Stromal Cell-derived Factor-1α Research Articles

Stromal Cell-Derived Factor-1a Autocrine/Paracrine Signaling Contributes to Spatiotemporal Gradients in the Brain.

Stromal cell derived factor-1a (SDF-1a) and its receptor CXCR4 modulate stem cell recruitment to neural injury sites. SDF-1a gradients originating from injury sites contribute to chemotactic cellular recruitment. To capitalize on this injury-induced cell recruitment, further investigation of SDF-1a/CXCR4 signaling dynamics are warranted. Here, we studied how exogenous SDF-1a delivery strategies impact spatiotemporal SDF-1a levels and the role autocrine/paracrine signaling plays. We first assessed total SDF-1a and CXCR4 levels over the course of 7days following intracortical injection of either bolus SDF-1a or SDF-1a loaded nanoparticles in CXCR4-EGFP mice. We then investigated cellular contributors to SDF-1a autocrine/paracrine signaling via time course in vitro measurements of SDF-1a and CXCR4 gene expression following exogenous SDF-1a application. Lastly, we created mathematical models that could recapitulate our in vivo observations. In vivo, we found sustained total SDF-1a levels beyond 3days post injection, indicating endogenous SDF-1a production. We confirmed in vitro that microglia, astrocytes, and brain endothelial cells significantly change SDF-1a and CXCR4 expression after exposure. We found that diffusion-only based mathematical models were unable to capture in vivo SDF-1a spatial distribution. Adding autocrine/paracrine mechanisms to the model allowed for SDF-1a temporal trends to be modeled accurately, indicating it plays an essential role in SDF-1a sustainment. We conclude that autocrine/paracrine dynamics play a role in endogenous SDF-1a levels in the brain following exogenous delivery. Implementation of these dynamics are necessary to improving SDF-1a delivery strategies. Further, mathematical models introduced here may be utilized in predicting future outcomes based upon new biomaterial designs.

Intra-Articular Injection of Stromal Cell-Derived Factor 1α Promotes Meniscal Healing via Macrophage and Mesenchymal Stem Cell Accumulation in a Rat Meniscal Defect Model.

The stromal-cell-derived factor-1α (SDF-1) is well-known for playing important roles in the regeneration of tissue by enhancing cell migration. However, the effect of SDF-1 in meniscal healing remains unknown. The purpose of this study is to investigate the effects of intra-articular injection of SDF-1 on meniscus healing in a rat meniscal defect model. The intra-articular SDF-1 injection was performed at meniscectomy and one week later. Macroscopic and histological assessments of the reparative meniscus were conducted at one, two and six weeks after meniscectomy in rats. In the macroscopic evaluation, the SDF-1 group showed an increase in the size of the reparative meniscus at six weeks after meniscectomy compared to the phosphate-buffered saline (PBS) injection (no-treatment) group. Histological findings showed that intra-articular injection of SDF-1 enhanced the migration of macrophages to the site of the regenerative meniscus at one and two weeks after meniscectomy. CD68- and CD163-positive cells in the SDF-1 group at one week after meniscectomy were significantly higher than in the no-treatment group. CD163-positive cells in the SDF-1 group at two weeks were significantly higher than in the no-treatment group. At one week after meniscectomy, there were cells expressing mesenchymal-stem-cell-related markers in the SDF-1 group. These results indicate the potential of regenerative healing of the meniscus by SDF-1 injection via macrophage and mesenchymal stem cell accumulation. In the present study, intra-articular administration of SDF-1 contributed to meniscal healing via macrophage, CD90-positive cell and CD105-positive cell accumulation in a rat meniscal defect model. The SDF-1–CXCR4 pathway plays an important role in the meniscal healing process. For potential clinical translation, SDF-1 injection therapy seems to be a promising approach for the biological augmentation in meniscal injury areas to enhance healing capacity.

Enhanced Biocompatibility and Differentiation Capacity of Mesenchymal Stem Cells on Poly(dimethylsiloxane) by Topographically Patterned Dopamine.

