Secreted Protein Acidic and Cysteine Rich Matricellular Protein is Enriched in the Bioactive Fraction of the Human Vascular Pericyte Secretome

Aims: To ascertain if human pericytes produce SPARC (acronym for Secreted Protein Acidic and Cysteine Rich), a matricellular protein implicated in the regulation of cell proliferation, migration, and cell-matrix interactions; clarify if SPARC expression in cardiac pericytes is modulated by hypoxia; and determine the functional consequences of SPARC silencing. Results: Starting from the recognition that the conditioned media (CM) of human pericytes promote proliferation and migration of cardiac stromal cells, we screened candidate mediators by mass-spectrometry analysis. Of the 14 high-confidence proteins (<1% FDR) identified in the bioactive fractions of the pericyte CM, SPARC emerged as the top-scored matricellular protein. SPARC expression was validated using ELISA and found to be upregulated by hypoxia/starvation in pericytes that express platelet-derived growth factor receptor α (PDGFRα). This subfraction is acknowledged to play a key role in extracellular matrix remodeling. Studies in patients with acute myocardial infarction showed that peripheral blood SPARC correlates with the levels of creatine kinase Mb, a marker of cardiac damage. Immunohistochemistry analyses of infarcted hearts revealed that SPARC is expressed in vascular and interstitial cells. Silencing of SPARC reduced the pericyte ability to secrete collagen1a1, without inhibiting the effects of CM on cardiac and endothelial cells. These data indicate that SPARC is enriched in the bioactive fraction of the pericyte CM, is induced by hypoxia and ischemia, and is essential for pericyte ability to produce collagen. Innovation: This study newly indicates that pericytes are a source of the matricellular protein SPARC. Conclusion: Modulation of SPARC production by pericytes may have potential implications for postinfarct healing.

Human adventitial pericytes secrete bioactive factors exerting distinct biological effects on cardiac cells: hints for cardiac repair

Background

Pericytes are attracting much attention as potential candidates for successful cell therapy of myocardial ischaemia. Intramyocardially delivered adventitial pericytes (APCs) secrete paracrine factors which stimulate angiogenesis and recruitment of cardiac stromal cells, reduce fibrosis and promote cardiomyocyte proliferation and viability. However, factors responsible for these biological effects have not been elucidated yet.

Purpose

To exploit the components of APC secretome exerting a biological effect on cardiac cells with the aim to discover new druggable targets with potential therapeutic activity.

Methods and results

APCs were derived from saphenous veins of adult patients (n=13, 68±11 yrs, all with coronary artery disease - CAD). The APC-conditioned medium (CM) stimulated the proliferation of human iPS-derived cardiomyocytes compared with unconditioned medium (UCM) (EdU incorporation, 1.3-fold increases, P=0.004). Stimulation with APC-CM increased the number of mitotic figures in cardiomyocytes (Aurora B, 1.5-fold increases compared to UCM, P=0.002). Furthermore, APC-CM abrogated the hypoxia-induced apoptosis in cardiomyocytes (2-fold increase in Caspase 3/7 activity in hypoxic cells exposed to UCM compared to normoxic cells, P=0.002). We also found that APC-CM stimulates the migration of human cardiac stromal cells (CSCs) obtained from healthy donors (n=6, 54±11 yrs) in both a transwell and scratch migration assays (n=6, P&lt;0.01 and P&lt;0.05 vs UCM respectively). Interestingly, APC-CM activated also the migration of HUVECs (n=6, P&lt;0.01 vs UCM) but did not attract fibroblasts. Next, we aimed to identify the biologically active components of the APC-CM. Depletion of exosomes and heat and RNase treatments did not abolish the pro-migratory action of the APC-CM, while this was abrogated by Proteinase K. Fractionation of the APC-CM based on the MW indicated that the bioactive peptides have MW &gt;30KDa. The pro-migratory fractions of the APC-CM obtained from size exclusion chromatography underwent mass spectrometry analysis (n=3 APCs). This identified 14 proteins uniquely present in the pro-migratory fractions. The two most relevant candidates were SPARC and TGFBI, both confirmed by ELISA. Intriguingly, the recombinant SPARC and TGFBI failed to reproduce the biological effect of APC-CM on CSC migration, suggesting that the secreted proteins may carry unique post-translational modifications not found in synthetic peptides. Further analyses are being carried out to reveal the biological properties of the endogenous SPARC and TGFBI.

Conclusions

This study suggests a fascinating approach based on the use of the active component of the APC-CM as a surrogate of APC therapy. If the biological properties of the cellular proteins will be successfully reproduced in synthetic peptides in vitro, this innovative approach may extend the benefits of APC therapy to all those patients with CAD for whom cell therapy is not an available option.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): British Heart Foundation programme grant “Unravelling mechanism of stem cell depletion for the preservation of regenerative fitness in patients with diabetes”

Correction to: Bone marrow pericyte dysfunction in individuals with type 2 diabetes

Unfortunately, three errors were made in the conversion of HbA_1c to per cent values.

Bone marrow pericyte dysfunction in individuals with type 2 diabetes

AIMS/HYPOTHESIS

Previous studies have shown that diabetes mellitus destabilises the integrity of the microvasculature in different organs by damaging the interaction between pericytes and endothelial cells. In bone marrow, pericytes exert trophic functions on endothelial cells and haematopoietic cells through paracrine mechanisms. However, whether bone marrow pericytes are a target of diabetes-induced damage remains unknown. Here, we investigated whether type 2 diabetes can affect the abundance and function of bone marrow pericytes.

METHODS

We conducted an observational clinical study comparing the abundance and molecular/functional characteristics of CD146⁺ pericytes isolated from the bone marrow of 25 individuals without diabetes and 14 individuals with uncomplicated type 2 diabetes, referring to our Musculoskeletal Research Unit for hip reconstructive surgery.

