Adipose tissue, angiogenesis and angio-MIR under physiological and pathological conditions

Visible light photo-crosslinking of biomimetic gelatin-hyaluronic acid hydrogels for adipose tissue engineering

Tissue engineering (TE) of adipose tissue (AT) is a promising strategy that can provide 3D constructs to be used for in vitro modelling, overcoming the limitations of 2D cell cultures by closely replicating the complex breast tissue extracellular matrix (ECM), cell-cell, and cell-ECM interactions. However, the challenge in developing 3D constructs of AT resides in designing artificial matrices that can mimic the structural properties of native AT and support adipocytes biological functions. Herein, we developed photocrosslinkable hydrogels by employing gelatin methacrylate (GelMA) and hyaluronic acid methacrylate (HAMA) to mimic the collagenous and glycosaminoglycan components of AT microenvironment, respectively. The physico-mechanical properties of the hydrogels were tuned to target AT biomimetic properties by varying the hydrogel formulation (with or without hyaluronic acid), and the amount of photoinitiator (ruthenium/sodium persulfate) used to crosslink the hydrogels via visible light. The physical and mechanical properties of the developed hydrogels were tuned by varying the material formulation and the photoinitiator concentration. Preadipocytes were encapsulated inside the hydrogels and differentiated into mature adipocytes. Findings enlightened that HAMA addition in hybrid hydrogels boosted an increased lipid accumulation. The engineered biomimetic adipocyte-based constructs resulted promising as scaffolds or 3D in vitro models of AT.

Adipose Tissue Plasticity: A Comprehensive Definition and Multidimensional Insight

Adipose tissue is composed of adipocytes, stromal vascular fraction, nerves, surrounding immune cells, and the extracellular matrix. Under various physiological or pathological conditions, adipose tissue shifts cellular composition, lipid storage, and organelle dynamics to respond to the stress; this remodeling is called "adipose tissue plasticity". Adipose tissue plasticity includes changes in the size, species, number, lipid storage capacity, and differentiation function of adipocytes, as well as alterations in the distribution and cellular composition of adipose tissue. This plasticity has a major role in growth, obesity, organismal protection, and internal environmental homeostasis. Moreover, certain thresholds exist for this plasticity with significant individualized differences. Here, we comprehensively elaborate on the specific connotation of adipose tissue plasticity and the relationship between this plasticity and the development of many diseases. Meanwhile, we summarize possible strategies for treating obesity in response to adipose tissue plasticity, intending to provide new insights into the dynamic changes in adipose tissue and contribute new ideas to relevant clinical problems.

Differentiation of Adipose Tissue Mesenchymal Stem Cells into Endothelial Cells Depends on Fat Depot Conditions: Regulation by miRNA

The development of obesity is associated with substantial modulation of adipose tissue (AT) structure. The plasticity of the AT is reflected by its remarkable ability to expand or reduce in size throughout the adult lifespan, which is linked to the development of its vasculature. This increase in AT vasculature could be mediated by the differentiation of adipose tissue-derived stem cells (ASCs) into endothelial cells (ECs) and form new microvasculature. We have already shown that microRNA (miRNA)-145 regulates the differentiation of ASCs into EC-like (ECL) cells. Here, we investigated whether ASCs-differentiation into ECs is governed by a miRNAs signature that depends on fat depot location and /or the metabolic condition produced by obesity. Human ASCs, which were obtained from white AT by surgical procedures from lean and obese patients, were induced to differentiate into ECL cells. We have identified that miRNA-29b-3p in both subcutaneous (s)ASCs and visceral ASCs and miRNA-424-5p and miRNA-378a-3p in subcutaneous (s)ASCs are involved in differentiation into EC-like cells. These miRNAs modulate their pro-angiogenic effects on ASCs by targeting FGFR1, NRP2, MAPK1, and TGF-β2, and the MAPK signaling pathway. We show for the first time that miRNA-29b-3p upregulation contributes to ASCs' differentiation into ECL cells by directly targeting TGFB2 in both sASCs and visceral ASCs. Moreover, our results reveal that, independent of sASCs' origin (obese/lean), the upregulation of miRNA-378a-3p and the downregulation of miRNA-424-5p inhibit MAPK1 and overexpress FGFR1 and NRP2, respectively. In summary, both the adipose depot location and obesity affect the differentiation of resident ASCs through the expression of specific miRNAs.

