UNCOVERING THE ROLE OF MATRIX METALLOPEPTIDASE 9 IN UTERINE SMOOTH MUSCLE ACTIVATION AND LABOR - PROJECT SUMMARY PRETERM BIRTH IS THE LEADING CAUSE OF NEONATAL DEATH AND DISABILITY IN THE DEVELOPED WORLD. DESPITE ITS SIGNIFICANT GLOBAL HEALTH IMPACT, THE UNDERLYING MOLECULAR MECHANISMS INITIATING UTERINE CONTRACTILITY AND LABOR ARE STILL NOT WELL UNDERSTOOD. THE LONG-TERM GOAL OF THIS RESEARCH IS TO UNDERSTAND HOW THE INFLAMMATION-ASSOCIATED PROTEASE MATRIX METALLOPEPTIDASE 9 (MMP9) ENHANCES UTERINE CONTRACTION AND TO DETERMINE IF MMP9 OR ITS TARGETS CAN BE LEVERAGED TO DEVELOP SAFE AND EFFECTIVE THERAPIES TO PREVENT OR HALT PRETERM LABOR. THE OVERALL OBJECTIVE OF THIS PROPOSAL IS TO DETERMINE HOW MMP9 AFFECTS INTRACELLULAR CALCIUM TRANSIENTS IN UTERINE SMOOTH MUSCLE CELLS AND TO DEVELOP PROTOCOLS TO DETECT UTERINE CALCIUM TRANSIENTS IN VIVO. THE CENTRAL HYPOTHESIS IS THAT MMP9 DIRECTLY REGULATES L-TYPE VOLTAGE-GATED CALCIUM CHANNELS CELLS TO ENHANCE CALCIUM SIGNALING AND CONTRACTION, AND THAT MMP9 INHIBITION ATTENUATES THESE RESPONSES. AIM 1 WILL TEST THE HYPOTHESIS THAT MMP9 ACTS THROUGH THE VOLTAGE-GATED L-TYPE CALCIUM CHANNEL (LTCC) TO ENHANCE CALCIUM INFLUX. AIM 2 WILL DETERMINE IF MMP9 PHYSICALLY INTERACTS WITH THE ALPHA-SUBUNIT OF VOLTAGE-GATED L-TYPE CALCIUM CHANNELS AND IDENTIFY NOVEL ENZYMATIC TARGETS AND INTERACTING PROTEINS. AIM 3 WILL UTILIZE IN VIVO INTRAUTERINE PRESSURE CATHETER TECHNIQUE COMBINED WITH A NOVEL GCAMP6 ANIMAL MODEL TO DETERMINE IF MMP9 PROMOTES CALCIUM TRANSIENTS AND CONTRACTILITY IN VIVO IN TERM AND PRETERM MOUSE MODELS OF LABOR. COMPLETION OF THESE AIMS WILL HAVE A POSITIVE IMPACT BY PROVIDING VITAL INSIGHT ON THE MOLECULAR MECHANISMS THAT PROMPT UTERINE CONTRACTION AND THE POTENTIAL WAYS IN WHICH MMP9 AND INTERACTING MOLECULES CAN BE TARGETED TO MODULATE CONTRACTILITY. FURTHER, THIS WORK WILL ENABLE THE SIMULTANEOUS DETECTION OF CALCIUM TRANSIENTS AND INTRAUTERINE PRESSURE IN MICE IN VIVO. THESE OUTCOMES WILL PROVIDE A FOUNDATION FOR DEVELOPING AND TESTING NEW TREATMENTS TO ADDRESS THE HIGH-PRIORITY GOAL OF REDUCING ADVERSE PREGNANCY CONDITIONS.