Multiscale mechanisms of cell migration during development: theory and experiment

Long-distance cell migration is an important feature of embryonic development, adult morphogenesis and cancer, yet the mechanisms that drive subpopulations of cells to distinct targets are poorly understood. Here, we use the embryonic neural crest (NC) in tandem with theoretical studies to evaluate model mechanisms of long-distance cell migration. We find that a simple chemotaxis model is insufficient to explain our experimental data. Instead, model simulations predict that NC cell migration requires leading cells to respond to long-range guidance signals and trailing cells to short-range cues in order to maintain a directed, multicellular stream. Experiments confirm differences in leading versus trailing NC cell subpopulations, manifested in unique cell orientation and gene expression patterns that respond to non-linear tissue growth of the migratory domain. Ablation experiments that delete the trailing NC cell subpopulation reveal that leading NC cells distribute all along the migratory pathway and develop a leading/trailing cellular orientation and gene expression profile that is predicted by model simulations. Transplantation experiments and model predictions that move trailing NC cells to the migratory front, or vice versa, reveal that cells adopt a gene expression profile and cell behaviors corresponding to the new position within the migratory stream. These results offer a mechanistic model in which leading cells create and respond to a cell-induced chemotactic gradient and transmit guidance information to trailing cells that use short-range signals to move in a directional manner

Neuropilin-2 mediates VEGF-C–induced lymphatic sprouting together with VEGFR3

If neuropilin-2 and the growth factor VEGF-C don’t come together, lymphatic vessels don’t branch apart

A dural lymphatic vascular system that drains brain interstitial fluid and macromolecules

The central nervous system (CNS) is considered an organ devoid of lymphatic vasculature. Yet, part of the cerebrospinal fluid (CSF) drains into the cervical lymph nodes (LNs). The mechanism of CSF entry into the LNs has been unclear. Here we report the surprising finding of a lymphatic vessel network in the dura mater of the mouse brain. We show that dural lymphatic vessels absorb CSF from the adjacent subarachnoid space and brain interstitial fluid (ISF) via the glymphatic system. Dural lymphatic vessels transport fluid into deep cervical LNs (dcLNs) via foramina at the base of the skull. In a transgenic mouse model expressing a VEGF-C/D trap and displaying complete aplasia of the dural lymphatic vessels, macromolecule clearance from the brain was attenuated and transport from the subarachnoid space into dcLNs was abrogated. Surprisingly, brain ISF pressure and water content were unaffected. Overall, these findings indicate that the mechanism of CSF flow into the dcLNs is directly via an adjacent dural lymphatic network, which may be important for the clearance of macromolecules from the brain. Importantly, these results call for a reexamination of the role of the lymphatic system in CNS physiology and disease.Peer reviewe

Tbx1 regulates Vegfr3 and is required for lymphatic vessel development

Defects in lymphangiogenesis are added to the broad clinical manifestations of DiGeorge syndrome, caused by deletion of the T box transcription factor Tbx1

Assessing interactions of two loci (rs4242382 and rs10486567) in familial prostate cancer : statistical evaluation of epistasis

Understanding the impact of multiple genetic variants and their interactions on the disease penetrance of familial multiple prostate cancer is very relevant to the overall understanding of carcinogenesis. We assessed the joint effect of two loci on rs4242382 at 8q24 and rs10486567 at 7p15.2 to this end. We analyzed the data from a Finnish family-based genetic study, which was composed of 947 men including 228 cases in 75 families, to evaluate the respective effects of the two loci on the disease penetrance; in particular, the occurrence and number of prostate cancer cases within a family were utilized to evaluate the interactions between the two loci under the additive and multiplicative Poisson regression models. The risk alleles A at rs4242382 (OR = 1.14, 95% CI 1.08–1.19, P<0.0001) and a risk allele A at rs10486567 (OR = 1.06, 96%CI 1.01–1.11, P = 0.0208) were found to be associated with an increased risk of familial PrCa, especially with four or more cases within a family. A multiplicative model fitted the joint effect better than an additive model (likelihood ratio test X2 = 13.89, P<0.0001). The influence of the risk allele A at rs10486567 was higher in the presence of the risk allele A at rs4242382 (OR = 1.09 (1.01–1.18) vs. 1.01 (0.95–1.07)). Similar findings were observed in non-aggressive PrCa, but not in aggressive PrCa. We demonstrated that two loci (rs4242382 and rs10486567) are highly associated with familial multiple PrCa, and the gene-gene interaction or statistical epistasis was consistent with the Fisher's multiplicative model. These loci's association and epistasis were observed for non-aggressive but not for aggressive tumors. The proposed statistical model can be further developed to accommodate multi-loci interactions to provide further insights into epistasis.Public Library of Science open acces

