Objective: Our objective was to investigate the expression and significance of Wnt proteins in adult human hematopoietic-supporting stromal cells.
Methods: Degenerate reverse transcription-polymerase chain reaction was performed to screen telomerized human stromal cells (hTERT-stromal cells) and multipotent mesenchymal cells (hTERT-MSCs) for expression of Wnt genes. We studied the actions of Wnt proteins by overexpressing them in stromal cells and MSCs by retrovirus-mediated gene transfer.
Results: The hTERT-stromal and primary stromal cells expressed Wnt5A, while hTERT-MSCs and primary MSCs expressed Wnt3 and Wnt5A. Gene transfer of Wnt5A slightly reduced the growth rate of hTERT-stromal cells, but did not affect their morphology. In contrast, gene transfer of Wnt3 into both hTERT-stromal cells and hTERT-MSCs enhanced Wnt-betacatenin signaling, and caused remarkable morphological changes and growth retardation. Upon 2-week co-culture, expansion of clonogenic cells on Wnt5A-stromal cells was superior to that on control stromal cells. However, expansion of CD34+ cells on Wnt3-stromal cells did not differ from that on control stromal cells. Moreover, there was a drastic reduction in the formation of cobblestone area (CA) underneath Wnt3-stromal cells compared with that underneath control stromal cells.
Conclusion: These results suggest that Wnt3 plays an important role in regulating characteristics and CA support activity of stromal cells.