatic niche in the liver.

The liver is the most common site of metastatic disease1. Although this metastatic tropism may reflect the mechanical trapping of circulating tumour cells, liver metastasis is also dependent, at least in part, on the formation of a 'pro-metastatic' niche that supports the spread of tumour cells to the liver2,3. The mechanisms that direct the formation of this niche are poorly understood. Here we show that hepatocytes coordinate myeloid cell accumulation and fibrosis within the liver and, in doing so, increase the susceptibility of the liver to metastatic seeding and outgrowth. During early pancreatic tumorigenesis in mice, hepatocytes show activation of signal transducer and activator of transcription 3 (STAT3) signalling and increased production of serum amyloid A1 and A2 (referred to collectively as SAA). Overexpression of SAA by hepatocytes also occurs in patients with pancreatic and colorectal cancers that have metastasized to the liver, and many patients with locally advanced and metastatic disease show increases in circulating SAA. Activation of STAT3 in hepatocytes and the subsequent production of SAA depend on the release of interleukin 6 (IL-6) into the circulation by non-malignant cells. Genetic ablation or blockade of components of IL-6-STAT3-SAA signalling prevents the establishment of a pro-metastatic niche and inhibits liver metastasis. Our data identify an intercellular network underpinned by hepatocytes that forms the basis of a pro-metastatic niche in the liver, and identify new therapeutic targets.

Physiologic homeostasis after pig-to-human kidney xenotransplantation.

Demand for kidney grafts outpaces supply, limiting kidney transplantation as a treatment for kidney failure. Xenotransplantation has the potential to make kidney transplantation available to many more patients with kidney failure, but the ability of xenografts to support human physiologic homeostasis has not been established. A brain-dead adult decedent underwent bilateral native nephrectomies followed by 10 gene-edited (four gene knockouts, six human transgenes) pig-to-human xenotransplantation. Physiologic parameters and laboratory values were measured for seven days in a critical care setting. Data collection aimed to assess homeostasis by measuring components of the renin-angiotensin-aldosterone system, parathyroid hormone signaling, glomerular filtration rate, and markers of salt and water balance. Mean arterial blood pressure was maintained above 60 mmHg throughout. Pig kidneys secreted renin (post-operative day three to seven mean and standard deviation: 47.3 ± 9 pg/mL). Aldosterone and angiotensin II levels were present (post-operative day three to seven, 57.0 ± 8 pg/mL and 5.4 ± 4.3 pg/mL, respectively) despite plasma renin activity under 0.6 ng/mL/hr. Parathyroid hormone levels followed ionized calcium. Urine output down trended from 37 L to 6 L per day with 4.5 L of electrolyte free water loss on post-operative day six. Aquaporin 2 channels were detected in the apical surface of principal cells, supporting pig kidney response to human vasopressin. Serum creatinine down trended to 0.9 mg/dL by day seven. Glomerular filtration rate ranged 90-240 mL/min by creatinine clearance and single-dose inulin clearance. Thus, in a human decedent model, xenotransplantation of 10 gene-edited pig kidneys provided physiologic balance for seven days. Hence, our in-human study paves the way for future clinical study of pig-to-human kidney xenotransplantation in living persons.

A multi-institutional study of renal outcomes and renal-related pregnancy outcomes in uterus transplant recipients.

Uterus transplantation (UTx) is an effective treatment option for uterine factor infertility. However, the need for immunosuppression and congenital renal anomalies that coexist with uterine agenesis in about 30% of women with Mayer-Rokitansky-Kuster-Hauser syndrome create a risk for renal dysfunction. We therefore examined renal function trajectory and related pregnancy complications in an international cohort of 18 UTx recipients from September 2016-February 2020 who had at least one live birth. All UTx recipients had a diminution in their renal function that was apparent starting at 30 days posttransplant and in half the reduction in eGFR was at least 20%; the decrease in eGFR persisted into the early post-partum period. Half met criteria for Stage 1 acute kidney injury (AKI) as defined by the AKI Network criteria during their pregnancy. Overall, 28% of UTx recipients developed pre-eclampsia. eGFR was lower at embryo transfer and throughout pregnancy among those who developed pre-eclampsia, reaching statistical significance at week 16 of pregnancy. This effect was independent of tacrolimus levels. Mean eGFR remained significantly lower in the first 1-3 months after delivery. In the subgroup who reached 12 months of postpartum follow up and had a graft hysterectomy (n = 4), there was no longer a statistical difference in eGFR (pretransplant 106.7 ml/m ± 17.7 vs. 12 mos postpartum 92.6 ml/m ± 21.7, p = .13) but the number was small. Further study is required to delineate long term renal risks for UTx recipients, improve patient selection, and make decisions regarding a second pregnancy.

