Insulin-like growth factor-1 increases synthesis of collagen type I via induction of the mRNA-binding protein LARP6 expression and binding to the 5' stem-loop of COL1a1 and COL1a2 mRNA

Physiologically activated mammary fibroblasts promote postpartum mammary cancer

Women diagnosed with breast cancer within 5 years of childbirth have poorer prognosis than nulliparous or pregnant women. Weaning-induced breast involution is implicated, as the collagen-rich, immunosuppressive microenvironment of the involuting mammary gland is tumor promotional in mice. To investigate the role of mammary fibroblasts, isolated mammary PDGFRα⁺ cells from nulliparous and postweaning mice were assessed for activation phenotype and protumorigenic function. Fibroblast activation during involution was evident by increased expression of fibrillar collagens, lysyl oxidase, Tgfb1, and Cxcl12 genes. The ability of mammary tumors to grow in an isogenic, orthotopic transplant model was increased when tumor cells were coinjected with involution-derived compared with nulliparous-derived mammary fibroblasts. Mammary tumors in the involution-fibroblast group had increased Ly6C⁺ monocytes at the tumor border, and decreased CD8⁺ T cell infiltration and tumor cell death. Ibuprofen treatment suppressed involution-fibroblast activation and tumor promotional capacity, concurrent with decreases in tumor Ly6C⁺ monocytes, and increases in intratumoral CD8⁺ T cell infiltration, granzyme levels, and tumor cell death. In total, our data identify a COX/prostaglandin E2 (PGE2)-dependent activated mammary fibroblast within the involuting mammary gland that displays protumorigenic, immunosuppressive activity, identifying fibroblasts as potential targets for the prevention and treatment of postpartum breast cancer.

Insulin-like growth factor-1 promotes osteogenic differentiation and collagen I alpha 2 synthesis via induction of mRNA-binding protein LARP6 expression

This study explored the mechanism underlying the stimulation of collagen synthesis and osteoblastic differentiation by insulin-like growth factor 1 (IGF1) in primary mouse osteoblasts. Primary mouse calvarial osteoblasts were cultured and treated with various doses of IGF1 before transfection with siRNA targeting the collagen type I alpha 2 (Col1a2) or La ribonucleoprotein domain family member 6 (Larp6) genes. Alkaline phosphatase (ALP) activity, osteocalcin staining, alizarin red quantification and the expression level of runt-related transcription factor 2 (RUNX2) were performed to assess the differentiation of pre-osteoblasts. Based on Western blot analysis, IGF1 up-regulated COL1A2 protein expression in the primary osteoblasts in a dose- and time-dependent manner. In addition, Col1a2 interference inhibited the differentiation and mineralization of osteoblasts. IGF1 also stimulated the differentiation of mouse primary osteoblasts and increased LARP6 expression during osteogenic differentiation. RNA-Immunoprecipitation (IP) indicated that LARP6 could bind to Col1a2 mRNA after IGF1 stimulation. However, transfection of Larp6-specific siRNA significantly reduced collagen and ALP secretion, mineralization and inhibited the expression of osteocalcin and RUNX2, indicating that Larp6 interference inhibited the differentiation ability of primary mouse calvarial osteoblasts, and these effects could not be reversed by IGF1. Thus, IGF1 could promote COL1A2 expression and osteoblast differentiation in primary mouse calvarial pre-osteoblasts by increasing LARP6 expression via a posttranscriptional mechanism.

Influence of cartilage interstitial fluid on the mRNA levels of matrix proteins, cytokines, metalloproteases and their inhibitors in synovial membrane

