Stromal cell derived factor-1 (SDF-1)/CXCL12 attenuates diabetes in mice and promotes pancreatic beta-cell survival by activation of the prosurvival kinase Akt

The Importance of the CXCL12/CXCR4 Axis in Therapeutic Approaches to Diabetes Mellitus Attenuation

The pleiotropic chemokine (C–X–C motif) ligand 12 (CXCL12) has emerged as a crucial player in several diseases. The role of CXCL12 in diabetes promotion and progression remains elusive due to its multiple functions and the overwhelming complexity of diabetes. Diabetes is a metabolic disorder resulting from a failure in glucose regulation due to β-cell loss and/or dysfunction. In view of its ability to stimulate the regeneration, proliferation, and survival of β-cells, as well as its capacity to sustain local immune-isolation, CXCL12 has been considered in approaches aimed at attenuating type 1 diabetes. However, a note of caution emerges from examinations of the involvement of CXCL12 in the development of diabetes and its complications, as research data indicate that CXCL12 displays effects that range from protective to detrimental. Therefore, as a beneficial effect of CXCL12 in one process could have deleterious consequences in another, a more complete understanding of CXCL12 effects, in particular its functioning in the cellular microenvironment, is essential before CXCL12 can be considered in therapies for diabetes treatment.

Improving pancreatic islet in vitro functionality and transplantation efficiency by using heparin mimetic peptide nanofiber gels

Pancreatic islet transplantation is a promising treatment for type 1 diabetes. However, viability and functionality of the islets after transplantation are limited due to loss of integrity and destruction of blood vessel networks. Thus, it is important to provide a proper mechanically and biologically supportive environment for enhancing both in vitro islet culture and transplantation efficiency. Here, we demonstrate that heparin mimetic peptide amphiphile (HM-PA) nanofibrous network is a promising platform for these purposes. The islets cultured with peptide nanofiber gel containing growth factors exhibited a similar glucose stimulation index as that of the freshly isolated islets even after 7 days. After transplantation of islets to STZ-induced diabetic rats, 28 day-long monitoring displayed that islets that were transplanted in HM-PA nanofiber gels maintained better blood glucose levels at normal levels compared to the only islet transplantation group. In addition, intraperitoneal glucose tolerance test revealed that animals that were transplanted with islets within peptide gels showed a similar pattern with the healthy control group. Histological assessment showed that islets transplanted within peptide nanofiber gels demonstrated better islet integrity due to increased blood vessel density. This work demonstrates that using the HM-PA nanofiber gel platform enhances the islets function and islet transplantation efficiency both in vitro and in vivo.

DPP4 in Diabetes

Dipeptidyl-peptidase 4 (DPP4) is a glycoprotein of 110 kDa, which is ubiquitously expressed on the surface of a variety of cells. This exopeptidase selectively cleaves N-terminal dipeptides from a variety of substrates, including cytokines, growth factors, neuropeptides, and the incretin hormones. Expression of DPP4 is substantially dysregulated in a variety of disease states including inflammation, cancer, obesity, and diabetes. Since the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide (GIP), are major regulators of post-prandial insulin secretion, inhibition of DPP4 by the gliptin family of drugs has gained considerable interest for the therapy of type 2 diabetic patients. In this review, we summarize the current knowledge on the DPP4–incretin axis and evaluate most recent findings on DPP4 inhibitors. Furthermore, DPP4 as a type II transmembrane protein is also known to be cleaved from the cell membrane involving different metalloproteases in a cell-type-specific manner. Circulating, soluble DPP4 has been identified as a new adipokine, which exerts both para- and endocrine effects. Recently, a novel receptor for soluble DPP4 has been identified, and data are accumulating that the adipokine-related effects of DPP4 may play an important role in the pathogenesis of cardiovascular disease. Importantly, circulating DPP4 is augmented in obese and type 2 diabetic subjects, and it may represent a molecular link between obesity and vascular dysfunction. A critical evaluation of the impact of circulating DPP4 is presented, and the potential role of DPP4 inhibition at this level is also discussed.

Recruitment of mesenchymal stem cells by stromal cell-derived factor 1α in pulp cells from deciduous teeth

Dental pulp cells (DPCs), including dental pulp (DP) stem cells, play a role in dentine repair under certain conditions caused by bacterial infections associated with caries, tooth fracture and injury. Mesenchymal stem cells (MSCs) have also been shown to be involved in this process of repair. However, the mechanisms through which MSCs are recruited to the DP have not yet been elucidated. Therefore, the aim of the present in vitro study was to investigate whether stromal cell-derived factor 1α (SDF1)-C-X-C chemokine receptor type 4 (CXCR4) signaling is involved in tissue repair in the DP of deciduous teeth. A single-cell clone from DPCs (SDP11) and UE7T-13 cells were used as pulp cells and MSCs, respectively. The MG-63 and HuO9 cells, two osteosarcoma cell lines, were used as positive control cells. Reverse transcription polymerase chain reaction (RT-PCR) revealed that all cell lines (SDP11, UE7T-13 MG-63 and HuO9) were positive for both SDF1 and CXCR4 mRNA expression. Moreover, immunocytochemical analysis indicated that SDF1 and CXCR4 proteins were expressed in the SDP11 and UE7T-13 cells. SDF1 was also detected in the cell lysates (CLs) and conditioned medium (CM) collected from the SDP11 and UE7T-13 cells, and AMD3100, a specific antagonist of CXCR4, inhibited the migration of the UE7T-13 cells; this migration was induced by treatment with CM, which was collected from the SDP11 cells. In addition, real-time PCR showed that the expression of SDF1 in the SDP11 cells was inhibited by treatment with 20 ng/ml fibroblast growth factor (FGF)-2, and exposure to AZD4547, an inhibitor of the FGF receptor, blocked this inhibition. Collectively, these data suggest that SDF1 produced by DP plays an important role in homeostasis, repair and regeneration via the recruitment of MSCs.

Endothelium-derived essential signals involved in pancreas organogenesis

Endothelial cells (ECs) are essential for pancreas differentiation, endocrine specification, and endocrine function. They are also involved in the physiopathology of type 1 and type 2 diabetes. During embryogenesis, aortic ECs provide specific factors that maintain the expression of key genes for pancreas development such as pancreatic and duodenal homeobox-1. Other unknown factors are also important for pancreatic endocrine specification and formation of insulin-producing beta cells. Endocrine precursors proliferate interspersed with ductal cells and exocrine precursors and, at some point of development, these endocrine precursors migrate to pancreatic mesenchyme and start forming the islets of Langerhans. By the end of the gestation and close to birth, these islets contain immature beta cells with the capacity to express vascular endothelial growth factor and therefore to recruit ECs from the surrounding microenvironment. ECs in turn produce factors that are essential to maintain insulin secretion in pancreatic beta cells. Once assembled, a cross talk between endocrine cells and ECs maintain the integrity of islets toward an adequate function during the whole life of the adult individual. This review will focus in the EC role in the differentiation and maturation of pancreatic beta cells during embryogenesis as well as the current knowledge about the involvement of endothelium to derive pancreatic beta cells in vitro from mouse or human pluripotent stem cells.

