Role of TPBG (Trophoblast Glycoprotein) Antigen in Human Pericyte Migratory and Angiogenic Activity.

Objective- To determine the role of the oncofetal protein TPBG (trophoblast glycoprotein) in normal vascular function and reparative vascularization. Approach and Results- Immunohistochemistry of human veins was used to show TPBG expression in vascular smooth muscle cells and adventitial pericyte-like cells (APCs). ELISA, Western blot, immunocytochemistry, and proximity ligation assays evidenced a hypoxia-dependent upregulation of TPBG in APCs not found in vascular smooth muscle cells or endothelial cells. This involves the transcriptional modulator CITED2 (Atypical chemokine receptor 3 CBP/p300-interacting transactivator with glutamic acid (E)/aspartic acid (D)-rich tail) and downstream activation of CXCL12 (chemokine [C-X-C motif] ligand-12) signaling through the CXCR7 (C-X-C chemokine receptor type 7) receptor and ERK1/2 (extracellular signal-regulated kinases 1/2). TPBG silencing by siRNA transfection downregulated CXCL12, CXCR7, and pERK (phospho Thr202/Tyr204 ERK1/2) and reduced the APC migratory and proangiogenic capacities. TPBG forced expression induced opposite effects, which were associated with the formation of CXCR7/CXCR4 (C-X-C chemokine receptor type 4) heterodimers and could be contrasted by CXCL12 and CXCR7 neutralization. In vivo Matrigel plug assays using APCs with or without TPBG silencing evidenced TPBG is essential for angiogenesis. Finally, in immunosuppressed mice with limb ischemia, intramuscular injection of TPBG-overexpressing APCs surpassed naïve APCs in enhancing perfusion recovery and reducing the rate of toe necrosis. Conclusions- TPBG orchestrates the migratory and angiogenic activities of pericytes through the activation of the CXCL12/CXCR7/pERK axis. This novel mechanism could be a relevant target for therapeutic improvement of reparative angiogenesis.

Nerve growth factor gene therapy improves bone marrow sensory innervation and nociceptor-mediated stem cell release in a mouse model of type 1 diabetes with limb ischaemia.

AIMS/HYPOTHESIS: Sensory neuropathy is common in people with diabetes; neuropathy can also affect the bone marrow of individuals with type 2 diabetes. However, no information exists on the state of bone marrow sensory innervation in type 1 diabetes. Sensory neurons are trophically dependent on nerve growth factor (NGF) for their survival. The aim of this investigation was twofold: (1) to determine if sensory neuropathy affects the bone marrow in a mouse model of type 1 diabetes, with consequences for stem cell liberation after tissue injury; and (2) to verify if a single systemic injection of the NGF gene exerts long-term beneficial effects on these phenomena. METHODS: A mouse model of type 1 diabetes was generated in CD1 mice by administration of streptozotocin; vehicle was administered to non-diabetic control animals. Diabetic animals were randomised to receive systemic gene therapy with either human NGF or ß-galactosidase. After 13 weeks, limb ischaemia was induced in both groups to study the recovery post injury. When the animals were killed, samples of tissue and peripheral blood were taken to assess stem cell mobilisation and homing, levels of substance P and muscle vascularisation. An in vitro cellular model was adopted to verify signalling downstream to human NGF and related neurotrophic or pro-apoptotic effects. Normally distributed variables were compared between groups using the unpaired Student's t test and non-normally distributed variables were assessed by the Wilcoxon-Mann-Whitney test. The Fisher's exact test was employed for categorical variables. RESULTS: Immunohistochemistry indicated a 3.3-fold reduction in the number of substance P-positive nociceptive fibres in the bone marrow of type 1 diabetic mice (p < 0.001 vs non-diabetic). Moreover, diabetes abrogated the creation of a neurokinin gradient which, in non-diabetic mice, favoured the mobilisation and homing of bone-marrow-derived stem cells expressing the substance P receptor neurokinin 1 receptor (NK1R). Pre-emptive gene therapy with NGF prevented bone marrow denervation, contrasting with the inhibitory effect of diabetes on the mobilisation of NK1R-expressing stem cells, and restored blood flow recovery from limb ischaemia. In vitro hNGF induced neurite outgrowth and exerted anti-apoptotic actions on rat PC12 cells exposed to high glucose via activation of the canonical neurotrophic tyrosine kinase receptor type 1 (TrkA) signalling pathway. CONCLUSIONS/INTERPRETATION: This study shows, for the first time, the occurrence of sensory neuropathy in the bone marrow of type 1 diabetic mice, which translates into an altered modulation of substance P and depressed release of substance P-responsive stem cells following ischaemia. NGF therapy improves bone marrow sensory innervation, with benefits for healing on the occurrence of peripheral ischaemia. Nociceptors may represent a new target for the treatment of ischaemic complications in diabetes.