MiR-221-3p/222-3p Cluster Expression in Human Adipose Tissue Is Related to Obesity and Type 2 Diabetes

The progression of obesity and type 2 diabetes (T2D) is intricately linked with adipose tissue (AT) angiogenesis. Despite an established network of microRNAs (miRNAs) regulating AT function, the specific role of angiogenic miRNAs remains less understood. The miR-221/222 cluster has recently emerged as being associated with antiangiogenic activity. However, no studies have explored its role in human AT amidst the concurrent development of obesity and T2D. Therefore, this study aims to investigate the association between the miR-221-3p/222-3p cluster in human AT and its regulatory network with obesity and T2D. MiR-221-3p/222-3p and their target gene (TG) expression levels were quantified through qPCR in visceral (VAT) and subcutaneous (SAT) AT from patients (n = 33) categorized based on BMI as normoweight (NW) and obese (OB) and by glycemic status as normoglycemic (NG) and type 2 diabetic (T2D) subjects. In silico analyses of miR-221-3p/222-3p and their TGs were conducted to identify pertinent signaling pathways. The results of a multivariate analysis, considering the simultaneous expression of miR-221-3p and miR-222-3p as dependent variables, revealed statistically significant distinctions when accounting for variables such as tissue depot, obesity, sex, and T2D as independent factors. Furthermore, both miRNAs and their TGs exhibited differential expression patterns based on obesity severity, glycemic status, sex, and type of AT depot. Our in silico analysis indicated that miR-221-3p/222-3p cluster TGs predominantly participate in angiogenesis, WNT signaling, and apoptosis pathways. In conclusion, these findings underscore a promising avenue for future research, emphasizing the miR-221-3p/222-3p cluster and its associated regulatory networks as potential targets for addressing obesity and related metabolic disorders.

Adipose endothelial cells mastering adipose tissues metabolic fate

Dynamic communication within adipose tissue depends on highly vascularized structural characteristics to maintain systemic metabolic homoeostasis. Recently, it has been noted that adipose endothelial cells (AdECs) act as essential bridges for biological information transmission between adipose-resident cells. Hence, paracrine regulators that mediate crosstalk between AdECs and adipose stromal cells were summarized. We also highlight the importance of AdECs to maintain adipocytes metabolic homoeostasis by regulating insulin sensitivity, lipid turnover and plasticity. The differential regulation of AdECs in adipose plasticity often depends on vascular density and metabolic states. Although choosing pro-angiogenic or anti-angiogenic therapies for obesity is still a matter of debate in clinical settings, the growing numbers of drugs have been confirmed to play an anti-obesity effect by affecting vascularization. Pharmacologic angiogenesis intervention has great potential as therapeutic strategies for obesity.

Human platelet lysate-derived extracellular vesicles enhance angiogenesis through miR-126

OBJECTIVES

Extracellular vesicles (EVs) are key biological mediators of several physiological functions within the cell microenvironment. Platelets are the most abundant source of EVs in the blood. Similarly, platelet lysate (PL), the best platelet derivative and angiogenic performer for regenerative purposes, is enriched of EVs, but their role is still too poorly discovered to be suitably exploited. Here, we explored the contribution of the EVs in PL, by investigating the angiogenic features extrapolated from that possessed by PL.

METHODS

We tested angiogenic ability and molecular cargo in 3D bioprinted models and by RNA sequencing analysis of PL-derived EVs.

RESULTS

A subset of small vesicles is highly represented in PL. The EVs do not retain aggregation ability, preserving a low redox state in human umbilical vein endothelial cells (HUVECs) and increasing the angiogenic tubularly-like structures in 3D endothelial bioprinted constructs. EVs resembled the miRNome profile of PL, mainly enriched with small RNAs and a high amount of miR-126, the most abundant angiogenic miRNA in platelets. The transfer of miR-126 by EVs in HUVEC after the in vitro inhibition of the endogenous form, restored angiogenesis, without involving VEGF as a downstream target in this system.