Controlling the behavior of mesenchymal stem cells (MSCs) through topographic patterns is an effective approach for stem cell studies. We, herein, reported a facile method to create a dopamine (DA) pattern on poly(dimethylsiloxane) (PDMS). The topography of micropatterned DA was produced on PDMS after plasma treatment. The grid-topographic-patterned surface of PDMS-DA (PDMS-DA-P) was measured for adhesion force and Young's modulus by atomic force microscopy. The surface of PDMS-DA-P demonstrated less stiff and more elastic characteristics compared to either nonpatterned PDMS-DA or PDMS. The PDMS-DA-P evidently enhanced the differentiation of MSCs into various tissue cells, including nerve, vessel, bone, and fat. We further designed comprehensive experiments to investigate adhesion, proliferation, and differentiation of MSCs in response to PDMS-DA-P and showed that the DA-patterned surface had good biocompatibility and did not activate macrophages or platelets in vitro and had low foreign body reaction in vivo. Besides, it protected MSCs from apoptosis as well as excessive reactive oxygen species (ROS) generation. Particularly, the patterned surface enhanced the differentiation capacity of MSCs toward neural and endothelial cells. The stromal cell-derived factor-1α/CXantiCR4 pathway may be involved in mediating the self-recruitment and promoting the differentiation of MSCs. These findings support the potential application of PDMS-DA-P in either cell treatment or tissue repair.

Dipeptidyl Peptidase-4 Inhibitor Decreases Allograft Vasculopathy Via Regulating the Functions of Endothelial Progenitor Cells in Normoglycemic Rats.

Chronic rejection induces the occurrence of orthotopic allograft transplantation (OAT) vasculopathy, which results in failure of the donor organ. Numerous studies have demonstrated that in addition to regulating blood sugar homeostasis, dipeptidyl peptidase-4 (DPP-4) inhibitors can also provide efficacious therapeutic and protective effects against cardiovascular diseases. However, their effects on OAT-induced vasculopathy remain unknown. Thus, the aim of this study was to investigate the direct effects of sitagliptin on OAT vasculopathy in vivo and in vitro. The PVG/Seac rat thoracic aorta graft to ACI/NKyo rat abdominal aorta model was used to explore the effects of sitagliptin on vasculopathy. Human endothelial progenitor cells (EPCs) were used to investigate the possible underlying mechanisms. We demonstrated that sitagliptin decreases vasculopathy in OAT ACI/NKyo rats. Treatment with sitagliptin decreased BNP and HMGB1 levels, increased GLP-1 activity and stromal cell-derived factor 1α (SDF-1α) expression, elevated the number of circulating EPCs, and improved the differentiation possibility of mononuclear cells to EPCs ex vivo. However, in vitro studies showed that recombinant B-type natriuretic peptide (BNP) and high mobility group box1 (HMGB1) impaired EPC function, whereas these phenomena were reversed by glucagon-like peptide 1 (GLP-1) receptor agonist treatment. We suggest that the mechanisms underlying sitagliptin-mediated inhibition of OAT vasculopathy probably occur through a direct increase in GLP-1 activity. In addition to the GLP-1-dependent pathway, sitagliptin may regulate SDF-1α levels and EPC function to reduce OAT-induced vascular injury. This study may provide new prevention and treatment strategies for DPP-4 inhibitors in chronic rejection-induced vasculopathy.

Acute effects of sitagliptin on progenitor cells and soluble mediators in newly diagnosed type 2 diabetes.

Studies have confirmed that endothelial progenitor cells (EPCs) are involved in diabetic complications. The present study assessed the action of the dipeptidyl peptidase-4 inhibitor sitagliptin on EPCs in newly diagnosed type 2 diabetes patients. 60 newly-diagnosed type 2 diabetes patients were randomly divided into three treatment groups: sitagliptin (n = 20), metformin (n = 20), and combination sitagliptin and metformin (n = 20). Patients were treated once daily for 3 days. Before and after each treatment, the number of EPCs and concentration of soluble mediators (glucagon-like peptide 1 (GLP-1), nitric oxide (NO), endothelin-1 (ET-1), and stromal cell-derived factor-1α (SDF-1α)) were determined. The number of CD34+KDR+ and CD34+CD133+KDR+ EPCs and concentration of GLP-1, NO, and SDF-1α in sitagliptin and combination groups were both increased (both p<0.05) but to a greater extent in the combination group (p<0.05). Pearson correlation analysis and multiple linear regression analyses showed that the change in EPC numbers correlated with changes in peripheral GLP-1, NO, and SDF-1α levels (p<0.05). Sitagliptin is able to directly increase the number of peripheral blood EPCs. This direct effect is to be important for lowering vascular risk in early diabetes before macrovascular complications appear.