Endogenous GLP-1 as a key self-defense molecule against lipotoxicity in pancreatic islets

The number of pro-α cells is known to increase in response to β cell injury and these cells then generate glucagon-like peptide-1 (GLP-1), thus attenuating the development of diabetes. The aim of the present study was to further examine the role and the mechanisms responsible for intra-islet GLP-1 production as a self-protective response against lipotoxicity. The levels of the key enzyme, prohormone convertase 1/3 (PC1/3), as well as the synthesis and release of GLP-1 in models of lipotoxicity were measured. Furthermore, islet viability, apoptosis, oxidative stress and inflammation, as well as islet structure were assessed after altering GLP-1 receptor signaling. Both prolonged exposure to palmitate and a high-fat diet facilitated PC1/3 expression, as well as the synthesis and release of GLP-1 induced by β cell injury and the generation of pro-α cells. Prolonged exposure to palmitate increased reactive oxygen species (ROS) production, and the antioxidant, N-acetylcysteine (NAC), partially prevented the detrimental effects induced by palmitate on β cells, resulting in decreased GLP-1 levels. Furthermore, the inhibition of GLP-1 receptor (GLP-1R) signaling by treatment with exendin‑(9-39) further decreased cell viability, increased cell apoptosis and caused a stronger inhibition of the β cell-specific transcription factor, pancreatic duodenal homeobox 1 (PDX1). Moreover, treatment with the GLP-1R agonist, liraglutide, normalized islet structure and function, resulting in a decrease in cell death and in the amelioration of β cell marker expression. Importantly, liraglutide maintained the oxidative balance and decreased inflammatory factor and p65 expression. Overall, our data demonstrate that an increase in the number of pro-α cells and the activation of the intra-islet GLP-1 system comprise a self-defense mechanism for enhancing β cell survival to combat lipid overload, which is in part mediated by oxidative stress and inflammation.

Cell-based bone regeneration for alveolar ridge augmentation--cell source, endogenous cell recruitment and immunomodulatory function

Alveolar ridge plays a pivotal role in supporting dental prosthesis particularly in edentulous and semi-dentulous patients. However the alveolar ridge undergoes atrophic change after tooth loss. The vertical and horizontal volume of the alveolar ridge restricts the design of dental prosthesis; thus, maintaining sufficient alveolar ridge volume is vital for successful oral rehabilitation. Recent progress in regenerative approaches has conferred marked benefits in prosthetic dentistry, enabling regeneration of the atrophic alveolar ridge. In order to achieve successful alveolar ridge augmentation, sufficient numbers of osteogenic cells are necessary; therefore, autologous osteoprogenitor cells are isolated, expanded in vitro, and transplanted to the specific anatomical site where the bone is required. Recent studies have gradually elucidated that transplanted osteoprogenitor cells are not only a source of bone forming osteoblasts, they appear to play multiple roles, such as recruitment of endogenous osteoprogenitor cells and immunomodulatory function, at the forefront of bone regeneration. This review focuses on the current consensus of cell-based bone augmentation therapies with emphasis on cell sources, transplanted cell survival, endogenous stem cell recruitment and immunomodulatory function of transplanted osteoprogenitor cells. Furthermore, if we were able to control the mobilization of endogenous osteoprogenitor cells, large-scale surgery may no longer be necessary. Such treatment strategy may open a new era of safer and more effective alveolar ridge augmentation treatment options.

Alginate encapsulant incorporating CXCL12 supports long-term allo- and xenoislet transplantation without systemic immune suppression

Islet transplantation represents a potentially curative approach for individuals with Type I Diabetes. The requirement for systemic immune suppression to control immune-mediated rejection of transplanted islets and the limited human islet supply represent significant roadblocks to progress for this approach. Islet microencapsulation in alginate offers limited protection in the absence of systemic immunosuppression, but does not support long-term islet survival. The chemokine, CXCL12, can repel effector T cells while recruiting immune-suppressive regulatory T cells (Tregs) to an anatomic site while providing a prosurvival signal for beta-cells. We proposed that coating or encapsulating donor islets with CXCL12 would induce local immune-isolation and protect and support the function of an allo- or xenograft without systemic immune suppression. This study investigated the effect of alginate microcapsules incorporating CXCL12 on islet function. Islet transplantation was performed in murine models of insulin-dependent diabetes. Coating of islets with CXCL12 or microencapsulation of islets with alginate incorporating the chemokine, resulted in long-term allo- and xenoislet survival and function, as well as a selective increase in intragraft Tregs. These data support the use of CXCL12 as a coating or a component of an alginate encapsulant to induce sustained local immune-isolation for allo- or xenoislet transplantation without systemic immunosuppression.

Protective Effects of the Mushroom Lactarius deterrimus Extract on Systemic Oxidative Stress and Pancreatic Islets in Streptozotocin-Induced Diabetic Rats

The aim of this study was to assess the in vivo effects of the extract of the medicinal mushroom, Lactarius deterrimus, when administered (60 mg/kg, i.p.) daily for four weeks to streptozotocin- (STZ-) induced diabetic rats. Diabetic rats treated with the L. deterrimus extract displayed several improved biochemical parameters in the circulation: reduced hyperglycemia, lower triglyceride concentration and reduced glycated hemoglobin, glycated serum protein, and advanced glycation end product (AGE) levels. This treatment also adjusted the diabetes-induced redox imbalance. Thus, higher activities of the antioxidative enzymes, superoxide dismutase, and catalase in the circulation were accompanied by increased levels of free intracellular thiols and glutathionylated proteins after treatment with the L. deterrimus extract. In addition to a systemic antioxidant effect, the administration of the extract to diabetic rats also had a positive localized effect on pancreatic islets where it decreased AGE formation, and increased the expression of chemokine CXCL12 protein that mediates the restoration of β-cell population through the activation of the serine/threonine-specific Akt protein kinase prosurvival pathway. As a result, the numbers of proliferating cell nuclear antigen- (PCNA-) and insulin-positive β-cells were increased. These results show that the ability of the L. deterrimus extract to alleviate oxidative stress and increase β-cell mass represents a therapeutic potential for diabetes management.

CXCL12-CXCR4 contributes to the implication of bone marrow in cancer metastasis

The CXCL12-CXCR4 axis is postulated to be a key pathway in the interaction between (cancer) stem cells and their surrounding supportive cells in the (cancer) stem cell niche. As the bone marrow constitutes a unique microenvironment for cancer cells, the CXCL12-CXCR4 axis assists the bone marrow in regulating cancer progression. This interaction can be disrupted by CXCR4 antagonists, and this concept is being used clinically to harvest hematopoietic stem/progenitor cells from the bone marrow. The functions of CXCL12-CXCR4 axis in cancer cell-tumor microenvironment interaction and angiogenesis have been recently studied. This review focuses on how CXCL12-CXCR4 helps the bone marrow in creating a tumor mircoenvironment that results in the cancer metastasis. It also discusses ongoing research regarding the clinical feasibility of CXCR4 inhibitors.

Glomerular endothelial cell injury and cross talk in diabetic kidney disease

Diabetic kidney disease (DKD) remains a leading cause of new-onset end-stage renal disease (ESRD), and yet, at present, the treatment is still very limited. A better understanding of the pathogenesis of DKD is therefore necessary to develop more effective therapies. Increasing evidence suggests that glomerular endothelial cell (GEC) injury plays a major role in the development and progression of DKD. Alteration of the glomerular endothelial cell surface layer, including its major component, glycocalyx, is a leading cause of microalbuminuria observed in early DKD. Many studies suggest a presence of cross talk between glomerular cells, such as between GEC and mesangial cells or GEC and podocytes. PDGFB/PDGFRβ is a major mediator for GEC and mesangial cell cross talk, while vascular endothelial growth factor (VEGF), angiopoietins, and endothelin-1 are the major mediators for GEC and podocyte communication. In DKD, GEC injury may lead to podocyte damage, while podocyte loss further exacerbates GEC injury, forming a vicious cycle. Therefore, GEC injury may predispose to albuminuria in diabetes either directly or indirectly by communication with neighboring podocytes and mesangial cells via secreted mediators. Identification of novel mediators of glomerular cell cross talk, such as microRNAs, will lead to a better understanding of the pathogenesis of DKD. Targeting these mediators may be a novel approach to develop more effective therapy for DKD.

