ABSTRACT
Wnt signaling is required for the development of the hair follicle, and for inciting the growth (anagen) phase of the hair cycle. Most strategies to enhance Wnt signaling for hair growth create a state of constitutive Wnt activation, which leads to neoplastic transformation of the epithelial hair matrix. Using Axin2(LacZ/+) and Axin2(Cre/+)R26R(mTmG/+) reporter mice and RNA analyses, we show that Wnt signaling is elevated during anagen, is reduced at the onset of catagen, and can be reamplified in the skin and surrounding hair follicles via intradermal injection of recombinant R-spondin2 protein. Using Lgr5(LacZ/+) reporter mice, we demonstrate that this amplified Wnt environment leads to activation of leucine-rich repeat-containing G-protein coupled receptor 5-positive stem cells in the hair follicle. The onset of catagen is repressed by R-spondin2 injection, and the anagen phase persists. As a consequence, hair shafts grow longer. We conclude that R-spondin2 treatment activates hair follicle stem cells and therefore may have therapeutic potential to promote hair growth.
Subject(s)
Axin Protein/genetics , Hair Follicle/cytology , Hair/growth & development , Stem Cells/cytology , Thrombospondins/genetics , Wnt Signaling Pathway , Aged , Animals , Cell Membrane/metabolism , Cell Proliferation , Cell Survival , Genes, Reporter , Hair Follicle/transplantation , Humans , Intercellular Signaling Peptides and Proteins/genetics , Leucine/chemistry , Male , Mice , Mice, SCID , Middle Aged , Receptors, G-Protein-Coupled/genetics , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Skin/metabolismABSTRACT
The therapeutic potential of Wnt proteins has long been recognized but challenges associated with in vivo stability and delivery have hindered their development as drug candidates. By exploiting the hydrophobic nature of the protein we provide evidence that exogenous Wnt3a can be delivered in vivo if it is associated with a lipid vesicle. Recombinant Wnt3a associates with the external surface of the lipid membrane; this association stabilizes the protein and leads to prolonged activation of the Wnt pathway in primary cells. We demonstrate the consequences of Wnt pathway activation in vivo using a bone marrow engraftment assay. These data provide validation for the development of WNT3A as a therapeutic protein.
Subject(s)
Stem Cells/drug effects , Stem Cells/metabolism , Wnt3A Protein/metabolism , Wnt3A Protein/pharmacology , Animals , Bone Marrow Cells/drug effects , Bone Marrow Cells/metabolism , Carrier Proteins/metabolism , Cell Survival/drug effects , Cholic Acids/pharmacology , Dose-Response Relationship, Drug , Humans , Hydrophobic and Hydrophilic Interactions , Lipids/pharmacology , Liposomes/chemistry , Liposomes/metabolism , Mice , Protein Binding , Protein Conformation/drug effects , Protein Stability , Recombinant Proteins/chemistry , Recombinant Proteins/pharmacology , Thermodynamics , Wnt Signaling Pathway/drug effects , Wnt3A Protein/chemistryABSTRACT
Wnt signaling is required for both the development and homeostasis of the skin, yet its contribution to skin wound repair remains controversial. By employing Axin2(LacZ/+) reporter mice we evaluated the spatial and temporal distribution patterns of Wnt responsive cells, and found that the pattern of Wnt responsiveness varies with the hair cycle, and correlates with wound healing potential. Using Axin2(LacZ/LacZ) mice and an ear wound model, we demonstrate that amplified Wnt signaling leads to improved healing. Utilizing a biochemical approach that mimics the amplified Wnt response of Axin2(LacZ/LacZ) mice, we show that topical application of liposomal Wnt3a to a non-healing wound enhances endogenous Wnt signaling, and results in better skin wound healing. Given the importance of Wnt signaling in the maintenance and repair of skin, liposomal Wnt3a may have widespread application in clinical practice.