First clinical-grade porcine kidney xenotransplant using a human decedent model.

A radical solution is needed for the organ supply crisis, and the domestic pig is a promising organ source. In preparation for a clinical trial of xenotransplantation, we developed an in vivo pre-clinical human model to test safety and feasibility tenets established in animal models. After performance of a novel, prospective compatible crossmatch, we performed bilateral native nephrectomies in a human brain-dead decedent and subsequently transplanted two kidneys from a pig genetically engineered for human xenotransplantation. The decedent was hemodynamically stable through reperfusion, and vascular integrity was maintained despite the exposure of the xenografts to human blood pressure. No hyperacute rejection was observed, and the kidneys remained viable until termination 74 h later. No chimerism or transmission of porcine retroviruses was detected. Longitudinal biopsies revealed thrombotic microangiopathy that did not progress in severity, without evidence of cellular rejection or deposition of antibody or complement proteins. Although the xenografts produced variable amounts of urine, creatinine clearance did not recover. Whether renal recovery was impacted by the milieu of brain death and/or microvascular injury remains unknown. In summary, our study suggests that major barriers to human xenotransplantation have been surmounted and identifies where new knowledge is needed to optimize xenotransplantation outcomes in humans.

The science of xenotransplantation for nephrologists.

PURPOSE OF REVIEW: The field of xenotransplantation has seen remarkable progress since its inception with recent preclinical trials in human recipients pushing kidney xenotransplantation one-step closer to clinical reality. In this review, we update practicing clinicians on recent advances in kidney xenotransplantation given the proximity of clinical trials in humans. RECENT FINDINGS: Early studies in the field established the physiologic basis of xenotransplantation and suggested that the pig kidney will support human physiology. Genetic engineering of source pigs has greatly reduced the immunogenicity of kidney grafts, and studies in nonhuman primates have demonstrated the viability of kidney xenotransplants for months after transplantation. Finally, a recent study in a novel preclinical human model demonstrated that key findings in NHP experiments are generalizable to humans, namely, the absence of hyperacute rejection. SUMMARY: Overall, it appears that critical physiologic, immunologic and technical barriers to implementation of clinical trials in humans have been overcome.

COVID-19 Vaccination and Remdesivir are Associated With Protection From New or Increased Levels of Donor-Specific Antibodies Among Kidney Transplant Recipients Hospitalized With COVID-19.

Alloimmune responses in kidney transplant (KT) patients previously hospitalized with COVID-19 are understudied. We analyzed a cohort of 112 kidney transplant recipients who were hospitalized following a positive SARS-CoV-2 test result during the first 20 months of the COVID-19 pandemic. We found a cumulative incidence of 17% for the development of new donor-specific antibodies (DSA) or increased levels of pre-existing DSA in hospitalized SARS-CoV-2-infected KT patients. This risk extended 8 months post-infection. These changes in DSA status were associated with late allograft dysfunction. Risk factors for new or increased DSA responses in this KT patient cohort included the presence of circulating DSA pre-COVID-19 diagnosis and time post-transplantation. COVID-19 vaccination prior to infection and remdesivir administration during infection were each associated with decreased likelihood of developing a new or increased DSA response. These data show that new or enhanced DSA responses frequently occur among KT patients requiring admission with COVID-19 and suggest that surveillance, vaccination, and antiviral therapies may be important tools to prevent alloimmunity in these individuals.

Immunologic and Infectious Concerns in Uterus Transplantation.

Pharmacologic immunosuppression is required for the success of uterus transplantation but can provoke several complications for the transplant recipient. In this review, we discuss the immunologic complications that can occur in the uterus transplant recipient. First, we provide the latest update on immunosuppression regimens used by programs throughout the world. Next, we discuss the prevalence, mechanisms, treatment, and outcome of rejection in uterus transplant recipients. Finally, we discuss infectious complications of varying severity alongside their treatment and impact.

Life underneath the VCA umbrella: Perspectives from the US Uterus Transplant Consortium.

The parallel emergence of uterus transplantation (UTx) and other transplantation innovations including face and hand transplantation led to the categorization of the uterus as a vascular composite allograft (VCA). With >60 transplants and >20 births worldwide, UTx is transitioning rapidly from a research endeavor to an effective treatment option for women with uterine factor infertility. While it originally made sense to group the innovations under one umbrella, it is time to revisit the designation of UTx as a VCA. We describe how UTx needs unique policy, procedural codes, insurance contracts, and educational initiatives. We contend that separating UTx from VCAs may become necessary in the future to avoid hindering the growth and regulation of this field.

