currently , liver transplantation is the only definitive treatment for the end  stage liver diseases . however , its widely used was limited by the expensive costs , shortage of donor organs and invasive procedure ( 1 ) . hepatocyte transplantation has emerged as a feasible alternative to liver transplantation in some liver diseases ( 2 ) , but it is limited by organ donors and the low cell quality of available liver tissues ( 3 , 4 ) . although human embryonic stem cells ( hescs ) and umbilical cord blood stem cells ( ucbsc ) could be induced into hepatocyte - like cells in vitro ( 5 ) , their widely used were limited by the low differentiation quality , ethics , and teratoma formation ( 6 ) . recently , the adult stem cells ( ascs ) derived from various tissues , including bone marrow derived mesenchymal stem cells ( bmscs ) , adipose tissue derived mesenchymal stem cells ( adscs ) , and peripheral blood mononuclear cells ( pbmcs ) have been developed as new cell sources contributing to liver regeneration for their high efficiency of hepatogenic differentiation using simple procedures and no ethnic issues ( 710 ) . in the present study , we investigated whether ascs are the ideal seed cells for the liver regeneration from the followings : ascs biology , including isolation , culture , differentiation to hepatocytes , and the further role of ascs in cell therapy and tissue engineering in recent studies , samples of human bone marrow were obtained by lumbar puncture ( lp ) , human adipose tissue were obtained from abdominal subcutaneous adipose tissue of gastric cancer patients or liposuction patients , human peripheral blood were obtained from patients with hbv or healthy adult blood donors , in accordance with the local ethics committee . most laboratory data showed that bmscs could be prepared through the density degree of centrifuge , flow cytometry sorting , and sidewall sieve method ( 1114 ) . side - wall sieve method has become popular one for its simple operation , lower cost , less injury to cell ( 15 ) . adipose tissue was minced with scissors and scalpels into less than 3 mm pieces and isolation of adscs proceeded as previously described ( 16 , 17 ) . generally , human peripheral blood monocytes isolated from donors were isolated by density gradient centrifugation and further purified by adherence separation . in order to obtain more pbscs in shortly time , g / kg / d , administered subcutaneously daily to mobilize pbmcs from bone marrow to peripheral blood ( 18 , 19 ) . then pbmcs were collected by means of aphaeresis . conget et al indicated that the bmscs express many surface agents including cd13 , cd44 , cd29 , cd105 , but did nt express cd1a , cd14 , cd31 , cd34 , cd56 , cd45 ( 20 ) . ascs derived from all three sources displayed no expression of hematopoietic markers ( cd14 , cd34 , cd45 ) , of the stem cell marker cd133 , or the marker for endothelial cells cd144 . more than 90% of mscs derived from the three sources expressed the typical msc marker proteins cd44 , cd73 , cd29 , and cd90 . however , the intensity of expression of cd90 of pbscs was significantly below that of the other tissues . more than 90% of the ascs derived from all three sources expressed hla i ; however , none of the mscs expressed hla ii . cd105 was expressed by a significantly lower percentage of pbscs compared with bm- or ad - scs , whereas , more pb- and bm - scs expressed cd106 than adscs . besides the fact , that they are more heterogeneous ( 23 ) , they reveal a surface antigen marker profile ( 22 , 2426 ) , and differentiation potential similar to bmscs ( 2732 ) . adscs are characterized as cd45 , cd34 + , cd105 + , cd31-(33 ) ( table 1 ) . some studies indicated that functional hepatocytes could be induced from ascs by some cytokines or through coculture with other cell types . however , the potential of the ascs transdifferentiation is generally low . therefore , researchers are keen to explore new methods to induce ascs differentiate into functional hepatocytes in vitro currently . the hepatocyte - like cells from ascs were confirmed from the gene and protein expression . gene expressions were identified by rt - pcr , using the common markers of hepatocytes , including alb , afp , ck18 , ck19 , and cyp3a4 ( 34 ) . protein expressions were usually identified by immunohistochemistry or mmunofluorescence , western blot , from the expression of albumin , ck18 , cyp3a4 , cyp1a1 , cyp2c9 and nadph - p450 ( 3538 ) . to compare the potential of hepatogenic differentiation of the different adult stem cells in vitro , researches indicated adscs have a similar differentiation potential towards the hepatic lineage , similar to bmscs . however , their longer culture period and proliferation capacity differ from the bmscs ( 3941 ) . in recent studies , samples of human bone marrow were obtained by lumbar puncture ( lp ) , human adipose tissue were obtained from abdominal subcutaneous adipose tissue of gastric cancer patients