Isolation, culture and identification of adult hepatic stem cells in vitro

Guoyue Lü; Ping ZHANG; Hong LI; Shuang LI; Guangyi WANG

ABSTRACT

BACKGROUND:

Multipotency of hepatic stem cells is of important value in liver transplantation. Stem cells have been successfully identified and isolated from the animal livers. However, reports on whether stem cells exist in human hepatic tissue and how to isolate and identify them ars few.

OBJECTIVE:

This study was in attempt to isolate hepatic stem cells from human para-cancerous tissues of hepatoma and in vitro culture them, also to identify the stem cell surface marker, in order to find a new source of heptatic stem cells.

DESIGN:

Cell observation experiment.

SETTING:

Department of Common Surgery, First Hospital, Jilin University; Department of Common Surgery,Dongfeng Hospital of Traditional Chinese Medicine.

PARTICIPANTS:

Samples were harvested from 10 patients with hepatoma admitted to Department of hepatobiliary surgery, First Clinical College, Jilin University between October 2005 and June 2006, with age of 45 to 58 years.Hepatic tissue 2 cm away from cancer nest was cut when patients underwent hepatectomy, and it was pathologically confirmed as carcinoma-free tissue. Written informed consents were obtained from each patient. DMEM/F12 dry powder used for cell culture was provided by Hyclone Company, USA. Fresh fetal bovine serum was prepared by Lianxing Biotech Co.,Ltd, Tianjin. Various cell growth factors were the products of Cytolay Company, USA.

METHODS:

Para-cancerous tissues of hepatoma was cut into pieces, rinsed with Hank's solution and digested with type Ⅳ collagenase. Then the isolated cells were re-suspended in the DMEM/F12 medium supplemented with 0.1 volume fraction of fetal bovine serum, and hepatocyte growth factors, epidermal growth factors and α- fibroblast growth factors of 25 μg/L each were added in the above medium. When the cultured cells covered 2/3 of bottom,they were digested with trypsinase for passage and inoculated at 2×107 L-1. When cells propagated to the 3rd and 4th generations, 2.60×109 L-1 cell suspension prepared with trypsinase was added, and subsequently, anti-human C-kit antibody, immunomagnetic beads and Buffer solution were added in order. C-kit+ cells were preliminarily isolated by immunomagnetic bead separation. Haematoxylin-eosin staining and immunofluorescent histochemical double-staining were used for detecting the hepatic stem cells in para-cancerous tissues.MAIN OUTCOME

MEASURES:

① Observation of cell morphology. ② Identification of hepatic stem cells from para-cancerous tissues. ③ Identification of C-kit+ cells by immunofluorescent histochemical double-staining.

RESULTS:

① After primarily cultured for 2 weeks, the adherent cells grew in colony. After one half of culture medium was renewed, mature hepatocytes were gradually broken and disappeared. Small round cells propagated, and most of them were located in the center and arranged in cluster. Most cells were found with one big nucleus in each, less cytoplasm and clear cell boundary. When cells propagated to the 1st and 2nd generations, they still grew in colony, but fast. Each C-kit+ cell isolated by immunomagnetic bead separation presented a spherical cell body with a very big nucleus and less cytoplasm. After in vitro cultured for 1 week, it presented broken pieces and apoptotic symptoms.② After para-cancerous tissue was stained by haematoxylin-eosin, atypically proliferated biliary tracts with small round cells could be seen in the portal area. After para-cancerous tissue was stained by immunofluorescent histochemical double-staining, small round cells in the biliary tracts proliferated in the portal arsa co-expressed red fluorescence AFP and green fluorescence cytokeratin (CK) 19 with yellow superposition arsa. ③ After C-kit+ cells were stained by fluorescence immunocytochemisty, cytoplasm expressed alpha-fetoprotein (AFP) red granules and CK19 green granules. The superposition area of both presented yellow fluorescence of AFP+/CK19+-positive cells.

CONCLUSION:

Hepatic stem cells exist in human para-cancerous tissues of hepatoma. Therefore, expressions of C-kit+/AFP+/CK19+, the surface markers of hepatic stem cells, can be used for identifying and isolating hepatic stem cells. Small round cells obtained by in vitro isolation and culture, i.e. hepatic oval cells possess bipotential differentiation of hepatocyte and hepatobiliary epithelial cells.