ATF3 and rheumatoid arthritis: Activating transcription factor 3 is not detectable in intact primary sensory neurons,63,66 but is consistently upregulated in the nucleus of injured peripheral neurons.38,66 In addition to models of peripheral nerve injury, ATF3 has been detected in an in vitro model of diabetic neuropathy,56 in a mice rheumatoid arthritis model,8 and in a MIA model of OA in the rat knee joint.30,64 However, these OA studies only detected ATF3 at early time points, and it is unclear whether this should be interpreted as toxicity from the MIA compound, or axon degeneration caused by the underlying disease.