Ginsenoside Rg1 prevents vascular intimal hyperplasia involved by SDF-1α/CXCR4, SCF/c-kit and FKN/CX3CR1 axes in a rat balloon injury

Ethnopharmacological relevancePanax ginseng C. A. Mey. is a traditional tonic that has been used for thousands of years, and has positive effects on vascular diseases. Ginsenoside Rg1 (GS-Rg1) is one of the active ingredients of Panax ginseng C. A. Mey. and has been shown to have beneficial effects against ischemia/reperfusion injury. Our previously study has found that GS-Rg1 can mobilize bone marrow stem cells and inhibit vascular smooth muscle proliferation and phenotype transformation. However, pharmacological effects and mechanism of GS-Rg1 in inhibiting intimal hyperplasia is still unknown. Aim of the studyThis study was aimed to investigate whether GS-Rg1 prevented vascular intimal hyperplasia, and the involvement of stromal cell-derived factor-1α (SDF-1α)/CXCR4, stem cell factor (SCF)/c-kit and fractalkine (FKN)/CX3CR1 axes. Materials and methodsRats were operated with carotid artery balloon injury. The treatment groups were injected with 4, 8 and 16 mg/kg of GS-Rg1 for 14 days. The degree of intimal hyperplasia was evaluated by histopathological examination. The expression of α-SMA (α-smooth muscle actin) and CD133 were detected by double-label immunofluorescence. Serum levels of SDF-1α, SCF and soluble FKN (sFKN) were detected by enzyme linked immunosorbent assay (ELISA). The protein expressions of SCF, SDF-1α and FKN, as well as the receptors c-kit, CXC chemokine receptor type 4 (CXCR4) and CX3C chemokine receptor type 1 (CX3CR1) were detected by immunochemistry. ResultsGS-Rg1 reduced intimal hyperplasia by evidence of the values of NIA, the ratio of NIA/MA, and the ratio of NIA/IELA and the ratio of NIA/LA, especially in 16 mg/kg group. Furthermore, GS-Rg1 8 mg/kg group and 16 mg/kg group decreased the protein expressions of the SDF-1α/CXCR4, SCF/c-kit and FKN/CX3CR1 axes in neointima, meanwhile GS-Rg1 8 mg/kg group and 16 mg/kg group also attenuated the expressions of SDF-1α, SCF and sFKN in serum. In addition, the expression of α-SMA and CD133 marked smooth muscle progenitor cells (SMPCs) was decreased after GS-Rg1 treatment. ConclusionsGS-Rg1 has a positive effect on inhibiting vascular intimal hyperplasia, and the underlying mechanism is related to inhibitory expression of SDF-1α/CXCR4, SCF/c-kit and FKN/CX3CR1 axes.

Neurotrophin-3 accelerates reendothelialization through inducing EPC mobilization and homing.

Rapid endothelialization is an effective way to treat intimal hyperplasia after intravascular stent implantation. Blood vessels and nerves coordinate with each other in function, while neurotrophin-3 (NT-3) is an important class of nerve growth factors. Our study found that NT-3 promoted endothelial progenitor cell (EPC) mobilization, and the proportion of EPCs in peripheral blood was increased by 1.774 times compared with the control group. Besides, NT-3 promoted the expression of stromal cell-derived factor-1α (SDF-1α), matrix metalloproteinase-9 (MMP9), and chemokine (C-X-C motif) receptor 4 (CXCR4) in EPCs, which increased by 59.89%, 74.46%, and 107.7%, respectively, compared with the control group. Transwell experiments showed that NT-3 enhanced the migration of EPCs by 1.31 times. Flow chamber experiments demonstrated that NT-3 captured more circulating EPCs. As shown by ELISA results, NT-3 can promote the paracrine of vascular endothelial growth factor, interleukin-8, MMP-9, and SDF-1 from EPCs. Such increased angiogenic growth factors further accelerated the closure of endothelial cell scratches. Additionally, EPC-conditioned medium in the NT-3 group significantly inhibited the proliferation of vascular smooth muscle cells. Then animal experiments also illustrated that NT-3 prominently accelerated the endothelialization of injured carotid artery. In short, NT-3 accelerated rapid reendothelialization of injured carotid artery through promoting EPC mobilization and homing.

