PEGylated liposomes associate with Wnt3A protein and expand putative stem cells in human bone marrow populations

Aim: To fabricate PEGylated liposomes which preserve the activity of hydrophobic Wnt3A protein, and to demonstrate their efficacy in promoting expansion of osteoprogenitors from human bone marrow. Methods: PEGylated liposomes composed of several synthetic lipids were tested for their ability to preserve Wnt3A activity in reporter and differentiation assays. Single-molecule microspectroscopy was used to test for direct association of protein with liposomes. Results: Labeled Wnt3A protein directly associated with all tested liposome preparations. However, Wnt3A activity was preserved or enhanced in PEGylated 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes but not in PEGylated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes. PEGylated Wnt3A liposomes associated with skeletal stem cell populations in human bone marrow and promoted osteogenesis. Conclusion: Active Wnt protein-containing PEGylated liposomes may have utility for systemic administration for bone repair.The authors acknowledge funding support from the Medical Research Council, UK (grant number MR/J004103/1), Wessex Medical Research (grant number SO2), UoS Research Management Committee and the Institute for Life Sciences, Southampton. The authors would like to thank the Royal Society for the University Research Fellowship of Steven F Lee (UF120277)