Biology subjects

Gallagher, K. M.

Publications and source records attributed to Gallagher, K. M..

3 recordsLinked to original sources

bioRxiv2022

Epigenetic Priming Enhances Chondrogenic Potential of Expanded Chondrocytes for Cartilage Repair

Expansion of chondrocytes presents a major obstacle in the cartilage regeneration procedure matrix-induced autologous chondrocyte implantation (MACI). Dedifferentiation of chondrocytes during the expansion process leads to the emergence of a fibrotic (chondrofibrotic) phenotype that decreases the chondrogenic potential of the implanted cells. We aim to 1) determine the extent that chromatin architecture of H3K27me3 and H3K9me3 remodels during dedifferentiation and persists when expanded chondrocytes are transferred to a 3D culture; and 2) to prevent this persistent remodeling to enhance the chondrogenic potential of expanded chondrocytes. Chromatin architecture remodeling of H3K27me3 and H3K9me3 was observed at 0, 8 and 16 population doublings in a two-dimensional (2D) culture and after encapsulation of the expanded chondrocytes in a three-dimensional (3D) hydrogel culture. Chondrocytes were treated with inhibitors of epigenetic modifiers (epigenetic priming) for 16 population doublings and then encapsulated in 3D hydrogels. Chromatin architecture of chondrocytes and gene expression were evaluated before and after encapsulation. We observed a change in chromatin architecture of epigenetic modifications H3K27me3 and H3K9me3 during chondrocyte dedifferentiation. Although inhibiting enzymes that modify H3K27me3 and H3K9me3 did not alter the dedifferentiation process in 2D culture, applying these treatments during the 2D expansion did increase the expression of select chondrogenic genes and protein deposition of type II collagen when transferred to a 3D environment. Overall, we found that epigenetic priming of expanded chondrocytes alters the cell fate when chondrocytes are later encapsulated into a 3D environment, providing a potential method to enhance the success of cartilage regeneration procedures.

bioengineering↗

bioRxiv2022

Single cell analysis of senescent epithelia reveals targetable mechanisms promoting fibrosis

Progressive fibrosis and maladaptive organ repair result in significant morbidity and millions of premature deaths annually. Senescent cells accumulate with ageing and after injury and are implicated in organ fibrosis, but the mechanisms by which senescence influences repair are poorly understood. Using two murine models of injury and repair we show that obstructive injury generates senescent epithelia which persist after resolution of the original injury, promote ongoing fibrosis and impede adaptive repair. Depletion of senescent cells with ABT263 reduces fibrosis in reversed ureteric obstruction and after renal ischaemia-reperfusion injury. We validate these findings in humans, showing that senescence and fibrosis persist after relieved renal obstruction. We next characterise senescent epithelia in murine renal injury using single cell RNA-Seq. We extend our classification to human kidney and liver disease and identify conserved pro-fibrotic proteins which we validate in vitro and in human disease. We demonstrate that one such molecule, Protein Disulfide Isomerase Family A Member 3 (PDIA3), is essential for TGF-beta mediated fibroblast activation. Inhibition of PDIA3 in vivo significantly reduces kidney fibrosis during ongoing renal injury and as such represents a new potential therapeutic pathway. Analysis of the signalling pathways of senescent epithelia connects senescence to organ fibrosis, permitting rational design of anti-fibrotic therapies.

cell biology↗

bioRxiv2020

Combined Effects of Standing and Passive Heating on Attenuating Sitting-Induced Vascular Dysfunction

Recent evidence suggests prolonged sitting strains the arteries through angulations that create turbulent blood flow. This turbulent flow reduces flow-mediated dilation (FMD), a key indicator of vascular health. The purpose of this study was to determine if arterial angulations (through sitting or standing), shear stress (through local heating), or a combination of these factors affected vascular function. In addition, we sought examined the impact of biological sex on these responses. MethodsTwenty-six healthy, young (18-40 years old) males (n=13) and females (n=13) participated. Participants completed two experimental trials (2-h sitting and 2-h standing), and, in a randomized fashion, one leg was passively heated. Flow-mediated dilation (FMD) at the superficial femoral artery (SFA), and central and peripheral pulse-wave velocity (PWV) were measured using vascular ultrasound. ResultsThere was a non-significant decrease in FMD (- 1.48%; p = .06) during sitting and the decline in FMD was not different between biological sexes (-1.96% vs -0.93%; p = .49, males and females respectively). Passive heating (1.42%; p < .05) and standing (1.42%; p < .05) both improved FMD in comparison to sitting. However, standing resulted in a significant increase in peripheral PWV (50 cm/s; p < .05). Interestingly, the standing was not well tolerated among female participants with seven participants having to stop their initial trial early due to lightheadedness. ConclusionsBoth interventions appear to be equally effective at mitigating reductions FMD associated with sitting, but standing increased peripheral PWV. In addition, it does not appear that biological sex moderates these physiological responses. New FindingsO_ST_ABSWhat is the central question of this study?C_ST_ABSProlonged sitting can cause acutely vascular dysfunction while interventions such as local heating or standing have been explored they have not been used in combination and the role of biological sex has not been fully explored. What is the main finding and its importance?In this study we demonstrate that either local heating or standing are effective at reducing some of the vascular dysfunction associated with prolonged sitting. Biological sex did not appear appear to play a role in this response. However, standing may also cause some negative effects such as increased arterial stiffness and increase the risk of syncope.

physiology↗