The liver is the largest solid organ in the body and is critical for metabolic and immune functions. However, little is known about the cells that make up the human liver and its immune microenvironment. Here we report a map of the cellular landscape of the human liver using single-cell RNA sequencing. We provide the transcriptional profiles of 8444 parenchymal and non-parenchymal cells obtained from the fractionation of fresh hepatic tissue from five human livers. Using gene expression patterns, flow cytometry, and immunohistochemical examinations, we identify 20 discrete cell populations of hepatocytes, endothelial cells, cholangiocytes, hepatic stellate cells, B cells, conventional and non-conventional T cells, NK-like cells, and distinct intrahepatic monocyte/macrophage populations. Together, our study presents a comprehensive view of the human liver at single-cell resolution that outlines the characteristics of resident cells in the liver, and in particular provides a map of the human hepatic immune microenvironment.

The critical functions of the human liver are coordinated through the interactions of hepatic parenchymal and non‐parenchymal cells. Recent advances in single‐cell transcriptional approaches have enabled an examination of the human liver with unprecedented resolution. However, dissociation‐related cell perturbation can limit the ability to fully capture the human liver’s parenchymal cell fraction, which limits the ability to comprehensively profile this organ. Here, we report the transcriptional landscape of 73,295 cells from the human liver using matched single‐cell RNA sequencing (scRNA‐seq) and single‐nucleus RNA sequencing (snRNA‐seq). The addition of snRNA‐seq enabled the characterization of interzonal hepatocytes at a single‐cell resolution, revealed the presence of rare subtypes of liver mesenchymal cells, and facilitated the detection of cholangiocyte progenitors that had only been observed during in vitro differentiation experiments. However, T and B lymphocytes and natural killer cells were only distinguishable using scRNA‐seq, highlighting the importance of applying both technologies to obtain a complete map of tissue‐resident cell types. We validated the distinct spatial distribution of the hepatocyte, cholangiocyte, and mesenchymal cell populations by an independent spatial transcriptomics data set and immunohistochemistry. Conclusion: Our study provides a systematic comparison of the transcriptomes captured by scRNA‐seq and snRNA‐seq and delivers a high‐resolution map of the parenchymal cell populations in the healthy human liver.

Plasmodium falciparum is the most lethal form of malaria and is increasing both in incidence and in its resistance to antimalarial agents. An improved understanding of the mechanisms of malarial clearance may facilitate the development of new therapeutic interventions. We postulated that the scavenger receptor CD36, an important factor in cytoadherence of P falciparum–parasitized erythrocytes (PEs), might also play a role in monocyte- and macrophage-mediated malarial clearance. Exposure of nonopsonized PEs to Fc receptor–blocked monocytes resulted in significant PE phagocytosis, accompanied by intense clustering of CD36 around the PEs. Phagocytosis was blocked 60% to 70% by monocyte pretreatment with monoclonal anti-CD36 antibodies but not by antibodies to αvβ3, thrombospondin, intercellular adhesion molecule-1, or platelet/endothelial cell adhesion molecule-1. Antibody-induced CD36 cross-linking did result in the early increase of surface CD11b expression, but there was no increase in, or priming for, tumor necrosis factor (TNF)-α secretion following either CD36 cross-linking or PE phagocytosis. CD36 clustering does support intracellular signaling: Antibody-induced cross-linking initiated intracellular tyrosine phosphorylation as well as extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) phosphorylation. Both broad-spectrum tyrosine kinase inhibition (genistein) and selective ERK and p38 MAPK inhibition (PD98059 and SB203580, respectively) reduced PE uptake to almost the same extent as CD36 blockade. Thus, CD36-dependent binding and signaling appears to be crucial for the nonopsonic clearance of PEs and does not appear to contribute to the increase in TNF-α that is prognostic of poor outcome in clinical malaria.

Background & Aim: Radiofrequency ablation (RFA) is an effective treatment for single hepatocellular carcinoma (HCC) 3cm. Disease recurrence is common, and in some patients will occur outside transplant criteria. We aimed to assess the incidence and risk factors for recurrence beyond Milan criteria (MC) in potentially transplantable patients treated with RFA as first-line therapy.Methods: We performed a retrospective cohort study of potentially transplantable patients with new diagnoses of unifocal HCC 3cm that underwent RFA as first-line therapy between 2000-2015. We defined potentially transplantable patients as those aged <70 years without any comorbidities that would preclude transplant surgery. Incidence of recurrence beyond MC was compared across two groups according to HCC diameter at the time of ablation: (HCC 2cm vs. HCC>2cm). Competing risks Cox regression was used to identify predictors of recurrence beyond MC. Results: We included 301 patients (167 134 HCC>2cm). Recurrence beyond MC respectively (p=0.01). The 1-, 3-and 5-years actuarial survival after RFA was 98.2%, 86.2% and (p=0.01). Tumor size >2cm [HR 1.94 (95%CI 1.25-3.02)] and alpha fetoprotein levels at the time of ablation [100-1000ng/mL: HR 2.05 (95%CI 1.10-3.83)] were found to be predictors of post-RFA recurrence outside MC. Conclusion: RFA for single HCC 3cm provides excellent short-to medium-term survival.However, we identified patients at higher risk of recurrence beyond MC. For these patients, liver transplantation should be considered right after the first HCC recurrence after RFA. HighlightsMost transplantable RFA will eventually develop recurrent HCC distant to the ablation site.Many transplantable patients treated with HCC will recur beyond the Milan criteria despite close post-RFA surveillance, losing the opportunity for cure.Transplantable patients with tumors >2cm and higher serum alpha fetoprotein have higher risk of recurrence beyond Milan criteria. Highlightswill eventually develop recurrent HCC distant to the ablation site.Many transplantable patients treated with HCC will recur beyond the Milan criteria despite close post-RFA surveillance, losing the opportunity for cure.Transplantable patients with tumors >2cm and higher serum alpha fetoprotein have higher risk of recurrence beyond Milan criteria.