A hypothesis on the role of primitive macrophages in initial embryonic lymphatic development

Recent evidences have shown that macrophages are tightly related to pathological lymphangiogenesis. However, the effects which primitive macrophages take in embryonic lymphatic development remains unclear. Here, we postulate that the primitive macrophages may play an important role in initial embryonic lymphatic development. The possible mechanism: primitive macrophages induce BECs to transdifferentiate into LECs and initiate the budding, moreover, the lymph sacs are not only formed by LECs but also some scattered cells with macrophage characteristics preferentially located in the loose mesenchyme.