Staff member

Hydrogel microparticles (HMPs) are powerful tools to study and manipulate cellular behavior in 3D cell culture systems and animal models. Here, fully DNA-based HMPs are presented, whose material properties can be precisely tuned by sequence-programmable design of self-assembling DNA nanostructures. These DNA-HMPs offer control over size, stiffness, viscoelasticity and ligand presentation. They are formed by microfluidic encapsulation of two types of orthogonal DNA nanostars and a sequence-complementary DNA linker in water-in-oil droplets. By varying the valency of the DNA nanostar designs, tunable mechanical properties are achieved - spanning three orders of magnitude in Young's modulus from to with distinct viscoelastic behavior. Click-chemistry based functionalization with the small fibronectin-derived peptide cyclic-RGD (c[RGD]) enables integration into fibroblast spheroids. DNA-HMPs are stably retained within the spheroids for several days and undergo remodeling, indicating active interactions between the cells and the DNA-HMPs. Combining programmable material properties and inherent biocompatibility of DNA with straightforward functionalization and stimuli-responsiveness, these DNA-HMPs represent a versatile tool to probe and manipulate tissue behaviors in 3D cell cultures.

JTD Keywords: 3d cell culture, Biomaterials, Complex, Dna hydrogel, Dna nanotechnology, Hydrogel microparticles, Mechanobiology, Microfluidics, Microrheology, Microscopy, Phase, Stiffness

Non-alcoholic fatty liver disease (NAFLD) is gaining in importance and is linked to obesity. Especially, the development of fibrosis and portal hypertension in NAFLD patients requires treatment. Transgenic TGR(mREN2)27 rats overexpressing mouse renin spontaneously develop NAFLD with portal hypertension but without obesity. This study investigated the additional role of obesity in this model on the development of portal hypertension and fibrosis. Obesity was induced in twelve-week old TGR(mREN2)27 rats after receiving Western diet (WD) for two or four weeks. Liver fibrosis was assessed using standard techniques. Hepatic expression of transforming growth factor-β1 (TGF-β1), collagen type Iα1, α-smooth muscle actin, and the macrophage markers Emr1, as well as the chemoattractant Ccl2, interleukin-1β (IL1β) and tumor necrosis factor-α (TNFα) were analyzed. Assessment of portal and systemic hemodynamics was performed using the colored microsphere technique. As expected, WD induced obesity and liver fibrosis as confirmed by Sirius Red and Oil Red O staining. The expression of the monocyte-macrophage markers, Emr1, Ccl2, IL1β and TNFα were increased during feeding of WD, indicating infiltration of macrophages into the liver, even though this increase was statistically not significant for the EGF module-containing mucin-like receptor (Emr1) mRNA expression levels. Of note, portal pressure increased with the duration of WD compared to animals that received a normal chow. Besides obesity, WD feeding increased systemic vascular resistance reflecting systemic endothelial and splanchnic vascular dysfunction. We conclude that transgenic TGR(mREN2)27 rats are a suitable model to investigate NAFLD development with liver fibrosis and portal hypertension. Tendency towards elevated expression of Emr1 is associated with macrophage activity point to a significant role of macrophages in NAFLD pathogenesis, probably due to a shift of the renin–angiotensin system towards a higher activation of the classical pathway. The hepatic injury induced by WD in TGR(mREN2)27 rats is suitable to evaluate different stages of fibrosis and portal hypertension in NAFLD with obesity.

JTD Keywords: ADGRE1, EMR1, F4/80, Immunity, Liver fibrosis, Macrophage, NAFLD, Portal hypertension, TGR(mREN2)27, Western diet

Prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing. Resulting fibrosis and portal hypertension, as a possible secondary event, may necessitate treatment. Overexpression of mouse renin in the transgenic rat model, TGR(mREN2)27, leads to spontaneous development of NAFLD. Therefore, we used TGR(mREN2)27 rats as a model of NAFLD where we hypothesized increased susceptibility and investigated fibrosis and portal hypertension and associated pathways. 12-week old TGR(mREN2)27 rats received either cholestatic (BDL) or toxic injury (CCl4 inhalation). Portal and systemic hemodynamic assessments were performed using microsphere technique with and without injection of the Janus-Kinase 2 (JAK2) inhibitor AG490 or the non-peptidic Ang(1-7) agonist, AVE0991. The extent of liver fibrosis was assessed in TGR(mREN2)27 and wild-type rats using standard techniques. Protein and mRNA levels of profibrotic, renin-angiotensin system components were assessed in liver and primary hepatic stellate cells (HSC) and hepatocytes. TGR(mREN2)27 rats developed spontaneous, but mild fibrosis and portal hypertension due to the activation of the JAK2/Arhgef1/ROCK pathway. AG490 decreased migration of HSC and portal pressure in isolated liver perfusions and in vivo. Fibrosis or portal hypertension after cholestatic (BDL) or toxic injury (CCl4) was not aggravated in TGR(mREN2)27 rats, probably due to decreased mouse renin expression in hepatocytes. Interestingly, portal hypertension was even blunted in TGR(mREN2)27 rats (with or without additional injury) by AVE0991. TGR(mREN2)27 rats are a suitable model of spontaneous liver fibrosis and portal hypertension but not with increased susceptibility to liver damage. After additional injury, the animals can be used to evaluate novel therapeutic strategies targeting Mas.

JTD Keywords: Mechanisms of disease, Molecular medicine