RESULTS

Immunohistochemistry revealed that diabetes causes capillary rarefaction and compression of arteriole size in bone marrow, without changing CD146⁺ pericyte counts. These data were confirmed by flow cytometry on freshly isolated bone marrow cells. We then performed an extensive functional and molecular characterisation of immunosorted CD146⁺ pericytes. Type 2 diabetes caused a reduction in pericyte proliferation, viability, migration and capacity to support in vitro angiogenesis, while inducing apoptosis. AKT is a key regulator of the above functions and its phosphorylation state is reportedly reduced in the bone marrow endothelium of individuals with diabetes. Surprisingly, we could not find a difference in AKT phosphorylation (at either Ser473 or Thr308) in bone marrow pericytes from individuals with and without diabetes. Nonetheless, the angiocrine signalling reportedly associated with AKT was found to be significantly downregulated, with lower levels of fibroblast growth factor-2 (FGF2) and C-X-C motif chemokine ligand 12 (CXCL12), and activation of the angiogenesis inhibitor angiopoietin 2 (ANGPT2). Transfection with the adenoviral vector carrying the coding sequence for constitutively active myristoylated AKT rescued functional defects and angiocrine signalling in bone marrow pericytes from diabetic individuals. Furthermore, an ANGPT2 blocking antibody restored the capacity of pericytes to promote endothelial networking.

CONCLUSIONS/INTERPRETATION

This is the first demonstration of pericyte dysfunction in bone marrow of people with type 2 diabetes. An altered angiocrine signalling from pericytes may participate in bone marrow microvascular remodelling in individuals with diabetes.

Transplantation of Allogeneic Pericytes Improves Myocardial Vascularization and Reduces Interstitial Fibrosis in a Swine Model of Reperfused Acute Myocardial Infarction

BACKGROUND

Transplantation of adventitial pericytes (APCs) promotes cardiac repair in murine models of myocardial infarction. The aim of present study was to confirm the benefit of APC therapy in a large animal model.

METHODS AND RESULTS

We performed a blind, randomized, placebo-controlled APC therapy trial in a swine model of reperfused myocardial infarction. A first study used human APCs (hAPCs) from patients undergoing coronary artery bypass graft surgery. A second study used allogeneic swine APCs (sAPCs). Primary end points were (1) ejection fraction as assessed by cardiac magnetic resonance imaging and (2) myocardial vascularization and fibrosis as determined by immunohistochemistry. Transplantation of hAPCs reduced fibrosis but failed to improve the other efficacy end points. Incompatibility of the xenogeneic model was suggested by the occurrence of a cytotoxic response following in vitro challenge of hAPCs with swine spleen lymphocytes and the failure to retrieve hAPCs in transplanted hearts. We next considered sAPCs as an alternative. Flow cytometry, immunocytochemistry, and functional/cytotoxic assays indicate that sAPCs are a surrogate of hAPCs. Transplantation of allogeneic sAPCs benefited capillary density and fibrosis but did not improve cardiac magnetic resonance imaging indices of contractility. Transplanted cells were detected in the border zone.

CONCLUSIONS

Immunologic barriers limit the applicability of a xenogeneic swine model to assess hAPC efficacy. On the other hand, we newly show that transplantation of allogeneic sAPCs is feasible, safe, and immunologically acceptable. The approach induces proangiogenic and antifibrotic benefits, though these effects were not enough to result in functional improvements.

The adipokine leptin modulates adventitial pericyte functions by autocrine and paracrine signalling

Transplantation of adventitial pericytes (APCs) improves recovery from tissue ischemia in preclinical animal models by still unknown mechanisms. This study investigates the role of the adipokine leptin (LEP) in the regulation of human APC biological functions. Transcriptomic analysis of APCs showed components of the LEP signalling pathway are modulated by hypoxia. Kinetic studies indicate cultured APCs release high amounts of immunoreactive LEP following exposure to hypoxia, continuing upon return to normoxia. Secreted LEP activates an autocrine/paracrine loop through binding to the LEP receptor (LEPR) and induction of STAT3 phosphorylation. Titration studies using recombinant LEP and siRNA knockdown of LEP or LEPR demonstrate the adipokine exerts important regulatory roles in APC growth, survival, migration and promotion of endothelial network formation. Heterogeneity in LEP expression and secretion may influence the reparative proficiency of APC therapy. Accordingly, the levels of LEP secretion predict the microvascular outcome of APCs transplantation in a mouse limb ischemia model. Moreover, we found that the expression of the Lepr gene is upregulated on resident vascular cells from murine ischemic muscles, thus providing a permissive milieu to transplanted LEP-expressing APCs. Results highlight a new mechanism responsible for APC adaptation to hypoxia and instrumental to vascular repair.

The bone marrow pericyte: an orchestrator of vascular niche

The concept of pericyte has been changing over years. This cell type was believed to possess only a function of trophic support to endothelial cells and to maintain vasculature stabilization. In the last years, the discovery of multipotent ability of perivascular populations led to the concept of vessel/wall niche. Likewise, several perivascular populations have been identified in animal and human bone marrow. In this review, we provide an overview on bone marrow perivascular population, their cross-talk with other niche components, relationship with bone marrow stromal stem cells, and similarities and differences with the perivascular population of the vessel/wall niche. Finally, we focus on the regenerative potential of these cells and the forthcoming challenges related to their use as cell therapy products.

Diabetes Stimulates Osteoclastogenesis by Acidosis-Induced Activation of Transient Receptor Potential Cation Channels

Patients with type 1 diabetes have lower bone mineral density and higher risk of fractures. The role of osteoblasts in diabetes-related osteoporosis is well acknowledged whereas the role of osteoclasts (OCLs) is still unclear. We hypothesize that OCLs participate in pathological bone remodeling. We conducted studies in animals (streptozotocin-induced type 1 diabetic mice) and cellular models to investigate canonical and non-canonical mechanisms underlying excessive OCL activation. Diabetic mice show an increased number of active OCLs. In vitro studies demonstrate the involvement of acidosis in OCL activation and the implication of transient receptor potential cation channel subfamily V member 1 (TRPV1). In vivo studies confirm the establishment of local acidosis in the diabetic bone marrow (BM) as well as the ineffectiveness of insulin in correcting the pH variation and osteoclast activation. Conversely, treatment with TRPV1 receptor antagonists re-establishes a physiological OCL availability. These data suggest that diabetes causes local acidosis in the BM that in turn increases osteoclast activation through the modulation of TRPV1. The use of clinically available TRPV1 antagonists may provide a new means to combat bone problems associated with diabetes.

