Hi!
I'm afraid not. You can
check the FAQ regarding multithreading.
We do not support background mesh or texture creation in Ogre 2.1.
Ogre 2.2 does support background texture streaming though, and is soon getting out of WIP state.
If you're creating the meshes yourself programmatically (e.g. procedurally generated content or similar), you can create the Mesh pointer in the main thread, map the buffers, and then fill them in a background thread, then unmap the buffers in the main thread when done, and create the Items.
Basically a ping pong of messages between the main thread and worker thread so that the main thread performs the API calls, and the worker thread does the heavy generation work and fill the GPU buffers.
That is how Ogre 2.2 deals with background texture streaming.
We've had an advanced user who somehow managed to use the NULLRenderSystem to fool the resource system and load the meshes in the background, then copy the buffers in RAM over to the actual RenderSystem. But this is a very advanced use case and we don't do it out of the box.