Surface tethering of stromal cell-derived factor-1α carriers to stem cells enhances cell homing to ischemic muscle

Mesenchymal stem cells are promising medicine for treating diseases and tissue defects because of their innate ability to secrete therapeutic factors. Intravenous delivery of stem cells, although favored for its minimal invasiveness, is often plagued by low cellular engraftment in the target tissue. To this end, this study hypothesizes that in situ activation of cellular expression of CXC chemokine 4 (CXCR4) would significantly improve cellular migration to injured tissue. This hypothesis was examined by tethering the surface of stem cells with poly(D,L-lactide-co-glycolide)-block-hyaluronic acid (HA) particles containing stromal cell-derived factor-1α, a model chemokine to sensitize CXCR4. The HA blocks in the particles enhanced the association rate constant to stem cells by 3.3-fold, and in turn, increased the number of cells expressing CXCR4 receptors. Consequently, these cells displayed 1.2-fold higher transendothelial migration in vitro and 1.7-fold greater trafficking to the ischemic hindlimb of a mouse than that of the untethered cells.

Dimethyloxalyl Glycine Regulates the HIF-1 Signaling Pathway in Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) are pluripotent stem cells with self-renewal and multidirectional differentiation capabilities. Dimethyloxalyl glycine (DMOG) mobilizes MSCs, and the hypoxia inducible factor-1 (HIF-1) signaling pathway plays an important role in MSC mobilization. We aimed to investigate the effect of DMOG on the HIF-1 pathway in MSCs. Rats were treated with DMOG, and the numbers of peripheral blood MSCs (PB-MSCs) and bone marrow MSCs (BM-MSCs) were detected by the Colony-forming unit fibroblastic (CFU-F) method. The growth curve, cell cycle and migration ability of PB-MSCs and BM-MSCs were detected by CCK-8, Flow cytometry and Transwell assays. Western blotting and real-time qPCR were used to detect the expression of the HIF-1 pathway. The number of bone marrow microvessels was detected by immunohistochemistry. DMOG significantly increased the numbers of PB-MSCs and BM-MSCs (P < 0.05). Further, the MSCs in peripheral blood and bone marrow still had the ability to proliferate and migrate after mobilization by DMOG. The expression levels of HIF-1α, stromal cell-derived factor-1α (SDF-1α) and vascular endothelial growth factor (VEGF) in MSCs were significantly regulated by DMOG (P < 0.05). The number of bone marrow microvessels decreased after the VEGF/VEGFR signaling pathway was blocked by SU5416 (P < 0.05). Therefore, these findings demonstrated that DMOG regulates the HIF-1α signaling pathway and promotes biological effects in MSCs.

Controlled autologous recellularization and inhibited degeneration of decellularized vascular implants by side-specific coating with stromal cell-derived factor 1α and fibronectin

Optimized biocompatibility is crucial for the durability of cardiovascular implants. Previously, a combined coating with fibronectin (FN) and stromal cell-derived factor 1α (SDF1α) has been shown to accelerate the in vivo cellularization of synthetic vascular grafts and to reduce the calcification of biological pulmonary root grafts. In this study, we evaluate the effect of side-specific luminal SDF1α coating and adventitial FN coating on the in vivo cellularization and degeneration of decellularized rat aortic implants. Aortic arch vascular donor grafts were detergent-decellularized. The luminal graft surface was coated with SDF1α, while the adventitial surface was coated with FN. SDF1α-coated and uncoated grafts were infrarenally implanted (n = 20) in rats and followed up for up to eight weeks. Cellular intima population was accelerated by luminal SDF1α coating at two weeks (92.4 ± 2.95% versus 61.1 ± 6.51% in controls, p < 0.001). SDF1α coating inhibited neo-intimal hyperplasia, resulting in a significantly decreased intima-to-media ratio after eight weeks (0.62 ± 0.15 versus 1.35 ± 0.26 in controls, p < 0.05). Furthermore, at eight weeks, media calcification was significantly decreased in the SDF1α group as compared to the control group (area of calcification in proximal arch region 1092 ± 517 μm2 versus 11 814 ± 1883 μm2, p < 0.01). Luminal coating with SDF1α promotes early autologous intima recellularization in vivo and attenuates neo-intima hyperplasia as well as calcification of decellularized vascular grafts.