Bone Marrow-Derived Stem Cells: a Mixed Blessing in the Multifaceted World of Diabetic Complications

Diabetes is one of the main economic burdens in health care, which threatens to worsen dramatically if prevalence forecasts are correct. What makes diabetes harmful is the multi-organ distribution of its microvascular and macrovascular complications. Regenerative medicine with cellular therapy could be the dam against life-threatening or life-altering complications. Bone marrow-derived stem cells are putative candidates to achieve this goal. Unfortunately, the bone marrow itself is affected by diabetes, as it can develop a microangiopathy and neuropathy similar to other body tissues. Neuropathy leads to impaired stem cell mobilization from marrow, the so-called mobilopathy. Here, we review the role of bone marrow-derived stem cells in diabetes: how they are affected by compromised bone marrow integrity, how they contribute to other diabetic complications, and how they can be used as a treatment for these. Eventually, we suggest new tactics to optimize stem cell therapy.

Expansion and characterization of neonatal cardiac pericytes provides a novel cellular option for tissue engineering in congenital heart disease

Background

Living grafts produced by combining autologous heart-resident stem/progenitor cells and tissue engineering could provide a new therapeutic option for definitive correction of congenital heart disease. The aim of the study was to investigate the antigenic profile, expansion/differentiation capacity, paracrine activity, and pro-angiogenic potential of cardiac pericytes and to assess their engrafting capacity in clinically certified prosthetic grafts.

Methods and Results

CD34^pos cells, negative for the endothelial markers CD31 and CD146, were identified by immunohistochemistry in cardiac leftovers from infants and children undergoing palliative repair of congenital cardiac defects. Following isolation by immunomagnetic bead-sorting and culture on plastic in EGM-2 medium supplemented with growth factors and serum, CD34^pos/CD31^neg cells gave rise to a clonogenic, highly proliferative (>20 million at P5), spindle-shape cell population. The following populations were shown to expresses pericyte/mesenchymal and stemness markers. After exposure to differentiation media, the expanded cardiac pericytes acquired markers of vascular smooth muscle cells, but failed to differentiate into endothelial cells or cardiomyocytes. However, in Matrigel, cardiac pericytes form networks and enhance the network capacity of endothelial cells. Moreover, they produce collagen-1 and release chemo-attractants that stimulate the migration of c-Kit^pos cardiac stem cells. Cardiac pericytes were then seeded onto clinically approved xenograft scaffolds and cultured in a bioreactor. After 3 weeks, fluorescent microscopy showed that cardiac pericytes had penetrated into and colonized the graft.

Conclusions

These findings open new avenues for cellular functionalization of prosthetic grafts to be applied in reconstructive surgery of congenital heart disease.

Migration towards SDF-1 selects angiogenin-expressing bone marrow monocytes endowed with cardiac reparative activity in patients with previous myocardial infarction

Introduction

Chemokine-directed migration is crucial for homing of regenerative cells to the infarcted heart and correlates with outcomes of cell therapy trials. Hence, transplantation of chemokine-responsive bone marrow cells may be ideal for treatment of myocardial ischemia. To verify the therapeutic activity of bone marrow mononuclear cells (BM-MNCs) selected by in vitro migration towards the chemokine stromal cell-derived factor-1 (SDF-1) in a mouse model of myocardial infarction (MI), we used BM-MNCs from patients with previous large MI recruited in the TransACT-1&2 cell therapy trials.

Methods

Unfractioned BM-MNCs, SDF-1-responsive, and SDF-1-nonresponsive BM-MNCs isolated by patients recruited in the TransACT-1&2 cell therapy trials were tested in Matrigel assay to evaluate angiogenic potential. Secretome and antigenic profile were characterized by flow cytometry. Angiogenin expression was measured by RT-PCR. Cells groups were also intramyocardially injected in an in vivo model of MI (8-week-old immune deficient CD1-FOXN1^nu/nu mice). Echocardiography and hemodynamic measurements were performed before and at 14 days post-MI. Arterioles and capillaries density, infiltration of inflammatory cells, interstitial fibrosis, and cardiomyocyte proliferation and apoptosis were assessed by immunohistochemistry.

Results

In vitro migration enriched for monocytes, while CD34⁺ and CD133⁺ cells and T lymphocytes remained mainly confined in the non-migrated fraction. Unfractioned total BM-MNCs promoted angiogenesis on Matrigel more efficiently than migrated or non-migrated cells. In mice with induced MI, intramyocardial injection of unfractionated or migrated BM-MNCs was more effective in preserving cardiac contractility and pressure indexes than vehicle or non-migrated BM-MNCs. Moreover, unfractioned BM-MNCs enhanced neovascularization, whereas the migrated fraction was unique in reducing the infarct size and interstitial fibrosis. In vitro studies on isolated cardiomyocytes suggest participation of angiogenin, a secreted ribonuclease that inhibits protein translation under stress conditions, in promotion of cardiomyocyte survival by migrated BM-MNCs.

Conclusions

Transplantation of bone marrow cells helps post-MI healing through distinct actions on vascular cells and cardiomyocytes. In addition, the SDF-1-responsive fraction is enriched with angiogenin-expressing monocytes, which may improve cardiac recovery through activation of cardiomyocyte response to stress. Identification of factors linking migratory and therapeutic outcomes could help refine regenerative approaches.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0028-y) contains supplementary material, which is available to authorized users.

Combined intramyocardial delivery of human pericytes and cardiac stem cells additively improves the healing of mouse infarcted hearts through stimulation of vascular and muscular repair

RATIONALE

Optimization of cell therapy for cardiac repair may require the association of different cell populations with complementary activities.