Articular cartilage and the synovial membrane both ensure the smooth action of synovial joints; however, the influence of chondrocytes on synovial metabolism remains unclear. The secretory activity of chondrocytes is usually studied in cell cultures and may differ from that in intact cartilage. According to McCutchen's theory of 'weeping' joint lubrication, loading of the articular cartilage during motion squeezes the fluid with lubricating properties from the cartilage. The purpose of the study was to obtain cartilage interstitial fluid (CIF) from intact cartilage and to evaluate its influence on gene expression in the synovial membrane cells. CIF was rinsed out from the cartilage of newborn rats at a pressure of three bar. The chondrocytes survived rinsing and grew in culture. Cytokines in CIF were detected using the enzyme-linked immunosorbent assay (ELISA). The influence of CIF and CIF-like cocktail (all cytokines found in CIF) on gene expression in the synovial membrane cells was studied after a 4 h-incubation, by real-time PCR. Data were analyzed using the Wilcoxon matched-pair test or by the Mann‑Whitney U test. CIF contained basic fibroblast growth factor (bFGF), insulin-like growth factor (IGF)‑1, transforming growth factor β1 (TGFβ1), bone morphogenetic protein 7 (BMP7), macrophage (M)-colony-stimulating factor (CSF), granulocyte (G)-CSF and leukemia inhibitory factor (LIF). CIF stimulated the expression of hyaluronan synthase (HAS)1 and 2, lubricin, collagen I, versican, aggrecan, matrix metalloproteinases (MMPs)2 and 3, tissue inhibitors of metalloproteinases (TIMPs) 1-3, interleukin (IL)-6 and TGFβ1, and decreased the expression of tumor necrosis factor (TNF) and IL-1β. Incubation of the synovial membrane with CIF-like cocktail partially imitated the effects of CIF. Analysis of CIF composition may help to characterize the secretory activity of chondrocytes in their natural environment under various physiological and pathological conditions and to understand the interactions between articular cartilage and the synovial membrane.

Endothelial to mesenchymal transition is common in atherosclerotic lesions and is associated with plaque instability

Endothelial to mesenchymal transition (EndMT) plays a major role during development, and also contributes to several adult cardiovascular diseases. Importantly, mesenchymal cells including fibroblasts are prominent in atherosclerosis, with key functions including regulation of: inflammation, matrix and collagen production, and plaque structural integrity. However, little is known about the origins of atherosclerosis-associated fibroblasts. Here we show using endothelial-specific lineage-tracking that EndMT-derived fibroblast-like cells are common in atherosclerotic lesions, with EndMT-derived cells expressing a range of fibroblast-specific markers. In vitro modelling confirms that EndMT is driven by TGF-β signalling, oxidative stress and hypoxia; all hallmarks of atherosclerosis. 'Transitioning' cells are readily detected in human plaques co-expressing endothelial and fibroblast/mesenchymal proteins, indicative of EndMT. The extent of EndMT correlates with an unstable plaque phenotype, which appears driven by altered collagen-MMP production in EndMT-derived cells. We conclude that EndMT contributes to atherosclerotic patho-biology and is associated with complex plaques that may be related to clinical events.

Intravenous delivery of adeno-associated virus 9-encoded IGF-1Ea propeptide improves post-infarct cardiac remodelling

The insulin-like growth factor Ea propeptide (IGF-1Ea) is a powerful enhancer of cardiac muscle growth and regeneration, also blocking age-related atrophy and beneficial in multiple skeletal muscle diseases. The therapeutic potential of IGF-1Ea compared with mature IGF-1 derives from its local action in the area of synthesis. We have developed an adeno-associated virus (AAV) vector for IGF-1Ea delivery to the heart to treat mice after myocardial infarction and examine the reparative effects of local IGF-1Ea production on left ventricular remodelling. A cardiotropic AAV9 vector carrying a cardiomyocyte-specific IGF-1Ea-luciferase bi-cistronic gene expression cassette (AAV9.IGF-1Ea) was administered intravenously to infarcted mice, 5 h after ischemia followed by reperfusion (I/R), as a model of myocardial infarction. Virally encoded IGF-1Ea in the heart improved global left ventricular function and remodelling, as measured by wall motion and thickness, 28 days after delivery, with higher viral titers yielding better improvement. The present study demonstrates that single intravenous AAV9-mediated IGF-1Ea Gene Therapy represents a tissue-targeted therapeutic approach to prevent the adverse remodelling after myocardial infarct.

