Biology subjects

Groeger, M.

Publications and source records attributed to Groeger, M..

3 recordsLinked to original sources

bioRxiv2022

Melanoma cells release DEL-1 via small extracellular vesicles

DEL-1 (developmental endothelial locus-1) induces integrin signaling and recognizes phosphatidylserine exposed on apoptotic cells. We show that DEL-1, which is thought to be a secreted molecule, is not found in melanoma cell culture supernatants but is exported by an endosomal pathway and released via small extracellular vesicles (sEV). Proteomics of DEL-1 positive sEV, but not of DEL-1 negative sEV contain proteins associated with poor survival in cancer. To determine whether DEL-1 is suitable to predict treatment responses, we isolated sEV from plasma of melanoma patients before and 90 days of treatment with checkpoint inhibitors. Although we could not detect DEL-1 in plasma sEV even in patients with progressive disease (most likely due to the very low protein yield from sEV isolated from 1ml plasma), the principal component analysis allowed a clear differentiation between controls and patients as well as between patients before and after treatment. Interestingly, in one patient with complete regression, in the post treatment sample, the protein expression profile remained in the pre-treatment cluster. The low protein yield of patient sEV and the low patient number are clear limitations of this study, but results demonstrate that this method could have the potential to predict treatment responses.

cancer biology↗

bioRxiv2022

Mesenchymal stem cells support human vascular endothelial cells to form vascular sprouts in human platelet lysate-based matrices.

During tissue regeneration, mesenchymal stem cells can support endothelial cells in the process of new vessel formation. For a functional interaction of endothelial cells with mesenchymal stem cells a vascular inductive microenvironment is required. Using a cellular model for neo-vessel formation, we could show that newly formed vascular structures emanated from the embedded aggregates, consisting of mesenchymal stem cells co-cultured with human umbilical vein endothelial cells, into the avascular HPL-based matrices bridging distances up to 5 mm to join with adjacent aggregates with the same morphology forming an interconnected network. These newly formed vascular sprouts showed branch points and generated a lumen as sign of mature vascular development. Mesenchymal stem cells in fluid phase could bind to and interact with adherent human umbilical vein endothelial cells when a shear-force of 2 dyne/mm2 was applied in the flow chamber using a Bioflux(R)200 device. Under these conditions, mesenchymal stem cells bind to human umbilical vein endothelial cells previously damaged by laser beam irradiation to interact and shed particles. In conclusion, we observed that mesenchymal stem cells support human umbilical vein endothelial cells to form new vessels in HPL-based matrices when co-cultured in spherical aggregates to generate complex vascular networks in a primarily avascular scaffold and bind to the damaged cells under shear-force to eventually aid in their regeneration.

bioengineering↗

bioRxiv2021

Human macrophage polarization determines bacterial persistence of Staphylococcus aureus in a liver-on-chip-based infection model

Infections with Staphylococcus aureus (S. aureus) have been reported from various organs ranging from asymptomatic colonization to severe infections and sepsis associated with multiple organ dysfunction. Although considered an extracellular pathogen, S. aureus can invade and persist in professional phagocytes such as monocytes and macrophages. Its capability to persist and manipulate phagocytes is considered a critical step to evade host antimicrobial reactions. For the first time we leveraged a human liver-on-chip model and tailored image analysis algorithms to demonstrate that S. aureus (USA300) specifically targets macrophages in the liver models as essential niche facilitating bacterial persistence and phenotype switching to small colony variants (SCVs). In vitro M2 polarization was found to favor SCV-formation and was associated with increased intracellular bacterial loads in macrophages, increased cell death, and impaired recruitment of circulating monocytes to sites of infection. These findings expand the knowledge about the role of liver macrophages in the course of systemic infection. Further, the results might be relevant for understanding infection mechanisms in patients with chronic liver disease such as fibrosis that display increased frequencies of M2 polarized liver macrophages and have a higher risk for developing chronic infections and relapsing bacteremia.

microbiology↗