OBJECTIVE

Compare the reparative potential of saphenous vein-derived pericytes (SVPs) with that of cardiac stem cells (CSCs) in a model of myocardial infarction, and investigate whether combined cell transplantation provides further improvements.

METHODS AND RESULTS

SVPs and CSCs were isolated from vein leftovers of coronary artery bypass graft surgery and discarded atrial specimens of transplanted hearts, respectively. Single or dual cell therapy (300 000 cells of each type per heart) was tested in infarcted SCID (severe combined immunodeficiency)-Beige mice. SVPs and CSCs alone improved cardiac contractility as assessed by echocardiography at 14 days post myocardial infarction. The effect was maintained, although attenuated at 42 days. At histological level, SVPs and CSCs similarly inhibited infarct size and interstitial fibrosis, SVPs were superior in inducing angiogenesis and CSCs in promoting cardiomyocyte proliferation and recruitment of endogenous stem cells. The combination of cells additively reduced the infarct size and promoted vascular proliferation and arteriogenesis, but did not surpass single therapies with regard to contractility indexes. SVPs and CSCs secrete similar amounts of hepatocyte growth factor, vascular endothelial growth factor, fibroblast growth factor, stem cell factor, and stromal cell-derived factor-1, whereas SVPs release higher quantities of angiopoietins and microRNA-132. Coculture of the 2 cell populations results in competitive as well as enhancing paracrine activities. In particular, the release of stromal cell-derived factor-1 was synergistically augmented along with downregulation of stromal cell-derived factor-1-degrading enzyme dipeptidyl peptidase 4.

CONCLUSIONS

Combinatory therapy with SVPs and CSCs may complementarily help the repair of infarcted hearts.

Gestational Diabetes Mellitus Impairs Fetal Endothelial Cell Functions Through a Mechanism Involving MicroRNA-101 and Histone Methyltransferase Enhancer of Zester Homolog-2

Objective—

Gestational diabetes mellitus (GDM) produces fetal hyperglycemia with increased lifelong risks for the exposed offspring of cardiovascular and other diseases. Epigenetic mechanisms induce long-term gene expression changes in response to in utero environmental perturbations. Moreover, microRNAs (miRs) control the function of endothelial cells (ECs) under physiological and pathological conditions and can target the epigenetic machinery. We investigated the functional and expressional effect of GDM on human fetal ECs of the umbilical cord vein (HUVECs). We focused on miR-101 and 1 of its targets, enhancer of zester homolog-2 (EZH2), which trimethylates the lysine 27 of histone 3, thus repressing gene transcription. EZH2 exists as isoforms α and β.

Approach and Results—

HUVECs were prepared from GDM or healthy pregnancies and tested in apoptosis, migration, and Matrigel assays. GDM-HUVECs demonstrated decreased functional capacities, increased miR-101 expression, and reduced EZH2- β and trimethylation of histone H3 on lysine 27 levels. MiR-101 inhibition increased EZH2 expression and improved GDM-HUVEC function. Healthy HUVECs were exposed to high or normal d -glucose concentration for 48 hours and then tested for miR-101 and EZH2 expression. Similar to GDM, high glucose increased miR-101 expression. Chromatin immunoprecipitation using an antibody for EZH2 followed by polymerase chain reaction analyses for miR-101 gene promoter regions showed that both GDM and high glucose concentration reduced EZH2 binding to the miR-101 locus in HUVECs. Moreover, EZH2-β overexpression inhibited miR-101 promoter activity in HUVECs.

Conclusions—

GDM impairs HUVEC function via miR-101 upregulation. EZH2 is both a transcriptional inhibitor and a target gene of miR-101 in HUVECs, and it contributes to some of the miR-101-induced defects of GDM-HUVECs.

Epigenetic profile of human adventitial progenitor cells correlates with therapeutic outcomes in a mouse model of limb ischemia

OBJECTIVE

We investigated the association between the functional, epigenetic, and expressional profile of human adventitial progenitor cells (APCs) and therapeutic activity in a model of limb ischemia.

APPROACH AND RESULTS

Antigenic and functional features were analyzed throughout passaging in 15 saphenous vein (SV)-derived APC lines, of which 10 from SV leftovers of coronary artery bypass graft surgery and 5 from varicose SV removal. Moreover, 5 SV-APC lines were transplanted (8×10(5) cells, IM) in mice with limb ischemia. Blood flow and capillary and arteriole density were correlated with functional characteristics and DNA methylation/expressional markers of transplanted cells. We report successful expansion of tested lines, which reached the therapeutic target of 30 to 50 million cells in ≈10 weeks. Typical antigenic profile, viability, and migratory and proangiogenic activities were conserved through passaging, with low levels of replicative senescence. In vivo, SV-APC transplantation improved blood flow recovery and revascularization of ischemic limbs. Whole genome screening showed an association between DNA methylation at the promoter or gene body level and microvascular density and to a lesser extent with blood flow recovery. Expressional studies highlighted the implication of an angiogenic network centered on the vascular endothelial growth factor receptor as a predictor of microvascular outcomes. FLT-1 gene silencing in SV-APCs remarkably reduced their ability to form tubes in vitro and support tube formation by human umbilical vein endothelial cells, thus confirming the importance of this signaling in SV-APC angiogenic function.

CONCLUSIONS

DNA methylation landscape illustrates different therapeutic activities of human APCs. Epigenetic screening may help identify determinants of therapeutic vasculogenesis in ischemic disease.

Increased antioxidant defense mechanism in human adventitia-derived progenitor cells is associated with therapeutic benefit in ischemia

AIMS

Vascular wall-resident progenitor cells hold great promise for cardiovascular regenerative therapy. This study evaluates the impact of oxidative stress on the viability and functionality of adventitia-derived progenitor cells (APCs) from vein remnants of coronary artery bypass graft (CABG) surgery. We also investigated the antioxidant enzymes implicated in the resistance of APCs to oxidative stress-induced damage and the effect of interfering with one of them, the extracellular superoxide dismutase (EC-SOD/SOD3), on APC therapeutic action in a model of peripheral ischemia.

