YAP and TAZ Regulate Skin Wound Healing

The Hippo signaling pathway regulates organ size, tissue regeneration, and stem cell self-renewal. The two key downstream transcription coactivators in this pathway, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), mediate the major gene regulation and biological functions of the Hippo pathway. The biological functions of YAP and TAZ in many tissues are known; however, their roles in skin wound healing remain unclear. To analyze whether YAP and/or TAZ are required for cutaneous wound healing, we performed small interfering RNA (siRNA)-mediated knockdown of YAP/TAZ in full-thickness skin wounds. YAP is strongly expressed in the nucleus and cytoplasm in the epidermis and hair follicle. Interestingly, YAP is expressed in the nucleus in the dermis at 2 and 7 days after wounding. TAZ normally localizes to the cytoplasm in the dermis but is distributed in both the nucleus and cytoplasm at 1 day after wounding. The knockdown of YAP and TAZ markedly delayed the rate of wound closure and reduced the transforming growth factor-β1 (TGF-β1) expression in the wound. YAP and TAZ also modulate the expression of TGF-β1 signaling pathway components such as Smad-2, p21, and Smad-7. These results suggest that YAP and TAZ localization to the nucleus is required for skin wound healing.