CONCLUSION

PL is a biological source of available EVs with angiogenic effects involving a miRNAs-based cargo. These properties can be exploited for targeted molecular/biological manipulation of PL, by potentially developing a product exclusively manufactured of EVs.

Celastrol inhibits pathologic neovascularization in oxygen-induced retinopathy by targeting the miR-17-5p/HIF-1α/VEGF pathway

Retinopathy of prematurity (ROP), which is characterized by retinal neovascularization (RNV), is a major cause of neonatal blindness. The primary treatment for ROP is anti-vascular endothelial growth factor (VEGF) therapy, which is costly and can rapidly lead to desensitization. Celastrol, a bioactive compound extracted from Tripterygium wilfordii Hook F. ("Thunder of God Vine"), has been shown to exert anticancer and anti-inflammatory effects. However, whether celastrol has antiangiogenic activity and can suppress inflammation to inhibit ROP progression is unclear. This was investigated in the present study in vitro as well as in vivo using a mouse model of oxygen-induced retinopathy (OIR). Our results showed that celastrol treatment reduced neovascular and avascular areas in the retina and inhibited microglia activation and inflammation in OIR mice. Celastrol also inhibited proliferation, migration, and tube formation in cultured human retinal microvascular endothelial cells, and reversed the activation of the microRNA (miR)-17-5p/hypoxia-inducible factor (HIF)-1α/VEGF pathway in the retina of OIR mice. These results indicate that celastrol alleviates pathologic RNV in the retina by protecting neuroglia and suppressing inflammation via inhibition of miR-17-5p/HIF-1α/VEGF signaling, and thus has therapeutic potential for the prevention and treatment of ROP.Abbreviations: BSA, bovine serum albumin; COX2, cyclooxygenase 2; ECM, endothelial cell medium; FBS, fetal bovine serum; HDAC, histone deacetylase; HIF-1, hypoxia-inducible factor 1; HRMEC, human retinal microvascular endothelial cell; Hsp70, heat shock protein; IB4, isolectin B4; ICAM-1, intercellular adhesion molecule 1; IL-1β/6, interleukin 1 beta/6; MAPK, mitogen-activated protein kinase; MCP-1, monocyte chemoattractant protein 1; miRNA, microRNA; MMP, matrix metalloproteinase; mTOR, mammalian target of rapamycin; NF-κB, nuclear factor-kappa B; OIR, oxygen-induced retinopathy; PBS, phosphate-buffered saline; PCNA, proliferating cell nuclear antigen; PI3K, phosphatidylinositol-3-kinase; qRT-PCR, quantitative real-time PCR; RNV, retinal neovascularization; ROP, retinopathy of prematurity; RTCA, real-time cell analyzer; RVO, retinal vaso-obliteration; TNF-α, tumor necrosis factor alpha; VCAM-1, vascular cell adhesion molecule 1; VEGF, vascular endothelial growth factor.

In vivo fluorescence molecular imaging of the vascular endothelial growth factor in rats with early diabetic retinopathy

Anti-vascular endothelial growth factor (anti-VEGF) therapy is effective for reducing the severity level of diabetic retinopathy (DR). However, it is difficult to determine the in vivo spatial and temporal expression of VEGF in the DR retina at an early stage. Here, we report a quantitatively fluorescence molecular imaging and image analysis method by creating a VEGF targeted fluorescence imaging probe, which can potentially detect and predict anti-VEGF treatment response. Moreover, the ex vivo multiscale fluorescence imaging demonstrated the spatial correlation between VEGF relative expression and vascular abnormalities in two and three dimensions. It revealed that VEGF was mainly abnormally expressed at the bifurcation of the microvessels, which advances the knowledge of the DR progression by molecular fluorescence imaging. Our study has the potential to achieve early detection of DR disease, provide more insight into understanding anti-VEGF treatment, and may help stratify patients based on the molecular imaging of retinal VEGF.

