Human peripheral blood CD34-positive cells enhance therapeutic regeneration of chronically injured liver in nude rats.

We investigated whether transplantation of purified human peripheral blood CD34(+) cells could reduce established liver fibrosis and up-regulate therapeutic regeneration. Human peripheral blood CD34(+) cells were isolated from total mononuclear cells of healthy volunteers by magnetic cell sorting. Recipient nude rats were injected intraperitoneally with carbon tetrachloride (CCl(4)) twice weekly for 3 weeks before single administration of CD34(+) cells. CCl(4) was then re-administered twice weekly for 3 more weeks, and the nude rats were sacrificed. Saline (control group), 1 × 10(5) (low-dose group), 5 × 10(5) (middle-dose group), or 2 × 10(6) (high-dose group) CD34(+) cells/kg body weight were intrasplenically transplanted after CCl(4) treatment for 3 weeks. Reverse transcriptase-polymerase chain reaction analysis of the freshly isolated CD34(+) cells revealed the expression of CD31, keratin19, α-smooth muscle actin (α-SMA), and epithelial growth factor, but not other liver related markers. The transplanted cells differentiated into vascular and sinusoidal endothelial cells, and vascular smooth muscle cells. CD34(+) cell transplantation reduced liver fibrosis in a dose-dependent fashion, with decreased collagen type-I and α-SMA-positive cells after 6 weeks of CCl(4) treatment by Mallory's Azan and immunohistochemical staining. Gelatin zymography showed that the expression levels of active matrix metalloproteinase-2 and -9 in CD34(+) cell transplanted livers were significantly stronger than those in saline-infused livers. In recipients of high-doses of CD34(+) cells, the number of PCNA-positive hepatocyte increased 6 weeks after CCl(4) treatment compared with saline-infused livers. We conclude that human peripheral blood CD34(+) cell transplantation halts established liver fibrosis and promotes hepatic regeneration in CCl(4)-induced chronic liver injury.