RESULTS

After exposure to hydrogen peroxide, APCs undergo apoptosis to a smaller extent than endothelial cells (ECs). This was attributed to up-regulation of antioxidant enzymes, especially SODs and catalase. Pharmacological inhibition of SODs increases reactive oxygen species (ROS) levels in APCs and impairs their survival. Likewise, APC differentiation results in SOD down-regulation and ROS-induced apoptosis. Oxidative stress increases APC migratory activity, while being inhibitory for ECs. In addition, oxidative stress does not impair APC capacity to promote angiogenesis in vitro. In a mouse limb ischemia model, an injection of naïve APCs, but not SOD3-silenced APCs, helps perfusion recovery and neovascularization, thus underlining the importance of this soluble isoform in protection from ischemia.

INNOVATION

This study newly demonstrates that APCs are endowed with enhanced detoxifier and antioxidant systems and that SOD3 plays an important role in their therapeutic activity in ischemia.

CONCLUSIONS

APCs from vein remnants of CABG patients express antioxidant defense mechanisms, which enable them to resist stress. These properties highlight the potential of APCs in cardiovascular regenerative medicine.

Reactive oxygen species adversely impacts bone marrow microenvironment in diabetes

Significance: Patients with diabetes mellitus suffer an excess of cardiovascular complications and recover worse from them as compared with their nondiabetic peers. It is well known that microangiopathy is the cause of renal damage, blindness, and heart attacks in patients with diabetes. This review highlights molecular deficits in stem cells and a supporting microenvironment, which can be traced back to oxidative stress and ultimately reduce stem cells therapeutic potential in diabetic patients.

RECENT ADVANCES

New research has shown that increased oxidative stress contributes to inducing microangiopathy in bone marrow (BM), the tissue contained inside the bones and the main source of stem cells. These precious cells not only replace old blood cells but also exert an important reparative function after acute injuries and heart attacks.

CRITICAL ISSUES

The starvation of BM as a consequence of microangiopathy can lead to a less efficient healing in diabetic patients with ischemic complications. Furthermore, stem cells from a patient's BM are the most used in regenerative medicine trials to mend hearts damaged by heart attacks.

FUTURE DIRECTIONS

A deeper understanding of redox signaling in BM stem cells will lead to new modalities for preserving local and systemic homeostasis and to more effective treatments of diabetic cardiovascular complications.

Antiangiogenic therapeutic approaches in multiple myeloma

Angiogenesis is a constant hallmark of multiple myeloma (MM) progression and has prognostic potential. The pathophysiology of MM-induced angiogenesis involves both direct production of angiogenic cytokines by plasma cells and their induction within the bone marrow microenvironment. An improved understanding of the importance of angiogenesis-related signaling in MM has allowed for the rational use of antiangiogenic therapies in this tumor. This review article summarizes the literature data concerning the employment of the most important antiangiogenic therapeutic agents actually used in preclinical models and clinical settings for the treatment of MM.

Retinoids: novel immunomodulators and tumour-suppressive agents?

Retinoids play important roles in the transcriptional activity of normal, degenerative and tumour cells. Retinoid analogues may be promising therapeutic agents for the treatment of immune disorders as different as type I diabetes and systemic lupus erythematosus. In addition, the use of retinoids in cancer treatment has progressed significantly in the last two decades; thus, numerous retinoid compounds have been synthesized and tested. In this paper, the actual or potential use of retinoids as immunomodulators or tumour-suppressive agents is discussed.

Diabetes causes bone marrow endothelial barrier dysfunction by activation of the RhoA-Rho-associated kinase signaling pathway

OBJECTIVE

Diabetes mellitus causes bone marrow (BM) microangiopathy. This study aimed to investigate the mechanisms responsible for BM endothelial dysfunction in diabetes mellitus.

METHODS AND RESULTS

The analysis of differentially expressed transcripts in BM endothelial cells (BMECs) from type-1 diabetic and nondiabetic mice showed an effect of diabetes mellitus on signaling pathways controlling cell death, migration, and cytoskeletal rearrangement. Type-1 diabetic-BMECs displayed high reactive oxygen species levels, increased expression and activity of RhoA and its associated protein kinases Rho-associated kinase 1/Rho-associated kinase 2, and reduced Akt phosphorylation/activity. Likewise, diabetes mellitus impaired Akt-related BMEC functions, such as migration, network formation, and angiocrine factor-releasing activity, and increased vascular permeability. Moreover, high glucose disrupted BMEC contacts through Src tyrosine kinase phosphorylation of vascular endothelial cadherin. These alterations were prevented by constitutively active Akt (myristoylated Akt), Rho-associated kinase inhibitor Y-27632, and Src inhibitors. Insulin replacement restored BMEC abundance, as assessed by flow cytometry analysis of the endothelial marker MECA32, and endothelial barrier function in BM of type-1 diabetic mice.

CONCLUSIONS

Redox-dependent activation of RhoA/Rho-associated kinase and Src/vascular endothelial cadherin signaling pathways, together with Akt inactivation, contribute to endothelial dysfunction in diabetic BM. Metabolic control is crucial for maintenance of endothelial cell homeostasis and endothelial barrier function in BM of diabetic mice.

A retrospective study of skeletal and disease-free survival benefits of zoledronic acid therapy in patients with multiple myeloma treated with novel agents

BACKGROUND

The large majority of patients with multiple myeloma develop bone lesions and typically receive bisphosphonates to maintain bone health and prevent/delay skeletal-related events. Recent clinical data show that the newer-generation bisphosphonate, zoledronic acid, may confer a survival benefit when combined with antimyeloma therapy. However, clinical data describing the combination of zoledronic acid with newer antimyeloma regimens are limited.

DESIGN AND METHODS

This retrospective study analyzed efficacy and safety outcomes in patients with multiple myeloma receiving first- and second-line treatment with bortezomib, lenalidomide, or thalidomide, with or without zoledronic acid.

