Development and characterization of a humanized mouse model of osteoarthritis.

OBJECTIVE: In light of the role of immune cells in OA pathogenesis, the development of sophisticated animal models closely mimicking the immune dysregulation during the disease development and progression could be instrumental for the preclinical evaluation of novel treatments. Among these models, immunologically humanized mice may represent a relevant system, particularly for testing immune-interacting DMOADs or cell therapies before their transfer to the clinic. Our objective, therefore, was to develop an experimental model of OA by destabilization of the medial meniscus (DMM) in humanized mice. METHOD: Irradiated 5-week-old NOD/LtSz-scid IL2Rγnull (NSG) mice were humanized by intravenous injection of CD34+ human hematopoietic stem cells. The engraftment efficiency was evaluated by flow cytometry 17 weeks after the humanization procedure. Humanized and non-humanized NSG mice underwent DMM or sham surgery and OA development was assessed 1, 6, and 12 weeks after the surgery. RESULTS: 120 days after the humanization, human T and B lymphocytes, macrophages and NK cells, were present in the blood and spleen of the humanized NSG mice. The DMM surgery induced articular cartilage and meniscal alterations associated with an increase in OA and the meniscal score. Moreover, the surgery triggered an inflammatory response that was sustained at a low grade in the DMM group. CONCLUSIONS: Our study shows for the first time the feasibility of inducing OA by DMM in humanized mice. This novel OA model could constitute a useful tool to bridge the gap between the preclinical and clinical evaluation of immune interacting DMOADs and cell-based therapies.

Correlation between magnetic resonance, X-ray imaging alterations and histological changes in an ovine model of age-related disc degeneration.

Sheep are one of the many animal models used to investigate the pathophysiology of disc degeneration and the regenerative strategies for intervertebral disc (IVD) disease. To date, few studies have thoroughly explored ageing of ovine lumbar IVDs. Hence, the objective of the present study was to concomitantly assess the development of spontaneous age-related lumbar IVD degeneration in sheep using X-ray, magnetic resonance imaging (MRI) as well as histological analyses. 8 young ewes (< 48 months old) and 4 skeletally mature ewes (> 48 months old) were included. Disc height, Pfirrmann and modified Pfirrmann grades as well as T2-wsi and T2 times were assessed by X-ray and MRI. The modified Boos score was also determined using histology sections. Pfirrmann (2 to 3) and modified Pfirrmann (2 to 4) grades as well as Boos scores (7 to 13) gradually increased with ageing, while T2-weighted signal intensity (1.18 to 0.75), T2 relaxation time (114.36 to 70.65 ms) and disc height (4.1 to 3.2 mm) decreased significantly. All the imaging modalities strongly correlated with the histology (p < 0.0001). The present study described the suitability of sheep as a model of age-related IVD degeneration by correlation of histological tissue alterations with the changes observed using X-ray and MRI. Given the structural similarities with humans, the study demonstrated that sheep warrant being considered as a pertinent animal model to investigate IVD regenerative strategies without induction of degeneration.

In vivo experimental imaging of osteochondral defects and their healing using (99m)Tc-NTP 15-5 radiotracer.

PURPOSE: A rabbit model of osteochondral defects (OD) and spontaneous healing was longitudinally followed over 12 weeks, by in vivo joint scintigraphy using (99m)Tc-NTP 15-5, and histology. METHODS: We used two models, one with one OD (OD1 group) in the femoral condyle of one knee and the other with two ODs (OD2 group) in the femoral condyle of one knee, with the contralateral knees serving as the reference. A serial longitudinal imaging study was performed with the scintigraphic ratio (SR, operated knee uptake/contralateral knee uptake) determined at each time-point. RESULTS: ODs were imaged as radioactive defects. The SR was decreased with respective to controls, with values of 0.73 ± 0.08 and 0.65 ± 0.07 in the OD1 and OD2 groups, respectively, at 4 weeks after surgery. Histology of both OD groups revealed the presence of repair tissue characterized by a small amount of sulphated glycosaminoglycans and collagen. CONCLUSION: (99m)Tc-NTP 15-5 imaging provided quantitative criteria useful for in vivo evaluation of cartilage trauma and healing.

Cartilage tissue engineering: From hydrogel to mesenchymal stem cells.

Articular cartilage does not repair itself spontaneously. To promote its repair, the transfer of stem cells from adipose tissue (ATSC) using an injectable self-setting cellulosic-hydrogel (Si-HPMC) appears promising. In this context, the objective of this work was to investigate the influence of in vitro chondrogenic differentiation of ATSC on the in vivo cartilage formation when combined with Si-HPMC. In a first set of experiments, we characterized ATSC for their ability to proliferate, self renew and express typical mesenchymal stem cell surface markers. Then, the potential of ATSC to differentiate towards the chondrogenic lineage and the optimal culture conditions to drive this differentiation were evaluated. Real-time RT-PCR and histological analysis for sulphated glycosaminoglycans and type II collagen revealed that 3-dimensional culture and hypoxic condition favored ATSC chondrogenesis regarding mRNA expression level and the corresponding proteins production. In order to assess the phenotypic stability of chondrogenically-differentiated ATSC, real-time RT-PCR for specific terminal chondrogenic markers and alkaline phosphatase activity assay were performed. In addition to promote chondrogenesis, our culture conditions seem to prevent the terminal differentiation of ATSC. Histological examination of ATSC/Si-HPMC implants suggested that the in vitro chondrogenic pre-commitment of ATSC in monolayer is sufficient to obtain cartilaginous tissue in vivo.