Does anyone know how to sharpen Rotary Blades?

I was wondering if anything has been developed to sharpen these blades? I've got several dull blades here and they are not cheap, and throughout the years I've often wondered if there was a way to sharpen them. I'm in the middle of cutting a couple of 100's of squares now and the blade on there it is starting to get dull.

Anyone know if such a sharpener exists?

Thank you..
A.