Secondary lymphedema is an intractable disease mainly caused by damage of the lymphatic system during surgery, yet studies are limited by the lack of suitable animal models. The purpose of this study was to create an improved model of secondary lymphedema in the hindlimbs of rodents with sustained effects and able to mimic human lymphedema. This was achieved by combining previously reported surgical methods and radiation to induce chronic lymphedema. Despite more radical surgical destruction of superficial and deep lymphatic vessels, surgery alone was not enough to sustain increased hindlimb volume. Radiotherapy was necessary to prolong these effects, with decreased lymphatic flow on lymphoscintigraphy, but hindlimb necrosis occurred after 4 weeks due to radiation toxicity. The applicability of this model for studies of therapeutic lymphangiogenesis was subsequently tested by injecting muscle-derived stem cells previously cocultured with the supernatant of human lymphatic endothelial cells in vitro. There was a tendency for increased lymphatic flow which significantly increased lymphatic vessel formation after cell injection, but attenuation of hindlimb volume was not observed. These results suggest that further refinement of the rodent hindlimb model is needed by titration of adequate radiation dosage, while stem cell lymphangiogenesis seems to be a promising approach.

Coronavirus disease 2019 (COVID-19) has had a major impact on global communities and healthcare. Paxlovid (nirmatrelvir/ritonavir) is an oral drug for the treatment of COVID-19 that has been approved by the U.S. Food and Drug Administration. In Korea, Paxlovid is the first-line drug for patients who are >60 years old or using immunosuppressants, or those who are >40 years old with chronic diseases such as obesity, diabetes, chronic kidney disease, or hypertension. One caveat of Paxlovid treatment is the potential risk of drug interaction as it is a strong cytochrome P450 (CYP) 3A and P-glycoprotein inhibitor. Tacrolimus is the key immunosuppressant used in kidney transplant (KT) recipients; however, it is metabolized by CYP 3A enzyme, which is strongly affected by Paxlovid. Here, we introduce a case of successful management of severe acute kidney injury (AKI) in a KT patient resulting from tacrolimus overdosage after Paxlovid; AKI was successfully reversed by phenytoin administration to induce CYP3A enzyme.