Search

Objectives miR-375 is one of the highly expressed micro RNAs (mi RNAs) found in pancreatic islets of both humans and mice. In this study, we investigated functions of mi RNA miR-375 in porcine pancreatic stem cells ( PSC). Materials and methods We transfected mimic and inhibitor of miR-375 in PSCs to measure functional roles of the micro RNA and its effects on cell cycle proliferation and cell differentiation were determined. Luciferase assays were also performed to reveal the target gene of miR-375. Results Overexpression of miR-375 suppressed proliferation, promoted apoptosis and inhibited differentiation into islet-like cells. PDK1 was identified as being a target of miR-375. Furthermore, we found that overexpression of miR-375 inhibited activation of the PDK1- AKT signalling pathway. Conclusion miR-375 directly targeted PDK1 in porcine PSCs, suppressing cell proliferation and differentiation into islet-like cells. [ABSTRACT FROM AUTHOR]

Different bioinks have been used to produce cell-laden alginate-based hydrogel constructs for cell replacement therapy but some of these approaches suffer from issues with print quality, long-term mechanical instability, and bioincompatibility. In this study, new alginate-based bioinks were developed to produce cell-laden grid-shaped hydrogel constructs with stable integrity and immunomodulating capacity. Integrity and printability were improved by including the co - block -polymer Pluronic F127 in alginate solutions. To reduce inflammatory responses, pectin with a low degree of methylation was included and tested for inhibition of Toll-Like Receptor 2/1 (TLR2/1) dimerization and activation and tissue responses under the skin of mice. The viscoelastic properties of alginate-Pluronic constructs were unaffected by pectin incorporation. The tested pectin protected printed insulin-producing MIN6 cells from inflammatory stress as evidenced by higher numbers of surviving cells within the pectin-containing construct following exposure to a cocktail of the pro-inflammatory cytokines namely, IL-1β, IFN-γ, and TNF-α. The results suggested that the cell-laden construct bioprinted with pectin-alginate-Pluronic bioink reduced tissue responses via inhibiting TLR2/1 and support insulin-producing β-cell survival under inflammatory stress. Our study provides a potential novel strategy to improve long-term survival of pancreatic islet grafts for Type 1 Diabetes (T1D) treatment. Diagram model of pectin molecules in alginate-based constructs allow revascularization, protect pancreatic β-cell from inflammatory damage and inhibit tissue responses by inhibit TLR2/1 activation (Created with BioRender.com). [Display omitted] • A tri-component bioink containing pectin was formulated. • Pectin-incorporated constructs support viability of pancreatic β-cells under inflammatory stress. • Pectin-incorporated constructs inhibit activation of Toll-Like Receptor 2/1. • Constructs containing pectin exhibit high biocompatibility in vivo. [ABSTRACT FROM AUTHOR]

Encapsulation of pancreatic islets in alginate-microcapsules is used to reduce or avoid the application of life-long immunosuppression in preventing rejection. Long-term graft function, however, is limited due to varying degrees of host tissue responses against the capsules. Major graft-longevity limiting responses include inflammatory responses provoked by biomaterials and islet-derived danger-associated molecular patterns (DAMPs). This paper reports on a novel strategy for engineering alginate microcapsules presenting immunomodulatory polymer pectin with varying degrees of methyl-esterification (DM) to reduce these host tissue responses. DM18-pectin/alginate microcapsules show a significant decrease of DAMP-induced Toll-Like Receptor-2 mediated immune activation in vitro , and reduce peri-capsular fibrosis in vivo in mice compared to higher DM-pectin/alginate microcapsules and conventional alginate microcapsules. By testing efficacy of DM18-pectin/alginate microcapsules in vivo , we demonstrate that low-DM pectin support long-term survival of xenotransplanted rat islets in diabetic mice. This study provides a novel strategy to attenuate host responses by creating immunomodulatory capsule surfaces that attenuate activation of specific pro-inflammatory immune receptors locally at the transplantation site. [ABSTRACT FROM AUTHOR]