Biology subjects

Ludwig, B.

Publications and source records attributed to Ludwig, B..

5 recordsLinked to original sources

bioRxiv2025

Effect of biogel C addition on biochar degradation and microbial activities

Biochar contributes to long-term soil carbon stabilization (C) by acting both as a stable carbon pool and as a sorbent for labile compounds. Biogels from roots and microbes are known to form persistent surface coatings with soil sorbents, where they host microbial hotspots. Yet research has mainly focused on their interactions with minerals. The interactive effects of biogels and biochar on soil carbon dynamics remain largely unexplored. This study aimed to assess the effects of biogel coatings on fresh and aged biochar, particularly under drought, with a focus on biochar degradation and microbial responses. We conducted a three-factorial soil incubation study to examine the effects of fresh and aged biochar, with or without biogel amendment, under two moisture levels (30% and 70% water holding capacity, WHC). Using 14C labelled biochar, we quantified biochar degradation and biochar- induced priming effects by measuring 14CO2respiration, microbial biomass carbon (MBC) and its 14C incorporation, hydrolytic and oxidative enzyme activities, and changes in biochar surface area. Mucilage strongly enhanced microbial incorporation of biochar-derived C, specifically from aged biochar under drought conditions, while the opposite effect was observed in soils amended with fresh biochar. This demonstrates the greater microbial accessibility of aged biochar surfaces and limited use of fresh biochar due to inaccessibility of the hydrophobic surfaces, and in consequence the preference for more easily accessible C sources. Additionally, mucilage significantly reduced the Michaelis Menten constant (Km) of {beta}-glucosidase by up to 58% in soils amended with aged biochar under drought. This indicates that under these conditions, the interaction of the aged biochar with the biogel may have created a unique habitat requiring specific enzyme systems with higher affinity. Our findings highlight the role of mucilage in regulating microbial surface access and thus the decomposition of biochar, particularly under moisture- limited conditions. The synergy between aged biochar and biogels provides a promising new perspective to further enhance biochar-based drought mitigation, specifically for managing microbial activity in drought-prone soils.

ecology↗

bioRxiv2023

Regulation of multiple signaling pathways promotes the consistent expansion of human pancreatic progenitors in defined conditions

The unlimited expansion of human progenitor cells in vitro could unlock many prospects for regenerative medicine. However, it remains an important challenge as it requires the decoupling of the mechanisms supporting progenitor self-renewal and expansion from those mechanisms promoting their differentiation. This study focuses on the expansion of human pluripotent stem (hPS) cell derived pancreatic progenitors (PP) to advance novel therapies for diabetes. We obtained mechanistic insights into PP expansion requirements and, through a hypothesis-driven iterative approach, identified conditions for the robust and unlimited expansion of hPS cell derived PP cells under GMP-compliant conditions. We show that the combined stimulation of specific mitogenic pathways, suppression of retinoic acid signaling and inhibition of selected branches of the TGF{beta} and Wnt signaling pathways are necessary for the effective decoupling of PP proliferation from differentiation. This enabled the reproducible, 2000-fold, over ten passages and 40-45 days, expansion of PDX1+/SOX9+/NKX6-1+ PP cells. Transcriptome analyses confirmed the stabilisation of PP identity and the effective suppression of differentiation. Using these conditions, PDX1+/SOX9+/NKX6-1+ PP cells, derived from different, both XY and XX, hPS cells lines, were enriched to nearly 90% homogeneity and expanded with very similar kinetics and efficiency. Furthermore, non-expanded and expanded PP cells, from different hPS cell lines, were differentiated in microwells into homogeneous islet-like clusters (SC-islets) with very similar efficiency. These clusters contained abundant {beta}-cells of comparable functionality as assessed by glucose-stimulated insulin secretion assays. These findings established the signaling requirements to decouple PP proliferation from differentiation and allowed the consistent expansion of hPS cell derived PP cells. They will enable the establishment of large banks of GMP-derived PP cells derived from diverse hPS cell lines. This approach will streamline SC-islet production for further development of the differentiation process, diabetes research, personalized medicine and cell therapies.

developmental biology↗

bioRxiv2022

Innovative multidimensional models in a high-throughput-format for different cell types of endocrine origin

The adrenal gland provides an important function by integrating neuronal, immune, vascular, metabolic and endocrine signals under a common organ capsule. It is the central organ of the stress response system and has been implicated in numerous stress-related disorders. While for other diseases, regeneration of healthy organ tissue has been aimed at such approaches are lacking for endocrine diseases - with the exception of type-I-diabetes. Moreover, tumor formation is very common, however, appropriate high-throughput applications reflecting the high heterogeneity and furthermore relevant 3D-structures in vitro are still widely lacking. Recently, we have initiated the development of standardized multidimensional models of a variety of endocrine cell/tissue sources in a new multiwell-format. Firstly, we confirmed common applicability for pancreatic pseudo-islets. Next, we translated applicability for spheroid establishment to adrenocortical cell lines as well as patient material to establish spheroids from malignant, but also benign adrenal tumors. We aimed furthermore at the development of bovine derived adrenal organoids and were able to establish steroidogenic active organoids containing both, cells of cortical and medullary origin. Overall, we hope to open new avenues for basic research, endocrine cancer and adrenal tissue-replacement-therapies as we demonstrate potential for innovative mechanistic insights and personalized medicine in endocrine (tumor)-biology.

cancer biology↗

bioRxiv2021

Sequential in vivo labeling of insulin secretory granule pools in INS-SNAP transgenic pigs

{beta}-cells produce, store and secrete insulin upon elevated blood glucose levels. Insulin secretion is a highly regulated process. The probability for insulin secretory granules to undergo fusion with the plasma membrane or being degraded is correlated with their age. However, the molecular features and stimuli connected to this behavior have not yet been fully understood. Furthermore, our understanding of {beta}-cell function is mostly derived from studies of ex vivo isolated islets and/or rodent models. To overcome this translational gap and study insulin secretory granule turnover in vivo, we have generated a transgenic pig model with the SNAP-tag fused to insulin. We demonstrate the correct targeting and processing of the tagged insulin and normal glycemic control of the pig model. Furthermore, we show specific single- and dual-color granular labeling of in vivo labeled pig pancreas. This model may provide unprecedented insights into the in vivo insulin secretory granule behavior in an animal close to humans.

cell biology↗

bioRxiv2020

Enhanced differentiation of functional human T cells in NSGW41 mice with tissue-specific expression of human interleukin-7.

Humanized mouse models have become increasingly valuable tools to study human hematopoiesis and infectious diseases. However, human T cell differentiation remains inefficient. We generated mice expressing human interleukin (IL-7), a critical growth and survival factor for T cells, under the control of murine IL-7 regulatory elements. After transfer of human cord blood-derived hematopoietic stem and progenitor cells, transgenic mice on the NSGW41 background, termed NSGW41hIL7, showed elevated and prolonged human cellularity in the thymus while maintaining physiological ratios of thymocyte subsets. As a consequence, numbers of functional human T cells in the periphery were increased without evidence for pathological lymphoproliferation or aberrant expansion of effector or memory-like T cells. We conclude that the novel NSGW41hIL7 strain represents an optimized mouse model for humanization to better understand human T cell differentiation in vivo and to generate a human immune system with a better approximation of human lymphocyte ratios.

immunology↗