Promotion of the immunomodulatory properties and osteogenic differentiation of adipose-derived mesenchymal stem cells in vitro by lentivirus-mediated mir-146a sponge expression

Epigenetics: Novel crucial approach for osteogenesis of mesenchymal stem cells

Bone has a robust regenerative potential, but its capacity to repair critical-sized bone defects is limited. In recent years, stem cells have attracted significant interest for their potential in tissue engineering. Applying mesenchymal stem cells (MSCs) for enhancing bone regeneration is a promising therapeutic strategy. However, maintaining optimal cell efficacy or viability of MSCs is limited by several factors. Epigenetic modification can cause changes in gene expression levels without changing its sequence, mainly including nucleic acids methylation, histone modification, and non-coding RNAs. This modification is believed to be one of the determinants of MSCs fate and differentiation. Understanding the epigenetic modification of MSCs can improve the activity and function of stem cells. This review summarizes recent advances in the epigenetic mechanisms of MSCs differentiation into osteoblast lineages. We expound that epigenetic modification of MSCs can be harnessed to treat bone defects and promote bone regeneration, providing potential therapeutic targets for bone-related diseases.

microRNA-146a mediates distraction osteogenesis via bone mesenchymal stem cell inflammatory response

Distraction osteogenesis (DO) is a widely used surgical technique to repair bone defects, partly owing to its high efficiency in inducing osteogenesis; however, the process of osteogenesis is complex, and the precise mechanism is still unclear. Among the factors identified for an effective DO procedure, well-controlled inflammation is essential. We aimed to explore how microRNA(miR)-146a, a negative regulator of inflammation, influences osteogenesis in DO. First, we established canine right mandibular DO and bone fracture models to evaluate the expression level of miR-146a in response to these procedures. Second, bone marrow mesenchymal stem cells (BMSCs) were isolated from healthy puppies and cultured with lipopolysaccharide (LPS) to observe how inflammation affects osteogenesis. Finally, the osteogenesis activity of BMSCs transfected with lentiviral vector either overexpressing (miR-146a-up) or inhibited for miR-146a expression was evaluated. miR-146a-up-transfected BMSCs were injected locally into the distraction gaps of the DO model canines. On days 42 and 56 post-surgery, the bone volume/tissue volume and bone mineral density values were evaluated via using micro-computed tomography, and newly formed tissues were harvested and evaluated via histological staining. The expression of miR-146a in both the DO canine model and LPS-stimulated BMSCs increased. Overexpression of miR-146a enhanced cell proliferation, migration, and osteogenic differentiation. Additionally, the newly formed callus was improved in canine mandibles injected with miR-146a-up-transfected BMSCs. In summary, miR-146a regulates mandibular DO by improving osteogenesis, and can serve as a potential target to shorten the therapy period of DO.

Hexon modification of human adenovirus type 5 vectors enables efficient transduction of human multipotent mesenchymal stromal cells

In adenovirus type 5 (HAdV-5)-derived viral vectors, the fiber protein has been the preferred locale for modifications to alter the natural viral tropism. Hexon, the most abundant capsid protein, has rarely been used for retargeting purposes, likely because the insertion of larger targeting peptides into Hexon often interferes with the assembly of the viral capsid. We previously observed that positively charged molecules enhance the transduction of human multipotent mesenchymal stromal cells (hMSCs)—a cell type of significant interest for clinical development but inefficiently transduced by unmodified HAdV-5-based vectors. As efficient HAdV-5-mediated gene transfer would greatly increase the therapeutic potential of hMSCs, we tested the hypothesis that introducing positively charged amino acids into Hexon might enhance the transduction of hMSCs, enabling efficient expression of selected transgenes. From the constructs that could be rescued as functional virions, one (HAdV-5-HexPos3) showed striking transduction of hMSCs with up to 500-fold increased efficiency. Evaluation of the underlying mechanism identified heparan sulfate proteoglycans (HSPGs) to be essential for virus uptake by the cells. The ease and efficiency of transduction of hMSCs with this vector will facilitate the development of genetically modified hMSCs as therapeutic vehicles in different disciplines, including oncology or regenerative medicine.

TGF-β1 signaling can worsen NAFLD with liver fibrosis backdrop

Non-Alcoholic Fatty Liver Disease (NAFLD) is characterized by the accumulation of fats in the liver. Relatively benign NAFLD often progresses to fibrosis, cirrhosis, and liver malignancies. Although NAFLD precedes fibrosis, continuous lipid overload keeps fueling fibrosis and the process of disease progression remains unhindered. It is well known that TGF-β1 plays its part in liver fibrosis, yet its effects on liver lipid overload remain unknown. As TGF-β1 signaling has been increasingly attempted to manage liver fibrosis, its actions on the primary suspect (NAFLD) are easily ignored. The complex interaction of inflammatory stress and lipid accumulation aided by mediators scuh as pro-inflammatory interleukins and TGF-β1 forms the basis of NAFLD progression. Anticipatorily, the inhibition of TGF-β1 signaling during anti-fibrotic treatment should reverse the NAFLD though the data remain scattered on this subject to date. TGF-β1 signaling pathway is an important drug target in liver fibrosis and abundant literature is available on it, but its direct effects on NAFLD are rarely studied. This review aims to cover the pathogenesis of NAFLD focusing on the role of the TGF-β1 in the disease progression, especially in the backdrop of liver fibrosis.

