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Heart transplantation is the gold standard for treating patients with advanced heart failure. Although improvements in immunosuppressive therapies have significantly reduced the frequency of cardiac graft rejection, the incidences of T cell-mediated rejection (TCMR) and antibody-mediated rejection remain almost unchanged. A four-archetype analysis (4AA) model, developed by Philip F. Halloran, illustrated this problem well. It provided a new dimension to improve the accuracy of diagnoses and an independent system for recalibrating the histology guidelines. However, this model was based on the invasive method of endocardial biopsy, which undoubtedly increased the postoperative risk of heart transplant patients. Currently, little is known regarding the associated genes and specific functions of the different phenotypes. We performed bioinformatics analysis (using machine-learning methods and the WGCNA algorithm) to screen for hub-specific genes related to different phenotypes, based Gene Expression Omnibus accession number GSE124897. More immune cell infiltration was observed with the ABMR, TCMR, and injury phenotypes than with the stable phenotype. Hub-specific genes for each of the four archetypes were verified successfully using an external test set (accession number GSE2596). Logistic-regression models based on TCMR-specific hub genes and common hub genes were constructed with accurate diagnostic utility (area under the curve > 0.95). RELA, NFKB1, and SOX14 were identified as transcription factors important for TCMR/injury phenotypes and common genes, respectively. Additionally, 11 Food and Drug Administration-approved drugs were chosen from the DrugBank Database for each four-archetype model. Tyrosine kinase inhibitors may be a promising new option for transplant rejection treatment. KRAS signaling in cardiac transplant rejection is worth further investigation. Our results showed that heart transplant rejection subtypes can be accurately diagnosed by detecting expression of the corresponding specific genes, thereby enabling precise treatment or medication.

Solid organ transplantation is more and more frequently done in children. Perioperative care of a child with liver failure undergoing transplantation is discussed. Additional topics reviewed include post-op care of children after cardiac transplantation and intra-op care of a small child receiving an adult-sized renal graft.

Autologous induced pluripotent stem cells (iPSCs) constitute an unlimited cell source for patient-specific cell-based organ repair strategies. However, their generation and subsequent differentiation into specific cells or tissues entail cell line-specific manufacturing challenges and form a lengthy process that precludes acute treatment modalities. These shortcomings could be overcome by using prefabricated allogeneic cell or tissue products, but the vigorous immune response against histo-incompatible cells has prevented the successful implementation of this approach. Here we show that both mouse and human iPSCs lose their immunogenicity when major histocompatibility complex (MHC) class I and II genes are inactivated and CD47 is over-expressed. These hypoimmunogenic iPSCs retain their pluripotent stem cell potential and differentiation capacity. Endothelial cells, smooth muscle cells, and cardiomyocytes derived from hypoimmunogenic mouse or human iPSCs reliably evade immune rejection in fully MHC-mismatched allogeneic recipients and survive long-term without the use of immunosuppression. These findings suggest that hypoimmunogenic cell grafts can be engineered for universal transplantation. Genetic engineering prevents immune rejection of allogeneic cell transplants derived from iPSCs.

After a cardiac transplantation, the steering of immunosuppression requires an active search for acute cellular rejection (ACR). Surveillance with endomyocardial biopsy (EMB) is the gold standard. Given the costs and potential complications, there is growing interest in the use of non-invasive screening methods. Thus, we have conducted a systematic review and meta-analysis to evaluate the role of speckle-tracking echocardiography as a screening method for ACR. We searched PubMed (CENTRAL) and gray literature for studies presenting data on speckle tracking echocardiography in heart-transplant patients experiencing acute cellular rejection. The primary outcomes of the meta-analysis were left and right ventricular global longitudinal strain. We used random effects models for all our calculations. We pre-registered our meta-analysis with PROSPERO (CRD42024508654). By incorporating data from over 2000 biopsies included in 18 studies, we found that both left (LVGLS, MD -1.96, 95% CI -2.85 to -1.07, p  < 0.0001), and right (RVGLS, MD -2.90, 95% CI -4.03 to -1.76, p  < 0.00001) ventricular longitudinal strain were lower among patients without ACR. The change of LVGLS from baseline over time was also greater among patients experiencing ACR (MD -2.43, 95% CI -4.82 to -0.05, p  = 0.045). Current data suggest that myocardial strain measured by speckle tracking echocardiography is affected in ACR and could potentially be used for early rejection detection as a rule-out strategy, leading to reduction of routine EMB in heart transplant follow-up.

