FOXO1 regulates developmental lymphangiogenesis by upregulating CXCR4 in the mouse-tail dermis.

Lymphangiogenesis plays important roles in normal fetal development and postnatal growth. However, its molecular regulation remains unclear. Here, we have examined the function of forkhead box protein O1 (FOXO1) transcription factor, a known angiogenic factor, in developmental dermal lymphangiogenesis using endothelial cell-specific FOXO1-deficient mice. FOXO1-deficient mice showed disconnected and dilated lymphatic vessels accompanied with increased proliferation and decreased apoptosis in the lymphatic capillaries. Comprehensive DNA microarray analysis of the causes of in vivo phenotypes in FOXO1-deficient mice revealed that the gene encoding C-X-C chemokine receptor 4 (CXCR4) was the most drastically downregulated in FOXO1-deficient primary lymphatic endothelial cells (LECs). CXCR4 was expressed in developing dermal lymphatic capillaries in wild-type mice but not in FOXO1-deficient dermal lymphatic capillaries. Furthermore, FOXO1 suppression impaired migration toward the exogenous CXCR4 ligand, C-X-C chemokine ligand 12 (CXCL12), and coordinated proliferation in LECs. These results suggest that FOXO1 serves an essential role in normal developmental lymphangiogenesis by promoting LEC migration toward CXCL12 and by regulating their proliferative activity. This study provides valuable insights into the molecular mechanisms underlying developmental lymphangiogenesis.

Efficacy of Rectal Systemic Administration of Mesenchymal Stem Cells to Injury Sites via the CXCL12/CXCR4 Axis to Promote Regeneration in a Rabbit Skeletal Muscle Injury Model.

Mesenchymal stem cells (MSCs) have been transplanted directly into lesions or injected intravenously. The administration of MSCs using these delivery methods requires specialized knowledge, techniques, and facilities. Here, we describe intrarectal systemic administration of MSCs, a simple, non-invasive route for homing to the injury sites to promote the regeneration of skeletal muscle injuries. Using a cardiotoxin (CTX)-induced rabbit skeletal muscle injury model, homing to the site of muscle injury was confirmed by intrarectal administration of MSCs; the time required for homing after intrarectal administration was approximately 5 days. In addition, the C-X-C chemokine ligand 12 (CXCL12)/C-X-C chemokine receptor-4 (CXCR4) axis was found to be involved in the homing process. Histopathological examinations showed that skeletal muscle regeneration was promoted in the MSCs-administered group compared to the CTX-only group. Myosin heavy polypeptide 3 (Myh3) expression, an indicator of early muscle regeneration, was detected earlier in the intrarectal MSCs group compared to the CTX-only group. These findings indicate that intrarectal administration of MSCs is effective in homing to the injured area, where they promote injury repair. Since intrarectal administration is a simple and non-invasive delivery route, these findings may be valuable in future research on stem cell therapy.

CXCL12/CXCR4 axis in the microenvironment of solid tumors: A critical mediator of metastasis.

Tumors are dynamic tissue masses, so requiring continuous exposure to the host cells, nurturing them into pave a path for tumor growth and metastasis. C-X-C chemokine ligand 12 (CXCL12)/C-X-C chemokine receptor type 4 (CXCR4) is the key signaling for such aim. Gathering knowledge about the activity within this axis would deepen our insight into the utmost importance this signaling taken to attract and cross-connect multiple cells within the tumor microenvironment (TME) aiming for tumor progression and metastasis. The concept behind this review is to underscore the multi-tasking roles taken by CXCL12/CXCR4 signaling in tumor metastasis, and to also suggest some strategies to target the activities within this axis.

Detecting Cell Surface Expression of the G Protein-Coupled Receptor CXCR4.

G protein-coupled receptors (GPCRs) are cell surface receptors that relay extracellular signals to the inside of the cells. C-X-C chemokine receptor 4 (CXCR4) is a GPCR that undergoes receptor internalization and recycling upon stimulation with its cognate ligand, C-X-C chemokine 12 (CXCL12). Using this receptor/ligand pair we describe the use of two techniques, enzyme-linked immunosorbent assay (ELISA) and flow cytometry, widely used to quantify GPCR internalization from the plasma membrane and its return to the cell surface by recycling.