A chronic pressure ulcer model in the nude mouse

Abstract

The pathophysiology of pressure ulcers is not yet fully understood. Widely used experimental models lead to pressure ulcers in the skin and the subcutaneous tissue only. The aim of the present study was to develop a clinically relevant deep pressure ulcer model in nude mice involving all relevant tissue layers. Balb/c nude mice were anesthetized and a steel disk was implanted under the great gluteus muscle. Full recovery was allowed for 10 days. Pressure was then periodically applied (2 hours compression, 1 hour recovery) using a Neodymium magnet in conjunction with the disk in the unanesthetized mouse. Cycles were repeated for 1, 4, 6, 8, or 10 times. Controls underwent the same procedure without placement of the magnet. The pressure ulcer grade was found to be cycle dependent,with the highest degree after 10 cycles. Histological evaluations revealed signs of necrosis in the skin and subcutaneous fat after four, and in the muscle after eight and 10 cycles of compression. Polymorphnuclear granulocyte infiltration in certain layers was found to be dependent on the number of cycles. We conclude that this clinically relevant nude mouse model can be used to investigate the mechanism of pressure ulcer development and to study new therapeutic approaches.

<b>Development and repair of experimental pressure ulcers in the rat abdominal wall induced by repeated compression using magnets</b>

“…To produce pressure ulcers, the use of magnets has been reported in the literature (Peirce et al, 2000;Reid et al, 2004;Şener et al, 2006;Saito et al, 2008;Wassermann et al, 2009). However, the pressure in previous studies was either not measured or was not as accurate as in our experiment.…”

“…In previous studies, a magnet or steel plate was implanted in the subcutaneous connective tissue (Peirce et al, 2000) or under the gluteus maximus muscle (Wassermann et al, 2009). In these cases, the healing process after skin breakdown is probably compromised by the implanted magnet or steel plate.…”

“…P e i r c e e t a l . (2000), Reid et al (2004) and Wassermann et al (2009) used magnets for models of pressure ulcers. They implanted a magnet or a steel plate into the subcutaneous connective tissue of the back or under a m u s c l e ( W a s s e r m a n n e t a l .…”

Murine Models of Human Wound Healing

“…The pathogenesis of pressure ulcers is thought to be mediated by cycles of ischemia followed by reperfusion injury. Wasserman et al implemented a model using a metal disk implanted below the mouse gluteal muscle [5]. A magnet is placed on the skin to cause ischemia in the tissue between the magnet and metal disk and is cycled on and off.…”

Investigation of cell death caused by the Nanopatch™ and its role in vaccine delivery as a physical immune enhancer

“…Using various animal models [628,[630][631][632][633], 44 g/ cm 2 were sufficient to induce mild ischemia tissue while muscle cell death were being induced by as little as 60-80 g/ cm 2 (6-8 kPa) and complete anoxia and tissue necrosis were induced by 200 g/ cm 2 [634]. These loads were much lower than loads required to induce cell death in static NP applications, where 85 g (530 g/ cm 2 ) and 500 g (3125 g/ cm 2 ) induced cell death in the skin.…”