Spatio-temporal Models of Lymphangiogenesis in Wound Healing

Several studies suggest that one possible cause of impaired wound healing is failed or insufficient lymphangiogenesis, that is the formation of new lymphatic capillaries. Although many mathematical models have been developed to describe the formation of blood capillaries (angiogenesis), very few have been proposed for the regeneration of the lymphatic network. Lymphangiogenesis is a markedly different process from angiogenesis, occurring at different times and in response to different chemical stimuli. Two main hypotheses have been proposed: 1) lymphatic capillaries sprout from existing interrupted ones at the edge of the wound in analogy to the blood angiogenesis case; 2) lymphatic endothelial cells first pool in the wound region following the lymph flow and then, once sufficiently populated, start to form a network. Here we present two PDE models describing lymphangiogenesis according to these two different hypotheses. Further, we include the effect of advection due to interstitial flow and lymph flow coming from open capillaries. The variables represent different cell densities and growth factor concentrations, and where possible the parameters are estimated from biological data. The models are then solved numerically and the results are compared with the available biological literature.Comment: 29 pages, 9 Figures, 6 Tables (39 figure files in total

Effects of Angiopoietin-2-Blocking Antibody on Endothelial Cell–Cell Junctions and Lung Metastasis

Background: Angiopoietin-2 (Ang2), a ligand for endothelial TEK (Tie2) tyrosine kinase receptor, is induced in hypoxic endothelial cells of tumors, where it promotes tumor angiogenesis and growth. However, the effects of Ang2 on tumor lymphangiogenesis and metastasis are poorly characterized. Methods: We addressed the effect of Ang2 on tumor progression and metastasis using systemic Ang2 overexpression in mice carrying tumor xenografts, endothelium-specific overexpression of Ang2 in VEC-tTA/Tet-OS-Ang2 transgenic mice implanted with isogenic tumors, and administration of Ang2-blocking antibodies to tumor-bearing immunodeficient mice. Fisher's exact test was used for analysis of metastasis occurrence, and repeated measures one-way analysis of variance was used for the analysis of primary tumor growth curves. Unpaired t test was used for all other analyses. All statistical tests were two-sided. Results: Adenoviral expression of Ang2 increased lymph node and lung metastasis in tumor xenografts. The metastatic burden in the lungs was increased in transgenic mice in which Ang2 expression was induced specifically in the vascular endothelium (tumor burden per grid, VEC-tTA/Tet-OS-Ang2 mice [n = 5] vs control mice [n = 4]: 45.23 vs 12.26 mm[superscript 2], difference = 32.67 mm[superscript 2], 95% confidence interval = 31.87 to 34.07, P < .001). Ang2-blocking antibodies reduced lymph node and lung metastasis, as well as tumor lymphangiogenesis, and decreased tumor cell homing to the lungs after intravenous injection. In the lung metastases, Ang2 overexpression decreased endothelial integrity, whereas the Ang2-blocking antibodies improved endothelial cell–cell junctions and basement membrane contacts of metastasis-associated lung capillaries. At the cellular level, the Ang2-blocking antibodies induced the internalization of Ang2-Tie2 receptor complexes from endothelial cell–cell junctions in endothelial–tumor cell cocultures. Conclusion: Our results indicate that blocking Ang2 inhibits metastatic dissemination in part by enhancing the integrity of endothelial cell–cell junctions