The endothelial protein PLVAP in lymphatics controls the entry of lymphocytes and antigens into lymph nodes.

In the lymphatic sinuses of draining lymph nodes, soluble lymph-borne antigens enter the reticular conduits in a size-selective manner and lymphocytes transmigrate to the parenchyma. The molecular mechanisms that control these processes are unknown. Here we unexpectedly found that PLVAP, a prototypic endothelial protein of blood vessels, was synthesized in the sinus-lining lymphatic endothelial cells covering the distal conduits. In PLVAP-deficient mice, both small antigens and large antigens entered the conduit system, and the transmigration of lymphocytes through the sinus floor was augmented. Mechanistically, the filtering function of the lymphatic sinus endothelium was dependent on diaphragms formed by PLVAP fibrils in transendothelial channels. Thus, in the lymphatic sinus, PLVAP forms a physical sieve that regulates the parenchymal entry of lymphocytes and soluble antigens.

Stabilin-1 expression defines a subset of macrophages that mediate tissue homeostasis and prevent fibrosis in chronic liver injury.

Macrophages are key regulators of fibrosis development and resolution. Elucidating the mechanisms by which they mediate this process is crucial for establishing their therapeutic potential. Here, we use experimental models of liver fibrosis to show that deficiency of the scavenger receptor, stabilin-1, exacerbates fibrosis and delays resolution during the recovery phase. We detected a subset of stabilin-1(+) macrophages that were induced at sites of cellular injury close to the hepatic scar in mouse models of liver fibrosis and in human liver disease. Stabilin-1 deficiency abrogated malondialdehyde-LDL (MDA-LDL) uptake by hepatic macrophages and was associated with excess collagen III deposition. Mechanistically, the lack of stabilin-1 led to elevated intrahepatic levels of the profibrogenic chemokine CCL3 and an increase in GFAP(+) fibrogenic cells. Stabilin-1(-/-) macrophages demonstrated a proinflammatory phenotype during liver injury and the normal induction of Ly6C(lo) monocytes during resolution was absent in stabilin-1 knockouts leading to persistence of fibrosis. Human stabilin-1(+) monocytes efficiently internalized MDA-LDL and this suppressed their ability to secrete CCL3, suggesting that loss of stabilin-1 removes a brake to CCL3 secretion. Experiments with cell-lineage-specific knockouts revealed that stabilin-1 expression in myeloid cells is required for the induction of this subset of macrophages and that increased fibrosis occurs in their absence. This study demonstrates a previously unidentified regulatory pathway in fibrogenesis in which a macrophage scavenger receptor protects against organ fibrosis by removing fibrogenic products of lipid peroxidation. Thus, stabilin-1(+) macrophages shape the tissue microenvironment during liver injury and healing.

Aeroallergen challenge promotes dendritic cell proliferation in the airways.

Aeroallergen provocation induces the rapid accumulation of CD11c(+)MHC class II (MHC II)(+) dendritic cells (DCs) in the lungs, which is driven by an increased recruitment of blood-derived DC precursors. Recent data show, however, that well-differentiated DCs proliferate in situ in various tissues. This may also contribute to their allergen-induced expansion; therefore, we studied DC proliferation in the airways of mice in the steady state and after local aeroallergen provocation. Confocal whole-mount microscopy was used to visualize proliferating DCs in different microanatomical compartments of the lung. We demonstrate that in the steady state, CD11c(+)MHC II(+) DCs proliferate in both the epithelial and subepithelial layers of the airway mucosa as well as in the lung parenchyma. A 1-h pulse of the nucleotide 5-ethynyl-2'-deoxyuridine was sufficient to label 5% of DCs in both layers of the airway mucosa. On the level of whole-lung tissue, 3-5% of both CD11b(+) and CD11b(-) DC populations and 0.3% of CD11c(+)MHC II(low) lung macrophages incorporated 5-ethynyl-2'-deoxyuridine. Aeroallergen provocation caused a 3-fold increase in the frequency of locally proliferating DCs in the airway mucosa. This increase in mucosal DC proliferation was later followed by an elevation in the number of DCs. The recruitment of monocyte-derived inflammatory DCs contributed to the increasing number of DCs in the lung parenchyma, but not in the airway mucosa. We conclude that local proliferation significantly contributes to airway DC homeostasis in the steady state and that it is the major mechanism underlying the expansion of the mucosal epithelial/subepithelial DC network in allergic inflammation.

Gellan gum-gelatin based cardiac models support formation of cellular networks and functional cardiomyocytes.

