Our evolution in the treatment of hepatic artery and portal vein thrombosis in pediatric liver transplantation: Success with catheter-directed therapies.

BACKGROUND: In pediatric liver transplant recipients, hepatic artery thrombosis and portal vein thrombosis are major causes of acute graft failure and mortality within 30 days of transplantation. There is, however, a strong possibility of graft salvage if flow can be re-established to reduce ischemic injury. The current standard treatment is surgical revascularization, and if unsuccessful, retransplantation. Due to our success in treating these complications with catheter-directed therapies, we sought to summarize and publish the outcomes of all patients who experienced hepatic artery thrombosis or portal vein thrombosis within 30 days of liver transplantation. METHODS: We conducted a retrospective cohort analysis of 27 pediatric liver transplant recipients who experienced hepatic artery thrombosis (n = 13), portal vein thrombosis (n = 9), or both (n = 5) between September 2012 and March 2021. We collected and tabulated data on the patients and therapies performed to treat them, including success rates, primary and secondary patency, and clinical outcomes. RESULTS: Among these patients, 6 were managed with anticoagulation and relisting for transplant and 21 had a primary revascularization attempt. Surgical recanalization was attempted in 7 patients of which 3 had successful recanalization (43%) and catheter-directed recanalization was attempted in 14 patients with 100% success in re-establishing blood flow to the graft. Additionally, patency was increased, and mortality was decreased in patients treated with catheter-directed recanalization compared to surgical revascularization or anticoagulation alone. CONCLUSION: This data illustrates the need to further investigate catheter-directed thrombolysis as a potential first-line treatment for postoperative HAT and PVT in pediatric liver transplant recipients.

Liver transplant in a recently COVID-19 positive child with hepatoblastoma.

We describe the successful pediatric liver transplant for unresectable hepatoblastoma in a 4-year-old male with COVID-19 prior to transplant. The first negative NP swab was documented 1 month after initial diagnosis, when SARS-CoV-2 antibodies were also detected. The patient was actively listed for liver transplant after completing four blocks of a SIOPEL-4 based regimen due to his PRETEXT IV disease which remained unresectable. Following three additional negative NP swabs and resolution of symptoms for 4 weeks, he underwent a whole-organ pediatric liver transplant. COVID-19 positivity determined via NP swab SARS-CoV-2 real-time RT-PCR (Hologic Aptima SARS-CoV-2 RT-PCR assay). IgG and IgM total SARS- CoV-2 antibodies detected by Ortho Clinical Diagnostics VITROS® Immunodiagnostics Products Anti-SARS-CoV-2 Test. Patient received standard prednisone and tacrolimus-based immunosuppression without induction therapy following transplant. Post-transplant course was remarkable for neutropenia and thrombocytopenia, with discharge home on post-transplant day #11. Surveillance tests have remained negative with persistent SARS-CoV-2 IgG antibodies at 6 weeks after transplant. We describe one of the earliest, if not the first case of liver transplant following recent recovery from COVID-19 in a pediatric patient with a lethal malignant liver tumor. A better understanding of how to balance the risk profile of transplant in the setting of COVID-19 with disease progression if transplant is not performed is needed. We followed existing ASTS guidelines to document clearance of the viral infection and resolution of symptoms before transplant. This case highlights that pediatric liver transplantation can be safely performed upon clearance of COVID-19.

The pediatric solid organ transplant experience with COVID-19: An initial multi-center, multi-organ case series.

