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 (CCl4) twice weekly for 3 weeks before single administration of CD34+ cells. CCl4 was then re‐administered twice weekly for 3 more weeks, and the nude rats were sacrificed. Saline (control group), 1 × 105 (low‐dose group), 5 × 105 (middle‐dose group), or 2 × 106 (high‐dose group) CD34+ cells/kg body weight were intrasplenically transplanted after CCl4 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 CCl4 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 CCl4 treatment compared with saline‐infused livers. We conclude that human peripheral blood CD34+ cell transplantation halts established liver fibrosis and promotes hepatic regeneration in CCl4‐induced chronic liver injury. J. Cell. Physiol. 227: 1538–1552, 2012. © 2011 Wiley Periodicals, Inc.