Uterus transplantation: the importance of uterine natural killer cells.

PURPOSE OF REVIEW: Murine studies have established that uterine natural killer (uNK) cells are critical regulators of normal placentation and fetal development in mammals. However, the biology of uNK cells in humans remains poorly understood. This ignorance represents a costly knowledge gap, as disordered placentation is thought to underpin a variety of pregnancy complications that impact maternal and neonatal health. In the context of uterus transplantation (UTx), uNK cells are anticipated to play a critical role within the allograft. Here, we review the current understanding of uNK cells in pregnancy biology and explore how this critically important cell population may contribute to pregnancy and graft outcomes in uterus transplant recipients. RECENT FINDINGS: Recent studies have characterized differences in NK cell populations between anatomic compartments in humans. In the endometrium, at least five phenotypically and functionally distinct subpopulations of uNK cells have been identified, with research into mechanisms regulating their differentiation and function currently underway. SUMMARY: Further elucidating uNK cell biology has the potential to influence the outcomes of pregnancy and UTx and benefit human health. UTx is a unique opportunity to study uNK cell biology and may shed light on mechanisms by which immunological tolerance is established at the maternal-fetal interface.

Guidelines for standardized nomenclature and reporting in uterus transplantation: An opinion from the United States Uterus Transplant Consortium.

Uterus transplantation is a nascent but growing field. To support this growth, the United States Uterus Transplant Consortium proposes guidelines for nomenclature related to operative technique, vascular anatomy, and donor, recipient, and offspring outcomes. In terms of anatomy, the group recommends reporting donor arterial inflow and recipient anastomotic site delivering inflow to the graft and offers standardization of the names for the 4 veins originating from the uterus because of current inconsistency in this particular nomenclature. Seven progressive stages with milestones of success are defined for reporting on uterus transplantation outcomes: (1) technical, (2) menstruation, (3) embryo implantation, (4) pregnancy, (5) delivery, (6) graft removal, and (7) long-term follow-up. The 3 primary metrics for success are recipient survival (as reported for other organ transplant recipients), graft survival, and uterus transplant live birth rate (defined as live birth per transplanted recipient). A number of secondary outcomes should also be reported, most of which capture stage-specific milestones, as well as data on graft failure. Outcome metrics for living donors include patient survival, survival free of operative intervention, and data on complications and hospitalizations. Finally, we make specific recommendations on follow-up for offspring born from uterine grafts, which includes specialty surveillance as well as collection and reporting of routine pediatric outcomes. The goal of standardization in reporting is to create consistency and improve the quality of evidence available on the efficacy and value of the procedure.

Kidney transplantation and donation in the transgender population: A single-institution case series.

The medical needs of the transgender population are increasingly recognized within the US health care system. Hormone therapy and gender-affirming surgery present distinct anatomic, hormonal, infectious, and psychosocial issues among transgender kidney transplant donors and recipients. We present the first reported experience with kidney transplantation and donation in transgender patients. A single-center case series (January 2014-December 2018) comprising 4 transgender kidney transplant recipients and 2 transgender living donors was constructed and analyzed. Experts in transplant surgery, transplant psychiatry, transplant infectious disease, pharmacy, and endocrinology were consulted to discuss aspects of care for these patients. Four transgender patients identified as male-to-female and 2 as female-to-male. Three of 6 had gender-affirming surgeries prior to transplant surgery, 1 of whom had further procedures posttransplant. Additionally, 4 patients were on hormone therapy. All 6 had psychiatric comorbidities. The 4 grafts have done well, with an average serum creatinine of 1.45 mg/dL at 2 years (range 1.01-1.85 mg/dL). However, patients encountered various postoperative complications, 1 of which was attributable to modified anatomy. Thus, transgender kidney transplant patients can present novel challenges in regard to surgical considerations as well as pre- and posttransplant care. Dedicated expertise is needed to optimize outcomes for this population.

Leveraging marginal structural modeling with Cox regression to assess the survival benefit of accepting vs declining kidney allograft offers.

