Doxorubicin induced dilated cardiomyopathy in a rabbit model: an update.

Dilated cardiomyopathy (DCM) is characterized by chamber dilation and cardiac dysfunction. Because of the poor prognosis, models are needed for the investigation of and development of new therapeutic approaches, as well as stem cell therapy. Doxorubicin (DOX), used as chemotherapeutic agent, is reported to be cumulative cardiotoxic causing DCM. The aim of the study was to investigate the onset of systolic dysfunction using echocardiography in rabbits receiving two different doses of DOX (1mg/kg twice a week and 2 mg/kg once a week). Twenty rabbits were treated with doxorubicin in two different doses for 6 weeks and compared with a control group treated with NaCl 0.9%. The effect of doxorubicin on the myocardium was investigated with histological analysis and scanning electron microscopy of left ventricle (LV), as well as in the interventricular septum (IVS) and right ventricle (RV). The results showed a high mortality rate for rabbits receiving 2 mg/kg once a week. A significant reduction in systolic function was present in animals treated with DOX after 6 weeks, with decreased ejection fraction and shortening fraction. Histology and electron microscopy revealed vacuolization, intracytoplasmic granulation, necrosis and interstitial fibrosis in LV, as well as in the IVS and RV. Doxorubicin induced changes are present in the LV, RV and IVS, and the administration at the dose of 1 mg/kg twice a week for only 6 weeks is safe and sufficient to induce DCM in rabbits.

Expression of matrix metalloproteinases, type IV collagen, and interleukin-10 in rabbits treated with morphine after lamellar keratectomy.

PURPOSE: To study the effects of topical administration of 1% morphine on corneal analgesia in rabbits submitted to lamellar keratectomy and to assess the expression of matrix metalloproteinase-1, metalloproteinase-2, metalloproteinase-9 (MMPs), type IV collagen, and interleukin-10 (IL-10) during the treatment. METHODS: Morphine group (MG) received 50 µL of topical 1% morphine four times daily, while the control group received saline instead. Corneal touch threshold (CTT) and the wound area were assessed until corneal healing. Corneal samples were processed for routine histology, immunohistochemistry, zymography, and ELISA. RESULTS: Following keratectomy, CTT increased significantly from 6 to 96 h time points. Mean corneal re-epithelization rate and scores of leukocyte infiltration did not differ significantly between treatment groups. Immunolabeling pattern for MMP-1, MMP-9, and type IV collagen was similar in both treatment groups. In the MG, zymography indicated significantly higher levels of active MMP-2 on days 6 and 12; and in the latent MMP-9, on days 3 and 6, and in the active MMP-9, on day 6. Latent MMP-2 and MMP-9, and active MMP-9 decreased to values close to those of healthy corneas on day 12, but levels of active MMP-2 remained significantly elevated in the MG. IL-10 levels measured on days 1-6 were reduced as compared to those of healthy corneal tissue and returned to levels close to those of healthy corneas on day 12. CONCLUSION: Topical morphine promoted corneal analgesia for up to 4 days and did not delay corneal re-epithelization. The re-establishment of MMPs and IL-10 to levels close to baseline values at the end of the study and the expression of type IV collagen in both groups reinforce that, with caution, 1% morphine can be used after lamellar keratectomy in rabbits.