Insulin-Like Growth Factor-1 Receptor Deficiency in Macrophages Accelerates Atherosclerosis and Induces an Unstable Plaque Phenotype in Apolipoprotein E-Deficient Mice

BACKGROUND

We have previously shown that systemic infusion of insulin-like growth factor-1 (IGF-1) exerts anti-inflammatory and antioxidant effects and reduces atherosclerotic burden in apolipoprotein E (Apoe)-deficient mice. Monocytes/macrophages express high levels of IGF-1 receptor (IGF1R) and play a pivotal role in atherogenesis, but the potential effects of IGF-1 on their function are unknown.

METHODS AND RESULTS

To determine mechanisms whereby IGF-1 reduces atherosclerosis and to explore the potential involvement of monocytes/macrophages, we created monocyte/macrophage-specific IGF1R knockout (MΦ-IGF1R-KO) mice on an Apoe(-/-) background. We assessed atherosclerotic burden, plaque features of stability, and monocyte recruitment to atherosclerotic lesions. Phenotypic changes of IGF1R-deficient macrophages were investigated in culture. MΦ-IGF1R-KO significantly increased atherosclerotic lesion formation, as assessed by Oil Red O staining of en face aortas and aortic root cross-sections, and changed plaque composition to a less stable phenotype, characterized by increased macrophage and decreased α-smooth muscle actin-positive cell population, fibrous cap thinning, and decreased collagen content. Brachiocephalic artery lesions of MΦ-IGF1R-KO mice had histological features implying plaque vulnerability. Macrophages isolated from MΦ-IGF1R-KO mice showed enhanced proinflammatory responses on stimulation by interferon-γ and oxidized low-density lipoprotein and elevated antioxidant gene expression levels. Moreover, IGF1R-deficient macrophages had decreased expression of ABCA1 and ABCG1 and reduced lipid efflux.

CONCLUSIONS

Our data indicate that macrophage IGF1R signaling suppresses macrophage and foam cell accumulation in lesions and reduces plaque vulnerability, providing a novel mechanism whereby IGF-1 exerts antiatherogenic effects.

Polymerase delta-interacting protein 2 regulates collagen accumulation via activation of the Akt/mTOR pathway in vascular smooth muscle cells

OBJECTIVES

Polymerase delta interacting protein 2 (Poldip2) has previously been implicated in migration, proliferation and extracellular matrix (ECM) production in vascular smooth muscle cells. To better understand the role of Poldip2 in ECM regulation, we investigated the mechanism responsible for collagen I accumulation in Poldip2(+/-) mouse aortic smooth muscle cells (MASMs).

APPROACH AND RESULTS

Protein degradation and protein synthesis pathways were investigated. Depletion of Poldip2 had no effect on proteasome activity, but caused a partial reduction in autophagic flux. However, the rate of collagen I degradation was increased in Poldip2(+/-) vs. Poldip2(+/+) MASMs. Conversely, activation of the PI3K/Akt/mTOR signaling pathway, involved in regulation of protein synthesis, was significantly elevated in Poldip2(+/-) MASMs as was β1-integrin expression. Suppressing mTOR signaling using Akt inhibitor or rapamycin and reducing β1-integrin expression using siRNA prevented the increase in collagen I production. While collagen I and fibronectin were increased in Poldip2(+/-) MASMs, overall protein synthesis was not different from that in Poldip2(+/)(+)MASMs, suggesting selectivity of Poldip2 for ECM proteins.

CONCLUSIONS

Poldip2(+/-) MASMs exhibit higher β1-integrin expression and activity of the PI3K/Akt/mTOR signaling pathway, leading to increased ECM protein synthesis. These findings have important implications for vascular diseases in which ECM accumulation plays a role.

Translational control mechanisms in angiogenesis and vascular biology

Among the multiple modes of regulation of gene expression, translational control is arguably the least investigated and understood, and its role in vascular biology and pathobiology is not an exception. Here, we review recent studies that have revealed exciting translational regulatory phenomena and mechanisms involving novel RNA binding proteins and microRNA machinery in vascular biology. From these studies, the importance of translational regulation in angiogenesis, atherosclerosis, and blood pressure maintenance is beginning to emerge. We believe that the recent development of powerful techniques such as ribosome profiling and translating ribosome affinity purification (TRAP) will motivate and facilitate additional research in these areas.