Prognostic Value of SDF-1α Expression in Patients with Esophageal Squamous Cell Carcinoma Receiving Esophagectomy.

Stromal cell-derived factor-1α (SDF-1α) is a chemokine that has been reported to be involved in tumor progression in several malignancies. This study aimed to evaluate the crucial role of SDF-1α in patients with esophageal squamous cell carcinoma (ESCC) who underwent esophagectomy. A total of 169 patients with ESCC were identified, including overexpression of SDF-1α in 60 patients and low expression of SDF-1α in 109 patients by immunohistochemical analysis. Two ESCC cell lines, TE1 and KYSE30, were selected to evaluate the tumor cell proliferative effect of SDF-1α. Univariate and multivariate analyses showed that high tumor (T) status, positive lymph node metastasis, tumors located in the upper esophagus, and SDF-1α overexpression were significantly related to worse disease-free survival and overall survival. In addition, the two cell lines were treated with SDF-1α, AMD3100 (an SDF-1α-ligand receptor antagonist), and chemotherapeutic agents (cisplatin). Our in vitro study results showed that SDF-1α promoted the proliferation of tumor cells, and blocking the SDF-1α pathway displayed a growth inhibition effect in a dose-dependent manner. SDF-1α plays an important role in the progression of ESCC and is an independent prognostic factor for ESCC patients who underwent esophagectomy.

Sustained release of collagen-affinity SDF-1α from book-shaped acellular fibrocartilage scaffold enhanced bone-tendon healing in a rabbit model.

Rapid and functional bone-tendon (B-T) healing remains a difficulty in clinical practice. Tissue engineering has emerged as a promising strategy to address this problem. However, the majority of tissue engineering scaffolds are loaded with stem cells to enhance the regenerability in B-T healing, which is complicated and inconvenient for clinical application. Accordingly, developing a cell-free scaffold with chemotactic function and chondrogenic inducibility may be an effective approach. In this study, a collagen affinity peptidederived from the A3 domain of von Willebrand factor (a hemostasis factor) was fused into the C-terminal of a stromal cell-derived factor-1α (SDF-1α) to synthesize a recombinant SDF-1α capable of binding collagen and chemotactic activity. The recombinant SDF-1α was then tethered on the collagen fibers of a book-shaped acellular fibrocartilage scaffold (BAFS), thus fabricating a novel scaffold (C-SDF-1α/BAFS) with chemotactic function and chondrogenic inducibility. In vitro tests determined that this scaffold was noncytotoxic and biomimetic, could attract stem cells migrating to the scaffold using sustainably released C-SDF-1α, and inducedthe interacting stem cells down the chondrogenic lineage. In vivo, the C-SDF-1α/BAFS significantly enhanced the B-T healing in a rabbit partial patellectomy model, as shown by the larger cartilaginous metaplasia region, better fibrocartilage regeneration, additional bone formation, and improved biomechanical properties. Therefore, the findings of the study demonstrate that the C-SDF-1α/BAFS could potentially be applied for B-T healing.

G protein βγ translocation to the Golgi activates the mitogen‐activated protein kinases via phosphoinositide 3‐kinase γ

