Migration of monocytes/macrophages in vitro and in vivo is accompanied by MMP12-dependent tunnel formation and by neovascularization

Comparison of the Behavior of Perivascular Cells (Pericytes and CD34+ Stromal Cell/Telocytes) in Sprouting and Intussusceptive Angiogenesis

Perivascular cells in the pericytic microvasculature, pericytes and CD34+ stromal cells/telocytes (CD34+SCs/TCs), have an important role in angiogenesis. We compare the behavior of these cells depending on whether the growth of endothelial cells (ECs) from the pre-existing microvasculature is toward the interstitium with vascular bud and neovessel formation (sprouting angiogenesis) or toward the vascular lumen with intravascular pillar development and vessel division (intussusceptive angiogenesis). Detachment from the vascular wall, mobilization, proliferation, recruitment, and differentiation of pericytes and CD34+SCs/TCs, as well as associated changes in vessel permeability and functionality, and modifications of the extracellular matrix are more intense, longer lasting over time, and with a greater energy cost in sprouting angiogenesis than in intussusceptive angiogenesis, in which some of the aforementioned events do not occur or are compensated for by others (e.g., sparse EC and pericyte proliferation by cell elongation and thinning). The governing mechanisms involve cell-cell contacts (e.g., peg-and-socket junctions between pericytes and ECs), multiple autocrine and paracrine signaling molecules and pathways (e.g., vascular endothelial growth factor, platelet-derived growth factor, angiopoietins, transforming growth factor B, ephrins, semaphorins, and metalloproteinases), and other factors (e.g., hypoxia, vascular patency, and blood flow). Pericytes participate in vessel development, stabilization, maturation and regression in sprouting angiogenesis, and in interstitial tissue structure formation of the pillar core in intussusceptive angiogenesis. In sprouting angiogenesis, proliferating perivascular CD34+SCs/TCs are an important source of stromal cells during repair through granulation tissue formation and of cancer-associated fibroblasts (CAFs) in tumors. Conversely, CD34+SCs/TCs have less participation as precursor cells in intussusceptive angiogenesis. The dysfunction of these mechanisms is involved in several diseases, including neoplasms, with therapeutic implications.

All-Trans Retinoic Acid Enhances Matrix Metalloproteinase 2 Expression and Secretion in Human Myeloid Leukemia THP-1 Cells

All-trans retinoic acid (ATRA) is an effective drug for the induction therapy of acute promyelocytic leukemia. However, the treatment is associated with adverse events such as retinoic acid syndrome (RAS) in some patients, whose histologic characteristics included organ infiltration by leukemic cells. Matrix metalloproteinase 2 (MMP-2) is often upregulated in tumor cells and plays a role in tumor cell migration and invasion by degrading the extracellular matrix. In this study, we examined the possible modulatory effects of ATRA on MMP-2 expression and secretion in human myeloid leukemia cell line THP-1. The cells were treated with various concentrations of ATRA, and MMP-2 expression and secretion were examined. MMP-2 expression and secretion started to increase with ATRA concentration as low as 0.1 nM and gradually increased thereafter. Agonists of retinoic acid receptor (RAR) or retinoid X receptor (RXR) alone could enhance MMP-2 secretion, and RAR or RXR antagonists alone could reverse ATRA-induced MMP-2 secretion. ATRA increased intracellular calcium ion levels, and a calcium-channel blocker inhibited ATRA-induced MMP-2 secretion. Dexamethasone suppressed ATRA-induced MMP-2 secretion. Our results suggest that ATRA enhances MMP-2 expression and secretion in human myeloid leukemia THP-1 cells in a calcium ion dependent manner through RAR/RXR signaling pathways, and this enhanced expression and secretion may be associated with the possible mechanisms of RAS.

Long non-coding RNA AK027294 involves in the process of proliferation, migration, and apoptosis of colorectal cancer cells

This study is aimed to investigate the differentially expressed long non-coding RNAs (lncRNAs) in colorectal cancer and its potential biological function. Colorectal adenoma is the precancerous lesions of colorectal cancer, so in this study, we used colorectal adenoma as negative control. The global lncRNA expression profile in colorectal cancer and adenoma was evaluated by bioinformatics. The biological functions and potential mechanism of AK027294 were investigated in HCT116, HCT8, and SW480 colorectal cancer cells. A total of 135 lncRNAs were found to be differentially expressed in colorectal cancer and adenoma tissues. Among them, 71 lncRNAs were up-regulated and 64 lncRNAs were down-regulated. Especially, AK027294 was found to be highly expressed in colorectal cancer tissues compared with colorectal adenoma tissues (fold change is 184.5). Our results indicated that AK027294 down-regulation significantly inhibited colorectal cancer cells proliferation and migration, but promoted cell apoptosis (P < 0.05). The potential mechanism of AK027294 might be associated with the regulation of caspase-3, caspase-8, Bcl-2, MMP12, MMP9, and TWIST. The lncRNA expression profile in colorectal cancer suggests lncRNAs may play important roles in the occurrence and progression of colorectal cancer. AK027294 is highly expressed in colorectal cancer and closely correlates with colorectal cells proliferation, migration, and apoptosis.

