Non-invasive intravital fluorescent microscopy of the hamster gingiva

Several attempts have been made to visualize the gingival microcirculation of small animals. Most of these attempts have required surgical procedures without control of the local tissue environment. In our current study of the hamster gingiva, a tissue bath was designed to allow microcirculatory observations of the periodontium of the superior incisors without the need for invasive surgical procedures and with controlled pH and temperature of the bathing solution. Dextrans (m.w. = 70,000 and m.w. = 150,000), bovine serum albumin (mw = 66,210) or a globulin fraction (mw = greater than 450,000 less than 825,000) were conjugated to fluorescein isothiocyanate and injected into the animal. Fluorescent images, produced by epi-illumination, were analyzed for the light intensity of the interstitium. There was a large and rapid increase in light intensity (leakage of the macromolecules) near the venules while capillaries of the gingival margin developed interstitial fluorescence at a slower rate and with a lower maximal effect. Molecular weight, shape or charge of the macromolecular or age of the animal did not affect the results. This new preparation could be used to study the contribution of the microcirculation to gingivitis, the role of gingivitis in the development of periodontal disease, or the effects of drugs and hormones on the microcirculation of the gingiva.