or liposuction patients , human peripheral blood were obtained from patients with hbv or healthy adult blood donors , in accordance with the local ethics committee . most laboratory data showed that bmscs could be prepared through the density degree of centrifuge , flow cytometry sorting , and sidewall sieve method ( 1114 ) . side - wall sieve method has become popular one for its simple operation , lower cost , less injury to cell ( 15 ) . adipose tissue was minced with scissors and scalpels into less than 3 mm pieces and isolation of adscs proceeded as previously described ( 16 , 17 ) . generally , human peripheral blood monocytes isolated from donors were isolated by density gradient centrifugation and further purified by adherence separation . in order to obtain more pbscs in shortly time , pbmcs were mobilized with recombinant g - csf at 510 g / kg / d , administered subcutaneously daily to mobilize pbmcs from bone marrow to peripheral blood ( 18 , 19 ) . conget et al indicated that the bmscs express many surface agents including cd13 , cd44 , cd29 , cd105 , but did nt express cd1a , cd14 , cd31 , cd34 , cd56 , cd45 ( 20 ) . ascs derived from all three sources displayed no expression of hematopoietic markers ( cd14 , cd34 , cd45 ) , of the stem cell marker cd133 , or the marker for endothelial cells cd144 . more than 90% of mscs derived from the three sources expressed the typical msc marker proteins cd44 , cd73 , cd29 , and cd90 . however , the intensity of expression of cd90 of pbscs was significantly below that of the other tissues . more than 90% of the ascs derived from all three sources expressed hla i ; however , none of the mscs expressed hla ii . cd105 was expressed by a significantly lower percentage of pbscs compared with bm- or ad - scs , whereas , more pb- and bm - scs expressed cd106 than adscs . besides the fact , that they are more heterogeneous ( 23 ) , they reveal a surface antigen marker profile ( 22 , 2426 ) , and differentiation potential similar to bmscs ( 2732 ) . adscs are characterized as cd45 , cd34 + , cd105 + , cd31-(33 ) ( table 1 ) . some studies indicated that functional hepatocytes could be induced from ascs by some cytokines or through coculture with other cell types . however , the potential of the ascs transdifferentiation is generally low . therefore , researchers are keen to explore new methods to induce ascs differentiate into functional hepatocytes in vitro currently . the hepatocyte - like cells from ascs were confirmed from the gene and protein expression . gene expressions were identified by rt - pcr , using the common markers of hepatocytes , including alb , afp , ck18 , ck19 , and cyp3a4 ( 34 ) . protein expressions were usually identified by immunohistochemistry or mmunofluorescence , western blot , from the expression of albumin , ck18 , cyp3a4 , cyp1a1 , cyp2c9 and nadph - p450 ( 3538 ) . to compare the potential of hepatogenic differentiation of the different adult stem cells in vitro , researches indicated adscs have a similar differentiation potential towards the hepatic lineage , similar to bmscs . however , their longer culture period and proliferation capacity differ from the bmscs ( 3941 ) . in the present study , we described different ascs could be induced into hepatocyte lineage cells in different culture systems in vitro . it is very safe and easy to acquire the enough ascs , and then induce them into functional hepatocytes in vitro . based on this progress , ascs transplantation might be a novel therapy for the severe liver diseases , and also will be ideal seed cells for liver tissue engineering . however , which ascs are better still needs us to investigate from their preparation , molecular characterization , and functional assay . this paper firstly provides such a concise review focused on ascs biology and differentiates potential , indicating ascs might be an ideal seed cells in cell transplant therapy and tissue engineering . we also believe in the future , some studies will show us the most appropriate ascs for cell transplant or tissue engineering .
adult stem cells ( ascs ) are undifferentiated cells found throughout the body that divide to replenish dying cells and regenerate damaged tissues , which are the powerful sources for cell therapy and tissue engineering . 
 bone marrow - derived mesenchymal stem cells ( bmscs ) , adipose tissue - derived mesenchymal stem cells ( adscs ) , and peripheral blood monocytes ( pbmcs ) are the common ascs , and many studies indicated that ascs isolated from various adult tissues could be induced to hepatocyte - like cells in vitro . however , the isolation , culture protocols , characterization of ascs and hepatocyte - like cells are different . 
 this review aims to describe the isolation and culture procedures for ascs , to summarize the molecular characterization of ascs , to characterize function of hepatocyte - like cells , and to discuss the future role of ascs in cell therapy and tissue engineering .