Visualization of intravital immune cell dynamics after conjunctival surgery using multiphoton microscopy

Abstract

PURPOSE. To visualize intravital immune cell dynamics in the subconjunctival tissue during the wound-healing process using multiphoton microscopy. METHODS. Gene-targeted mice expressing enhanced green fluorescent protein under the control of the endogenous lysozyme M promoter (LysM-eGFP mice) were anesthetized with isoflurane, and injured by a 10-0 nylon conjunctival suture. Vessels were visualized by intravenous injection of 70 kDa rhodamine-conjugated dextran. Using a multiphoton microscope, the three-dimensional images of the subconjunctival tissue were acquired every minute for 20 minutes before and 0.5, 3, 6, and 72 hours after injury. Raw imaging data were processed for four-dimensional images and analyzed for the number and the velocity of the LysM-eGFP-positive cells using Imaris software. RESULTS. The intravital LysM-eGFP-positive cells and the red-labeled vessels were successfully visualized using a multiphoton microscope. The conjunctival and scleral collagen fibers were detected as secondary harmonic generation signals, which were colored blue. Compared with mice without injury, the number of LysM-eGFP-positive cells in the subconjunctival tissue after conjunctival surgery increased in a time-dependent manner. The cell velocities significantly increased until 3 hours after surgery (5.9 ± 3.2 lm/min; P < 0.0001) and the elevated level was sustained until 72 hours after injury (5.9 ± 3.3 µm/min). CONCLUSION. This is the first report to visualize and evaluate intravital cellular dynamics during inflammation in the subconjunctival tissue using multiphoton microscopy. This technique may be a useful tool to characterize the molecular mechanisms of the wound-healing process after various ocular injuries, such as glaucoma surgery.