Background The diagnosis of acute rejection in cardiac transplant recipients requires invasive technique with endomyocardial biopsy (EMB) which has risks and limitations. Cardiovascular magnetic resonance imaging (CMR) with T2 and T1 mapping is a promising technique for characterizing myocardial tissue. The purpose of the study was to evaluate T2, T1 and extracellular volume fraction (ECV) quantification as novel tissue markers to diagnose acute rejection. Methods CMR was prospectively performed in 20 heart transplant patients providing 31 comparisons EMB-CMR. CMR was performed close to EMB. Images were acquired on a 1.5 Tesla scanner including T2 mapping (T2 prepared balanced steady state free precession) and T1 mapping (modified Look-Locker inversion recovery sequences: MOLLI) at basal, mid and apical level in short axis view. Global and segmental T2 and T1 values were measured before and 15 min (for T1 mapping) after contrast administration. Results Acute rejection was diagnosed in seven patients: six cellular rejections (4 grade IR, 2 grade 2R) and one antibody mediated rejection. Patients with acute rejection had significantly higher global T2 values at 3 levels: 58.5 ms [55.0–60.3] vs 51.3 ms [49.5–55.2] ( p  = 0.007) at basal; 55.7 ms [54.0–59.7] vs 51.8 ms [50.1–53.6] ( p  = 0.002) at median and 58.2 ms [54.0–63.7] vs 53.6 ms [50.8–57.4] ( p  = 0.026) at apical level. The area under the curve (AUC) for each level was 0.83, 0.79 and 0.78 respectively. Patients with acute rejection had significantly higher ECV at basal level: 34.2% [32.8–37.4] vs 27.4% [24.6–30.6] ( p  = 0.006). The AUC for basal level was 0.84. The sensitivity, specificity and diagnosis accuracy for basal T2 (cut off: 57.7 ms) were 71, 96 and 90% respectively; and for basal ECV: (cut off 32%) were 86, 85 and 85% respectively. Combining basal T2 and basal ECV allowed diagnosing all acute rejection and avoiding 63% of EMB. Conclusions In heart transplant patients, a combined CMR approach using T2 mapping and ECV quantification provides a high diagnostic accuracy for acute rejection diagnosis and could potentially decrease the number of routine EMB.

Cardiac magnetic resonance (CMR) has changed the management of suspected viral myocarditis by providing a ‘positive’ diagnostic test and has lead to new insights into myocardial involvement in systemic inflammatory conditions. In this review we analyse the use of CMR tissue characterisation techniques across the available studies including T2 weighted imaging, early gadolinium enhancement, late gadolinium enhancement, Lake Louise Criteria, T2 mapping, T1 mapping and extracellular volume assessment. We also discuss the use of multiparametric CMR in acute cardiac transplant rejection and a variety of inflammatory conditions such as sarcoidosis, systemic lupus erythrematous, rheumatoid arthritis and systemic sclerosis.

Acute antibody-mediated rejection (AAMR) is an important cause of cardiac allograft dysfunction, and more effective strategies need to be explored to improve allograft prognosis. Interleukin (IL)-6/IL-6R signaling plays a key role in the activation of immune cells including B cells, T cells and macrophages, which participate in the progression of AAMR. In this study, we investigated the effect of IL-6/IL-6R signaling blockade on the prevention of AAMR in a mouse model. We established a mouse model of AAMR for cardiac transplantation via presensitization of skin grafts and addition of cyclosporin A, and sequentially analyzed its features. Tocilizumab, anti-IL-6R antibody, and recipient IL-6 knockout were used to block IL-6/IL-6R signaling. We demonstrated that blockade of IL-6/IL-6R signaling significantly attenuated allograft injury and improved survival. Further mechanistic research revealed that signaling blockade decreased B cells in circulation, spleens, and allografts, thus inhibiting donor-specific antibody production and complement activation. Moreover, macrophage, T cell, and pro-inflammatory cytokine infiltration in allografts was also reduced. Collectively, we provided a highly practical mouse model of AAMR and demonstrated that blockade of IL-6/IL-6R signaling markedly alleviated AAMR, which is expected to provide a superior option for the treatment of AAMR in clinic.