Mechanical Stimulation and IGF-1 Enhance mRNA Translation Rate in Osteoblasts Via Activation of the AKT-mTOR Pathway

Insulin-like growth factor-1 (IGF-1) is anabolic for muscle by enhancing the rate of mRNA translation via activation of AKT and subsequent activation of the mammalian target of rapamycin complex 1 (mTOR), thereby increasing cellular protein production. IGF-1 is also anabolic for bone, but whether the mTOR pathway plays a role in the rate of bone matrix protein production by osteoblasts is unknown. We hypothesized that anabolic stimuli such as mechanical loading and IGF-1 stimulate protein synthesis in osteoblasts via activation of the AKT-mTOR pathway. MC3T3-E1 osteoblasts were either or not subjected for 1 h to mechanical loading by pulsating fluid flow (PFF) or treated with or without human recombinant IGF-1 (1-100 ng/ml) for 0.5-6 h, to determine phosphorylation of AKT and p70S6K (downstream of mTOR) by Western blot. After 4 days of culture with or without the mTOR inhibitor rapamycin, total protein, DNA, and gene expression were quantified. IGF-1 (100 ng/ml) reduced IGF-1 gene expression, although PFF enhanced IGF-1 expression. IGF-1 did not affect collagen-I gene expression. IGF-1 dose-dependently enhanced AKT and p70S6K phosphorylation at 2 and 6 h. PFF enhanced phosphorylation of AKT and p70S6K already within 1 h. Both IGF-1 and PFF enhanced total protein per cell by ∼30%, but not in the presence of rapamycin. Our results show that IGF-1 and PFF activate mTOR, thereby stimulating the rate of mRNA translation in osteoblasts. The known anabolic effect of mechanical loading and IGF-1 on bone may thus be partly explained by mTOR-mediated enhanced protein synthesis in osteoblasts.

The La-Related Proteins, a Family with Connections to Cancer

The evolutionarily-conserved La-related protein (LARP) family currently comprises Genuine La, LARP1, LARP1b, LARP4, LARP4b, LARP6 and LARP7. Emerging evidence suggests each LARP has a distinct role in transcription and/or mRNA translation that is attributable to subtle sequence variations within their La modules and specific C-terminal domains. As emerging research uncovers the function of each LARP, it is evident that La, LARP1, LARP6, LARP7 and possibly LARP4a and 4b are dysregulated in cancer. Of these, LARP1 is the first to be demonstrated to drive oncogenesis. Here, we review the role of each LARP and the evidence linking it to malignancy. We discuss a future strategy of targeting members of this protein family as cancer therapy.

Molecular Pathways Regulating Macrovascular Pathology and Vascular Smooth Muscle Cells Phenotype in Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) is a disease reaching a pandemic proportion in developed countries and a major risk factor for almost all cardiovascular diseases and their adverse clinical manifestations. T2DM leads to several macrovascular and microvascular alterations that influence the progression of cardiovascular diseases. Vascular smooth muscle cells (VSMCs) are fundamental players in macrovascular alterations of T2DM patients. VSMCs display phenotypic and functional alterations that reflect an altered intracellular biomolecular scenario of great vessels of T2DM patients. Hyperglycemia itself and through intraparietal accumulation of advanced glycation-end products (AGEs) activate different pathways, in particular nuclear factor-κB and MAPKs, while insulin and insulin growth-factor receptors (IGFR) are implicated in the activation of Akt and extracellular-signal-regulated kinases (ERK) 1/2. Nuclear factor-κB is also responsible of increased susceptibility of VSMCs to pro-apoptotic stimuli. Down-regulation of insulin growth-factor 1 receptors (IGFR-1R) activity in diabetic vessels also influences negatively miR-133a levels, so increasing apoptotic susceptibility of VSMCs. Alterations of those bimolecular pathways and related genes associate to the prevalence of a synthetic phenotype of VSMCs induces extracellular matrix alterations of great vessels. A better knowledge of those biomolecular pathways and related genes in VSMCs will help to understand the mechanisms leading to macrovascular alterations in T2DM patients and to suggest new targeted therapies.