Identification of transcription factors involved in the transcriptional regulation of the CXCL12 gene in rat pancreatic insulinoma Rin-5F cell line

Diabetes is characterized by a deficit in the number of functional pancreatic β-cells. Understanding the mechanisms that stimulate neogenesis of β-cells should contribute to improved maintenance of β-cell mass. Chemokine CXCL12 has recently become established as a novel β-cell growth factor, however the mechanisms controlling its expression require clarification. We investigated the proteins involved in the transcriptional regulation of the rat β-cell CXCL12 gene (Cxcl12). Using the electrophoretic mobility shift assay and chromatin immunoprecipitation, we established the in vitro and in vivo binding of C/EBPβ, C/EBPα, STAT3, p53, FOXO3a, and HMG I/Y to the Cxcl12 promoter. Co-immunoprecipitation experiments revealed protein-protein interactions between YY1 and PARP-1, FOXO3a and PARP-1, Sp1 and PARP-1, p53 and PARP-1, C/EBPβ and PARP-1, YY1 and p53, YY1 and FOXO3a, p53 and FOXO3a, Sp1 and FOXO3a, C/EBPβ and FOXO3a, C/EBPα and FOXO3a, Sp1 and STAT3. Our data lay the foundation for research into the interplay of signaling pathways that determine the β-cell Cxcl12 expression profile.

CXC chemokine ligand 12 protects pancreatic β-cells from necrosis through Akt kinase-mediated modulation of poly(ADP-ribose) polymerase-1 activity

The diabetes prevention paradigm envisages the application of strategies that support the maintenance of appropriate β-cell numbers. Herein we show that overexpression of CXC chemokine ligand12 (CXCL12) considerably improves the viability of isolated rat Langerhans islet cells and Rin-5F pancreatic β-cells after hydrogen peroxide treatment. In rat islets and wt cells hydrogen peroxide treatment induced necrotic cell death that was mediated by the rapid and extensive activation of poly(ADP-ribose) polymerase-1 (PARP-1). In contrast, CXCL12-overexpressing cells were protected from necrotic cell death as a result of significantly reduced PARP-1 activity. CXCL12 downstream signalling through Akt kinase was responsible for the reduction of PARP-1 activity which switched cell death from necrosis to apoptosis, providing increased protection to cells from oxidative stress. Our results offer a novel aspect of the CXCL12-mediated improvement of β-cell viability which is based on its antinecrotic action through modulation of PARP-1 activity.

SDF-1/CXCR4 signaling preserves microvascular integrity and renal function in chronic kidney disease

The progressive decline of renal function in chronic kidney disease (CKD) is characterized by both disruption of the microvascular architecture and the accumulation of fibrotic matrix. One angiogenic pathway recently identified as playing an essential role in renal vascular development is the stromal cell-derived factor-1α (SDF-1)/CXCR4 pathway. Because similar developmental processes may be recapitulated in the disease setting, we hypothesized that the SDF-1/CXCR4 system would regulate microvascular health in CKD. Expression of CXCR4 was observed to be increased in the kidneys of subtotally nephrectomized (SNx) rats and in biopsies from patients with secondary focal segmental glomerulosclerosis (FSGS), a rodent model and human correlate both characterized by aberration of the renal microvessels. A reno-protective role for local SDF-1/CXCR4 signaling was indicated by i) CXCR4-dependent glomerular eNOS activation following acute SDF-1 administration; and ii) acceleration of renal function decline, capillary loss and fibrosis in SNx rats treated with chronic CXCR4 blockade. In contrast to the upregulation of CXCR4, SDF-1 transcript levels were decreased in SNx rat kidneys as well as in renal fibroblasts exposed to the pro-fibrotic cytokine transforming growth factor β (TGF-β), the latter effect being attenuated by histone deacetylase inhibition. Increased renal SDF-1 expression was, however, observed following the treatment of SNx rats with the ACE inhibitor, perindopril. Collectively, these observations indicate that local SDF-1/CXCR4 signaling functions to preserve microvascular integrity and prevent renal fibrosis. Augmentation of this pathway, either purposefully or serendipitously with either novel or existing therapies, may attenuate renal decline in CKD.

DPP-4 inhibition with alogliptin on top of angiotensin II type 1 receptor blockade ameliorates albuminuria via up-regulation of SDF-1α in type 2 diabetic patients with incipient nephropathy

Dipeptidyl peptidase-4 (DPP-4) inhibitor is a new class of anti-diabetic drug which exerts its glucose-lowering action by suppressing the degradation of a gut incretin hormone glucagon-like peptide-1 (GLP-1). To elucidate whether treatment with stronger DPP-4 inhibitor on top of angiotensin II type 1 receptor blocker (ARB) provides greater renal protective effects, we performed a crossover study with two DPP-4 inhibitors, sitagliptin and alogliptin, in twelve type 2 diabetic patients with incipient nephropathy taking ARBs. This study consisted of three treatment periods: sitagliptin 50 mg/day for 4 weeks (first period), alogliptin 25 mg/day for 4 weeks (second period), and sitagliptin 50 mg/day for 4 weeks (third period). Significant changes in body mass index, blood pressure, serum lipids, serum creatinine, estimated glomerular filtration rate, and HbA1c were not observed among the three treatment periods. Reduced urinary levels of albumin and an oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG), increased urinary cAMP levels, and elevated plasma levels of stromal cell-derived factor-1α (SDF-1α) which is a physiological substrate of DPP-4 were observed after the switch from sitagliptin to a stronger DPP-4 inhibitor alogliptin. Given a large body of evidence indicating anti-oxidative action of cAMP and up-regulation of cellular cAMP production by SDF-1α, the present results suggest that more powerful DPP-4 inhibition on top of angiotensin II type 1 receptor blockade would offer additional protection against early-stage diabetic nephropathy beyond that attributed to glycemic control, via reduction of renal oxidative stress by SDF-1α-cAMP pathway activation.

HDLs protect the MIN6 insulinoma cell line against tunicamycin-induced apoptosis without inhibiting ER stress and without restoring ER functionality

HDLs protect pancreatic beta cells against apoptosis induced by several endoplasmic reticulum (ER) stressors, including thapsigargin, cyclopiazonic acid, palmitate and insulin over-expression. This protection is mediated by the capacity of HDLs to maintain proper ER morphology and ER functions such as protein folding and trafficking. Here, we identified a distinct mode of protection exerted by HDLs in beta cells challenged with tunicamycin (TM), a protein glycosylation inhibitor inducing ER stress. HDLs were found to inhibit apoptosis induced by TM in the MIN6 insulinoma cell line and this correlated with the maintenance of a normal ER morphology. Surprisingly however, this protective response was neither associated with a significant ER stress reduction, nor with restoration of protein folding and trafficking in the ER. These data indicate that HDLs can use at least two mechanisms to protect beta cells against ER stressors. One that relies on the maintenance of ER function and one that operates independently of ER function modulation. The capacity of HDLs to activate several anti-apoptotic pathways in beta cells may explain their ability to efficiently protect these cells against a variety of insults.