RESULTS

Records data from 94 patients with Durie-Salmon stage 3A/B multiple myeloma were collated. Most patients (~80%) had bone lesions at study entry. Almost all patients received zoledronic acid at some time during their treatment. Adding zoledronic acid was associated with a numerical, but statistically nonsignificant, benefit in the 1-year progression-free survival rate in both the first- and second-line setting. A similar benefit was observed on the 2-year skeletal-related event rate. Notably, combining zoledronic acid with newer antimyeloma agents was feasible, tolerable, and did not affect the duration of antimyeloma treatment. Three cases of osteonecrosis of the jaw were reported; there were no reports of acute renal failure.

CONCLUSIONS

This retrospective analysis suggests that extended treatment with zoledronic acid in combination with bortezomib, lenalidomide, or thalidomide is safe and tolerable in patients receiving these therapies as first- or second-line treatment. The addition of zoledronic acid may improve both myeloma and skeletal-related outcomes.

Nitric oxide-donating statin improves multiple functions of circulating angiogenic cells

BACKGROUND AND PURPOSE

Statins, a major component of the prevention of cardiovascular disease, aid progenitor cell functions in vivo and in vitro. Statins bearing a NO-releasing moiety were developed for their enhanced anti-inflammatory/anti-thrombotic properties. Here, we investigated if the NO-donating atorvastatin (NCX 547) improved the functions of circulating angiogenic cells (CACs).

EXPERIMENTAL APPROACH

Circulating angiogenic cells (CACs) were prepared from peripheral blood monocytes of healthy volunteers and type-2 diabetic patients and were cultured in low (LG) or high glucose (HG) conditions, in presence of atorvastatin or NCX 547 (both at 0.1 µM) or vehicle. Functional assays (outgrowth, proliferation, viability, senescence and apoptosis) were performed in presence of the endothelial NOS inhibitor L-NIO, the NO scavenger c-PTIO or vehicle.

KEY RESULTS

Culturing in HG conditions lowered NO in CACs, inhibited outgrowth, proliferation, viability and migration, and induced cell senescence and apoptosis. NCX 547 fully restored NO levels and functions of HG-cultured CACs, while atorvastatin prevented only apoptosis in CACs. The activity of Akt, a pro-survival kinase, was increased by atorvastatin in LG-cultured but not in HG-cultured CACs, whereas NCX 547 increased Akt activity in both conditions. L-NIO partially blunted and c-PTIO prevented NCX 547-induced improvements in CAC functions. Finally, NCX 547 improved outgrowth and migration of CACs prepared from patients with type 2 diabetes.

CONCLUSIONS AND IMPLICATIONS

NCX 547 was more effective than atorvastatin in preserving functions of CACs. This property adds to the spectrum of favourable actions that would make NO-releasing statins more effective agents for treating cardiovascular disease.

Four proteins governing overangiogenic endothelial cell phenotype in patients with multiple myeloma are plausible therapeutic targets

Bone marrow (BM) angiogenesis has an important role in the initiation and progression of multiple myeloma (MM). We looked at novel mechanisms of vessel formation in patients with MM through a comparative proteomic analysis between BM endothelial cells (ECs) of patients with active MM (MMECs) and ECs of patients with monoclonal gammopathy of undetermined significance (MGECs) and of subjects with benign anemia (normal ECs). Four proteins were found overexpressed in MMECs: filamin A, vimentin, α-crystallin B and 14-3-3ζ/δ protein, not yet linked to overangiogenic phenotype. These proteins gave a typical distribution in the BM of MM patients and in MMECs versus MGECs, plausibly according to a different functional state. Their expression was enhanced by vascular endothelial growth factor, fibroblast growth factor 2, hepatocyte growth factor and MM plasma cell conditioned medium in step with enhancement of MMEC angiogenesis. Their silencing RNA knockdown affected critical MMEC angiogenesis-related functions, such as spreading, migration and tubular morphogenesis. A gradual stabilization of 14-3-3ζ/δ protein was observed, with transition from normal ECs to MGECs and MMECs that may be a critical step for the angiogenic switch in MMECs and maintenance of the cell overangiogenic phenotype. These proteins were substantially impacted by anti-MM drugs, such as bortezomib, lenalidomide and panobinostat. Results suggest that these four proteins could be new targets for the antiangiogenic management of MM patients.

Diabetes mellitus induces bone marrow microangiopathy

OBJECTIVE

The impact of diabetes on the bone marrow (BM) microenvironment was not adequately explored. We investigated whether diabetes induces microvascular remodeling with negative consequence for BM homeostasis.

METHODS AND RESULTS

We found profound structural alterations in BM from mice with type 1 diabetes with depletion of the hematopoietic component and fatty degeneration. Blood flow (fluorescent microspheres) and microvascular density (immunohistochemistry) were remarkably reduced. Flow cytometry verified the depletion of MECA-32(+) endothelial cells. Cultured endothelial cells from BM of diabetic mice showed higher levels of oxidative stress, increased activity of the senescence marker beta-galactosidase, reduced migratory and network-formation capacities, and increased permeability and adhesiveness to BM mononuclear cells. Flow cytometry analysis of lineage(-) c-Kit(+) Sca-1(+) cell distribution along an in vivo Hoechst-33342 dye perfusion gradient documented that diabetes depletes lineage(-) c-Kit(+) Sca-1(+) cells predominantly in the low-perfused part of the marrow. Cell depletion was associated to increased oxidative stress, DNA damage, and activation of apoptosis. Boosting the antioxidative pentose phosphate pathway by benfotiamine supplementation prevented microangiopathy, hypoperfusion, and lineage(-) c-Kit(+) Sca-1(+) cell depletion.

CONCLUSIONS

We provide novel evidence for the presence of microangiopathy impinging on the integrity of diabetic BM. These discoveries offer the framework for mechanistic solutions of BM dysfunction in diabetes.

