Biology subjects

Stepniewski, J.

Publications and source records attributed to Stepniewski, J..

3 recordsLinked to original sources

bioRxiv2026

miR-378a Controls Cardiomyocyte Metabolism and Angiogenic Signaling

AimsWhile the muscle-enriched microRNA-378a (miR-378a) has been implicated in cardiac hypertrophy and stress responses, its role in maintaining cardiomyocyte metabolic homeostasis, mitochondrial function, and angiogenic paracrine signaling under physiological and post-injury conditions remains unclear. This study addresses these gaps by examining the molecular and functional consequences of miR-378a deficiency in murine heart and human cardiomyocytes. Methods and ResultsCardiac structure and function were analyzed in miR-378a-deficient (miR-378a-/-) and wild-type (miR-378a+/+) mice at 12 weeks and 17 months of age, revealing that miR-378a loss promoted myocardial fibrosis, altered IGF1R-AKT signaling, and impaired cardiac performance, with age-dependent effects. Integrated transcriptomic and proteomic analyses in miR-378a-/- and control mice, as well as in human iPSC-derived cardiomyocytes (hiPSC-CM) of both genotypes, revealed deregulated pathways related to translation, metabolism, and cardiomyopathy-associated signaling. In hiPSC-CM, miR-378a knockout (KO) impaired mitochondrial respiration, disrupted mitochondrial morphology, and reduced mitochondrial DNA content, accompanied by altered mitophagy and biogenesis. KO cells also showed increased glucose uptake but reduced glycogen storage, accompanied by changes in key metabolic regulators, and displayed diminished angiogenic potential. Finally, hiPSC-CM overexpressing miR-378a were delivered in a mouse model of acute myocardial infarction, but overexpression did not further enhance their therapeutic effect. ConclusionsThis study broadens our understanding of miR-378as physiological role in murine hearts and human cardiomyocytes, demonstrating its impact on contractility, mitochondrial integrity, glucose metabolism, and angiogenic paracrine signaling. However, overexpression of miR-378a in hiPSC-CM offers limited additional benefit in cell therapy for acute myocardial infarction.

cell biology↗

bioRxiv2025

Fresh Paraformaldehyde Preserves Thrombus Biochemistry - An ATR-FTIR and PCA Investigation of Pulmonary Artery Thrombi

BackgroundBiochemical analyses of pulmonary embolism derived thrombi depend critically on fixative quality. ObjectiveTo quantify the impact of paraformaldehyde (PFA) shelf life on thrombus molecular integrity using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and time-of-flight secondary ion mass spectroscopy (SIMS) combined with principal component analysis. MethodsTen pulmonary artery thrombi were fixed in either aged PFA (6 months; n = 6) or freshly prepared 4% PFA (n = 4); an in-vitro plasma clot control received the same fresh PFA. Triplicate ATR-FTIR spectra (400-4000 cm-1) were collected and vector-normalized to the Amide I band. ToF-SIMS measurements were performed using a 30 keV Bi primary ion beam Fixative chemistry was assessed by the carbonyl absorbance at 1700 cm-1. ResultsFreshly fixed thrombi displayed narrow Amide I (~1650 cm-1) and Amide II (~1540 cm-1) bands with a higher signal-to-noise ratio (SNR; median 41.8) than aged-PFA samples (18.2; P < .01). Carbonyl absorbance at 1700 cm-1 was markedly higher in fresh PFA. Aged PFA introduces chemical variances of biological samples in low-mass molecule fragments. PCA showed clear separation of fresh versus aged specimens and alignment of fresh thrombi with plasma controls across spectral windows. ConclusionsPFA solutions older than three months markedly deteriorate thrombus biochemical fidelity. ATR-FTIR and ToF-SIMS offer a rapid quality-control assay prior to molecular analyses. Key pointsO_LIPFA stored [≥]3 months loses >70% of reactive aldehydes, yielding broad Amide envelopes, attenuated lipid bands and a two fold SNR drop. C_LIO_LIAged PFA introduces chemical variances of biological samples in low-mass molecule fragments. C_LIO_LIPCA of fingerprint, protein or lipid windows cleanly separates aged from fresh fixations (PC1 up to 80% variance). C_LIO_LIA rapid QC workflow (carbonyl absorbance [≥]0.25 a.u. plus PCA verification) safeguards molecular integrity irrespective of patient age, DVT history or clinical severity. C_LIO_LIAdopting this workflow will harmonise multi centre clot biorepositories and enhance the reproducibility of proteomic, lipidomic and imaging studies. C_LI

biophysics↗

bioRxiv2025

Loss of cell-autonomously secreted laminin-α2 drives muscle stem cell dysfunction in LAMA2-related muscular dystrophy

The extracellular matrix protein laminin-2 is essential for preserving the integrity of skeletal muscle fibers during contraction. Its importance is reflected by the severe, congenital LAMA2-related muscular dystrophy (LAMA2 MD) caused by loss-of-function mutations in the LAMA2 gene. While laminin-2 has an established role in structurally supporting muscle fibers, it remains unclear whether it exerts additional functions that contribute to the maintenance of skeletal muscle integrity. Here, we report that in healthy muscle, activated muscle stem cells (MuSCs) express Lama2 and remodel their microenvironment with laminin-2. By characterizing LAMA2 MD-afflicted MuSCs and inducing MuSC-specific Lama2 knockouts, we show that MuSC-derived laminin-2 is essential for rapid MuSC expansion and regeneration. In humans, we identify LAMA2 expression in MuSCs and demonstrate that loss-of-function mutations impair the cell-cycle progression of myogenic precursors. In summary, we show that self-secreted laminin-2 supports MuSC proliferation post-injury, thus implicating MuSC dysfunction in LAMA2 MD pathology.

molecular biology↗