Biology subjects

Riecken, K.

Publications and source records attributed to Riecken, K..

7 recordsLinked to original sources

bioRxiv2026

CD73-derived adenosine at the blood-brain barrier confers protection in a mouse model of ischemic stroke

Ischemic stroke remains a leading cause of death and disability, and current reperfusion therapies do not address the secondary neuroinflammatory response following blood-brain barrier (BBB) disruption. Purinergic signaling critically regulates this process: extracellular ATP promotes inflammation, whereas its enzymatic conversion into adenosine exerts tissue-protective effects. Notably, the ectonucleotidase CD73 (NT5E), which catalyzes AMP-to-adenosine conversion, is highly expressed by human but not murine brain endothelial cells (BECs). Here, we investigated the role of endothelial CD73 in ischemic stroke using an AAV vector engineered for selective transduction of murine BECs to induce BBB-specific CD73 expression. Endothelial CD73 enhanced extracellular ATP degradation toward adenosine generation and established a purine metabolism profile resembling that of human BECs. In the transient middle cerebral artery occlusion (tMCAO) mouse model, BBB-targeted CD73 expression reduced infarct volume by 40% and prevented early mortality within 48 h after reperfusion. Transcriptomic and flow cytometric analyses revealed altered leukocyte responses, including increased recruitment of monocytes/macrophages whose gene expression signatures were consistent with inflammation-resolving programs. These findings identify endothelial CD73 as an important regulator of post-ischemic neuroinflammation and highlight species-specific differences in BBB purine metabolism with implications for translational stroke research.

neuroscience↗

bioRxiv2025

Unravelling drug resistant proteotypes through phenotype-resolved proteomics of single-cell derived colonies

Drug resistance remains a major cause of treatment failure and disease progression and is closely linked to intratumoral heterogeneity. Mass spectrometry (MS)-based single-cell proteomics (SCP) can resolve drug-resistant cell states, but current methods lack clonal and phenotype information and are often confounded by cell-cycle and cell-size effects. Here, we introduce PhenoSCoP, a microscopy-guided discovery proteomics framework that profiles single-cell-derived colonies to map proteomic heterogeneity while preserving clonal origin and image-defined phenotypes. In head and neck squamous cell carcinoma models, PhenoSCoP distinguished heritable clone-intrinsic cisplatin (CP) response programs from adaptive treatment-induced changes, uncovered pre-existing resistant-like proteotypes in treatment-naive populations, and identified an NDUFB11-associated mitochondrial vulnerability in a resistant clone. In patient-derived primary HNSCC cells, CP-tolerant cells resolved into two proteomic states with distinct phenotypes and high or low S100A7/A8/A9 expression. These programs were also detected in HNSCC patient tissues and, in an illustrative matched progression case, increased across metastatic sites. PhenoSCoP therefore provides a phenotype-resolved framework for discovering stable and adaptive proteotypes associated with therapeutic response.

systems biology↗

bioRxiv2024

TAM receptors control actomyosin dynamics in osteoclasts via RHOA-COFILIN-MYOSIN II signaling

The TAM family of receptor tyrosine kinases were recently identified to regulate bone homeostasis by controlling osteoblasts and bone formation. Despite extensive knowledge of TAM receptor function in the mononuclear phagocyte system, the role of TAM receptors in osteoclasts remains largely unknown. Here, we identify a physiological regulatory system including MERTK and TYRO3 in osteoclasts controlling RHOA-ROCK-COFILIN/Myosin II signaling, thereby antagonistically regulating osteoclast-mediated bone remodeling to maintain bone homeostasis. Myeloid-specific lysozyme M-mediated deletion of Mertk led to increased bone mass in mice. In early stages of RANKL-induced osteoclast differentiation MERTK promotes amoeboid migration mode in osteoclast precursor cells by inducing RHOA-COFILIN-MLC2 pathway leading to increased osteoclast formation. In contrast, TYRO3 inhibits RHOA-ROCK signaling in osteoclast precursor cells thereby inhibiting these processes. Furthermore, we unraveled an inhibitory role of MERTK as well as TYRO3 in osteoclast differentiation and function. In line with this, mice with cathepsin K-mediated deletion of Mertk and Tyro3 exhibited an osteoporotic bone phenotype. We found that osteoclast precursor cell morphology dictates its fusion capacity and identified MERTK as a negative regulator of osteoclast fusion. In multinucleated cells, deletion of Mertk inhibits actin ring formation by mediating central actomyosin contraction and inactivation of COFILIN. In contrast, spatially well-ordered RHOA activation at adhesion structures, induced by loss of Tyro3, improves osteoclast biomechanotransduction to ameliorate podosome belt formation and enhance osteoclast function. By using a syngeneic breast cancer bone metastasis osteolysis models we identified TYRO3 as a bone protective receptor for osteolytic bone diseases, whereas MERTK represents a pharmacologic accessible target to inhibit osteoclast formation because its stimulatory effects of osteoclast precursors prevail the inhibitory effects on mature osteoclasts. Next to the recently uncovered role of MERTK as a target for osteoanabolic therapy MERTK may represent a one-drug two-target treatment strategy to increase osteoblast function and reduce osteoclast formation for treatments of bone diseases.