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.

Genetic Analysis Reveals a Longevity-Associated Protein Modulating Endothelial Function and Angiogenesis.

RATIONALE: Long living individuals show delay of aging, which is characterized by the progressive loss of cardiovascular homeostasis, along with reduced endothelial nitric oxide synthase activity, endothelial dysfunction, and impairment of tissue repair after ischemic injury. OBJECTIVE: Exploit genetic analysis of long living individuals to reveal master molecular regulators of physiological aging and new targets for treatment of cardiovascular disease. METHODS AND RESULTS: We show that the polymorphic variant rs2070325 (Ile229Val) in bactericidal/permeability-increasing fold-containing-family-B-member-4 (BPIFB4) associates with exceptional longevity, under a recessive genetic model, in 3 independent populations. Moreover, the expression of BPIFB4 is instrumental to maintenance of cellular and vascular homeostasis through regulation of protein synthesis. BPIFB4 phosphorylation/activation by protein-kinase-R-like endoplasmic reticulum kinase induces its complexing with 14-3-3 and heat shock protein 90, which is facilitated by the longevity-associated variant. In isolated vessels, BPIFB4 is upregulated by mechanical stress, and its knock-down inhibits endothelium-dependent vasorelaxation. In hypertensive rats and old mice, gene transfer of longevity-associated variant-BPIFB4 restores endothelial nitric oxide synthase signaling, rescues endothelial dysfunction, and reduces blood pressure levels. Furthermore, BPIFB4 is implicated in vascular repair. BPIFB4 is abundantly expressed in circulating CD34(+) cells of long living individuals, and its knock-down in endothelial progenitor cells precludes their capacity to migrate toward the chemoattractant SDF-1. In a murine model of peripheral ischemia, systemic gene therapy with longevity-associated variant-BPIFB4 promotes the recruitment of hematopoietic stem cells, reparative vascularization, and reperfusion of the ischemic muscle. CONCLUSIONS: Longevity-associated variant-BPIFB4 may represent a novel therapeutic tool to fight endothelial dysfunction and promote vascular reparative processes.

Sensory neuropathy hampers nociception-mediated bone marrow stem cell release in mice and patients with diabetes.

AIMS/HYPOTHESIS: Upon tissue injury, peripheral sensory neurons release nociceptive factors (e.g. substance P [SP]), which exert local and systemic actions including the recruitment of bone marrow (BM)-derived haematopoietic stem and progenitor cells (HSPCs) endowed with paracrine pro-angiogenic properties. We herein explore whether diabetic neuropathy interferes with these phenomena. METHODS: We first investigated the presence of sensory neuropathy in the BM of patients with type 2 diabetes by immunohistochemistry and morphometry analyses of nerve size and density and assessment of SP release by ELISA. We next analysed the association of sensory neuropathy with altered HSPC release under ischaemia or following direct stimulation with granulocyte colony-stimulating factor (G-CSF). BM and circulating HSPCs expressing the neurokinin 1 receptor (NK1R), which is the main SP receptor, were measured by flow cytometry. We finally assessed whether an altered modulation of SP secretion interferes with the mobilisation and homing of NK1R-HSPCs in a mouse model of type 2 diabetes after limb ischaemia (LI). RESULTS: Nociceptive fibres were reduced in the BM of patients and mice with type 2 diabetes. Patients with neuropathy showed a remarkable reduction in NK1R-HSPC mobilisation under ischaemia or upon G-CSF stimulation. Following LI, diabetic mice manifested an altered SP gradient between BM, peripheral blood and limb muscles, accompanied by a depressed recruitment of NK1R-HSPCs to the ischaemic site. CONCLUSIONS/INTERPRETATION: Sensory neuropathy translates into defective liberation and homing of reparative HSPCs. Nociceptors may represent a new target for treatment of diabetic complications.

Multi-Omics Analysis of Diabetic Heart Disease in the db/db Model Reveals Potential Targets for Treatment by a Longevity-Associated Gene.

