Oxazolone as a Model to Induce Edema in the Lower Limb of Rats




Castillo, Rudy
Pastrana, Christopher
Hodge, Lisa M.


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Purpose: Peripheral edema is a condition characterized by the accumulation of excess interstitial fluid in distal tissues and commonly manifests in the arms or legs. Untreated complex peripheral edema can progress into chronic lymphedema as impaired fluid drainage and chronic inflammation cause irreversible damage to the surrounding tissue and local lymphatics. The overall goal of our research is to study the effectiveness of osteopathic manipulative medicine treatments on edema, infection and inflammation. The aim of this research was to evaluate to the oxazolone (OXA)-induced acute skin inflammation model to induce lower limb edema in the rat. Specifically, we hypothesized that the application of OXA would induce create a local inflammatory response, induce edema in the lower limbs decrease lymphatic vessel function. Methods: Female Sprague Dawley rats, weighing 200-250 g, were used for this study. To induce edema, on day zero the right lower limb was shaved and 750 µl of 5% OXA-acetone solution or 5% PBS-acetone solution vehicle (VEH) was applied to the exposed skin. Lower limb measurements were made at days zero and six using a Vernier caliper. Measurements were taken at the midpoints of the hind paw, ankle, tibia and femur of their right lower limbs to establish paw thickness; distance between paw-to-ankle and ankle-to-tibia were taken to calculate lower limb volume by truncated cone formula. At day six, the rats were euthanized, and the bilateral hind paws were removed above the calcaneus and weighed. The spleen and bilateral inguinal lymph nodes were removed, homogenized, centrifuged and cells were washed. Cell pellets were stained with PE mouse anti-rat granulocytes, FITC anti-rat CD3, and APC anti-rat CD161 antibodies. The percentage of granulocytes, T cells and dendritic cells were measured by flow cytometry. Data were analyzed by ANOVA followed a Tukey post-test. Comparisons were made between OXA and VEH groups at day six post-induction. Results: OXA did not induce significant (p [greater than] 0.05) changes in either hind paw thickness or lower limb volume. OXA significantly (P Conclusions: OXA induced an acute inflammatory response in the draining inguinal lymph nodes. However, as used in this approach, OXA did not induce peripheral edema. In future studies we investigate alternate strategies to induce lower limb edema in the rat.