Increased Haematopoietic Supportive Function of USSC from Umbilical Cord Blood Compared to CB MSC and Possible Role of DLK-1
Figure 2
DLK-1 in USSC: inhibitor of adipogenesis? (a) Representative immunofluorescence staining of CB MSC (), USSC () and HepG2. USSC revealed a clear DLK-1 expression, detected by immunofluorescence, while CB MSC were completely negative. The hepatocarcinoma cell line HepG2 served as biological positive control. (b) DLK-1 flowcytometry analysis was applied to clearly distinguish between intracellular and extracellular expression of DLK-1 protein. No DLK-1 expression could be determined in USSC by extracellular staining. After permeabilization a small DLK-1 positive subpopulation was detected in the USSC lines by intracellular staining. DLK-1 overexpressing CB MSC were used a positive control for extracellular staining. (c) By ectodomain shedding, the soluble and adipogenic inhibitory DLK-1 protein is cleaved. To validate whether USSC express the functional DLK-1, an ELISA was performed. The supernatant of 3 days standard cultures of USSC () and CB MSC () was analyzed, maternal plasma was used as positive control. No specific DLK-1 release was detected in any of the analyzed USSC or CB MSC, questioning function of DLK-1 expression in USSC. However, a clear secretion of DLK-1 was detected in the CB MSC overexpressing DLK-1. (d) A heterogeneous expression of CEBPα (CB MSC , CB MSC-derived clones , USSC , USSC-derived clones ) could be detected in different USSC and CB MSC cell lines analyzed by real time PCR analysis. (e) Real time PCR analysis revealed a heterogenous expression of PPARγ2 expression (CB MSC , USSC ) in the USSC and CB MSC cell lines.