Il1rl1 (also known as ST2) is a member of the IL-1 superfamily, and its only known ligand is IL-33. ST2 exists in two forms as splice variants: a soluble form (sST2), which acts as a decoy receptor, sequesters free IL-33, and does not signal, and a membrane-bound form (ST2), which activates the MyD88/NF-κB signaling pathway to enhance mast cell, Th2, regulatory T cell (Treg), and innate lymphoid cell type 2 functions. sST2 levels are increased in patients with active inflammatory bowel disease, acute cardiac and small bowel transplant allograft rejection, colon and gastric cancers, gut mucosal damage during viral infection, pulmonary disease, heart disease, and graft-versus-host disease. Recently, sST2 has been shown to be secreted by intestinal pro-inflammatory T cells during gut inflammation; on the contrary, protective ST2-expressing Tregs are decreased, implicating that ST2/IL-33 signaling may play an important role in intestinal disease. This review will focus on what is known on its signaling during various inflammatory disease states and highlight potential avenues to intervene in ST2/IL-33 signaling as treatment options.

Cardiovascular magnetic resonance (CMR) is emerging as an important tool for cardiac allograft assessment. Native T1 mapping may add value in identifying rejection and in assessing graft dysfunction and myocardial fibrosis burden. We hypothesized that CMR native T1 values and features of textural analysis of T1 maps would identify acute rejection, and in a secondary analysis, correlate with markers of graft dysfunction, and with fibrosis percentage from endomyocardial biopsy (EMB). Fifty cases with simultaneous EMB, right heart catheterization, and 1.5 T CMR with breath-held T1 mapping via modified Look-Locker inversion recovery (MOLLI) in 8 short-axis slices and subsequent quantification of mean and peak native T1 values, were performed on 24 pediatric subjects. A single mid-ventricular slice was used for image texture analysis using nine gray-level co-occurrence matrix features. Digital quantification of Masson trichrome stained EMB samples established degree of fibrosis. Markers of graft dysfunction, including serum brain natriuretic peptide levels and hemodynamic measurements from echocardiography, catheterization, and CMR were collated. Subjects were divided into three groups based on degree of rejection: acute rejection requiring new therapy, mild rejection requiring increased ongoing therapy, and no rejection with no change in treatment. Statistical analysis included student’s t-test and linear regression. Peak and mean T1 values were significantly associated with acute rejection, with a monotonic trend observed with increased grade of rejection. Texture analysis demonstrated greater spatial heterogeneity in T1 values, as demonstrated by energy, entropy, and variance, in cases requiring treatment. Interestingly, 2 subjects who required increased therapy despite low grade EMB results had abnormal peak T1 values. Peak T1 values also correlated with increased BNP, right-sided filling pressures, and capillary wedge pressures. There was no difference in histopathological fibrosis percentage among the 3 groups; histopathological fibrosis did not correlate with T1 values or markers of graft dysfunction. In pediatric heart transplant patients, native T1 values identify acute rejection requiring treatment and may identify graft dysfunction. CMR shows promise as an important tool for evaluation of cardiac grafts in children, with T1 imaging outperforming biopsy findings in the assessment of rejection.

Cardiac allograft rejection remains a major cause of graft dysfunction post-transplant. While histology is the current diagnostic standard, it may miss early immune and inflammatory events. This study evaluated the immunohistochemical expression of matrix metalloproteinases 2 (MMP2), 9 (MMP9), and interleukin-1 beta (IL-1β) in cardiac transplant patients, correlating their expression with acute cellular rejection (ACR), antibody-mediated rejection (AMR), inflammation, vasculitis, the Quilty effect, and immune markers. Fifty-nine endomyocardial biopsy specimens were retrospectively analyzed. Immunohistochemical staining for MMP2, MMP9, and IL-1β was assessed based on nuclear, cytoplasmic, and membranous expression. Correlations were evaluated using Fisher’s exact test and odds ratios (ORs) with 95% confidence intervals (CIs). IL-1β nuclear expression showed strong associations with ACR (p = 0.0001), inflammation, vasculitis, and immune/endothelial markers (all p < 0.003). Nuclear MMP9 expression correlated with ACR and immune cell markers and was borderline significant for AMR (p ≈ 0.05). Cytoplasmic MMP2 (>50%) was significantly associated with AMR (OR = 7.47, p = 0.0002). No marker correlated with the Quilty effect. The immunohistochemical profiles of IL-1β and MMP9 support their involvement in immune-mediated injury in cardiac allograft rejection, with IL-1β emerging as a sensitive marker of early inflammation. MMP2 appears to be more relevant to humoral rejection processes. These findings suggest that selected tissue biomarkers may enhance diagnostic precision and support early detection of graft injury when integrated with conventional histology.