Managing myelodysplastic symptoms in elderly patients

Most patients with myelodysplastic syndromes (MDS) are elderly (median age range 65 to 70 years); as a consequence, the incidence and prevalence of these diseases are rising as the population ages. Physicians are often uncertain about how to identify patients who may benefit from specific treatment strategies. The International Prognostic Scoring System is a widely used tool to assess the risk of transformation to leukemia and to guide treatment decisions, but it fails to take into account many aspects of treating elderly patients, including comorbid illnesses, secondary causes of MDS, prior therapy for MDS, and other age-related health, functional, cognitive, and social problems that affect the outcome and managing of myelodysplastic symptoms. Patients with low-risk disease traditionally have been given only best supportive care, but evidence is increasing that treatment with novel non-conventional drugs such as lenalidomide or methyltransferase inhibitors may influence the natural history of the disease and should be used in conjunction with supportive-care measures. Supportive care of these patients could also be improved in order to enhance their quality of life and functional performance. Elderly patients commonly have multiple medical problems and use medications to deal with these. In addition, they are more likely to have more than one health care provider. These factors all increase the risk of drug interactions and the consequent treatment of toxicities. Manifestations of common toxicities or illnesses may be more subtle in the elderly, owing to age-associated functional deficits in multiple organ systems. Particularly important to the elderly MDS patient is the age-related decline in normal bone marrow function, including the diminished capacity of response to stressors such as infection or myelosuppressive treatments. Through the integration of geriatric and oncological strategies, a personalized approach toward this unique population may be applied. As with many diseases in the elderly, reliance on family members or friends to maintain the prescribed treatments, including travel to and from appointments, may place additional stressors on the patient and his/her support network. Careful evaluation and knowledge of functional status, ability to tolerate treatments, effect of disease progression, and general overall health conditions can provide the best opportunity to support these patients. Immediate assessment of daily living activities may detect deficiencies or deficits that often require early interventions.

Human CD133+ progenitor cells promote the healing of diabetic ischemic ulcers by paracrine stimulation of angiogenesis and activation of Wnt signaling

We evaluated the healing potential of human fetal aorta-derived CD133(+) progenitor cells and their conditioned medium (CD133(+) CCM) in a new model of ischemic diabetic ulcer. Streptozotocin-induced diabetic mice underwent bilateral limb ischemia and wounding. One wound was covered with collagen containing 2x10(4) CD133(+) or CD133(-) cells or vehicle. The contralateral wound, covered with only collagen, served as control. Fetal CD133(+) cells expressed high levels of wingless (Wnt) genes, which were downregulated following differentiation into CD133(-) cells along with upregulation of Wnt antagonists secreted frizzled-related protein (sFRP)-1, -3, and -4. CD133(+) cells accelerated wound closure as compared with CD133(-) or vehicle and promoted angiogenesis through stimulation of endothelial cell proliferation, migration, and survival by paracrine effects. CD133(+) cells secreted high levels of vascular endothelial growth factor (VEGF)-A and interleukin (IL)-8. Consistently, CD133(+) CCM accelerated wound closure and reparative angiogenesis, with this action abrogated by co-administering the Wnt antagonist sFRP-1 or neutralizing antibodies against VEGF-A or IL-8. In vitro, these effects were recapitulated following exposure of high-glucose-primed human umbilical vein endothelial cells to CD133(+) CCM, resulting in stimulation of migration, angiogenesis-like network formation and induction of Wnt expression. The promigratory and proangiogenic effect of CD133(+) CCM was blunted by sFRP-1, as well as antibodies against VEGF-A or IL-8. CD133(+) cells stimulate wound healing by paracrine mechanisms that activate Wnt signaling pathway in recipients. These preclinical findings open new perspectives for the cure of diabetic ulcers.

Delayed complete remission in a patient with multiple myeloma

We report a strikingly positive, late response to bortezomib in conjunction with pegylated liposomal doxorubicin in a 79-year old woman with multiple myeloma (MM). The patient obtained a partial remission after eight courses of therapy and a complete remission about 10 months after the end of therapy. This delayed complete remission may be similar to the spontaneous regression reported for other malignancies such as melanoma or lymphoma. We postulate that the immune response and a persistent anti-angiogenic effect of bortezomib could well explain the delayed complete remission in our patient.

Role of kinin B2 receptor signaling in the recruitment of circulating progenitor cells with neovascularization potential

Reduced migratory function of circulating angiogenic progenitor cells (CPCs) has been associated with impaired neovascularization in patients with cardiovascular disease (CVD). Previous findings underline the role of the kallikrein-kinin system in angiogenesis. We now demonstrate the involvement of the kinin B2 receptor (B(2)R) in the recruitment of CPCs to sites of ischemia and in their proangiogenic action. In healthy subjects, B(2)R was abundantly present on CD133(+) and CD34(+) CPCs as well as cultured endothelial progenitor cells (EPCs) derived from blood mononuclear cells (MNCs), whereas kinin B1 receptor expression was barely detectable. In transwell migration assays, bradykinin (BK) exerts a potent chemoattractant activity on CD133(+) and CD34(+) CPCs and EPCs via a B(2)R/phosphoinositide 3-kinase/eNOS-mediated mechanism. Migration toward BK was able to attract an MNC subpopulation enriched in CPCs with in vitro proangiogenic activity, as assessed by Matrigel assay. CPCs from cardiovascular disease patients showed low B(2)R levels and decreased migratory capacity toward BK. When injected systemically into wild-type mice with unilateral limb ischemia, bone marrow MNCs from syngenic B(2)R-deficient mice resulted in reduced homing of sca-1(+) and cKit(+)flk1(+) progenitors to ischemic muscles, impaired reparative neovascularization, and delayed perfusion recovery as compared with wild-type MNCs. Similarly, blockade of the B(2)R by systemic administration of icatibant prevented the beneficial effect of bone marrow MNC transplantation. BK-induced migration represents a novel mechanism mediating homing of circulating angiogenic progenitors. Reduction of BK sensitivity in progenitor cells from cardiovascular disease patients might contribute to impaired neovascularization after ischemic complications.