The activation of G protein‐coupled receptors (GPCRs) induces the translocation of G protein βγ complex from the plasma membrane (PM). However, its functions are not well known. Here we demonstrated that among the entire twelve Gγ family members, Gγ9 is the most translocatable Gγ subunit. More than 80% of Gγ9, in complex with Gβ1, relocated from the PM to the Golgi in response to CXCR4 activation by stromal cell‐derived factor 1α (SDF1α) and the half time of the translocation was about 5 seconds. To study the function of Gβγ translocation to the Golgi, we focused on the activation of the mitogen‐activated protein kinases (MAPK) ERK1/2. CRISPR‐Cas9‐mediated knockout of Gγ9 abolished ERK1/2 activation by SDF1α, whereas knockout of the least‐translocatable Gγ3 had no effect. To investigate if Gβγ‐mediated ERK1/2 activation indeed occurred on the Golgi, we employed an inducible system to specifically express Gβγ onto the Golgi. Interestingly, the targeted expression of Gγ2, Gγ3 and Gγ9, in complex with Gβ1, onto the Golgi each induced remarkable ERK1/2 activation. Such constitutive ERK1/2 activation was blocked by the expression of Gα subunits, the targeted expression of the Gβγ blocker GRK2ct at the Golgi, and chemical treatments to disrupt the Golgi structure. By contrast, the expression of individual Gγ subunits at the PM did not activate ERK1/2. To define the downstream effectors of Gβγ, we determined the effect of selective pharmacological inhibition of phosphoinositide 3‐kinase (PI3K), phospholipase C, PKC and PKD on ERK1/2 activation. This strategy identified PI3Kγ and PI3Kδ to be essential for Gβγ‐mediated ERK1/2 activation. Indeed, knockout of PI3Kγ by CRISPR‐Cas9 almost abolished ERK1/2 activation induced by both SDF1α and Gγ9 targeting to the Golgi. Similar to CXCR4, α2‐adrenergic receptor‐mediated ERK1/2 activation was also dramatically inhibited by Gγ9 and PI3Kγ knockout. We further showed that knockout of Gγ9 and PI3Kγ markedly suppressed the migration and invasion of prostate cancer PC3 cells in response to SDF1α stimulation in vitro. Gγ9 and PI3Kγ knockout also significantly reduced the bone metastasis of PC3 tumors following intra‐cardiac injection of PC3‐Luc cells in athymic nude mice. Overall, our data demonstrate a novel function for Gβγ translocation to the Golgi to spatiotemporally control the activation of the MAPK pathway by GPCRs and tumor progression.Support or Funding InformationNIH R01 GM118915

Angiogenic T cells are decreased in people with type 2 diabetes mellitus and recruited by the dipeptidyl peptidase‐4 inhibitor Linagliptin: A subanalysis from a randomized, placebo‐controlled trial (RELEASE study)

Angiogenic T (Tang) cells are mediators of vascular repair, and are characterized by surface expression of CXCR4. This receptor for stromal cell‐derived factor‐1α (SDF‐1α) is cleaved by dipeptidyl peptidase‐4 (DPP‐4). Tang cell levels were investigated in people with type 2 diabetes mellitus (T2DM) compared with matched healthy controls and after treatment with the DPP‐4 inhibitor Linagliptin. People with T2DM were randomized to 5 mg/day Linagliptin (n = 20) or placebo (n = 21) for 26 weeks. Tang cell frequency was identified in peripheral blood mononuclear cells (CD3+CD31+CXCR4+) and levels of endothelial progenitor cells (EPCs) (CD34+CD133+KDR+) were also assessed in whole blood. Circulating Tang cell levels were significantly lower in people with T2DM compared with the healthy control group. SDF‐1α levels increased significantly in Linagliptin‐treated people with T2DM compared to placebo, and a trend was observed in change of Tang cell levels, while EPC count did not change. In conclusion, circulating Tang cell levels were considerably lower in people with T2DM, while a trend was observed in recruitment of Tang cells after 26 weeks of treatment with Linagliptin. These data suggest that DPP‐4 inhibitors may potentially exert beneficial effects on bone marrow‐driven vascular repair.

IPSC-derived endothelial cell response to hypoxia via SDF1a/CXCR4 axis facilitates incorporation to revascularize ischemic retina.

Ischemic retinopathies are major causes of blindness worldwide. Local hypoxia created by loss of vascular supply leads to tissue injury and aberrant neovascularization in the retina. There is a great need for therapies that enhance revascularization of hypoxic neuroretinal tissue. To test the therapeutic feasibility of human-induced pluripotent stem cell-derived endothelial cells (hiPSC-ECs) for the treatment of ischemic retinopathies, we compared the angiogenic potential of hiPSC-ECs with mature human retinal endothelial cells (HRECs) in response to hypoxia. hiPSC-ECs formed more robust and complex vascular networks in collagen gels, whereas HRECs displayed minimal sprouting. The cells were further tested in the mouse oxygen-induced retinopathy (OIR) model. Retinas with hiPSC-EC injection showed colocalization with host vessels, whereas HRECs lacked such responses. hiPSC-ECs markedly reduced vaso-obliteration and pathological neovascularization. This beneficial effect of hiPSC-ECs was explained by the stromal cell-derived factor-1a (SDF1a)/CXCR4 axis; hiPSC-ECs exhibited much higher cell-surface expression of CXCR4 than HRECs and greater chemotaxis toward SDF1a-embedded 3D collagen hydrogel. Furthermore, treatment with neutralizing antibody to CXCR4 abolished recruitment of hiPSCs in the OIR model. These findings suggest superior angiogenic potential of hiPSC-ECs under hypoxia and underscore the importance of SDF1a/CXCR4 in the reparative function of hiPSC-ECs in ischemic diseases.

