Noncanonical NF-κB activation and SDF-1 expression in human endothelial cells

Intra-articular Injections of CXCR4-Overexpressing Human Cartilage-Derived Progenitor Cells Improve Meniscus Healing and Protect Against Posttraumatic Osteoarthritis in Immunocompetent Rabbits

BACKGROUND

Meniscal injuries that fail to heal instigate catabolic changes in the knee's microenvironment, posing a high risk for developing posttraumatic osteoarthritis (PTOA). Previous research has suggested that human cartilage-derived progenitor cells (hCPCs) can stimulate meniscal repair in a manner that depends on stromal cell-derived factor 1 (SDF-1) pathway activity.

HYPOTHESIS

Overexpressing the SDF-1 receptor CXCR4 in hCPCs will increase cell trafficking and further improve the repair efficacy of meniscal injuries.

STUDY DESIGN

Controlled laboratory study.

METHODS

hCPCs were genetically modified to overexpress CXCR4 (CXCR4-overexpressing [OE] hCPCs) using lentivirus. In vitro characterization was performed using cell viability assay, cell migration assay, and immunoblotting. These cells were then used to treat a meniscal injury in rabbits. A medial meniscal tear was surgically created in the right knees of New Zealand White rabbits, followed by 2 intra-articular injections (5.0 × 106 cells each) of either CXCR4-OE hCPCs, wild-type hCPCs, or saline alone. A histological assessment of menisci and cartilage was performed using safranin O/fast green staining. Joints were assessed for PTOA changes using the modified Osteoarthritis Research Society International scoring system. Fluorescence imaging and DNA analysis were performed to examine tissue for human cells.

RESULTS

SDF-1 inhibited NF-κB and ERK pathways in both wild-type and CXCR4-OE hCPCs. CXCR4 overexpression increased hCPC trafficking toward sources of SDF-1, including injured meniscal fibrocartilage and an SDF-1-presoaked collagen scaffold. Intra-articular injections of CXCR4-OE hCPCs significantly improved meniscus healing, as evidenced by the complete absence of tears in 5 of 6 (83%) animals that received CXCR4-OE hCPCs compared with only 3 of 6 (50%) wild-type hCPC-treated animals and 2 of 6 (33%) animals in the saline control group. CXCR4-OE hCPC-treated animals also showed significantly less erosion in their knee cartilage compared with control animals.

CONCLUSION

Overall, CXCR4 overexpression inhibited catabolic pathway signaling in hCPCs and increased cell migration. Evidence suggests that intra-articular injections of these cells into the injured knee allow them to home in on sites of fibrocartilage injuries and ultimately result in meniscal tear healing and PTOA inhibition in immunocompetent animals.

CLINICAL RELEVANCE

This study demonstrated that cartilage progenitors with elevated CXCR4 expression have the potential to be a potent therapeutic tool for stimulating meniscal tear healing.

Vagus nerve stimulation-induced stromal cell-derived factor-l alpha participates in angiogenesis and repair of infarcted hearts

AIMS

We aim to explore the role and mechanism of vagus nerve stimulation (VNS) in coronary endothelial cells and angiogenesis in infarcted hearts.

