MKP-1 knock out (KO) mice and wild type (WT) mice were provided by Bristol-Myers Squibb Pharmaceutical Research Institute and bred at Medical University of South Carolina. These mice are maintained on a mixed C57/129 background. Eight-week-old male Sprague-Dawley rats were purchased from Charles River Laboratory (Wilmington, MA, USA) with food and tap water ad libitum. All animal-related work was performed in accordance with NIH guidelines. The Institutional Animal Care and Use Committee (IACUC) at the Medical University of South Carolina approved all experimental protocols. For adenoviral gene expression experiment, 8-week-old male Sprague-Dawley rats were injected with 4 μl of either 1×109 plague-forming unit (pfu) dose (21 rats/group) or 5×108 pfu dose (21 rats/group) of Ad.LacZ at palatal gingival tissues. The rats were sacrificed at 3, 21, or 28 days following adenovirus delivery. For bone resorption experiment, 8-week-old male Sprague-Dawley rats were injected with 4 μl of either 1×109 pfu of Ad.MKP-1 (n=17) or control Ad.LacZ (n=17), or HEPES buffered saline (n=17) at interproximal palatal regions between the maxilla first and second molars. Forty-eight hours after delivery of adenovirus, the rats were injected with 2 μl of PBS (n=7) or 2 μl/20 μg of LPS (n=10) three times a week for four weeks. The rats were sacrificed at the end of 4 weeks following LPS injection.