Characterisation of animal models of diabetic cardiomyopathy may help unravel new molecular targets for therapy. Long-living individuals are protected from the adverse influence of diabetes on the heart, and the transfer of a longevity-associated variant (LAV) of the human BPIFB4 gene protects cardiac function in the db/db mouse model. This study aimed to determine the effect of LAV-BPIFB4 therapy on the metabolic phenotype (ultra-high-performance liquid chromatography-mass spectrometry, UHPLC-MS) and cardiac transcriptome (next-generation RNAseq) in db/db mice. UHPLC-MS showed that 493 cardiac metabolites were differentially modulated in diabetic compared with non-diabetic mice, mainly related to lipid metabolism. Moreover, only 3 out of 63 metabolites influenced by LAV-BPIFB4 therapy in diabetic hearts showed a reversion from the diabetic towards the non-diabetic phenotype. RNAseq showed 60 genes were differentially expressed in hearts of diabetic and non-diabetic mice. The contrast between LAV-BPIFB4- and vehicle-treated diabetic hearts revealed eight genes differentially expressed, mainly associated with mitochondrial and metabolic function. Bioinformatic analysis indicated that LAV-BPIFB4 re-programmed the heart transcriptome and metabolome rather than reverting it to a non-diabetic phenotype. Beside illustrating global metabolic and expressional changes in diabetic heart, our findings pinpoint subtle changes in mitochondrial-related proteins and lipid metabolism that could contribute to LAV-BPIFB4-induced cardio-protection in a murine model of type-2 diabetes.

Transfer of a human gene variant associated with exceptional longevity improves cardiac function in obese type 2 diabetic mice through induction of the SDF-1/CXCR4 signalling pathway.

AIMS: Homozygosity for a four-missense single-nucleotide polymorphism haplotype of the human BPIFB4 gene is enriched in long-living individuals. Delivery of this longevity-associated variant (LAV) improved revascularisation and reduced endothelial dysfunction and atherosclerosis in mice through a mechanism involving the stromal cell-derived factor-1 (SDF-1). Here, we investigated if delivery of the LAV-BPIFB4 gene may attenuate the progression of diabetic cardiomyopathy. METHODS AND RESULTS: Compared with age-matched lean controls, diabetic db/db mice showed altered echocardiographic indices of diastolic and systolic function and histological evidence of microvascular rarefaction, lipid accumulation, and fibrosis in the myocardium. All these alterations, as well as endothelial dysfunction, were prevented by systemic LAV-BPIFB4 gene therapy using an adeno-associated viral vector serotype 9 (AAV9). In contrast, AAV9 wild-type-BPIFB4 exerted no benefit. Interestingly, LAV-BPIFB4-treated mice showed increased SDF-1 levels in peripheral blood and myocardium and up-regulation of the cardiac myosin heavy chain isoform alpha, a contractile protein that was reduced in diabetic hearts. SDF-1 up-regulation was instrumental to LAV-BPIFB4-induced benefit as both haemodynamic and structural improvements were inhibited by an orally active antagonist of the SDF-1 CXCR4 receptor. CONCLUSIONS: In mice with type-2 diabetes, LAV-BPIFB4 gene therapy promotes an advantageous remodelling of the heart, allowing it to better withstand diabetes-induced stress. These results support the viability of transferring healthy characteristics of longevity to attenuate diabetic cardiac disease.

Immunological responses in mice to full-thickness corneal grafts engineered from porcine collagen.

Tissue-engineered (TE) corneas were fabricated from porcine collagen cross-linked with 1-ethyl-3-(3-dimethyl aminoproplyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS), and were transplanted into BALB/c mice orthotopically using a full-thickness penetrating keratoplasty (PKP) procedure. The biocompatibility was evaluated by assessing both local and systemic immune responses. Myeloid cells including granulocytes and macrophages were the main infiltrating cells in recipient cornea and in retro-TE corneal membrane which developed 7-10 days post surgery. Sodium citrate was found to be effective in reducing fibrin accumulation in anterior chamber post grafting at early time points, but it did not prevent formation of the retro-TE corneal membrane. No significant T cell activation was observed in the submandibular draining lymph nodes (SMDLN) by flow cytometry. Anti-porcine type I collagen IgG antibodies were detected in the serum of grafted mice from 2 weeks post grafting and the concentration of antibodies increased with time. Overall, porcine collagen-EDC/NHS TE corneas were tolerated well in murine recipients, causing mainly a self-limiting local innate immune response and a low-grade humoral response with little evidence of sustained T cell activation. Retro-TE corneal membrane formation was the main complication and barrier to clarity.

Soluble antigen traffics rapidly and selectively from the corneal surface to the eye draining lymph node and activates T cells when codelivered with CpG oligonucleotides.