The clinical course of COVID-19 in pediatric solid organ transplant recipients remains ambiguous. Though preliminary experiences with adult transplant recipients have been published, literature centered on the pediatric population is limited. We herein report a multi-center, multi-organ cohort analysis of COVID-19-positive transplant recipients ≤ 18 years at time of transplant. Data were collected via institutions' respective electronic medical record systems. Local review boards approved this cross-institutional study. Among 5 transplant centers, 26 patients (62% male) were reviewed with a median age of 8 years. Six were heart recipients, 8 kidney, 10 liver, and 2 lung. Presenting symptoms included cough (n = 12 (46%)), fever (n = 9 (35%)), dry/sore throat (n = 3 (12%)), rhinorrhea (n = 3 (12%)), anosmia (n = 2 (8%)), chest pain (n = 2 (8%)), diarrhea (n = 2 (8%)), dyspnea (n = 1 (4%)), and headache (n = 1 (4%)). Six patients (23%) were asymptomatic. No patient required supplemental oxygen, intubation, or ECMO. Eight patients (31%) were hospitalized at time of diagnosis, 3 of whom were already admitted for unrelated problems. Post-transplant immunosuppression was reduced for only 2 patients (8%). All symptomatic patients recovered within 7 days. Our multi-institutional experience suggests the prognoses of pediatric transplant recipients infected with COVID-19 may mirror those of immunocompetent children, with infrequent hospitalization and minimal treatment, if any, required.

Donor and transplant candidate selection for solid organ transplantation during the COVID-19 pandemic.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), a novel coronavirus responsible for a worldwide pandemic has forced drastic changes in medical practice in an alarmingly short period of time. Caregivers must modify their strategies as well as optimize the utilization of resources to ensure public and patient safety. For organ transplantation, in particular, the loss of lifesaving organs for transplantation could lead to increased waitlist mortality. The priority is to select uninfected donors to transplant uninfected recipients while maintaining safety for health care systems in the backdrop of a virulent pandemic. We do not yet have a standard approach to evaluating donors and recipients with possible SARS-CoV-2 infection. Our current communication shares a protocol for donor and transplant recipient selection during the coronavirus disease 2019 (COVID-19) pandemic to continue lifesaving solid organ transplantation for heart, lung, liver, and kidney recipients. The initial results using this protocol are presented here and meant to encourage dialogue between providers, offering ideas to improve safety in solid organ transplantation with limited health care resources. This protocol was created utilizing the guidelines of various organizations and from the clinical experience of the authors and will continue to evolve as more is understood about SARS-CoV-2 and how it affects organ donors and transplant recipients.

Doppler ultrasound for post-angioplasty follow-up in pediatric segmental branch renal artery stenosis: A case report.

INTRODUCTION: Segmental branch renal artery stenosis is an important cause of renovascular hypertension in the pediatric population that is often managed with angioplasty and may require imaging multiple times pre- and post-procedure. Gold standard imaging is angiography, which exposes children to radiation and intravenous contrast. There is not a clear guideline for imaging during follow-up, but patients are monitored for symptom recurrence, which could then trigger repeat imaging. The following case highlights a method of follow-up that has not been broadly studied that may offer benefits over clinical monitoring alone, and how interprofessional cooperation could offer effective surveillance and reassurance for families through a cost-effective method that minimizes potential for harm. CASE AND OUTCOMES: This report describes the clinical course of a child with hypertension secondary to segmental branch renal artery stenosis who was treated with angioplasty and who received follow-up imaging with renal Doppler ultrasound. This method allows the care team to ensure stability of the caliber of the repaired vessel and non-recurrence of stenosis at follow-ups through monitoring for intra-arterial velocity and waveform changes. DISCUSSION: Close follow-up of children with renal artery stenosis is vital following intervention due to high risk of recurrence. Clinical follow-up alone could be sufficient for some patients, however many still require CTA, sometimes even more than once, when symptoms worsen or there is evidence of end-organ damage. During follow-up, collaboration with skilled sonographers to monitor post-repair velocities and waveforms using Doppler ultrasound presents several possible advantages. This includes providing reassurance to patient families, minimizing harmful radiation and contrast exposure, and the potential for early detection of recurrence of stenosis. Especially in cooperative, older pediatric patients with a normal BMI who have a main renal artery stenosis or even in those with a segmental branch stenosis identified through CTA such as in this case. CONCLUSION: This case demonstrates how coordination with sonographers and the use of ultrasound with Doppler could improve the follow-up of pediatric patients with segmental branch renal artery stenosis post-angioplasty to provide further reassurance to families, minimize harm to patients, and ensure post-procedure stability beyond just clinical parameters.