(1)H, (15)N and (13)C chemical shift assignments of the La motif and RRM1 from human LARP6

We report here the nearly complete (1)H, (15)N and (13)C resonance assignment of the La motif and RNA recognition motif 1 of human LARP6, an RNA binding protein involved in regulating collagen synthesis.

Genetic loci that regulate ectopic calcification in response to knee trauma in LG/J by SM/J advanced intercross mice

This study reports on genetic susceptibility to ectopic calcification in the LG/J and SM/J advanced intercross mice. Using 347 mice in 98 full-sibships, destabilization of medial meniscus (DMM) was performed to induce joint injury. We found that joint destabilization instigated ectopic calcifications as detected and quantified by micro-CT. We performed quantitative trait locus (QTL) analysis to map ectopic calcification phenotypes to discrete genomic locations. To validate the functional significance of the selected QTL candidate genes, we compared mRNA expression between parental LG/J and SM/J inbred strains. Overall, we detected 20 QTLs affecting synovial and meniscus calcification phenotypes with 11 QTLs linked to synovial calcification. Functional and bioinformatic analyses of single nucleotide polymorphism (SNP) identified functional classifications relevant to angiogenesis (Myo1e, Kif26b, Nprl3, Stab2, Fam105b), bone metabolism/calcification (Tle3, Tgfb2, Lipc, Nfe2l1, Ank, Fam105b), arthritis (Stab2, Tbx21, Map4k4, Hoxb9, Larp6, Col1a2, Adam10, Timp3, Nfe2l1, Trpm3), and ankylosing-spondylitis (Ank, Pon1, Il1r2, Tbkbp1) indicating that ectopic calcification involves multiple mechanisms. Furthermore, the expression of 11 out of 78 candidate genes was significantly different between LG/J and SM/J. Correlation analysis showed that Aff3, Fam81a, Syn3, and Ank were correlated with synovial calcification. Taken together, our findings of multiple genetic loci suggest the involvement of multiple genes contributing to ectopic calcification.

Heterogeneous susceptibility for uraemic media calcification and concomitant inflammation within the arterial tree

Background

End-stage renal disease (ESRD) is strongly associated with arterial calcification of the tunica media, decreased vascular compliance and sudden cardiac death. Here, we analysed the distribution pattern of uraemic media calcification and concomitant inflammation in mice and men.

Methods

Uraemia was induced in DBA/2 mice with high-phosphate diet. Subsequently, we analysed arterial medial calcification using histology, mass spectrometry, and wire myography. Gene expression was quantified using a whole transcriptome array and quantitative PCR. In a cohort of 36 consecutive patients with CKD stage 4–5, we measured the calcium score of the coronary arteries, the ascending thoracic aorta and the infrarenal abdominal aorta using computed tomography scans.

Results

Uraemic DBA/2 mice showed only minor calcifications in thoracic aortas, whereas there was overt media calcification in abdominal aortas. The transcriptional profile and immunohistochemistry revealed induction of Vcam1 expression by vascular smooth muscle cells in uraemic abdominal aortas. Macrophages infiltrated the tunica media of the abdominal aorta. Anti-inflammatory treatment did not improve uraemic media calcification in our animal model. Arterial calcifications in ESRD patients showed a similar distribution pattern in computed tomography scans, with higher calcium scores of the abdominal aorta when compared with the thoracic aorta.

Conclusion

Taken together, there was a similar heterogeneous pattern of calcification in both mice and humans, where the abdominal aorta was more prone to media calcification when compared with the thoracic aorta. In uraemia, smooth muscle cells of the abdominal aorta showed a phenotypic switch to an inflammatory and osteoblastic phenotype.