A liposome/gelatin methacrylate nanocomposite hydrogel system for delivery of stromal cell-derived factor-1α and stimulation of cell migration

Chronic, non-healing skin and soft tissue wounds are susceptible to infection, difficult to treat clinically, and can severely reduce a patient's quality of life. A key aspect of this issue is the impaired recruitment of mesenchymal stem cells (MSCs), which secrete regenerative cytokines and modulate the phenotypes of other effector cells that promote healing. We have engineered a therapeutic delivery system that can controllably release the pro-healing chemokine stromal cell derived factor-1α (SDF-1α) to induce the migration of MSCs. In order to protect the protein cargo from hydrolytic degradation and control its release, we have loaded SDF-1α in anionic liposomes (lipoSDF) and embedded them in gelatin methacrylate (GelMA) to form a nanocomposite hydrogel. In this study, we quantify the release of SDF-1α from our hydrogel system and measure the induced migration of MSCs in vitro via a transwell assay. Lastly, we evaluate the ability of this system to activate intracellular signaling in MSCs by using Western blots to probe for the phosphorylation of key proteins in the mTOR pathway. To our knowledge, this is the first study to report the delivery of liposomal SDF-1α using a nanocomposite approach. The results of this study expand on our current understanding of factors that can be modified to affect MSC behavior and phenotype. Furthermore, our findings contribute to the development of new hydrogel-based therapeutic delivery strategies for clinical wound healing applications. Statement of SignificanceChronic, non-healing wounds promote an inflammatory environment that inhibits the migration of mesenchymal stem cells (MSCs), which secrete pro-healing and regenerative cytokines. The goal of this project is to apply principles of tissue engineering to achieve controllable release of the pro-healing chemokine SDF-1α to modulate the intracellular signaling and migratory behavior of MSCs. In this work, we introduce a nanocomposite strategy to tailor the release of SDF-1α using a liposome/gelatin methacrylate hydrogel approach. We are the first group to report the delivery of liposomal SDF-1α using this strategy. Our findings aim to further elucidate the role of MSCs in directing wound healing and guide the development of immunomodulatory and therapeutic delivery strategies for clinical wound healing applications.

Aerogel sponges of silk fibroin, hyaluronic acid and heparin for soft tissue engineering: Composition-properties relationship

This work aims to design biocompatible aerogel sponges that can host and control the release of stromal cell-derived factor-1α (SDF-1α or CXCL12), a key protein for applications ranging from regenerative medicine to cancer therapy (notably for neural tissues). Miscibility of silk fibroin (SF) and hyaluronic acid (HA) was investigated by means of fluorescence and scanning electron microscopy to identify processing conditions. Series of freeze-dried sponges were prepared by associating and cross-linking within the same 3D structure, HA, SF, poly-l-lysine (PLL) and heparin (hep). Aerogel sponges presented high swelling degree and porosity (∼90 %), adequate mean pore diameter (ca. 60 μm) and connectivity for welcoming cells, and a soft texture close to that of the brain (6–13 kPa Young’s Modulus). Addition of SF yielded sponges with slower biodegradation. SF-HA and SF-HA-hep sponges retained 75 % and 93 % of the SDF-1α respectively after 7 days and were found to be cytocompatible in vitro.