cell biology↗

bioRxiv2022

Generation of adult hippocampal neural stem cells occurs in the early postnatal dentate gyrus and depends on cyclin D2

In the hippocampus, lifelong neurogenesis is maintained by a pool of multipotent adult neural stem cells (aNSCs) residing in the subgranular zone of the dentate gyrus (DG). Yet, the mechanisms guiding the transition of NSCs from developmental to adult remain unclear. By using nestin-reporter mice deficient for D2, a cyclin expressed mainly postnatally, we show that the aNSC pool is established through D2-dependent proliferation during the first two weeks of life. The absence of D2 allows the normal development of the DG until birth but prevents the postnatal formation of radial glia-like aNSCs. Additionally, retroviral fate mapping demonstrates that aNSCs are born on-site from precursors located in the DG shortly after birth. Altogether, our data suggest that aNSCs are a population distinct from developmental NSCs and thus imply that adult hippocampal neurogenesis is not a mere continuation of development.

neuroscience↗

bioRxiv2022

Microglial colonisation of the developing brain is facilitated by clonal expansion of highly proliferative progenitors and follows an allometric scaling

Microglia are the resident immune cells of the brain and arise from yolk sac-derived macrophages during early embryogenesis. On entering the brain, microglia undergo in situ proliferation and eventually colonise the entire brain by the second and third postnatal weeks in mice. However, the intricate dynamics of their developmental expansion remain unclear. Here, we examine and characterise the proliferative dynamics of microglia during embryonic and postnatal development. Using complementary fate-mapping techniques, we demonstrate that the developmental colonisation of the brain by microglia is facilitated by clonal expansion of highly proliferative microglial progenitors that occupy spatial niches throughout the brain. We also find that the distribution of microglia switches from a clustered to a random pattern between embryonic and late postnatal development. Moreover, the developmental increase in microglia follows the proportional growth of the brain in an allometric manner with the density of microglia eventually stabilising when the mosaic distribution has been established. Overall, our findings offer insight into how the competition for space acts as a driving force for microglial colonisation by clonal expansion during development.

neuroscience↗

bioRxiv2021

Digital PCR to quantify ChAdOx1 nCoV-19 copies in blood and tissues

Vaccination with the adenoviral-vector based Astra Zeneca ChAdOx1 nCov-19 vaccine is efficient and safe. However, in rare cases vaccinated individuals developed life-threatening thrombotic complications, including thrombosis in cerebral sinus and splanchnic veins. Monitoring of the applied vector in vivo represents an important precondition to study the molecular mechanisms underlying vaccine-driven adverse effects now referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT). We previously have shown that digital PCR is an excellent tool to quantify transgene copies in vivo. Here we present a highly sensitive digital PCR for in-situ quantification of ChAdOx1 nCoV-19 copies. Using this method, we quantified vector copies in human serum 24, 72 and 168 hours post vaccination, and in a variety of murine tissues in an experimental vaccination model 30 minutes post injection. We describe a method for high-sensitivity quantitative detection of ChAdOx1 nCoV-19 with possible implications to elucidate the mechanisms of severe ChAdOx1 nCov-19 vaccine complications.

microbiology↗

bioRxiv2020

In vivo inducible reverse genetics in patients' tumors to identify individual therapeutic targets

High-throughput sequencing describes multiple alterations in each tumor (1), but their functional relevance is often unclear. Clinic-close, individualized molecular model systems are required for functional validation and to identify therapeutic targets of high significance for each patient (2). Here, we established a Cre-ERT2-loxP based inducible RNAi-mediated gene silencing system in patient-derived xenograft (PDX) models of acute leukemias in vivo. Mimicking anti-cancer therapy in patients, gene inhibition was initiated in mice harboring orthotopic tumors. Fluorochrome guided, competitive in vivo trials identified a major tumor-maintaining potency of the MLL-AF4 fusion protein and validated MCL1 as vulnerability in some, but not all patients tumors. We could prove DUX4 to play an essential role in patients leukemias carrying the recently described DUX4-IGH translocation. By individualizing functional genomics in established tumors in vivo, our technique decisively complements the value chain of precision oncology. Being broadly applicable to tumors of all kinds, it will considerably reinforce personalizing anti-cancer treatment in the future.

cancer biology↗