Pericytes: multitasking cells in the regeneration of injured, diseased, and aged skeletal muscle

Pericytes are perivascular cells that envelop and make intimate connections with adjacent capillary endothelial cells. Recent studies show that they may have a profound impact in skeletal muscle regeneration, innervation, vessel formation, fibrosis, fat accumulation, and ectopic bone formation throughout life. In this review, we summarize and evaluate recent advances in our understanding of pericytes' influence on adult skeletal muscle pathophysiology. We also discuss how further elucidating their biology may offer new approaches to the treatment of conditions characterized by muscle wasting.

Tumor-associated macrophages (TAMs) form an interconnected cellular supportive network in anaplastic thyroid carcinoma

BACKGROUND

A relationship between the increased density of tumor-associated macrophages (TAMs) and decreased survival was recently reported in thyroid cancer patients. Among these tumors, anaplastic thyroid cancer (ATC) is one of the most aggressive solid tumors in humans. TAMs (type M2) have been recognized as promoting tumor growth. The purpose of our study was to analyze with immunohistochemistry the presence of TAMs in a series of 27 ATC.

METHODOLOGY/PRINCIPAL FINDINGS

Several macrophages markers such as NADPH oxidase complex NOX2-p22phox, CD163 and CD 68 were used. Immunostainings showed that TAMs represent more than 50% of nucleated cells in all ATCs. Moreover, these markers allowed the identification of elongated thin ramified cytoplasmic extensions, bestowing a "microglia-like" appearance on these cells which we termed "Ramified TAMs" (RTAMs). In contrast, cancer cells were totally negative. Cellular stroma was highly simplified since apart from cancer cells and blood vessels, RTAMs were the only other cellular component. RTAMs were evenly distributed and intermingled with cancer cells, and were in direct contact with other RTAMs via their ramifications. Moreover, RTAMs displayed strong immunostaining for connexin Cx43. Long chains of interconnected RTAMs arose from perivascular clusters and were dispersed within the tumor parenchyma. When expressed, the glucose transporter Glut1 was found in RTAMs and blood vessels, but rarely in cancer cells.

CONCLUSION

ATCs display a very dense network of interconnected RTAMs in direct contact with intermingled cancer cells. To our knowledge this is the first time that such a network is described in a malignant tumor. This network was found in all our studied cases and appeared specific to ATC, since it was not found in differentiated thyroid cancers specimens. Taken together, these results suggest that RTAMs network is directly related to the aggressiveness of the disease via metabolic and trophic functions which remain to be determined.

The Local Injection of Peritoneal Macrophages Induces Neovascularization in Rat Ischemic Hind Limb Muscles

Macrophages play a pivotal role in the development of newly formed vascular networks, in addition to their normal immunological functions. This research focuses on peritoneal macrophages as a novel source in cell implantation therapy for ischemic diseases. In this study, production of angiogenic growth factors by peritoneal macrophages and its in vivo effect of neovascularization were evaluated. Mononuclear cells from the peritoneal cavity (P-MNCs) enriched with macrophages were isolated and stimulated with hypoxia and interleukin-1β (IL-1β) to mimic an ischemic tissue environment in vitro. Expression of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) of mRNA in P-MNCs was apparently enhanced by hypoxic stimulation, and the production of VEGF protein was also augmented by hypoxia and IL-1β. A rat ischemic hind limb model was created and P-MNCs (8 × 106/limb) were injected into the ischemic muscles. The blood flow, which was assessed using the colored microsphere method, showed that the percentage blood flow was significantly increased by P-MNCs injection 4 weeks after surgery (48.3 ± 16.8% in noninjected ischemic limb vs. 84.3 ± 13.0% in the P-MNCs-injected limb). A histological analysis revealed that the number of capillaries detected by alkaline phosphatase staining was increased in the P-MNCs group 4 weeks after injection. Furthermore, the number of α-smooth muscle actin-positive vessels also showed a significant increase following P-MNC injection. The injected P-MNCs labeled with fluorescence were detected in the interstitial space of ischemic muscles, and VEGF protein expression of the implanted cells was confirmed by immunohistochemistry. These results indicate that peritoneal macrophages stimulate capillary formation and arteriogenesis in the ischemic limbs, possibly through the production of angiogenic growth factors. These findings suggest that the physiological angiogenic property of peritoneal macrophages could therefore be utilized for neovascularization in cell implantation therapy.