METHODS AND RESULTS

Seven days after rat myocardial infarction (MI) was prepared by ligation of the left anterior descending coronary artery, the left cervical vagus nerve was treated with electrical stimulation 1 h after intraperitoneal administration of the α7-nicotinic acetylcholine inhibitor mecamylamine or the mAChR inhibitor atropine or 3 days after local injection of Ad-shSDF-1α into the infarcted heart. Cardiac tissue acetylcholine (ACh) and serum ACh, tumour necrosis factor α (TNF-α), interleukin 1β (IL-1β) and interleukin 6 (IL-6) levels were detected by ELISA to determine whether VNS was successful. An inflammatory injury model in human coronary artery endothelial cells (HCAECs) was established by lipopolysaccharide and identified by evaluating TNF-α, IL-1β and IL-6 levels and tube formation. Immunohistochemistry staining was performed to evaluate CD31-positive vessel density and stromal cell-derived factor-l alpha (SDF-1α) expression in the MI heart in vivo and the expression and distribution of SDF-1α, C-X-C motif chemokine receptor 4 and CXCR7 in HCAECs in vitro. Western blotting was used to detect the levels of SDF-1α, V-akt murine thymoma viral oncogene homolog (AKT), phosphorylated AKT (pAKT), specificity protein 1 (Sp1) and phosphorylation of Sp1 in HCAECs. Left ventricular performance, including left ventricular systolic pressure, left ventricular end-diastolic pressure and rate of the rise and fall of ventricular pressure, should be evaluated 28 days after VNS treatment. VNS was successfully established for MI therapy with decreases in serum TNF-α, IL-1β and IL-6 levels and increases in cardiac tissue and serum ACh levels, leading to increased SDF-1α expression in coronary endothelial cells of MI hearts, triggering angiogenesis of MI hearts with increased CD31-positive vessel density, which was abolished by the m/nAChR inhibitors mecamylamine and atropine or knockdown of SDF-1α by shRNA. ACh promoted SDF-1α expression and its distribution along with the branch of the formed tube in HCAECs, resulting in an increase in the number of tubes formed in HCAECs. ACh increased the levels of pAKT and phosphorylation of Sp1 in HCAECs, resulting in inducing SDF-1α expression, and the specific effects could be abolished by mecamylamine, atropine, the PI3K/AKT blocker wortmannin or the Sp1 blocker mithramycin. Functionally, VNS improved left ventricular performance, which could be abolished by Ad-shSDF-1α.

CONCLUSIONS

VNS promoted angiogenesis to repair the infarcted heart by inducing SDF-1α expression and redistribution along new branches during angiogenesis, which was associated with the m/nAChR-AKT-Sp1 signalling pathway.

Nur77-deficiency in bone marrow-derived macrophages modulates inflammatory responses, extracellular matrix homeostasis, phagocytosis and tolerance

Background

The nuclear orphan receptor Nur77 (NR4A1, TR3, or NGFI-B) has been shown to modulate the inflammatory response of macrophages. To further elucidate the role of Nur77 in macrophage physiology, we compared the transcriptome of bone marrow-derived macrophages (BMM) from wild-type (WT) and Nur77-knockout (KO) mice.

Results

In line with previous observations, SDF-1α (CXCL12) was among the most upregulated genes in Nur77-deficient BMM and we demonstrated that Nur77 binds directly to the SDF-1α promoter, resulting in inhibition of SDF-1α expression. The cytokine receptor CX3CR1 was strongly downregulated in Nur77-KO BMM, implying involvement of Nur77 in macrophage tolerance. Ingenuity pathway analyses (IPA) to identify canonical pathways regulation and gene set enrichment analyses (GSEA) revealed a potential role for Nur77 in extracellular matrix homeostasis. Nur77-deficiency increased the collagen content of macrophage extracellular matrix through enhanced expression of several collagen subtypes and diminished matrix metalloproteinase (MMP)-9 activity. IPA upstream regulator analyses discerned the small GTPase Rac1 as a novel regulator of Nur77-mediated gene expression. We identified an inhibitory feedback loop with increased Rac1 activity in Nur77-KO BMM, which may explain the augmented phagocytic activity of these cells. Finally, we predict multiple chronic inflammatory diseases to be influenced by macrophage Nur77 expression. GSEA and IPA associated Nur77 to osteoarthritis, chronic obstructive pulmonary disease, rheumatoid arthritis, psoriasis, and allergic airway inflammatory diseases.

Conclusions

Altogether these data identify Nur77 as a modulator of macrophage function and an interesting target to treat chronic inflammatory disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2469-9) contains supplementary material, which is available to authorized users.