Growth-stimulating effect of kallikrein on rat neural stem cells--II. Immunocytochemical analysis and specificity of the enzyme for neural stem cells.

In a previous paper we reported a new function of tissue kallikrein: rat urinary kallikrein (RUK) has a marked growth-stimulatory effect on neural stem cells prepared from brains of prenatal rats. We here report that conspicuous differentiation of neural stem cells to neurons and/or glial cells did not occur during stimulation by kallikrein, and this growth-stimulating effect of kallikrein is considerably specific for neural stem cells, i.e., RUK showed no detectable stimulatory effect on rat glial, PC12, GH(3), and HeLa cells. Thus this new function of kallikrein suggests the potential involvement of this enzyme on brain physiology. In addition, this effect of kallikrein for neural stem cells may have value in the treatment of cerebral ischemic stroke-induced injuries etc., i.e., kallikrein administered into the body stimulates neural stem cell proliferation and new neurons may be generated from them.