The transport of antigen to the secondary lymphoid tissue is a central component in the initiation of the adaptive immune response. The mechanism of antigen delivery to the DLN from the avascular cornea has not been fully explored. Previous studies in the mouse have shown that cell-associated corneal antigen is delivered within 6 h to the eye draining SM DLN via DCs and macrophages. In this study, we used a system in which antigen and the processed p-MHCII complexes derived from the antigen could be tracked in vivo. We report that soluble antigen applied to an abraded cornea in the mouse is transported rapidly (within 30 min) to the SM DLN, where a proportion is taken up by resident DCs and presented as p-MHCII complexes, while the larger part is cleared by 8 h. At a later time, a second wave of antigen transport in migratory DCs enters the DLN and participates in further continued antigen presentation. With the use of an antigen-specific TCR transgenic mouse system, we demonstrate that T cell activation does not occur during the early stages of soluble antigen delivery to LN, even though p-MHCII complexes are generated. Antigen-specific T cell activation occurs in the later, presumed cell-associated phase but requires codelivery of a "danger" signal, such as the TLR ligand CpG. We suggest that the early delivery of soluble antigen is more likely to induce T cell nonresponsiveness (anergy) unless presented in the context of an innate-immune cell activation (danger) signal.

Tubular atrophy and interstitial fibrosis after renal transplantation is dependent on galectin-3.

BACKGROUND: Chronic allograft injury (CAI), characterized by interstitial fibrosis and tubular atrophy, leads to a progressive decline in graft function, resulting in the loss of 5% of renal transplants per annum, and eludes specific therapies. Galectin-3 (gal-3) is a ß-galactoside-binding lectin expressed in diverse fibrotic tissue, and mice deficient in gal-3 have reduced fibrosis in kidney, liver, and lung models. The role of gal-3 in CAI is examined in this study. METHODS: We adopted a murine model of CAI, characterized by a single class II mismatch between BM12 donor and C57BL/6 recipient strains. Syngeneic transplants served as controls (C57BL/6). Transplants were then performed between BM12 donors and gal-3 null recipients on a C57BL/6 background. RESULTS: Transplantation of BM12 kidneys into C57BL6 mice was associated with interstitial fibrosis (P<0.0001), tubular atrophy (P<0.0001), and upregulation in gal-3 expression (P=0.002), compared with syngeneic controls. Transplanting BM12 kidneys into gal-3 null mice resulted in significant preservation of tubules (P=0.008) and reduced interstitial fibrosis (P=0.01), with decreased myofibroblast activation (P=0.01) and collagen I expression (P=0.04), compared with wild type controls. The number of infiltrating leukocytes was unaltered by abrogation of gal-3, but reduced expression of YM1 (P=0.0001), a marker of alternative macrophage activation, along with a reduction in the number of circulating CD4-positive T cells (P=0.01), and reduced expression of interleukin-4 (P=0.02) in gal-3 null mice suggest possible mechanisms by which gal-3 may promote renal transplant fibrosis. CONCLUSION: Our results suggest a potential role for gal-3 in CAI, and this represents a potentially exciting therapeutic target.

Nourish and nurture: development of a nutrient ocular lubricant.

PURPOSE: The authors aimed to produce a new tear substitute capable of providing both lubrication and nutrition, based on a novel nutrient-containing therapeutic ocular surface medium (TOSM). METHODS: Viscous substances, including hypromellose (HPMC), carbopol, and sodium hyaluronate (SH) were added to the TOSM at various concentrations. Three commercial preservative-free artificial tear substitutes, Hypromellose (Pharmacy of Moorfields Eye Hospital, London, UK), Thilo-Tears (a carbomer; Alcon Pharma GmbH, Freiburg, Germany), and Vislube (a hyaluronate; Chemedica AG, Munich, Germany) were used as control preparations. Their viscosity and surface tension were measured. Human corneal (HCE-T) and conjunctival (IOBA-NHC) cell lines were used to investigate cell proliferation and viability in response to the formulations by means of a luminescence-based ATP assay and a calcein AM/EthD-1 assay. RESULTS: HPMC, carbopol, and SH increased the viscosity of TOSM significantly. The surface tension of TOSM was reduced by HPMC, but not by carbopol or SH. TOSM-HPMC supported cell proliferation and viability better than TOSM-carbopol and TOSM-SH. TOSM-HPMC and TOSM-carbopol supported cell proliferation significantly better than the corresponding commercial artificial tears. However, TOSM-Vislube supported cell growth significantly better than TOSM-SH. CONCLUSIONS: TOSM-HPMC showed superior lubricant and nutrient properties with moderate viscosity and little cytotoxicity. It thus could be an ideal nutrient and lubricant tear substitute for dry eyes and should be evaluated in a clinical study.