COVID-19 Vaccine Efficacy and Immunogenicity in End-Stage Renal Disease Patients and Kidney Transplant Recipients.

Purpose of Review: To summarize the current literature with respect to COVID-19 vaccine efficacy patients with end-stage renal disease on dialysis and kidney transplant recipients. Recent Findings: Immunosuppressed patients are at greater risk of morbidity and mortality from COVID-19 infection. Patients with ESRD and KTR are immunosuppressed and mount a weaker antibody response to COVID-19 mRNA vaccination, and factors including immunosuppressant medications have been implicated for this weakened response. Third and fourth doses of vaccine doses have been shown to increase seropositivity and antibody production in kidney transplant recipients and patients on dialysis. Retrospective studies have demonstrated decreased mortality in vaccinated, immunosuppressed patients. Summary: ESRD and KTR patients have decreased antibody response to COVID-19 vaccines, but third and fourth doses have been shown to increase antibody production. Though a correlate of protection between antibody production and efficacy has yet to be fully established in this subset of the population, all US professional bodies who treat ESRD and KTR patients advocate for full vaccination against SARS-CoV-2 based on the data available. Studies demonstrating decreased mortality in vaccinated patients are promising on efficacy. Importantly, because KTR patients mount a weaker antibody response than ESRD patients, vaccination prior to kidney transplantation is critical.

Splenic Artery Transposition for Liver Transplantation: An Underutilized Technique?

BACKGROUND: Successful liver transplantation is dependent on restoration of hepatic arterial (HA) flow. Although uncommon, some native recipient HAs are not suitable or inadequate for anastomosis, thereby necessitating extra-anatomic HA reconstruction. Splenic artery transposition (SAT) is 1 method of HA reconstruction, in which the recipient splenic artery is transposed to reestablish perfusion of the donor liver. Due to the rarity of the technique, literature describing outcomes is limited. In the current report, we describe 3 patients (2 adults, 1 pediatric) who underwent complex upper abdominal surgery before whole-organ deceased donor liver transplantation with SAT. METHODS: The demographic and patient care information was collected prospectively and subsequently reviewed retrospectively. Given the de-identified nature of the data included, this study was exempt from approval from an ethics board. RESULTS: Recipient splenic arteries were dissected from their origin at the celiac trunk, for approximately 3-5 cm to ensure a gentle anterior-cranial curve toward the right upper quadrant, allowing anastomosis to the donor celiac trunk in an end-to-end fashion. Postoperatively, all 3 patients had rapid normalization of liver function tests and brisk HA flow demonstrated by Doppler ultrasound. Longer-term follow-up, ranging from 1 to 3 years, reveals continued patency of the reconstructed HAs and liver function tests within normal limits. CONCLUSIONS: Our experience points to SAT as a safe and effective technique for extra-anatomic HA reconstruction.

Management of Acute Portal Vein Thrombosis With Serial Mechanical Thrombectomy and tPA in a Pediatric Liver Transplant Recipient: A Case Report.

BACKGROUND: Acute portal vein thrombosis is a major cause of fulminant allograft failure in pediatric liver transplantation. Timely intervention is critical to save the graft and patient. Serial interventional radiologic management of this condition is scarcely reported in the literature. CASE SUMMARY: A recently transplanted 17-year-old male presented to the emergency department with abdominal pain. Rising liver enzymes prompted discovery of a diffuse portal thrombus, which precipitated fulminant liver failure. The adolescent developed respiratory failure, vasodilatory shock, acute kidney injury, and hepatic encephalopathy, complicating treatment. Multiple interventions attempted to clear the thrombus, including interventional radiologic and medical therapies. Uniquely, a continuous infusion catheter was placed at the thrombosis, delivering local tissue plasminogen activator during a 5-day period. Upon thrombus clearance, the patient made a full recovery with no complications during 12 months of follow-up. CONCLUSIONS: When used as a component of multidisciplinary management, continuous locally directed tissue plasminogen activator may be a useful tool for clearance of persistent portal vein thrombosis.