SDF-1-CXCR4 differentially regulates autoimmune diabetogenic T cell adhesion through ROBO1-SLIT2 interactions in mice

AIMS/HYPOTHESIS

We had previously reported that stromal cell-derived factor 1 (SDF-1) mediates chemorepulsion of diabetogenic T cell adhesion to islet microvascular endothelium through unknown mechanisms in NOD mice. Here we report that SDF-1-mediated chemorepulsion occurs through slit homologue (SLIT)2-roundabout, axon guidance receptor, homologue 1 (Drosophila) (ROBO1) interactions.

METHODS

C-X-C receptor (CXCR)4 and ROBO1 protein expression was measured in mouse and human T cells. Parallel plate flow chamber adhesion and detachment studies were performed to examine the molecular importance of ROBO1 and SLIT2 for SDF-1-mediated T cell chemorepulsion. Diabetogenic splenocyte transfer was performed in NOD/LtSz Rag1(-/-) mice to examine the effect of the SDF-1 mimetic CTCE-0214 on adoptive transfer of diabetes.

RESULTS

CXCR4 and ROBO1 protein expression was elevated in diabetic NOD/ShiLtJ T cells over time and coincided with the onset of hyperglycaemia. CXCR4 and ROBO1 expression was also increased in human type 1 diabetic T cells, with ROBO1 expression maximal at less than 1 year post diagnosis. Cell detachment studies revealed that immunoneutralisation of ROBO1 prevented SDF-1-mediated chemorepulsion of NOD T cell firm adhesion to TNFα-stimulated islet endothelial cells. SDF-1 increased NOD T cell adhesion to recombinant adhesion molecules, a phenomenon that was reversed by recombinant SLIT2. Finally, we found that an SDF-1 peptide mimetic prevented NOD T cell adhesion in vitro and significantly delayed adoptive transfer of autoimmune diabetes in vivo.

CONCLUSIONS/INTERPRETATION

These data reveal a novel molecular pathway, which regulates diabetogenic T cell recruitment and may be useful in modulating autoimmune diabetes.

Global gene expression profiling of pancreatic islets in mice during streptozotocin-induced β-cell damage and pancreatic Glp-1 gene therapy

Streptozotocin (STZ), a glucosamine-nitrosourea compound, has potent genotoxic effects on pancreatic β-cells and is frequently used to induce diabetes in experimental animals. Glucagon-like peptide-1 (GLP-1) has β-cell protective effects and is known to preserve β-cells from STZ treatment. In this study, we analyzed the mechanisms of STZ-induced diabetes and GLP-1-mediated β-cell protection in STZ-treated mice. At 1 week after multiple low-dose STZ administrations, pancreatic β-cells showed impaired insulin expression, while maintaining expression of nuclear Nkx6.1. This was accompanied by significant upregulation of p53-responsive genes in islets, including a mediator of cell cycle arrest, p21 (also known as Waf1 and Cip1). STZ treatment also suppressed expression of a wide range of genes linked with key β-cell functions or diabetes development, such as G6pc2, Slc2a2 (Glut2), Slc30a8, Neurod1, Ucn3, Gad1, Isl1, Foxa2, Vdr, Pdx1, Fkbp1b and Abcc8, suggesting global β-cell defects in STZ-treated islets. The Tmem229B, Prss53 and Ttc28 genes were highly expressed in untreated islets and strongly suppressed by STZ, suggesting their potential roles in β-cell function. When a pancreas-targeted adeno-associated virus (AAV) vector was employed for long-term Glp-1 gene delivery, pancreatic GLP-1 expression protected mice from STZ-induced diabetes through preservation of the β-cell mass. Despite its potent β-cell protective effects, however, pancreatic GLP-1 overexpression showed limited effects on the global gene expression profiles in the islets. Network analysis identified the programmed-cell-death-associated pathways as the most relevant network in Glp-1 gene therapy. Upon pancreatic GLP-1 expression, upregulation of Cxcl13 and Nptx2 was observed in STZ-damaged islets, but not in untreated normal islets. Given the pro-β-cell-survival effects of Cxcl12 (Sdf-1) in inducing GLP-1 production in α-cells, pancreatic GLP-1-mediated Cxcl13 induction might also play a crucial role in maintaining the integrity of β-cells in damaged islets.

A novel mechanism by which SDF-1β protects cardiac cells from palmitate-induced endoplasmic reticulum stress and apoptosis via CXCR7 and AMPK/p38 MAPK-mediated interleukin-6 generation

We studied the protective effect of stromal cell-derived factor-1β (SDF-1β) on cardiac cells from lipotoxicity in vitro and diabetes in vivo. Exposure of cardiac cells to palmitate increased apoptosis by activating NADPH oxidase (NOX)-associated nitrosative stress and endoplasmic reticulum (ER) stress, which was abolished by pretreatment with SDF-1β via upregulation of AMP-activated protein kinase (AMPK)-mediated p38 mitogen-activated protein kinase (MAPK) phosphorylation and interleukin-6 (IL-6) production. The SDF-1β cardiac protection could be abolished by inhibition of AMPK, p38 MAPK, or IL-6. Activation of AMPK or addition of recombinant IL-6 recaptured a similar cardiac protection. SDF-1β receptor C-X-C chemokine receptor type 4 (CXCR4) antagonist AMD3100 or CXCR4 small interfering RNA could not, but CXCR7 small interfering RNA completely abolished SDF-1β's protection from palmitate-induced apoptosis and activation of AMPK and p38 MAPK. Administration of SDF-1β to diabetic rats, induced by feeding a high-fat diet, followed by a small dose of streptozotocin, could significantly reduce cardiac apoptosis and increase AMPK phosphorylation along with prevention of diabetes-induced cardiac oxidative damage, inflammation, hypertrophy, and remodeling. These results showed that SDF-1β protects against palmitate-induced cardiac apoptosis, which is mediated by NOX-activated nitrosative damage and ER stress, via CXCR7, to activate AMPK/p38 MAPK-mediated IL-6 generation. The cardiac protection by SDF-1β from diabetes-induced oxidative damage, cell death, and remodeling was also associated with AMPK activation.

Nitric oxide inhibits CXCL12 expression in neuroinflammation

Chemokine CXCL12 (C-X-C motif chemokine ligand 12) restricts immune cell invasion of the central nervous system (CNS) and limits neuroinflammation in experimental autoimmune encephalomyelitis (EAE), an animal model of inflammatory and demyelinating disease of the CNS, multiple sclerosis (MS). Nitric oxide (NO), by contrast, predominantly contributes to CNS tissue destruction in MS and EAE. Thus, the influence of NO on CXCL12 in the inflamed CNS was investigated. Excess expression of inducible NO synthase was inversely correlated to CXCL12 gene expression in spinal cord homogenates of rats immunized to develop EAE. NO inhibited gene expression of CXCL12 in astrocytes and endothelial cells in vitro. The inhibition was paralleled with reduction of p38 mitogen-activated protein kinase (MAPK) phosphorylation and it was mimicked with inhibitors of p38 MAPK activation in astrocytes. In vivo suppression of nitric generation recovered CXCL12 expression in the CNS and attenuated EAE in Dark Agouti rats. On the contrary, in vivo NO donation decreased CXCL12 expression in the CNS of EAE-resistant Albino Oxford (AO) rats. However, the effect was not paralleled with induction of EAE in AO rats. It is suggested that NO acting through suppression of p38 MAPK inhibits CXCL12 expression in neuroinflammation. These results imply that downregulation of NO release and protection of CXCL12 expression within the CNS might present the potential approaches in MS therapy.

