The liver sinusoids are a unique type of microvascular beds. The specialized phenotype of sinusoidal cells is essential for their communication, and for the function of all hepatic cell types, including hepatocytes. Liver sinusoidal endothelial cells (LSECs) conform the inner layer of the sinusoids, which is permeable due to the fenestrae across the cytoplasm; hepatic stellate cells (HSCs) surround LSECs, regulate the vascular tone, and synthetize the extracellular matrix, and Kupffer cells (KCs) are the liver-resident macrophages. Upon injury, the harmonic equilibrium in sinusoidal communication is disrupted, leading to phenotypic alterations that may affect the function of the whole liver if the damage persists. Understanding how the specialized sinusoidal cells work in coordination with each other in healthy livers and chronic liver disease is of the utmost importance for the discovery of new therapeutic targets and the design of novel pharmacological strategies. In this manuscript, we summarize the current knowledge on the role of sinusoidal cells and their communication both in health and chronic liver diseases, and their potential pharmacologic modulation. Finally, we discuss how alterations occurring during chronic injury may contribute to the development of hepatocellular carcinoma, which is usually developed in the background of chronic liver disease.

The poor prognosis of chronic liver disease (CLD) generates the need to investigate the evolving mechanisms of disease progression, thus disclosing therapeutic targets before development of clinical complications. Considering the central role of liver sinusoidal endothelial cells (LSECs) in pre-neoplastic advanced CLD, the present study aimed at investigating the progression of CLD from an endothelial holistic perspective. RNAseq defined the transcriptome of primary LSECs isolated from three pre-clinical models of advanced CLD, during the progression of the disease, and from fresh human cirrhotic tissue. At each stage of the disease, the effects of LSECs secretome on neighboring cells and proteomic analysis of LSECs-derived extracellular vesicles (EVs) were also determined. CLD was associated with deep common modifications in the transcriptome of LSECs in the pre-clinical models. Pathway enrichment analysis showed predominance of genes related with pro-oncogenic, cellular communication processes, and EVs biogenesis during CLD progression. Crosstalk experiments revealed endothelial EVs as potent angiocrine effectors. The proteome of LSECs EVs showed stage-specific signatures, including over-expression of tropomyosin-1. Proof-of-principle experiments treating cirrhotic HSCs with recombinant tropomyosin-1 suggested de-activating effects. Our data provide the basis for discovering novel biomarkers and therapeutic targets for new disease-modifying treatments for patients with advanced CLD.

The elimination of senescent cells by senotherapeutic interventions is being evaluated in several clinical trials for the treatment of age-related diseases; however, these approaches present several limitations, including a low senotherapeutic index (i.e., the safety margin between the dose of the drug that produces a desired effect and the dose that produces unwanted side effects is relatively low) and, in some cases, concerns regarding their elimination. Here, we report a nanoparticle (NP) formulation selected from a library of 42 polymeric NP formulations that is biocompatible, fully degradable, and presents a senotherapeutic index at least 44 times greater than that observed for the soluble drug. The NP is endocytosed by both proliferative and senescent cells, but only in the latter is it degraded at a sufficient level in the endolysosome to release the encapsulated senotherapeutic drug, which can then cross a damaged endolysosomal membrane, reach the cell cytoplasm and induce apoptosis. Importantly, our results show that the release kinetics of the senotherapeutic drug from the NP affect its efficacy. We demonstrate the full potential of this formulation in the aged liver, particularly in the vascular compartment. The NP formulation, which is injected intravenously into naturally aged Wistar rats, accumulates significantly in the aged liver, reducing the senescence burden in the endothelial cell compartment. This contributes to decreases in portal pressure and liver fibrosis. Taken together, the strategy reported here increases the safety and efficacy of pharmacological interventions to treat age-related diseases.