UC San Diego

The objective of this thesis was to test various mouse models to determine a genetic or pharmacological method of accelerating the wound healing process. Specifically, we were trying to determine a mouse model that could result in wound regeneration without scarring. To achieve this, we developed different methods to knockdown heparan sulfate (HS) expression because of its role in the three steps of the wound repair process, inflammation, proliferation, and remodeling. First, we investigated the phenotypic effect on healing with Ext1+/-Ext2+/- gene mutation in C57BL/6 mice. Ext1+/-Ext2+/- mutation has proven to enhance wound healing significantly, observing a difference after two days post wound, whereas the wildtype lagged significantly. In vivo HS expression in the skin of wildtype and Ext1+/-Ext2+/- mice, resulted in a knockdown of more than 50%. For the first time, chondroitin sulfate expression in mouse skin was determined, ranging between 50-60 µg/gram of tissue. Second, K14-CreERExt1f/f mice showed significant wound repair compared to the control, resulting in 53.4% to 22.7% wound healing, respectively. Not only did the K14-Cre+Ext1f/f mice have an accelerated repair rate, but there were also the beginning stages of regeneration. Thirdly, although NMX enhanced wound healing significantly in dorsal wounds, it was not well translated to the wound repair in the ear. The addition of the two aromatic rings bound to the xyloside in NMX allowed for more efficient priming of HS because it created an optimal planar configuration. Lastly, while the Prrx-CreER Rosa26-LSL Luc mouse model did not indicate enhanced wound healing, it did provide a better understanding on how cartilage repair occurs. Through IVIS imaging we could track the increase of Prrx expression after wounding. Indicating that after initial wounding Prrx-CreER was recruited to the wound site to assist in the repair process. The elevated expression stayed consistent over four weeks demonstrating that the wound healing occurs for an extended period of time. Overall, the investigation into the discovery of a mammalian model for wound regeneration caused by the manipulation of HS expression, genetically and pharmacologically, did result in some models that had enhanced and accelerated the wound repair and regeneration.