Project description:The liverM-bM-^@M-^Ys remarkable capacity to regenerate allows it to carry out vital life-supporting functions despite unrelenting pathogen and toxin-induced injury. Unchecked, this capability also leads to cirrhosis, a burgeoning global disease burden. Existing animal models only partially recapitulate human liver regeneration, which hitherto has not been systematically studied. We investigated human liver regeneration in a unique model of liver transplantation. Here we show coordinated changes in expression of microRNA (miRNA) during regeneration that drive proliferation, innate immunity and angiogenesis. Failed regeneration is associated with distinct miRNAs enforcing cell cycle inhibition and DNA methylation. The miRNA expression associated with successful or failed regeneration when recapitulated in vitro, triggered expression of cardinal regeneration-linked genes promoting cell cycle entry or inhibition, respectively. Furthermore, inhibition of three miRNAs whose downregulation is associated with successful regeneration, induced proliferation in vitro. Our data indicate that human liver regeneration is orchestrated by distinct miRNAs determining cell cycle fate. Their manipulation may obviate the need for transplantation by enforcing successful regeneration in the liver and other solid organs. We compared a group of seven patients with successful regeneration (RG) after auxiliary liver transplant (ALT) to four patients who also had ALT but failed to regenerate (NRG). Regeneration was quantified by volume expansion using radiographic imaging; functional recovery was assessed using nuclear isotope scanning and hepatocellular regeneration using histology. Based on histological assessment, three time points were selected for both groups (RG and NRG). Biopsies were taken at the time of transplant and at different intervals post-transplant. Since sample acquisition was driven by clinical necessity, widely discrepant time intervals existed between T=1, T=2 and T=3 for the patients. RNA was extracted from archived histology samples of the RG and NRG, and miRNA expression was analysed using the Affymetrix GeneChip miRNA 1.0 assays. This submission does not include NRG samples taken at time point 3.

Project description:Introduction: Bone healing is a well-orchestrated process involving various bone cells and signaling pathways, where disruptions can result in delayed or incomplete healing. MicroRNAs (miRNAs) are small non-coding RNAs capable of influencing various cellular processes, including bone remodeling. Due to their biological relevance and stable presence in biofluids, miRNAs may serve as candidates for diagnosis and prognosis of delayed bone healing. The aim of this study was to investigate changes in miRNAs circulating in the blood during the healing of rat calvaria defects as biomarkers of successful bone regeneration. Methods: Standardized calvaria defects were created in 36 Wistar rats with a trephine drill and treated with collagen hydroxyapatite (CHA) scaffolds. The treatment groups included CHA scaffolds only, CHA scaffolds containing a plasmid coding for bone morphogenetic protein 2 (BMP2) and miR-590-5p, CHA scaffolds containing mesenchymal stromal cell-derived extracellular vesicles, and empty defects as a control group. After 1, 4 and 8 weeks of healing, the animals were evaluated by microcomputed tomography (microCT), as well as subjected to histological analyses. Blood was sampled from the tail vein prior to surgeries and after 1, 4, and 8 weeks of healing. miRNAs circulating in the plasma were determined using next generation sequencing. Results: Variability of bone regeneration within the four groups was unexpectedly high and did not result in significant differences between the groups, as indicated by the microCT and histological analyses of the newly formed bone tissue. However, irrespective of the treatment group and regenerative activity, we identified miRNAs with distinct expression patterns of up- and downregulation at different time points. Furthermore, rats with high and low regenerative activity were characterized by distinct circulating miRNA profiles. miR-133-3p was identified as the top up-regulated miRNA and miR-375-3p was identified as the top down- regulated miRNA in animals exhibiting good regeneration over all time points evaluated. Conclusion: Our study indicates that regardless of the treatment group, success or lack of bone regeneration is associated with a distinct expression pattern of circulating microRNAs. While for some of these microRNAs functional association with skeletal regeneration has previously been reported, further research is needed to evaluate whether their levels in the blood can be used as predictive factors of successful bone regeneration. Keywords: gene-activated scaffold; osteogenesis; bone regeneration, biomarkers, circulating microRNAs

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