Chitinase 3-like-1 contributes to acetaminophen-induced liver injury by promoting hepatic platelet recruitment.

Background: Hepatic platelet accumulation contributes to acetaminophen (APAP)-induced liver injury (AILI). However, little is known about the molecular pathways involved in platelet recruitment to the liver and whether targeting such pathways could attenuate AILI. Methods: Mice were fasted overnight before intraperitoneally (i.p.) injected with APAP at a dose of 210 mg/kg for male mice and 325 mg/kg for female mice. Platelets adherent to Kupffer cells were determined in both mice and patients overdosed with APAP. The impact of α-chitinase 3-like-1 (α-Chi3l1) on alleviation of AILI was determined in a therapeutic setting, and liver injury was analyzed. Results: The present study unveiled a critical role of Chi3l1 in hepatic platelet recruitment during AILI. Increased Chi3l1 and platelets in the liver were observed in patients and mice overdosed with APAP. Compared to wild-type (WT) mice, Chil1-/- mice developed attenuated AILI with markedly reduced hepatic platelet accumulation. Mechanistic studies revealed that Chi3l1 signaled through CD44 on macrophages to induce podoplanin expression, which mediated platelet recruitment through C-type lectin-like receptor 2. Moreover, APAP treatment of Cd44-/- mice resulted in much lower numbers of hepatic platelets and liver injury than WT mice, a phenotype similar to that in Chil1-/- mice. Recombinant Chi3l1 could restore hepatic platelet accumulation and AILI in Chil1-/- mice, but not in Cd44-/- mice. Importantly, we generated anti-Chi3l1 monoclonal antibodies and demonstrated that they could effectively inhibit hepatic platelet accumulation and AILI. Conclusions: We uncovered the Chi3l1/CD44 axis as a critical pathway mediating APAP-induced hepatic platelet recruitment and tissue injury. We demonstrated the feasibility and potential of targeting Chi3l1 to treat AILI. Funding: ZS received funding from NSFC (32071129). FWL received funding from NIH (GM123261). ALFSG received funding from NIDDK (DK 058369). ZA received funding from CPRIT (RP150551 and RP190561) and the Welch Foundation (AU-0042-20030616). CJ received funding from NIH (DK122708, DK109574, DK121330, and DK122796) and support from a University of Texas System Translational STARs award. Portions of this work were supported with resources and the use of facilities of the Michael E. DeBakey VA Medical Center and funding from Department of Veterans Affairs I01 BX002551 (Equipment, Personnel, Supplies). The contents do not represent the views of the US Department of Veterans Affairs or the US Government.

Acetaminophen, also called paracetamol outside the United States, is a commonly used painkiller, with over 50 million people in the United States taking the drug weekly. While paracetamol is safe at standard doses, overdose can cause acute liver failure, which leads to 30,000 patients being admitted to emergency care in the United States each year. There is only one approved antidote to overdoses, which becomes significantly less effective if its application is delayed by more than a few hours. This has incentivized research into identify new drug targets that could lead to additional treatment options. Acetaminophen overdose triggers blood clotting and inflammation, contributing to liver injury. It also causes a decrease in cells called platelets circulating in the blood, which has been observed in both mice and humans. In mice, this occurs because platelets accumulate in the liver. Removing these excess cells appears to reduce the severity of the damage caused by acetaminophen, but it remains unclear how the drug triggers their accumulation in the liver. In 2018, researchers showed that a protein called Chi3l1 plays an important role in another form of liver damage. Shan et al. ­ including many of the researchers involved in the 2018 study ­ have examined whether the protein also contributes to acetaminophen damage in the liver. Shan et al. showed that mice lacking the gene that codes for Chi3l1 developed less severe liver injury and had fewer platelets in the liver following acetaminophen overdose. They also found that human patients with acute liver failure due to acetaminophen had high levels of Chi3l1 and significant accumulation of platelets in the liver. To test whether damage could be prevented, Shan et al. used antibodies to neutralize Chi3l1 in mice after giving them an acetaminophen overdose. This reduced platelet accumulation in the liver and the associated damage. These findings suggest that targeting Chi3l1 may be an effective strategy to prevent liver damage caused by acetaminophen overdose. Further research could help develop new treatments for acetaminophen-induced liver injury and perhaps other liver conditions.

