Biology subjects

Kaltschmidt, B.

Publications and source records attributed to Kaltschmidt, B..

4 recordsLinked to original sources

bioRxiv2026

A Cellular Cytotoxicity Assay using Ready-to-Thaw Target Cells without Washing Steps

Functional testing of cytotoxic lymphocytes is essential for research and quality control (QC), but most assays require freshly prepared target cells and extensive handling. A ready-to-thaw, no-wash, flow cytometry-based cytotoxicity assay was developed using pre-labeled K562 targets cryopreserved in STEM-CELLBANKER(R) EX (SCB) as suitably sized aliquots. SCB tolerability was evaluated in K562, NK-92, and primary natural killer (NK) cells; post-cryopreservation label stability of CellTrace Violet (CTV) and carboxyfluorescein succinimidyl ester (CFSE) was assessed; freezing and thawing conditions were optimized; and wash versus no-wash workflows were compared using viability-based and absolute-count readouts, across effector-to-target (E:T) ratios with NK donors and NK-92 cells. Effector viability remained high at SCB concentrations up to 10%, and 5% SCB was selected for assay design. After cryopreservation, CTV labeling remained stable over the tested storage period, whereas CFSE showed substantial signal loss. Warm-medium thawing performed comparably to water-bath thawing, and the consolidated protocol (SCB plus fetal calf serum and thermal buffering) maintained high post-thaw target viability and recovery. In killing assays, lysis increased with increasing E:T ratios; omission of the post-thaw wash had minimal impact, and 5% SCB did not impair cytotoxic function. This ready-to-thaw workflow reduces hands-on time and sample manipulation, while improving standardization for reproducible results and enabling high-throughput functional testing and QC.

immunology↗

bioRxiv2021

Human Sex Matters: Y-linked lysine demethylase 5D drives accelerated male osteogenic differentiation

Female sex is increasingly associated to a loss of bone mass during aging and an increased risk for fractures developing nonunion. Hormonal factors and cell-intrinsic mechanisms are suggested to drive these sexual dimorphisms, although underlying molecular mechanisms are still a matter of debate. Here, we observed a decreased capacity of calvarial bone recovery in female rats and a profound sexually dimorphic osteogenic differentiation human adult neural crest-derived stem cells (NCSCs). Next to an elevated expression of pro-osteogenic regulators, global trancriptomics revealed Lysine Demethylase 5D (KDM5D) to be highly upregulated in differentiating male NCSCs. Loss of function by siRNA or pharmacological inhibition of KDM5D significantly reduced the osteogenic differentiation capacity of male NCSCs. In summary, we demonstrate craniofacial osteogenic differentiation to be sexually dimorphic with the expression of KDM5D as a prerequisite for accelerated male osteogenic differentiation, emphasizing the analysis of sex-specific differences as a crucial parameter for treating bone defects.

cell biology↗

bioRxiv2019

NF-κB-c-REL impairement drives human stem cells into the oligodendroglial fate

Molecular mechanisms underlying fate decisions of human neural stem cells (NSCs) between neurogenesis and gliogenesis are critical during neuronal development and progression of neurodegenerative diseases. Despite its crucial role in murine nervous system development, the potential role of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-{kappa}B) in fate shifts of human stem cells is poorly understood.\n\nFacing this challenge, we demonstrate here that NF-{kappa}B-c-REL drives glutamatergic differentiation of adult human stem cells, while its impairment results in a shift towards the oligodendroglial fate. We particularly observed an opposing balance switch from NF-{kappa}B-RELB/p52 to NF-{kappa}B-c-REL during early neuronal differentiation of NSCs originating from neural crest-derived stem cells. Exposure of differentiating human NSCs to the c-REL inhibiting approved drug pentoxifylline (PTXF) resulted in elevated levels of cell death and significantly decreased amounts of NF200+/VGLUT2+ neurons. PTXF-mediated inhibition of c-REL further drove human NSCs into the oligodendrocyte fate, as demonstrated by a complete switch to OLIG2+/O4+ oligodendrocytes, which also showed PDGFR, NG2 and MBP transcripts.\n\nIn summary, we present here a novel human cellular model of neuronal differentiation with an essential role of NF-{kappa}B-c-REL in fate choice between neurogenesis and oligodendrogenesis potentially relevant for multiple sclerosis and schizophrenia.

cell biology↗

bioRxiv2019

Identification of a human adult cardiac stem cell population with neural crest origin

Cardiovascular diseases are the major cause of death worldwide, emphasizing the necessity to better understand adult human cardiac cell biology and development. Although the adult heart was considered as a terminally differentiated organ, rare populations of cardiac stem cells (CSCs) have been described so far, with their developmental origin and endogenous function still being a matter of debate.\n\nHere, we identified a Nestin+/S100+/CD105+/Sca1+/cKit- population of CSCs in the myocardium of the adult human heart auricle. Isolated cells showed expression of characteristic neural crest-derived stem cell (NCSC) markers and kept their genetic stability during cultivation in vitro. Cultivated hCSCs efficiently gave rise to functional, beating cardiomyocytes, osteoblasts, adipocytes and neurons. Global transcriptome analysis via RNAseq showed a high similarity between the expression profiles of Nestin+/S100+/CD105+/Sca1+/cKit- hCSCs and adult human NCSCs from the nasal cavity (inferior turbinate stem cells, ITSCs). In detail, 88.1 % of all genes were significantly expressed in both stem cell populations particularly including common NCSC-markers. Based on these observations, we suggest a similar developmental origin of both stem cell populations.\n\nIn summary, we identified a human adult cardiac stem cell population with neural crest-origin, which may also contribute to endogenous cardiac tissue homeostasis and tissue repair in vivo.

cell biology↗