Intra-articular IL-1β over-expression in the adult Col1-IL1β
XAT transgenic mouse results in joint pathology with behavioral changes. (A) Intra-articular injection of FIV(gfp) in Col1-IL1βXAT transgenic (Tg) mice (10 μL containing a total of 106 infectious particles) had no effect on IL-1β expression in the joints. In contrast, (B) intra-articular injection of FIV(Cre) in age matched transgenic mice (10 μL containing a total of 106 infectious particles) induced the expression of human IL-1β as detected by immunohistochemistry employing an antibody raised against the mature form of human IL-1β. Moreover, (C) cells infected by FIV(Cre) vector were detected by immunofluorescence (red) utilizing a Texas-Red conjugated antibody raised against the V5 epitope that tagged Cre recombinase in the FIV(Cre) vector (red fluorescence). The reporter gene β-galactosidase (the second ORF in the bicistronic Col1-IL1βXAT transgene) was detected by a polyclonal antibody coupled to Alexa Fluor® 488 (green fluorescence). Therefore, cells infected by FIV(Cre) appear red and cells expressing β-galactosidase appear yellow due to the overlap of green+red. (D) Col1-IL1βXAT transgenic (Tg) mice injected with the control vector FIV(gfp) (10 μL containing a total of 106 infectious particles) did not develop any articular pathology. (E) Conversely, Tg mice injected with FIV(Cre) intra-articularly developed joint pathology, (F) characterized by chondrocyte cloning, erosions and fibrillations. (G) Joint pathology was assessed on histology sections by a 0 - 5 scale. It was found that the mice that received FIV(Cre) intraarticularly (Cre) were characterized by a significant degree of joint pathology. (H) Articular cloning was employed as an additional measure of arthritis, whereby mice with intra-articular FIV(Cre) injection (Cre) were characterized by a significantly higher number of cloned chondrocytes in the articular cartilage. Furthermore, mice with arthritis displayed significantly decreased rotarod activity (I), employed here as a measure of joint dysfunction, as well as (J) significantly increased body grooming, as a measure of discomfort. *p < 0.05; **p < 0.01; ***p < 0.0001; Bar = 100 μM.