Eosinophils attenuate hepatic ischemia-reperfusion injury in mice through ST2-dependent IL-13 production.

Eosinophils are a myeloid cell subpopulation that mediates type 2 T helper cell immune responses. Unexpectedly, we identified a rapid accumulation of eosinophils in 22 human liver grafts after hepatic transplantation. In contrast, no eosinophils were detectable in healthy liver tissues before transplantation. Studies with two genetic mouse models of eosinophil deficiency and a mouse model of antibody-mediated eosinophil depletion revealed exacerbated liver injury after hepatic ischemia and reperfusion. Adoptive transfer of bone marrow-derived eosinophils normalized liver injury of eosinophil-deficient mice and reduced hepatic ischemia and reperfusion injury in wild-type mice. Mechanistic studies combining genetic and adoptive transfer approaches identified a critical role of suppression of tumorigenicity (ST2)-dependent production of interleukin-13 by eosinophils in the hepatoprotection against ischemia-reperfusion-induced injury. Together, these data provide insight into a mechanism of eosinophil-mediated liver protection that could serve as a therapeutic target to improve outcomes of patients undergoing liver transplantation.

Human cord blood-derived regulatory T-cell therapy modulates the central and peripheral immune response after traumatic brain injury.

Traumatic brain injury (TBI) causes a profound inflammatory response within the central nervous system and peripheral immune system, which contributes to secondary brain injury and further morbidity and mortality. Preclinical investigations have demonstrated that treatments that downregulate microglia activation and polarize them toward a reparative/anti-inflammatory phenotype have improved outcomes in preclinical models. However, no therapy to date has translated into proven benefits in human patients. Regulatory T cells (Treg) have been shown to downregulate pathologic immune responses of the innate and adaptive immune system across a variety of pathologies. Furthermore, cellular therapy has been shown to augment host Treg responses in preclinical models; yet, studies investigating the use of Treg as a therapeutic for TBI are lacking. In a rodent TBI model, we demonstrate that human umbilical cord blood Treg modulate the central and peripheral immune response after injury in vitro and in vivo.

Efficient correction of a deleterious point mutation in primary horse fibroblasts with CRISPR-Cas9.

Phenotypic selection during animal domestication has resulted in unwanted incorporation of deleterious mutations. In horses, the autosomal recessive condition known as Glycogen Branching Enzyme Deficiency (GBED) is the result of one of these deleterious mutations (102C > A), in the first exon of the GBE1 gene (GBE1102C>A). With recent advances in genome editing, this type of genetic mutation can be precisely repaired. In this study, we used the RNA-guided nuclease CRISPR-Cas9 (clustered regularly-interspaced short palindromic repeats/CRISPR-associated protein 9) to correct the GBE1102C>A mutation in a primary fibroblast cell line derived from a high genetic merit heterozygous stallion. To correct this mutation by homologous recombination (HR), we designed a series of single guide RNAs (sgRNAs) flanking the mutation and provided different single-stranded donor DNA templates. The distance between the Cas9-mediated double-stranded break (DSB) to the mutation site, rather than DSB efficiency, was the primary determinant for successful HR. This framework can be used for targeting other harmful diseases in animal populations.