Developmental tissues go through regression, remodeling, and apoptosis. In these processes, macrophages phagocytize dead cells and induce apoptosis directly. In hyaloid vascular system (HVS), macrophages induce apoptosis of vascular endothelial cells (VECs) by cooperation between the Wnt and angiopoietin (Ang) pathways through cell-cell interaction. However, it remains unclear how macrophages are activated and interact with VECs. Here we show that Ninjurin1 (nerve injury-induced protein; Ninj1) was temporally increased in macrophages during regression of HVS and these Ninj1-expressing macrophages closely interacted with hyaloid VECs. Systemic neutralization using an anti-Ninj1 antibody resulted in the delay of HVS regression in vivo. We also found that Ninj1 increased cell-cell and cell-matrix adhesion of macrophages. Furthermore, Ninj1 stimulated the expression of Wnt7b in macrophages and the conditioned media from Ninj1-overexpressing macrophages (Ninj1-CM) decreased Ang1 and increased Ang2 in pericytes, which consequently switched hyaloid VEC fate from survival to death. Collectively, these findings suggest that macrophages express Ninj1 to increase the death signal through cell-cell interaction and raise the possibility that Ninj1 may act similarly in other developmental regression mediated by macrophages.

We investigated the critical conditions to realize reliable and nano-engineered templates for surface-plasmon enhanced Raman scattering (SERS). Ultra-sensitive SERSs of thymine oligonucleotides were successfully realized on the template of Au nanoparticle arrays which were prepared by the combination of electron-beam lithography and post-chemical modification techniques. Drastic enhancement of Raman signal from the thymine oligonucleotides was only observed on the optimized templates, where the tuning of the plasmon resonance condition and the formation of the hot spots were both critical. Our results suggest that the artificial generation of reproducible and controlled hot spots can be achieved by our approach.