MiR-486-3p promotes osteogenic differentiation of BMSC by targeting CTNNBIP1 and activating the Wnt/β-catenin pathway

BACKGROUND

Dysfunction in the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) leads to bone loss/osteoporosis. The catenin beta interacting protein 1 (CTNNBIP1) is an inhibitor of Wnt/β-catenin signaling, whose role in osteogenesis remains elusive. This study aimed to reveal the effects of miR-486-3p/CTNNBIP1 in osteogenesis.

METHODS

Bone marrow samples from healthy individuals and osteoporosis patients and mice with sham or ovariectomy (OVX) surgeries were collected. Levels of CTNNBIP1 and miR-486-3p were assessed. A dual-luciferase reporter assay was used to confirm the interactions between CTNNBIP1 and miR-486-3p. MiR-486-3p mimics/inhibitor or CTNNBIP1 overexpression lentiviruses were transfected to human BMSCs (hBMSCs) and an osteogenic assay was performed. Alizarin red S (ARS) and Alkaline phosphatase (ALP) intensity and expression of osteogenic genes Runx2, Alp, Cola1 and Bglap were measured. Key proteins in the Wnt/β-catenin pathway including active β-catenin, Bcl-2, and Cyclin D1 were assessed.

RESULTS

CTNNBIP1 was upregulated while miR-486-3p was downregulated in osteoporosis patients and OVX mice. CTNNBIP1 was confirmed as a target of miR-486-3p. MiR-486-3p overexpression promoted, while miR-486-3p knockdown suppressed, osteogenic differentiation and Wnt/β-catenin signaling. Rescue experiments confirmed the negative effects of CTNNBIP1 overexpression on osteoblastic differentiation and that miR-486-3p mimics could reverse canonical Wnt signaling.

CONCLUSION

This study demonstrated that miR-486-3p targets CTNNBIP1, thus activating the Wnt/β-catenin signaling pathway to promote osteogenesis of BMSCs.

3,5-Diiodo-L-Thyronine (T2) Administration Affects Visceral Adipose Tissue Inflammatory State in Rats Receiving Long-Lasting High-Fat Diet

3,5-diiodo-thyronine (T2), an endogenous metabolite of thyroid hormones, exerts beneficial metabolic effects. When administered to overweight rats receiving a high fat diet (HFD), it significantly reduces body fat accumulation, which is a risk factor for the development of an inflammatory state and of related metabolic diseases. In the present study, we focused our attention on T2 actions aimed at improving the adverse effects of long-lasting HFD such as the adipocyte inflammatory response. For this purpose, three groups of rats were used throughout: i) receiving a standard diet for 14 weeks; ii) receiving a HFD for 14 weeks, and iii) receiving a HFD for 14 weeks with a simultaneous daily injection of T2 for the last 4 weeks. The results showed that T2 administration ameliorated the expression profiles of pro- and anti-inflammatory cytokines, reduced macrophage infiltration in white adipose tissue, influenced their polarization and reduced lymphocytes recruitment. Moreover, T2 improved the expression of hypoxia markers, all altered in HFD rats, and reduced angiogenesis by decreasing the pro-angiogenic miR126 expression. Additionally, T2 reduced the oxidative damage of DNA, known to be associated to the inflammatory status. This study demonstrates that T2 is able to counteract some adverse effects caused by a long-lasting HFD and to produce beneficial effects on inflammation. Irisin and SIRT1 pathway may represent a mechanism underlying the above described effects.

Role of VEGFs in metabolic disorders

Obesity and metabolic disorders are important public health problems. In this review, the role of vasculature network and VEGF in the adipose tissue maintenance and supplementation is discussed. Angiogenesis is a key process implicated in regulation of tissues homeostasis. Dysregulation of new blood vessels formation may be crucial and contribute to the onset of several pathological conditions, including metabolic syndrome-associated disorders. Adipose tissue homeostasis is fine regulated by vascular network. Vessels support adipose structure. Vasculature modulates the balance between positive and negative regulator factors. In white adipose tissue, vascular endothelial growth factor (VEGF) controls the metabolic activities of adipocytes promoting the trans-differentiation from white to beige phenotype. Trans-differentiation results in an increase of energy consumption. VEGF exerts an opposite effect on brown adipose tissue, where VEGF increases oxygen supply and improves energy expenditure inducing the whitening of adipocytes.