Endothelial differentiation of hematopoietic stem and progenitor cells from patients with multiple myeloma

PURPOSE

Vasculogenesis is a physiologic process typical of fetal development in which new blood vessels develop from undifferentiated precursors (or angioblasts). In tumors, near angiogenesis, vasculogenesis contributes to the formation of the microvascular plexus that is important for diffusion. Here, we show that hematopoietic stem and progenitor cells (HSPC) of multiple myeloma (MM) patients are able to differentiate into cells with endothelial phenotype on exposure to angiogenic cytokines.

EXPERIMENTAL DESIGN

Circulating HSPCs were purified with an anti-CD133 antibody from patients with newly diagnosed MM before autologous transplantation and exposed to vascular endothelial growth factor (VEGF), fibroblast growth factor-2 and insulin-like growth factor in a 3-week culture.

RESULTS

HSPCs gradually lost CD133 expression and acquired VEGF receptor-2, factor VIII-related antigen, and vascular endothelial-cadherin expression. The expression pattern overlapped with paired MM endothelial cells (MMEC). During culture, cells adhered to fibronectin, spread, and acquired an endothelial cell shape. Differentiated HSPCs also became capillarogenic in the Matrigel assay with maximal activity at the third week of culture. Bone marrow biopsies revealed HSPCs inside the neovessel wall in patients with MM but not in those with monoclonal gammopathy of undetermined significance.

CONCLUSIONS

In patients with MM, but not in those with monoclonal gammopathy of undetermined significance, HSPCs contribute to the neovessel wall building together with MMECs. Therefore, besides angiogenesis, HSPC-linked vasculogenesis contributes to neovascularization in MM patients. Tentatively, we hypothesize that in HSPC cultures a multipotent cell population expressing low VEGF receptor-2 levels corresponds to the endothelial progenitor cell precursor and seems to be the MMEC precursor.

Zoledronic acid affects over-angiogenic phenotype of endothelial cells in patients with multiple myeloma

Therapeutic doses of zoledronic acid markedly inhibit in vitro proliferation, chemotaxis, and capillarogenesis of bone marrow endothelial cells of patients with multiple myeloma. Zoledronic acid also induces a sizeable reduction of angiogenesis in the in vivo chorioallantoic membrane assay. These effects are partly sustained by gene and protein inhibition of vascular endothelial growth factor and vascular endothelial growth factor receptor 2 in an autocrine loop. Mevastatin, a specific inhibitor of the mevalonate pathway, reverts the zoledronic acid antiangiogenic effect, indicating that the drug halts this pathway. Our results provide evidence of a direct antiangiogenic activity of zoledronic acid on multiple myeloma patient-derived endothelial cells due to at least four different mechanisms identified either in vitro or in vivo. Tentatively, we suggest that the zoledronic acid antitumoral activity in multiple myeloma is also sustained by antiangiogenesis, which would partly account for its therapeutic efficacy in multiple myeloma.

Vasculogenic mimicry by bone marrow macrophages in patients with multiple myeloma

Bone marrow macrophages of patients with active and nonactive multiple myeloma (MM), monoclonal gammopathies of undetermined significance (MGUS) and benign anemia (controls) were stimulated for 7 days with vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), and analysed for the expression of endothelial cell (EC) markers by reverse transcription (RT)-PCR, real-time RT-PCR, western blot and immunofluorescence. Their vasculogenic ability was investigated in vitro in a Matrigel assay and in vivo on bone marrow biopsies through dual immunofluorescence and confocal laser microscopy. Active MM macrophages exposed to VEGF and bFGF acquired EC markers and formed capillary-like structures mimicking paired bone marrow ECs (multiple myeloma patient-derived endothelial cells, MMECs), with major responsiveness compared to macrophages from nonactive MM, MGUS or controls. Bone marrow biopsies of active MM harbored 'mosaic' vessels, being formed by MMECs, EC-like macrophages and macrophages themselves. These figures were rare in nonactive MM and absent in MGUS or controls. Our data indicate that macrophages contribute to build neovessels in active MM through vasculogenic mimicry, and this ability proceeds parallel to progression of the plasma cell tumors. Macrophages may be a target for the MM antivascular treatment.

Stephen Paget and the 'seed and soil' theory of metastatic dissemination

The outcome of cancer metastasis depends on multiple interactions between selected metastatic cells and homeostatic mechanisms unique to some organ microenvironments. The English surgeon Stephen Paget (1855-1926) is credited with being the first to postulate the important role played by microenvironment in metastasis formation. The concept of his 'seed and soil' theory has been supported and confirmed by numerous publications. This review article summarises the most important literature data about this matter.

Immune tolerance to drugs. I. Long-term tolerability of rokitamycin in patients with antibiotics hypersensitivity

Macrolides are considered one of the safest anti-infective groups in clinical use and are well-tolerated as alternative antibiotics in patients with a previous adverse reaction to other classes of antibiotics. However there is scarce information in the literature about their long-term tolerability. The present study was performed to determine whether the results of a challenge test with rokitamycin could predict the response to ingestion of rokitamycin during illness. The study was carried out on 335 patients, who experienced adverse reactions to one or more antibiotics. All patients received peroral challenges with rokitamycin (granules or capsules). On the first day patients received a number of placebo doses equivalent to the rokitamycin doses. One week later, the test was administered by increasing doses of rokitamycin at 60 min intervals until the common daily therapeutic dose of 406.25mg was reached (31.25-93.75-125-156.25mg). A questionnaire was distributed to all subjects. In particular, subjects were asked to clarify any reactive symptom they had developed after ingestion of the drug. It was found that only 3.1% (4/129) of subjects, who used this drug, reported adverse reactions: three experienced urticaria/angioedema and one patient experienced erythema multiforme during treatment. This study, points out a low percentage of adverse reactions to rokitamycin after a negative challenge test, thus, emphasizing both safety and good predictive value as a challenge test.