PARP-1 and YY1 are important novel regulators of CXCL12 gene transcription in rat pancreatic beta cells

Despite significant progress, the molecular mechanisms responsible for pancreatic beta cell depletion and development of diabetes remain poorly defined. At present, there is no preventive measure against diabetes. The positive impact of CXCL12 expression on the pancreatic beta cell prosurvival phenotype initiated this study. Our aim was to provide novel insight into the regulation of rat CXCL12 gene (Cxcl12) transcription. The roles of poly(ADP-ribose) polymerase-1 (PARP-1) and transcription factor Yin Yang 1 (YY1) in Cxcl12 transcription were studied by examining their in vitro and in vivo binding affinities for the Cxcl12 promoter in a pancreatic beta cell line by the electrophoretic mobility shift assay and chromatin immunoprecipitation. The regulatory activities of PARP-1 and YY1 were assessed in transfection experiments using a reporter vector with a Cxcl12 promoter sequence driving luciferase gene expression. Experimental evidence for PARP-1 and YY1 revealed their trans-acting potential, wherein PARP-1 displayed an inhibitory, and YY1 a strong activating effect on Cxcl12 transcription. Streptozotocin (STZ)-induced general toxicity in pancreatic beta cells was followed by changes in Cxcl12 promoter regulation. PARP-1 binding to the Cxcl12 promoter during basal and in STZ-compromised conditions led us to conclude that PARP-1 regulates constitutive Cxcl12 expression. During the early stage of oxidative stress, YY1 exhibited less affinity toward the Cxcl12 promoter while PARP-1 displayed strong binding. These interactions were accompanied by Cxcl12 downregulation. In the later stages of oxidative stress and intensive pancreatic beta cell injury, YY1 was highly expressed and firmly bound to Cxcl12 promoter in contrast to PARP-1. These interactions resulted in higher Cxcl12 expression. The observed ability of PARP-1 to downregulate, and of YY1 to upregulate Cxcl12 promoter activity anticipates corresponding effects in the natural context where the functional interplay of these proteins could finely balance Cxcl12 transcription.

Alpha cells come of age

The alpha cells that coinhabit the islets with the insulin-producing beta cells have recently captured the attention of diabetes researchers because of new breakthrough findings highlighting the importance of these cells in the maintenance of beta cell health and functions. In normal physiological conditions alpha cells produce glucagon but in conditions of beta cell injury they also produce glucagon-like peptide-1 (GLP-1), a growth and survival factor for beta cells. In this review we consider these new findings on the functions of alpha cells. Alpha cells remain somewhat enigmatic inasmuch as they now appear to be important in the maintenance of the health of beta cells, but their production of glucagon promotes diabetes. This circumstance prompts an examination of approaches to coax alpha cells to produce GLP-1 instead of glucagon.

The role of CXCL12-CXCR4 signaling pathway in pancreatic development

Chemokine (C-X-C motif) receptor 4 (CXCR4) is the receptor for chemokine (C-X-C motif) ligand 12 (CXCL12, also known as stromal derived factor-1, Sdf1). CXCR4, a protein consisting 352 amino acids, is known to transduce various signals such as cell differentiation, cell survival, cell proliferation, cell chemotaxis and apoptosis [1, 2]. The expression of CXCR4 is observed in embryonic stem cells, blood cells, haematopoietic stem cells, endothelial cells, angioblasts and smooth muscle cells [3-9]. The CXCL12-CXCR4 signaling pathway has very important roles in the embryonic development. Mutant mice for CXCL12 or CXCR4 genes showed lethality due to defects in neurogenesis, angiogenesis, cardiogenesis, myelopoiesis, lymphopoiesis and germ cell development [10-13]. Recently, we reported that CXCL12-CXCR4 signaling pathway has a crucial role in regional specification of the gut endoderm during early development [14]. Here, we would like to focus on the role of CXCL12-CXCR4 signaling pathway in pancreatic development and summarize recent findings of its role in the induction of the pancreatic progenitor cells.

Trefoil factor 2 promotes cell proliferation in pancreatic β-cells through CXCR-4-mediated ERK1/2 phosphorylation

Decreased β-cell mass is a hallmark of type 2 diabetes, and therapeutic approaches to increase the pancreatic β-cell mass have been expected. In recent years, gastrointestinal incretin peptides have been shown to exert a cell-proliferative effect in pancreatic β-cells. Trefoil factor 2 (TFF2), which is predominantly expressed in the surface epithelium of the stomach, plays a role in antiapoptosis, migration, and proliferation. The TFF family is expressed in pancreatic β-cells, whereas the role of TFF2 in pancreatic β-cells has been obscure. In this study, we investigated the mechanism by which TFF2 enhances pancreatic β-cell proliferation. The effects of TFF2 on cell proliferation were evaluated in INS-1 cells, MIN6 cells, and mouse islets using an adenovirus vector containing TFF2 or a recombinant TFF2 peptide. The forced expression of TFF2 led to an increase in bromodeoxyuridine (BrdU) incorporation in both INS-1 cells and islets, without any alteration in insulin secretion. TFF2 significantly increased the mRNA expression of cyclin A2, D1, D2, D3, and E1 in islets. TFF2 peptide increased ERK1/2 phosphorylation and BrdU incorporation in MIN6 cells. A MAPK kinase inhibitor (U0126) abrogated the TFF2 peptide-mediated proliferation of MIN6 cells. A CX-chemokine receptor-4 antagonist also prevented the TFF2 peptide-mediated increase in ERK1/2 phosphorylation and BrdU incorporation in MIN6 cells. These results indicated that TFF2 is involved in β-cell proliferation at least partially via CX-chemokine receptor-4-mediated ERK1/2 phosphorylation, suggesting TFF2 may be a novel target for inducing β-cell proliferation.

The SDF-1α/CXCR4 axis is required for proliferation and maturation of human fetal pancreatic endocrine progenitor cells

The chemokine receptor CXCR4 and ligand SDF-1α are expressed in fetal and adult mouse islets. Neutralization of CXCR4 has previously been shown to diminish ductal cell proliferation and increase apoptosis in the IFNγ transgenic mouse model in which the adult mouse pancreas displays islet regeneration. Here, we demonstrate that CXCR4 and SDF-1α are expressed in the human fetal pancreas and that during early gestation, CXCR4 colocalizes with neurogenin 3 (ngn3), a key transcription factor for endocrine specification in the pancreas. Treatment of islet like clusters (ICCs) derived from human fetal pancreas with SDF-1α resulted in increased proliferation of epithelial cells in ICCs without a concomitant increase in total insulin expression. Exposure of ICCs in vitro to AMD3100, a pharmacological inhibitor of CXCR4, did not alter expression of endocrine hormones insulin and glucagon, or the pancreatic endocrine transcription factors PDX1, Nkx6.1, Ngn3 and PAX4. However, a strong inhibition of β cell genesis was observed when in vitro AMD3100 treatment of ICCs was followed by two weeks of in vivo treatment with AMD3100 after ICC transplantation into mice. Analysis of the grafts for human C-peptide found that inhibition of CXCR4 activity profoundly inhibits islet development. Subsequently, a model pancreatic epithelial cell system (CFPAC-1) was employed to study the signals that regulate proliferation and apoptosis by the SDF-1α/CXCR4 axis. From a selected panel of inhibitors tested, both the PI 3-kinase and MAPK pathways were identified as critical regulators of CFPAC-1 proliferation. SDF-1α stimulated Akt phosphorylation, but failed to increase phosphorylation of Erk above the high basal levels observed. Taken together, these results indicate that SDF-1α/CXCR4 axis plays a critical regulatory role in the genesis of human islets.