RADA16-I Hydrogel-Released CXCL12 Stably Promotes Stem Cell Migration

Introduction: CXCL12 (Stromal cell-derived factor 1α, SDF - 1α) plays an important role in the nervous system development and neural repair, and is gradiently expressed in the central nervous system, mediating proper neural progenitor cell (NPCs) migration and survival. Due to a relatively short half-life and restriction of the blood-brain barrier (BBB) in systemic bioactive factor delivery, the delivery of CXCL12 and other bioactive factors has become a great challenge in research and clinical application. Aims: In order to observe the change of concentration grade and release time of CXCL12we studied the dynamic CXCL12 prolonged release pattern with the injectable, nontoxic, modifiable and degradable RADA16-I peptide hydrogel. The hydrogel resulted in a relatively stable CXCL12 concentration and provided more suitable microenvironment for stem cell survival and migration in vitro. The following major experiments were conducted: 1. Anti-adhesion and neural protection with RADA16-I were performed in rabbit skull trauma model; 2. Fluorescent semi-quantitative CLSM was used for analysis of CXCL12 released from CXCL12 hydrogel mixture, and ELISA for detecting CXCL12 release kinetic curve was utilized; 3. Effective concentration was estimated through the peak concentration of CXCL12 load and was determined with trans-well migration assay. Results: 1. RADA16-I alone potentially played a role in anti-adhesion and neural repair. Furthermore, RADA16-I hydrogel slow-release system smoothly released chemokine CXCL12 in vitro. 2. Stable CXCL12 released system was more effective to be used for tissue repair compared to quickly declined CXCL12 without hydrogel system. 3. The peak concentration (50 ng/ml) of CXCL12 load released from hydrogel was the functional concentration for the induction of directional migration in mouse neuronal progenitor cells (mNPCs). Conclusions: Slow-released hydrogel system and mixture, RADA16-I and CXCL12, offered effective grade level for cell migration. This system is potentially beneficial for neural tissue protection and neural repair in clinic.

Characterization of gene expression changes in human neural stem cells and endothelial cells modeling a neurovascular microenvironment

Angiogenesis-mediated neovascularization correlates with recovery after intracerebral implantation of neural stem cells (NSCs) in stroke. To elucidate NSCs’ mechanism of action, it is essential to understand how these interact with the brain’s vasculature after implantation. Using an all-human endothelial cell (EC, D3 cell line) and NSC (STROC05 and CTXOE03) co-culture model, fluorescently activated cell sorting (FACS) was used to isolate each cell type for a comparison of gene expression between monocultures of undifferentiated proliferating and differentiated non-proliferating cells. Gene expression for angiogenic factors (vascular endothelial growth factor, platelet derived growth factor, angiopoietin), as well as cell survival (brain derived neurotrophic factor, fibroblast growth factor) and migration (stromal cell-derived factor-1a) were measured and contrasted with the corresponding receptors on each cell type. The cellular source of extracellular matrix defining the basement membrane (vitronectin, fibronectin, laminin, collagen I and IV) and neuropil (hyaluronic acid, aggrecan, neurocan, thrombospondin, nidogen and brain associated link protein-1) was evaluated for NSCs and ECs. Co-culturing dramatically changed the expression profiles of each cell type in comparison to undifferentiated, but also differentiated cells. These results indicate that monocultures provide a poor model to investigate the cellular signaling involved in a tissue repair response. Co-cultures of NSCs and ECs forming vasculature-like structures (VLS) provide a more complex model to investigate NSC-induced neovascularization. These in vitro studies are essential to tease out individual cell signaling in NSCs and ECs to develop a mechanistic understanding of the efficacy of NSCs as a therapeutic for stroke.

Extracellular ubiquitin levels are increased in coronary heart disease and associated with the severity of the disease

Aim: This study aimed to evaluate concentration of plasma extracellular ubiquitin (UB) in coronary heart disease (CHD) patients and its correlation with the disease severity.Methods: Levels of UB and stromal cell-derived factor-1a (SDF-1a) were measured in 60 healthy controls and 67 CHD cases. Coronary atherosclerosis was assessed with Gensini scoring system. Spearman correlation was used to evaluate the correlation between UB and low-density lipoprotein cholesterol (LDL-C), C-reactive protein (CRP), creatine kinase-MB (CK-MB), cardiac troponin I (cTnI) or SDF-1a. The receiver-operating characteristic (ROC) curve was established to assess the predictive value of UB.Results: Plasma UB levels were significantly higher in CHD patients than in controls (p < .0001), and the levels in those with acute myocardial infarction (AMI) were higher than stable angina pectoris (SAP) and unstable angina pectoris (UAP) groups (both p < .01). UB was also positively correlated with Gensini score, CRP, CK-MB and cTnI in CHD. ROC analysis of UB showed that the area under the curve (AUC) were 0.711 (95%CI, 0.623–0.799) and 0.778 (95%CI, 0.666–0.890) for CHD and acute coronary syndrome (ACS), respectively. Plasma SDF-1a levels were elevated in CHD patients but showed no significant correlation with UB concentration or the severity of the disease.Conclusion: Plasma UB concentration was increased in CHD and the change of UB levels may reflect the progression of CHD.