Cardiovascular diseases remain as the most common cause of death worldwide. To reveal the underlying mechanisms in varying cardiovascular diseases, in vitro models with cells and supportive biomaterial can be designed to recapitulate the essential components of human heart. In this study, we analyzed whether 3D co-culture of cardiomyocytes (CM) with vascular network and with adipose tissue-derived mesenchymal stem/stromal cells (ASC) can support CM functionality. CM were cultured with either endothelial cells (EC) and ASC or with only ASC in hydrazide-modified gelatin and oxidized gellan gum hybrid hydrogel to form cardiovascular multiculture and myocardial co-culture, respectively. We studied functional characteristics of CM in two different cellular set-ups and analyzed vascular network formation, cellular morphology and orientation. The results showed that gellan gum-gelatin hydrogel supports formation of two different cellular networks and functional CM. We detected formation of a modest vascular network in cardiovascular multiculture and extensive ASC-derived alpha smooth muscle actin -positive cellular network in multi- and co-culture. iPSC-CM showed elongated morphology, partly aligned orientation with the formed networks and presented normal calcium transients, beating rates, and contraction and relaxation behavior in both setups. These 3D cardiac models provide promising platforms to study (patho) physiological mechanisms of cardiovascular diseases. Supplementary Information: The online version contains supplementary material available at 10.1007/s10616-024-00630-5.

Coronary artery disease patient-derived iPSC-hepatocytes have distinct miRNA profile that may alter lipid metabolism.

Metabolic dysfunction, partly driven by altered liver function, predisposes to coronary artery disease (CAD), but the role of liver in vulnerable atherosclerotic plaque development remains unclear. Here we produced hepatocyte-like cells (HLCs) from 27 induced pluripotent stem cell (iPSC) lines derived from 15 study subjects with stable CAD (n = 5), acute CAD (n = 5) or healthy controls (n = 5). We performed a miRNA microarray screening throughout the differentiation, as well as compared iPSC-HLCs miRNA profiles of the patient groups to identify miRNAs involved in the development of CAD. MicroRNA profile changed during differentiation and started to resemble that of the primary human hepatocytes. In the microarray, 35 and 87 miRNAs were statistically significantly deregulated in the acute and stable CAD patients, respectively, compared to controls. Down-regulation of miR-149-5p, -92a-3p and -221-3p, and up-regulation of miR-122-5p was verified in the stable CAD patients when compared to other groups. The predicted targets of deregulated miRNAs were enriched in pathways connected to insulin signalling, inflammation and lipid metabolism. The iPSC-HLCs derived from stable CAD patients with extensive lesions had a distinct genetic miRNA profile possibly linked to metabolic dysfunction, potentially explaining the susceptibility to developing CAD. The iPSC-HLCs from acute CAD patients with only the acute rupture in otherwise healthy coronaries did not present a distinct miRNA profile, suggesting that hepatic miRNAs do not explain susceptibility to plaque rupture.

The Junctophilin-2 Mutation p.(Thr161Lys) Is Associated with Hypertrophic Cardiomyopathy Using Patient-Specific iPS Cardiomyocytes and Demonstrates Prolonged Action Potential and Increased Arrhythmogenicity.

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic cardiac diseases; it is primarily caused by mutations in sarcomeric genes. However, HCM is also associated with mutations in non-sarcomeric proteins and a Finnish founder mutation for HCM in non-sarcomeric protein junctophilin-2 (JPH2) has been identified. This study aimed at assessing the issue of modelling the rare Finnish founder mutation in cardiomyocytes (CMs) differentiated from iPSCs; therefore, presenting the same cardiac abnormalities observed in the patients. To explore the abnormal functions in JPH2-HCM, skin fibroblasts from a Finnish patient with JPH2 p.(Thr161Lys) were reprogrammed into iPSCs and further differentiated into CMs. As a control line, an isogenic counterpart was generated using the CRISPR/Cas9 genome editing method. Finally, iPSC-CMs were evaluated for the morphological and functional characteristics associated with JPH2 mutation. JPH2-hiPSC-CMs displayed key HCM hallmarks (cellular hypertrophy, multi-nucleation, sarcomeric disarray). Moreover, JPH2-hiPSC-CMs exhibit a higher degree of arrhythmia and longer action potential duration associated with slower inactivation of calcium channels. Functional evaluation supported clinical observations, with differences in beating characteristics when compared with isogenic-hiPSC-CMs. Thus, the iPSC-derived, disease-specific cardiomyocytes could serve as a translationally relevant platform to study genetic cardiac diseases.