Peri-articular bone damage was assessed using micro-computed tomography (µ-CT). The three-dimensional images allow an overall evaluation of bone loss in the ankles, while the parasagittal slices would provide more refined details. When compared to the healthy ankle (Fig. 5a), substantial bone damage was observed in the joints injected with BVCAR alone (Fig. 5b), and extensive bone loss was also visible in the joints treated with HAdV5-PUMA alone (Fig. 5c). In contrast, only minor morphological changes were observed in joints administered with BVCARHAdV5-PUMA (Fig. 5d,e), as compared to ankle joints from healthy rats (Fig. 5c). The only bone loss marker detectable in BVCARHAdV5-PUMA-treated joints was a modification in porosity, characteristic of the early phase of arthritis before the administration of any treatment. Further microarchitecture alterations consecutive to extended inflammation, was not observed in the BVCARHAdV5-PUMA-treated joints.Fig. 5Analysis of rat ankle tissues. Ankle tissue imaging by micro-computed tomography (µ-CT) was performed on rat ankle joints from a a healthy rat, rats injected with b BVCAR alone, c HAdV5-PUMA alone and animals injected with BVCAR HAdV5-PUMA at vector doses of d 107 PFU per joint, and e 109 PFU per joint respectively. (left) Parasagittal three-dimensional views of the whole rat ankles. (right) The enlarged images of the µ-CT parasagittal slices showing, from left to right, the intermediate cuneiform, navicular and distal talus. The white arrows point at local bone erosions. Scale bars, 1 mm. f Histological analysis and quantification of infiltrates was also performed. The bar graph shows the number of infiltrating cells, expressed as the ratio to their number in BVCAR control samples (mean ± s.e.m.; data from 30 slides per group). ANOVA: analysis of variance; §§§: ANOVA, P < 0.001; ***P < 0.0001 by Newman–Keuls post-hoc tests. Note that (i) BVCARHAdV5-PUMA strongly reduced the density of inflammatory cells in the joints, compared to control BVCAR or HAdV5-PUMA; (ii) BVCARHAdV5-PUMA was more effective at 109 PFU, compared to 107 PFU, demonstrating a dose-dependent effect