Existing studies evaluating the survival benefit of kidney transplantation were unable to incorporate time-updated information on decisions related to each organ offer. We used national registry data, including organ turndown data, to evaluate the survival benefit of accepting vs turning down kidney offers in candidates waitlisted from 2007-2013. Among candidates who declined their first offer, only 43% ultimately received organ transplantations. Recipients who later underwent organ transplantation after declining their first offer had markedly longer wait times than recipients who accepted their first offer, and 56% received kidney transplants that were of similar or lower quality compared to their initial offer. In marginal structural modeling analyses accounting for time-updated offer characteristics (including Kidney Donor Profile Index, Public Health System risk status, and pumping), after 3 months posttransplant, there was a significant survival benefit of accepting an offer (adjusted hazard ratio 0.76, 95% confidence interval 0.66-0.89) that was similar among diabetics, candidates aged >65 years, and candidates living in donor service areas with the longest waitlist times. After carefully accounting for the effect of donor quality, we confirm that the survival benefit of accepting an organ offer is clinically meaningful and persistent beyond 3 months post-kidney transplantation, including high-risk subgroups of organ transplantation candidates.

Early emergence of anti-HCV antibody implicates donor origin in recipients of an HCV-infected organ.

Hepatitis C virus (HCV) seroconversion among HCV-uninfected transplant recipients from HCV-infected (NAT+/Antibody+) or HCV-exposed (NAT-/Antibody+) donors has been reported. However, the origin of anti-HCV antibody and the implications of seroconversion remain unknown. We longitudinally tested plasma from HCV-uninfected kidney (n = 31) or heart transplant recipients (n = 9) of an HCV NAT+ organ for anti-HCV antibody (both IgG and IgM isotypes). Almost half of all participants had detectable anti-HCV antibody at any point during follow-up. The majority of antibody-positive individuals became positive within 1-3 days of transplantation, and 6 recipients had detectable antibody on the first day posttransplant. Notably, all anti-HCV antibody was IgG, even in samples collected posttransplant day 1. Late seroconversion was uncommon (≈20%-25% of antibody+ recipients). Early antibody persisted over 30 days in kidney recipients, whereas early antibody dropped below detection in 50% of heart recipients within 2 weeks after transplant. Anti-HCV antibody is common in HCV-uninfected recipients of an HCV NAT+ organ. The IgG isotype of this antibody and the kinetics of its appearance and durability suggest that anti-HCV antibody is donor derived and is likely produced by a cellular source. Our data suggest that transfer of donor humoral immunity to a recipient may be much more common than previously appreciated.

Interleukins 27 and 6 induce STAT3-mediated T cell production of interleukin 10.

Interleukin 10 (IL-10) has a prominent function in regulating the balance between protective and pathological T cell responses. Consistent with that activity, many sources of this cytokine are found in vivo, including from myeloid cells and a variety of T cell subsets. However, although there are many pathways that regulate innate production of IL-10, the factors that govern its synthesis by the adaptive response are poorly understood. Here we report that IL-27 and IL-6 induced T helper type 1 and type 2 cells, as well as T helper cells that produce IL-17, to secrete IL-10. This effect was dependent on the transcription factors STAT1 and STAT3 for IL-27 and on STAT3 for IL-6. Our studies identify a previously unknown pathway that allows the immune system to temper inflammatory responses.

Biologic mechanisms and clinical consequences of pregnancy alloimmunization.

Alloimmunization occurs during pregnancy when tissue antigens derived from the fetus and/or placenta prime maternal immune cells to divide and differentiate. For many women, the result of pregnancy alloimmunization is the formation of anti-HLA antibody that can endure for decades and preclude transplantation by limiting donor compatibility. Pregnancy alloimmunization may also generate memory B cells that can rapidly produce anti-HLA antibody after transplantation as well as pathogenic memory T cells, which pose a threat to graft survival. However, emerging data suggest that pregnancy also programs the differentiation of anergic, dysfunctional, and regulatory T cell populations, which may not mediate accelerated graft rejection. Hence, some of the immune mechanisms responsible for maternal immunologic tolerance of the fetus may persist into postpartum life and affect the response to an allograft. This review discusses these emerging data as well as the persistent knowledge gaps that affect women at multiple stages of their transplant care.

Migratory and lymphoid-resident dendritic cells cooperate to efficiently prime naive CD4 T cells.

To initiate an adaptive immune response, rare antigen-specific naive CD4(+) T cells must interact with equally rare dendritic cells (DCs) bearing cognate peptide-major histocompatibility complex (MHC) complexes. Lymph nodes (LNs) draining the site of antigen entry are populated by lymphoid-resident DCs as well as DCs that have immigrated from tissues, although the requirement for each population in initiating the T cell response remains unclear. Here, we show that antigen processing and presentation by both lymphoid-resident and migratory DCs was required for clonal selection and expansion of CD4(+) T cells after subcutaneous immunization. Early antigen presentation by lymphoid-resident DCs initiated activation and trapping of antigen-specific T cells in the draining LN, without sufficing for clonal expansion. Migratory DCs, however, interacted with the CD4(+) T cells retained in the LN to induce proliferation. Therefore, distinct DC subsets cooperate to alert and trap the appropriate cell and then license its expansion and differentiation.

