Cytokine loaded layer-by-layer ultrathin matrices to deliver single dermal papilla cells for spot-by-spot hair follicle regeneration.

The dermal papilla cell (DPC) is a type of highly specialized mesenchymal cells located in hair follicles (HF). Due to the primary role in the epithelial-mesenchymal interaction that enables hair-follicle morphogenesis and hair cycling, DPC has become an attractive cell source for hair regeneration to treat alopecia patients. However, DPCs tend to lose their function during in vitro culture. Hence, there exists a clear need to develop a microenvironment that can recapitulate the interactions within the native milieu of DPCs. Since layer-by-layer (LBL) nano-coating with biocompatible materials on the cell surface displays the versatility with tunable loading and release properties, which can provide a remodeled microenvironment for regulating cell function. Here, we developed a LBL self-assembly technique to single DPCs to create a nano-scale ultrathin extracellular matrix (ECM). We studied that the single cell-based LBL-encapsulation would not impact the viability, morphology, proliferation and intrinsic properties of DPCs using Western blot and mRNA expressions of β-catenin, ALP and α-SMA. We then included fibroblast growth factor-2 (FGF-2) into the LBL nano-structure to regulate the DPC function. Finally, we performed in vivo hair reconstitution assays using LBL-encapsulated DPCs combined with freshly isolated epidermal cells (EPCs) and found this strategy can treat hair loss.