α-cell role in β-cell generation and regeneration

This review considers the role of α-cells in β-cell generation and regeneration. We present recent evidence obtained from lineage-tracing studies showing that α-cells can serve as progenitors of β-cells and present a hypothetical model how injured β-cells might activate α-cells in adult islets to promote β-cell regeneration. β-cells appear to arise by way of their trans-differentiation from undifferentiated α progenitor cells, pro-α-cells, both during embryonic development of the islets and in the adult pancreas in response to β-cell injuries. Plasticity of α-cells is endowed by the expression of the gene encoding proglucagon, a prohormone that can give rise to glucagon and glucagon-like peptides (GLPs). The production of glucagon from proglucagon is characteristic of fully-differentiated α-cells whereas GLP-1 is a product of undifferentiated α-cells. GLP-1, a cell growth and survival factor, is proposed to promote the expansion of neurogenin3-expressing, undifferentiated pro-α-cells during development. β-cells arise from pro-α-cells by a change in the relative amounts of the transcription factors Arx and Pax4, master regulators of the α- and β-cell lineages, respectively. A paracrine/autocrine model is proposed whereby injuries of β-cells in adult islets induce the production and release of factors, such as stromal cell-derived factor-1, that cause the de-differentiation of adjacent α-cells into pro-α-cells. Pro-α-cells produce GLP-1 and its receptor that renders them competent to trans-differentiate into β-cells. The trans-differentiation of pro-α-cells into β-cells provides a potentially exploitable mechanism for the regeneration of β-cells in individuals with type 1 diabetes.

Recent advances in understanding the biochemical and molecular mechanism of diabetic retinopathy

One of the major complications in patients with diabetes is diabetic retinopathy (DR), a leading cause of blindness worldwide. It takes several years before any clinical signs of retinopathy appear in diabetic patients, which gives an ample opportunity for scientists to uncover biochemical and molecular mechanism implicated early in the development and progression of the disease. During the past few decades, research progress has been made in investigating the pathophysiology of the disease; however, due to nonavailability of human retinal samples at different stages of the disease and also due to lack of a proper animal model of DR, the exact molecular mechanism has not been elucidated, making therapeutic a difficult task. In this review article, we have discussed a number of diabetes-induced metabolites such as glucose, lipids, amino acids, and other related factors and molecules that are implicated in the pathophysiology of the DR. Furthermore, we have highlighted neurodegeneration and regulation of neurotrophic factors, being recognized as early events that may be involved in the pathology of the disease in the course of DR. An understanding of the biochemical and molecular changes especially early in the diabetic retina may lead to new and effective therapies towards prevention and amelioration of DR, which is important for the millions of individuals who already have or are likely to develop the disease before a cure becomes available.

G protein-coupled receptor signaling and sphingosine-1-phosphate play a phylogenetically conserved role in endocrine pancreas morphogenesis

During development pancreatic endocrine cells migrate in a coordinated fashion. This migration is necessary to form fully functional islets, but the mechanisms involved remain unknown. Therapeutic strategies to restore β-cell mass and islet functionality by reprogramming endogenous exocrine cells would be strengthened from simultaneous treatments that enhance endocrine cell clustering. We found that endocrine progenitors respond to and regulate G protein-coupled receptor (GPCR) signaling in order to cluster in islets. Rgs4, a dedicated regulator of GPCR signaling, was specifically expressed in early epithelial endocrine progenitors of both zebrafish and mouse, and its expression in the mouse endocrine progenitors was strictly dependent upon Ngn3, the key specification gene of the endocrine lineage. Rgs4 loss of function resulted in defects in islet cell aggregation. By genetically inactivating Gα(i)-mediated GPCR signaling in endocrine progenitors, we established its role in islet cell aggregation in both mouse and zebrafish. Finally, we identified sphingosine-1-phosphate (S1P) as a ligand mediating islet cell aggregation in both species acting through distinct but closely related receptors.

SDF-1/CXCR4 mediates acute protection of cardiac function through myocardial STAT3 signaling following global ischemia/reperfusion injury

Stromal cell-derived factor-1α (SDF-1) has been reported to mediate cardioprotection through the mobilization of stem cells into injured tissue and an increase in local angiogenesis after myocardial infarction. However, little is known regarding whether SDF-1 induces acute protection following global myocardial ischemia/reperfusion (I/R) injury and if so, by what molecular mechanism. SDF-1 binding to its cognate receptor CXCR4 has been shown to activate STAT3 in a variety of cells. STAT3 is a cardioprotective factor and may mediate SDF-1/CXCR4-induced acute protection. We hypothesized that SDF-1 would improve myocardial function through CXCR4-increased STAT3 activation following acute I/R. Isolated mouse hearts were subjected to 25-min global ischemia/40-min reperfusion and divided into groups of 1) vehicle; 2) SDF-1; 3) AMD3100, a CXCR4 inhibitor; 4) SDF-1 + AMD3100; 5) Stattic, a STAT3 inhibitor; 6) SDF-1 + Stattic; 7) cardiomyocyte-restricted ablation of STAT3 (STAT3KO); 8) STAT3KO + SDF-1; 9) Ly294002, an inhibitor of the Akt pathway; and 10) SDF-1 + Ly294002. Reagents were infused into hearts within 5 min before ischemia. SDF-1 administration significantly improved postischemic myocardial functional recovery in a dose-dependent manner. Additionally, pretreatment with SDF-1 reduced cardiac apoptotic signaling and increased myocardial STAT3 activation following acute I/R. Inhibition of the SDF-1 receptor CXCR4 neutralized these protective effects by SDF-1 in hearts subjected to I/R. Notably, inhibition of the STAT3 pathway or use of STAT3KO hearts abolished SDF-1-induced acute protection following myocardial I/R. Our results represent the first evidence that the SDF-1/CXCR4 axis upregualtes myocardial STAT3 activation and, thereby, mediates acute cardioprotection in response to global I/R.

Stromal cell-derived factor-1 (SDF-1)/chemokine (C-X-C motif) receptor 4 (CXCR4) axis activation induces intra-islet glucagon-like peptide-1 (GLP-1) production and enhances beta cell survival

AIMS/HYPOTHESIS

The endogenous production of stromal cell-derived factor-1 (SDF-1) in beta cells in transgenic mice attenuates the development of diabetes in response to streptozotocin. Here we propose that beta cell injury induces SDF-1 production, and the SDF-1/chemokine (C-X-C motif) receptor 4 (CXCR4) interaction auto-activates Sdf1 expression, resulting in the autocrine production of SDF-1 by beta cells and the paracrine activation of glucagon-like peptide-1 (GLP-1) production by alpha cells.

METHODS

SDF-1 production in adult mouse and human islets and rat INS-1 cells was measured in models of beta cell injury. The paracrine actions of SDF-1 on GLP-1 production in alpha cells were explored. The potential synergism between the growth-promoting actions of GLP-1 and the pro-survival actions of SDF-1 on the preservation of cell mass was evaluated by cell viability assays.

RESULTS

In adult islets and INS-1 cells, Sdf1 expression was re-induced in response to injury. The interaction of SDF-1 with its receptor on alphaTC1 cells activated protein kinase Akt, stimulated cell proliferation and induced the expression of prohormone convertase 1/3 and the consequent production of GLP-1 in alpha cells. The combination of GLP-1 and SDF-1 additively enhanced both the growth and longevity of INS-1 beta cells.

CONCLUSIONS/INTERPRETATION

The results of these studies suggest that in response to beta cell injury and the ensuing induction of SDF-1, the biological function of alpha cells switches from the production of glucagon to the provision of the local growth factor GLP-1 which, in combination with SDF-1, promotes the growth, survival and viability of the beta cells.