A subpopulation of peritoneal macrophages form capillarylike lumens and branching patterns in vitro

Objective: We have previously shown that monocytes/macrophages (MC/Mph) influence neovascularization by extracellular matrix degradation, and by direct incorporation into growing microvessels. To date, neither the phenotype of these cells, nor the stages of their capillary-like conversion were sufficiently characterized. Methods: We isolated mouse peritoneal Mph from transgenic mice expressing fluorescent proteins either ubiquitously, or specifically in the myelocytic lineage. These Mph were embedded in Matrigel which contained fluorescent protease substrates, exposed to an MCP-1 chemotactic gradient, and then examined by confocal microscopy after various intervals. Results: Within 3 hrs after gel embedding, we detected TIMP-1 and MMP-12 dependent proteolysis of the matrix surrounding Mph, mostly in the direction of high concentrations of MCP-1. After 2 days, Mph developed intracellular vacuoles containing degradation product. At 5 days these vacuoles were enlarged and/or fused to generate trans-cellular lumens in approximately 10% of cells or more (depending on animal’s genetic background). At this stage, Mph became tubular, and occasionally organized in three-dimensional structures resembling branched microvessels. Conclusion: Isolated mouse peritoneal Mph penetrate Matrigel and form tunnels via a metalloprotease-driven proteolysis and phagocytosis. Following a morphological adjustment driven by occurrence, enlargement and/or fusion process of intracellular vacuoles, similar to that described in bona fide endothelium, a subpopulation of these cells end up by lining a capillary-like lumen in vitro. Thus we show that adult Mph, not only the more primitive ‘endothelial progenitors’, have functional properties until now considered defining of the endothelial phenotype.

Monocytes/macrophages cooperate with progenitor cells during neovascularization and tissue repair: conversion of cell columns into fibrovascular bundles

The potential of monocytes/macrophages (MC/Mph) to contribute to neovascularization has recently become a topic of intense scrutiny. Here, we characterized the behavior of MC/Mph in cellular infiltrates, with emphasis on their spatial organization and localization in newly formed microvessels. To this end, we studied MC/Mph migration and assembly in basic fibroblast growth factor-supplemented Matrigel plugs placed in transgenic Tie2-beta-galactosidase mice for up to 4 weeks. In these plugs, along with Nile Red-positive adipocytes, we found MC/Mph distributed in cell cords, also containing various mature and progenitor tissue cells; and functional Tie2-positive or -negative microvessels embedded in bundles of fibrillar collagen surrounded by F4/80-positive MC/Mph. At earlier stages of infiltration, we found tubular destruction of the matrix (tunnels) and MC/Mph-lined capillary-like structures occasionally containing erythrocytes, indicating their propensity for endothelial trans-differentiation. We also analyzed in vitro the MCP-1-induced chemotactic migration of fluorescently labeled peritoneal MC/Mph incorporated in Matrigel-containing fluorescent protease substrates. Many of these MC/Mph produced MMP-12- and TIMP-1-dependent tunnels coupled with acquisition of a lumen. In conclusion, long-term implantation of Matrigel plugs qualifies as a novel experimental model of tissue regeneration, in which neovascularization intimately couples with fibrosis and organogenesis and in which cells of MC/Mph phenotype play a key structural role.

Impaired revascularization in a mouse model of type 2 diabetes is associated with dysregulation of a complex angiogenic-regulatory network

OBJECTIVE

Diabetes is a risk factor for the development of cardiovascular diseases associated with impaired angiogenesis or increased endothelial cell apoptosis.

METHODS AND RESULTS

Here it is shown that angiogenic repair of ischemic hindlimbs was impaired in Lepr(db/db) mice, a leptin receptor-deficient model of diabetes, compared with wild-type (WT) C57BL/6 mice, as evaluated by laser Doppler flow and capillary density analyses. To identify molecular targets associated with this disease process, hindlimb cDNA expression profiles were created from adductor muscle of Lepr(db/db) and WT mice before and after hindlimb ischemia using Affymetrix GeneChip Mouse Expression Set microarrays. The expression patterns of numerous angiogenesis-related proteins were altered in Lepr(db/db) versus WT mice after ischemic injury. These transcripts included neuropilin-1, vascular endothelial growth factor-A, placental growth factor, elastin, and matrix metalloproteinases implicated in blood vessel growth and maintenance of vessel wall integrity.

CONCLUSIONS

These data illustrate that impaired ischemia-induced neovascularization in type 2 diabetes is associated with the dysregulation of a complex angiogenesis-regulatory network.

Proangiogenic activity of beta-carotene is coupled with the activation of endothelial cell chemotaxis

Endothelial cells play an important role in angiogenesis (formation of new vessels from preexisting ones), which is essential for organogenesis, tissue remodeling but also inflammatory response, carcinogenesis in all periods of our life. Beta-carotene (BC) in non-toxic concentrations (up to 3 microM) had no detectable effect on HUVECs (human umbilical vein endothelial cells) proliferation or apoptosis, despite significant changes of the expression patterns of pro- and anti-apoptotic genes. However beta-carotene did not change the tubulogenic activity of HUVEC in the in vitro angiogenesis model, it potently accelerated the bFGF-induced development of microcapillaries, as well as the migration of endothelial cells, in matrigel plug injected subcutaneously to mice. Potent activation of endothelial cell migration in the in vitro model of chemotaxis was also observed. According to the microarray data, genes involved in cell/cell and cell/matrix adhesion, matrix reorganization, activation of chemotaxis, the G-protein regulated intracellular signaling as well as genes involved in the rapid remodeling of protein cytoskeleton were the most affected by BC in HUVEC. We conclude that beta-carotene in the physiological concentration range stimulates early steps of angiogenesis by the activation of cellular migration as well as matrix reorganization and decrease of cell adhesion.