Bridge with a left ventricular assist device to a simultaneous heart and kidney transplant: Review of the United Network for Organ Sharing database.

BACKGROUND: Left ventricular assist device (LVAD) implantation as a bridge to cardiac transplantation (BTT) is an effective treatment for end-stage heart failure patients. Currently, there is an increasing number of patients with a LVAD who need a heart and kidney transplant (HKT). Little is known of the prognostic outcomes in these patients. This study was undertaken to determine whether an equivalent outcome would be present in HKTs as compared to a non-LVAD primary HKT cohort. METHODS: We reviewed the United Network for Organ Sharing database from 2004 to 2013. Orthotropic heart transplant recipients (n = 49 799) were subcategorized as dual organ HKT (n = 1 921) and then divided into cohorts of HKT following continuous flow left ventricular assist device placement (CF-VAD-HKT, n = 113) or no LVAD placement (HKT, n = 1 808). Survival after transplantation was analyzed. RESULTS: For CF-LVAD-HKT and HKT cohorts, preoperative characteristics were similar regarding age (50.8 ± 13.7, 50.1 ± 13.7, p = 0.75) and panel reactive antibody (12.3 ± 18.4 vs 7.1 ± 18.4, p = 0.06). Donors were similar in age, gender, creatinine, and ejection fraction. Post-transplant, there was no difference in complications. Survival for CF-LVAD-HKT and HKT were similar at 1 year (77% vs 82%) and 3 years (75% vs 77%, log rank p = 0.2814). CONCLUSIONS: For patients with advanced heart failure and persistent renal dysfunction, simultaneous HKT is a safe option. Survival after CF-LVAD-HKT is equivalent to conventional HKT.

National outcomes of kidney transplantation from deceased diabetic donors.

Use of deceased diabetic donor kidneys has increased over recent decades. However, scarce patient and allograft survival data are available taking into account recipient diabetes status. Here we performed a retrospective cohort study using data from the United Network of Organ Sharing in patients transplanted from 1994 to 2014. Multivariable Cox regression assessed recipient outcomes of 9074 diabetic vs. 152,555 non-diabetic donor kidneys. Recipients of diabetic donor kidneys had elevated rates of all-cause allograft failure (hazard ratio 1.21, 95% confidence interval 1.16-1.26) and death (1.19, 1.13-1.24) compared to recipients of kidneys from non-diabetic donors. Younger recipients of diabetic donor kidneys had worse allograft survival than older recipients of non-diabetic donor kidneys. There was significant interaction between donor and recipient diabetes status. To minimize the effect of unmeasured confounders, we used paired analyses of recipients of mate-kidneys from the same donor, with one diabetic recipient and the other non-diabetic. Among discordant recipient pairs of diabetic donor kidneys, diabetic recipients had significantly higher risk of allograft failure (1.27, 1.05-1.53) and death (1.53, 1.22-1.93) than non-diabetic recipients. After stratifying by Kidney Donor Profile Index risk category, diabetic recipients of diabetic donor kidneys continued to have worse allograft survival compared to all other patients. Thus, risks are associated with the use of diabetic donor kidneys. Understanding these risks will enable clinicians to better educate potential recipients.Kidney International advance online publication, 21 October 2015; doi:10.1038/ki.2015.325.

Innate immunity in transplant tolerance and rejection.

Historically, research on transplant rejection and tolerance has focused on cells of the adaptive immune system, especially T cells. Anti-graft effector T cells are necessary and sufficient for the rejection of most allografts, while regulatory T cells, either arising naturally or as a result of a specific treatment regimen, are crucial to long-term graft tolerance. Although the role of T cells in transplant rejection and tolerance is well-established, the role that the innate immune system plays in these processes is only recently being appreciated. Cells of the innate immune system, such as dendritic cells (DCs) and natural killer cells, can become activated by microbial products or endogenous pro-inflammatory ligands released during the mechanical and ischemia-reperfusion injury associated with transplantation surgery, promoting the initiation of T-cell responses against the graft. In addition, innate immune cells are required for acute and chronic rejection in certain animal transplant models and by extension perhaps in clinical transplantation. However, innate immune cells are also implicated in the establishment of transplant tolerance through mechanisms including elimination or inhibition of activated host effector T cells and killing of donor DCs. A deeper understanding of the functions of the innate immune system during transplantation may lead to more successful tolerance strategies.