i wouldn't use an indoor fixture outdoors, but is there any reason you couldn't use an outdoor fixture indoors?
No reason why you can't.. go for it..
We used outdoor flushmount lighting in our indoor closets. Electrician said it was fine.
The difference between indoor and outdoor lights is usually a matter of watertightness of the circuits... not a worry indoors, but of high concern outdoors. That just means that as said, outdoor fixtures can come inside, but inside fixtures shouldn't be used outside.