Micro-RNAs: A safety net to protect hematopoietic stem cell self-renewal

The hematopoietic system is sustained over time by a small pool of hematopoietic stem cells (HSCs). They reside at the apex of a complex hierarchy composed of cells with progressively more restricted lineage potential, regenerative capacity, and with different proliferation characteristics. Like other somatic stem cells, HSCs are endowed with long-term self-renewal and multipotent differentiation ability, to sustain the high turnover of mature cells such as erythrocytes or granulocytes, and to rapidly respond to acute peripheral stresses including bleeding, infections, or inflammation. Maintenance of both attributes over time, and of the proper balance between these opposite features, is crucial to ensure the homeostasis of the hematopoietic system. Micro-RNAs (miRNAs) are short non-coding RNAs that regulate gene expression posttranscriptionally upon binding to specific mRNA targets. In the past 10 years they have emerged as important players for preserving the HSC pool by acting on several biological mechanisms, such as maintenance of the quiescent state while preserving proliferation ability, prevention of apoptosis, premature differentiation, lineage skewing, excessive expansion, or retention within the BM niche. miRNA-mediated posttranscriptional fine-tuning of all these processes constitutes a safety mechanism to protect HSCs, by complementing the action of transcription factors and of other regulators and avoiding unwanted expansion or aplasia. The current knowledge of miRNAs function in different aspects of HSC biology, including consequences of aberrant miRNA expression, will be reviewed; yet unsolved issues will be discussed. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.

miR-155 Contributes to the Immunoregulatory Function of Human Mesenchymal Stem Cells

Objectives

Mesenchymal stem/stromal cells (MSCs) are widely investigated in regenerative medicine thanks to their immunomodulatory properties. They exert their anti-inflammatory function thanks to the secretion of a number of mediators, including proteins and miRNAs, which can be released in the extracellular environment or in the cargo of extracellular vesicles (EVs). However, the role of miRNAs in the suppressive function of MSCs is controversial. The aim of the study was to identify miRNAs that contribute to the immunomodulatory function of human bone marrow-derived MSCs (BM-MSCs).

Methods

Human BM-MSCs were primed by coculture with activated peripheral blood mononuclear cells (aPBMCs). High throughput miRNA transcriptomic analysis was performed using Human MicroRNA TaqMan® Array Cards. The immunosuppressive function of miRNAs was investigated in mixed lymphocyte reactions and the delayed type hypersensitivity (DTH) murine model.

Results

Upon priming, 21 out of 377 tested miRNAs were significantly modulated in primed MSCs. We validated the up-regulation of miR-29a, miR-146a, miR-155 and the down-regulation of miR-149, miR-221 and miR-361 in additional samples of primed MSCs. We showed that miR-155 significantly reduced the proliferation of aPBMCs in vitro and inflammation in vivo, using the DTH model. Analysis of miRNA-mRNA interactions revealed miR-221 as a potential target gene that is down-regulated by miR-155 both in primed MSCs and in aPBMCs.

Conclusion

Here, we present evidence that miR-155 participates to the immunosuppressive function of human BM-MSCs and down-regulates the expression of miR-221 as a possible inflammatory mediator.

A comparative study on the cellular stressors in mesenchymal stem cells (MSCs) and pancreatic β-cells under hyperglycemic milieu

β-cell dysfunction is a critical determinant for both type 1 diabetes and type 2 diabetes and β-cells are shown to be highly susceptible to cellular stressors. Mesenchymal stem cells (MSCs) on the other hand are known to have immunomodulatory potential and preferred in clinical applications. However, there is paucity of a comparative study on these cells in relation to several cellular stressors in response to hyperglycemia and this forms the rationale for the present study. INS1 β-cells and MSCs were subjected to high-glucose treatment without and with Metformin, Lactoferrin, or TUDCA and assessed for stress signaling alterations using gene expression, protein expression, as well as functional read-outs. Compared to the untreated control cells, INS1 β-cells or MSCs treated with high glucose showed significant increase in mRNA expressions of ER stress, senescence, and proinflammation. This was accompanied by increased miR146a target genes and decreased levels of SIRT1, NRF2, and miR146a in both the cell types. Consistent with the mRNA results, protein expression levels do reflect the same alterations. Notably, the alterations are relatively less extent in MSCs compared to INS1 β-cells. Interestingly, three different agents, viz., Metformin, Lactoferrin, or TUDCA, were found to overcome the high glucose-induced cellular stresses in a concerted and inter-linked way and restored the proliferation and migration capacity in MSCs as well as normalized the glucose-stimulated insulin secretion in INS1 β-cells. While our study gives a directionality for potential supplementation of metformin/lactoferrin/TUDCA in optimization protocols of MSCs, we suggest that in vitro preconditioning of MSCs with such factors should be further explored with in-depth investigations to harness and enhance the therapeutic capacity/potential of MSCs.