Endoderm and mesoderm reciprocal signaling mediated by CXCL12 and CXCR4 regulates the migration of angioblasts and establishes the pancreatic fate

We have discovered that angioblasts trigger an early inductive event in pancreatic differentiation. This event occurs soon after gastrulation, before the formation of blood vessels. Morphological studies revealed that Lmo2-expressing angioblasts reside in proximity to the somitic mesoderm and the gut endoderm from which pancreatic progenitors arise. The chemokine ligand CXCL12 expressed in the gut endoderm functions to attract the angioblasts that express its receptor CXCR4. Angioblasts then signal back to the gut endoderm to induce Pdx1 expression. Gain-of-function and loss-of-function experiments for CXCL12 and CXCR4 were performed to test their function in blood vessel formation and pancreatic differentiation. The ectopic expression of Cxcl12 in the endoderm attracted the angioblasts and induced ectopic Pdx1 expression, resulting in an expanded pancreatic bud and an increased area of insulin-expressing cells. By contrast, in chick embryos treated with beads soaked in AMD3100, an inhibitor of CXCR4, the migration of angioblasts towards the Cxcl12-expressing gut endoderm was arrested, causing a malformation of blood vessels. This led to the generation of a smaller pancreatic bud and a reduced area of insulin-expressing cells. Taken together, these results indicate that the gut endoderm and angioblasts attract each other through reciprocal CXCL12 and CXCR4 signaling. This has a pivotal role in the fate establishment of the pancreatic progenitor cells and in the potentiation of further differentiation into endocrine β-cells.

Regulation of the stromal cell-derived factor-1alpha-CXCR4 axis in human dental pulp cells

INTRODUCTION

Although the presence of the stromal cell-derived factor (SDF)-1alpha-CXCR4 axis has been reported in dental pulp tissue, little has been known about the underlying regulation of this axis in dental pulp stem cells (DPSCs). The purpose of this study was to investigate whether inflammation or hypoxia can regulate this axis in cultured human dental pulp cells (DPCs).

METHODS

Primary cultures of DPCs were stimulated by various concentrations of lipopolysaccharide (LPS) for 48 hours, and the production of SDF-1alpha or CXCR4 was assessed through the enzyme-linked immunosorbent assay and Western blotting, respectively. Additionally, DPCs were incubated in a hypoxic condition (1% O(2)) for 24 hours, and the cell proliferation ability was detected by methylthiazol tetrazolum assay. Quantitative reverse-transcription polymerase chain reaction (RT-PCR) was used to observe messenger RNA level changes of hypoxia inducible factor-1alpha(HIF-alpha), SDF-1alpha, and CXCR4. The effects of hypoxia on cell migration ability were further confirmed by transmigration assay.

RESULTS

All concentrations of LPS inhibited SDF-1alpha production except that 1 microg/mL LPS increased the expression of CXCR4. Hypoxia promoted the proliferation of DPCs in a 24-hour culture period. Quantitative RT-PCR showed that messenger RNA levels of HIF-alpha and CXCR4 increased, whereas SDF-1alpha decreased in hypoxic DPCs. Transmigration assay indicated that hypoxia increased the migration ability of DPCs.

CONCLUSIONS

These results suggested that inflammation and hypoxia might play an important role in regulating the SDF-1alpha-CXCR4 axis, which further recruits DPSCs to participate in reparative dentinogenesis.

Interference with islet-specific homing of autoreactive T cells: an emerging therapeutic strategy for type 1 diabetes

Pathogenesis of type 1 diabetes involves the activation of autoimmune T cells, consequent homing of activated lymphocytes to the pancreatic islets and ensuing destruction of insulin-producing b cells. Interaction between activated lymphocytes and endothelial cells in the islets is the hallmark of the homing process. Initial adhesion, firm adhesion and diapedesis of lymphocytes are the three crucial steps involved in the homing process. Cell-surface receptors including integrins, selectins and hyaluronate receptor CD44 mediate the initial steps of homing. Diapedesis relies on a series of proteolytic events mediated by matrix metalloproteinases. Here, molecular mechanisms governing transendothelial migration of the diabetogenic effector cells are discussed and resulting pharmacological strategies are considered.

The emerging relationship between regenerative medicine and physical therapeutics

Dramatic changes in the health care landscape over the next few decades undoubtedly will affect rehabilitation specialists' practice. In the multidisciplinary field of regenerative medicine, cell, tissue, or organ substitutes are used to enhance the healing potential of the body. Given that the restoration of normal functioning of injured or diseased tissues is expected to be the ultimate goal of these therapies, the future of regenerative medicine is, undeniably, tightly intertwined with that of rehabilitation. Rehabilitation specialists not only must be aware of cutting-edge medical advances as they relate to regenerative medicine but also must work closely with basic scientists to guide the development of clinically relevant protocols. The purposes of this article are to provide a current perspective on biological approaches to the management of musculoskeletal disorders and to highlight the needed integration of physical therapeutics with regenerative medicine.

Continuous Delivery of Stromal Cell-Derived Factor-1 from Alginate Scaffolds Accelerates Wound Healing

Proper wound diagnosis and management is an increasingly important clinical challenge and is a large and growing unmet need. Pressure ulcers, hard-to-heal wounds, and problematic surgical incisions are emerging at increasing frequencies. At present, the wound-healing industry is experiencing a paradigm shift towards innovative treatments that exploit nanotechnology, biomaterials, and biologics. Our study utilized an alginate hydrogel patch to deliver stromal cell-derived factor-1 (SDF-1), a naturally occurring chemokine that is rapidly overexpressed in response to tissue injury, to assess the potential effects SDF-1 therapy on wound closure rates and scar formation. Alginate patches were loaded with either purified recombinant human SDF-1 protein or plasmid expressing SDF-1 and the kinetics of SDF-1 release were measured both in vitro and in vivo in mice. Our studies demonstrate that although SDF-1 plasmid- and protein-loaded patches were able to release therapeutic product over hours to days, SDF-1 protein was released faster (in vivo Kd 0.55 days) than SDF-1 plasmid (in vivo Kd 3.67 days). We hypothesized that chronic SDF-1 delivery would be more effective in accelerating the rate of dermal wound closure in Yorkshire pigs with acute surgical wounds, a model that closely mimics human wound healing. Wounds treated with SDF-1 protein ( n = 10) and plasmid ( n = 6) loaded patches healed faster than sham ( n = 4) or control ( n = 4). At day 9, SDF-1-treated wounds significantly accelerated wound closure (55.0 ± 14.3% healed) compared to nontreated controls (8.2 ± 6.0%, p < 0.05). Furthermore, 38% of SDF-1-treated wounds were fully healed at day 9 (vs. none in controls) with very little evidence of scarring. These data suggest that patch-mediated SDF-1 delivery may ultimately provide a novel therapy for accelerating healing and reducing scarring in clinical wounds.

Mechanism of primitive duct formation in the pancreas and submandibular glands: a role for SDF-1

Background

The exocrine pancreas is composed of a branched network of ducts connected to acini. They are lined by a monolayered epithelium that derives from the endoderm and is surrounded by mesoderm-derived mesenchyme. The morphogenic mechanisms by which the ductal network is established as well as the signaling pathways involved in this process are poorly understood.