Use of ultrasound-targeted microbubble destruction to transfect IGF-1 cDNA to enhance the regeneration of rat wounded Achilles tendon in vivo

The purpose of this study was to determine whether using ultrasound-targeted microbubble destruction (UTMD) to transfect rat wounded Achilles tendon with insulin-like growth factor-1 (IGF-1) cDNA would enhance tissue regeneration. Forty rats with injured Achilles tendons were transfected with IGF-1 cDNA and divided into: (1) control group, (2) plasmid-only group, (3) plasmid+ultrasound group and (4) plasmid+microbubbles+ultrasound group. The IGF-1 cDNA expression of the Achilles tendons was evaluated by histological adhesion finding, quantitative real-time reverse transcription PCR examination and biomechanical test. The adhesion scores in group 4 were lowest at weeks 2 and 8 (P<0.05). The IGF-1 expression in the Achilles tendons was highest in group 4 at weeks 2 and 8 (P<0.05). Compared with those of other three groups, the granulation tissues and inflammatory-cell infiltration were lighter in group 4 at week 2, and the scars on the tendons in group 4 were less evident at week 8. The messenger RNA (mRNA) of IGF-1 of group 4 was upregulated at weeks 2 and 8 (P<0.01). Groups 4 and 3 showed a greater maximum load, stiffness and ultimate stress (P<0.05). Maximum load, stiffness and ultimate stress of healing Achilles tendons in group 4 were highest at weeks 2 and 8 (P<0.05).

Regulation of prostate stromal fibroblasts by the PIM1 protein kinase

The PIM1 oncogene is over-expressed in human prostate cancer epithelial cells. Importantly, we observe that in human hyperplastic and cancerous prostate glands PIM1 is also markedly elevated in prostate fibroblasts, suggesting an important role for this kinase in epithelial/stromal crosstalk. The ability of PIM1 to regulate the biologic activity of stromal cells is demonstrated by the observation that expression of PIM1 kinase in human prostate fibroblasts increases the level and secretion of the extracellular matrix molecule, collagen 1A1 (COL1A1), the pro-inflammatory chemokine CCL5, and the platelet-derived growth factor receptors (PDGFR). PIM1 is found to regulate the transcription of CCL5. In co-cultivation assays where PIM1 over-expressing fibroblasts are grown with BPH1 prostate epithelial cells, PIM1 activity markedly enhances the ability of these fibroblasts to differentiate into myofibroblasts and express known markers of cancer-associated fibroblasts (CAFs). This differentiation can be reversed by the addition of small molecule PIM kinase inhibitors. Western blots demonstrate that PIM1 expression in prostate fibroblasts stimulates the phosphorylation of molecules that regulate 5'Cap driven protein translation, including 4EBP1 and eIF4B. Consistent with the hypothesis that the kinase controls translation of specific mRNAs in prostate fibroblasts, we demonstrate that PIM1 expression markedly increases the level of COL1A1 and PDGFRβ mRNA bound to polysomes. Together these results point on PIM1 as a novel factor in regulation of the phenotype and differentiation of fibroblasts in prostate cancer by controlling both the transcription and translation of specific mRNAs.

Collagen and related extracellular matrix proteins in atherosclerotic plaque development

PURPOSE OF REVIEW

The structure, composition and turnover of the extracellular matrix (ECM) as well as cell-matrix interactions are crucial in the developing atherosclerotic plaque. There is a need for further insight into specific proteins in the ECM and their functions in the developing plaque, and during the last few years a number of publications have highlighted this very important field of research. These novel findings will be addressed in the present review.

RECENT FINDINGS

This review covers literature focused on collagen and ECM proteins interacting with collagen, and what their roles may be in plaque development.

SUMMARY

Acute myocardial infarction and stroke are common diseases that cause disability and mortality, and the underlying mechanism is often the rupture of a vulnerable atherosclerotic plaque. The vascular ECM and the tissue repair in the atherosclerotic lesion are important players in plaque progression. Understanding how specific proteins in the ECM interact with cells in the plaque and affect the fate of the plaque can lead to new treatments for cardiovascular disease.