Results

By morphological analyzis of wild-type and mutant mouse embryos and using cultured embryonic explants we investigated how epithelial morphogenesis takes place and is regulated by chemokine signaling. Pancreas ontogenesis displayed a sequence of two opposite epithelial transitions. During the first transition, the monolayered and polarized endodermal cells give rise to tissue buds composed of a mass of non polarized epithelial cells. During the second transition the buds reorganize into branched and polarized epithelial monolayers that further differentiate into tubulo-acinar glands. We found that the second epithelial transition is controlled by the chemokine Stromal cell-Derived Factor (SDF)-1. The latter is expressed by the mesenchyme, whereas its receptor CXCR4 is expressed by the epithelium. Reorganization of cultured pancreatic buds into monolayered epithelia was blocked in the presence of AMD3100, a SDF-1 antagonist. Analyzis of sdf1 and cxcr4 knockout embryos at the stage of the second epithelial transition revealed transient defective morphogenesis of the ventral and dorsal pancreas. Reorganization of a globular mass of epithelial cells in polarized monolayers is also observed during submandibular glands development. We found that SDF-1 and CXCR4 are expressed in this organ and that AMD3100 treatment of submandibular gland explants blocks its branching morphogenesis.

Conclusion

In conclusion, our data show that the primitive pancreatic ductal network, which is lined by a monolayered and polarized epithelium, forms by remodeling of a globular mass of non polarized epithelial cells. Our data also suggest that SDF-1 controls the branching morphogenesis of several exocrine tissues.

A case of WHIM syndrome associated with diabetes and hypothyroidism

The WHIM syndrome is a rare immunological disorder characterized by warts, hypogammaglobulinemia, infections, and myelokathexis. We hypothesized that immunological or genetic mechanisms may link WHIM syndrome and type 1 diabetes. We report that the young girl with WHIM syndrome developed diabetes and transient hypothyroidism. A nonsense mutation (C-->T) truncating the CXC chemokine receptor 4 (CXCR4) C-terminal cytoplasmic tail domain occurred at nucleotide position 1000(R334X) of the CXCR4 gene in one allele of the patient was identified, and the person was diagnosed as having WHIM syndrome. Recent observation suggested that the CXCR4, a G-protein-coupled receptor with a unique ligand, CXCL12, might be involved in the pathogenesis for type 1 diabetes. Taken into consideration the concurrent prevalence of the two disorders and the speculated common pathogenesis associated with the CXCR4, our patient may enable us to understand the genetic damage related to accelerated apoptosis.

Podocytes produce homeostatic chemokine stromal cell-derived factor-1/CXCL12, which contributes to glomerulosclerosis, podocyte loss and albuminuria in a mouse model of type 2 diabetes

AIMS/HYPOTHESIS

Chemokine (C-X-C motif) ligand 12 (CXCL12) (also known as stromal cell-derived factor-1 [SDF-1]-alpha) is a homeostatic chemokine with multiple roles in cell homing, tumour metastasis, angiogenesis and tissue regeneration after acute injuries. However, its role in chronic diseases remains poorly defined, e.g. in chronic glomerular diseases like diabetic glomerulosclerosis. We hypothesised that CXCL12 may have a functional role during the evolution of diabetic glomerulosclerosis, either by assisting glomerular repair or by supporting the maladaptive tissue remodelling in response to hyperglycaemia and glomerular hyperfiltration.

METHODS

To define the functional role of CXCL12 in the progression of glomerular disease, we used the CXCL12-specific inhibitor NOX-A12, an L: -enantiomeric RNA oligonucleotide (Spiegelmer). A mouse model of type 2 diabetes (db/db mice) was used. Male db/db mice, uni-nephrectomised at 6 weeks of age, received subcutaneous injections with a PEGylated form of NOX-A12, non-functional control Spiegelmer or vehicle on alternate days from 4 to 6 months of age.

RESULTS

Immunostaining localised renal CXCL12 production to glomerular podocytes in db/db mice with early or advanced diabetic nephropathy. CXCL12 inhibition significantly reduced the degree of glomerulosclerosis, increased the number of podocytes, prevented the onset of albuminuria and maintained the peritubular vasculature without affecting blood glucose levels, body weight or glomerular macrophage infiltration.

CONCLUSIONS/INTERPRETATION

We conclude that podocytes produce CXCL12, which contributes to proteinuria and glomerulosclerosis in our mouse model of type 2 diabetes. This novel pathomechanism provides the first evidence that CXCL12 could be a therapeutic target in (diabetic) glomerulosclerosis.

Airway smooth muscle chemokine receptor expression and function in asthma

BACKGROUND

Chemokine receptors play an important role in cell migration and wound repair. In asthma, CCR3 and 7 are expressed by airway smooth muscle (ASM) and CCR7 has been implicated in the development of ASM hyperplasia. The expression profile of other chemokine receptors by ASM and their function needs to be further explored.

OBJECTIVE

We sought to investigate ASM chemokine receptor expression and function in asthma.

METHODS

ASM cells were derived from 17 subjects with asthma and 36 non-asthmatic controls. ASM chemokine receptor expression was assessed by flow cytometry and immunofluorescence. The function of chemokine receptors expressed by more than 10% of ASM cells was investigated by intracellular calcium measurements, chemotaxis, wound healing, proliferation and survival assays.

RESULTS

In addition to CCR3 and 7, CXCR1, 3 and 4 were highly expressed by ASM. These CXC chemokine receptors were functional with an increase in intracellular calcium following ligand activation and promotion of wound healing [CXCL10 (100 ng/mL) 34 +/- 2 cells/high-powered field (hpf) vs. control 29 +/- 1; P=0.03; n=8]. Spontaneous wound healing was inhibited by CXCR3 neutralizing antibody (mean difference 7 +/- 3 cells/hpf; P=0.03; n=3). CXC chemokine receptor activation did not modulate ASM chemotaxis, proliferation or survival. No differences in chemokine receptor expression or function were observed between ASM cells derived from asthmatic or non-asthmatic donors.

CONCLUSIONS

Our findings suggest that the chemokine receptors CXCR1, 3 and 4 modulate some aspects of ASM function but their importance in asthma is uncertain.

Altered SDF-1-mediated differentiation of bone marrow-derived endothelial progenitor cells in diabetes mellitus

In diabetic patients and animal models of diabetes mellitus (DM), circulating endothelial progenitor cell (EPC) number is lower than in normoglycaemic conditions and EPC angiogenic properties are inhibited. Stromal cell derived factor-1 (SDF-1) plays a key role in bone marrow (BM) c-kit⁺ stem cell mobilization into peripheral blood (PB), recruitment from PB into ischemic tissues and differentiation into endothelial cells. The aim of the present study was to examine the effect of DM in vivo and in vitro, on murine BM-derived c-kit⁺ cells and on their response to SDF-1. Acute hindlimb ischemia was induced in streptozotocin-treated DM and control mice; circulating c-kit⁺ cells exhibited a rapid increase followed by a return to control levels which was significantly faster in DM than in control mice. CXCR4 expression by BM c-kit⁺ cells as well as SDF-1 protein levels in the plasma and in the skeletal muscle, both before and after the induction of ischemia, were similar between normoglycaemic and DM mice. However, BM-derived c-kit⁺ cells from DM mice exhibited an impaired differentiation towards the endothelial phenotype in response to SDF-1; this effect was associated with diminished protein kinase phosphorylation. Interestingly, SDF-1 ability to induce differentiation of c-kit⁺ cells from DM mice was restored when cells were cultured under normoglycaemic conditions whereas c-kit⁺ cells from normoglycaemic mice failed to differentiate in response to SDF-1 when they were cultured in hyperglycaemic conditions. These results show that DM diminishes circulating c-kit⁺ cell number following hindlimb ischemia and inhibits SDF-1-mediated AKT phosphorylation and differentiation towards the endothelial phenotype of BM-derived c-kit⁺ cells.