Joint instability and cartilage compression in a mouse model of posttraumatic osteoarthritis

Joint instability and cartilage trauma have been previously studied and identified as key mediators in the development of posttraumatic osteoarthritis (PTOA). The purpose of this study was to use an in vivo model to compare the effect of joint instability, caused by the rupture of the anterior cruciate ligament (ACL), versus cartilage compression. In this study, mice were subjected to cyclical axial loads of twelve Newtons (N) for 240 cycles or until the ACL ruptured. One and eight weeks after this procedure, knees were sectioned coronally and evaluated for osteoarthritis by histology. Using a scoring scale established by [Pritzker K, Gay S, Jimenez S, et al. (2006): Osteoarthritis Cartilage 14:13–29], the articular cartilage across each surface was scored and combined to produce a total degeneration score. The ACL‐ruptured group had a significantly greater total degeneration score than either control or compression treated joints at 1 and 8 weeks. Additionally, only sections from ACL‐ruptured knees consistently showed synovitis after 1 week and osteophyte formation after 8 weeks. Thus, it appears using that ACL rupture consistently creates a severe osteoarthritis phenotype, while axial cartilage compression alone does not appear to be an appropriate method of inducing PTOA in vivo. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:318–323, 2014.     

A humanized mouse model of idiopathic nephrotic syndrome suggests a pathogenic role for immature cells

Idiopathic nephrotic syndrome is characterized by glomerular proteinuria in the absence of infiltrating cells or immunoglobulin deposits. Although it is suspected that T cells secrete a circulating factor that leads to proteinuria by altering the permeability of the glomerular filtration barrier, the precise etiology of this syndrome is unknown. Because an animal model that mimics human idiopathic nephrotic syndrome does not exist, we developed a humanized mouse model of the disease by injecting CD34(+) stem cells or CD34(-) peripheral blood mononuclear cells from afflicted patients into immunocompromised mice. Even though both CD34(+) and CD34(-) cells induced the engraftment of human CD45(+) leukocytes in mice, only the injection of CD34(+) stem cells induced albuminuria. Ultrastructural analysis of glomeruli from the resulting proteinuric mice revealed effacement of podocyte foot processes, similar to the pathology observed in the human disease. Therefore, our data suggest that the cells responsible for the pathogenesis of idiopathic nephrotic syndrome are more likely to be immature differentiating cells rather than mature peripheral T cells.     

Generation and characterization of a novel shoulder contracture mouse model

Frozen shoulder is a relatively common disorder that leads to severe pain and stiffness in the shoulder joint. Although this disorder is self‐limiting in nature, the symptoms often persist for years, resulting in severe disability. Recent studies using human specimens and animal models have shown distinct changes in the gene expression patterns in frozen shoulder tissue, indicating that novel therapeutic intervention could be achieved by controlling the genes that are potentially involved in the development of frozen shoulder. To achieve this goal, it is imperative to develop a reliable animal joint contracture model in which gene expression can be manipulated by gene targeting and transgenic technologies. Here, we describe a novel shoulder contracture mouse model. We found that this model mimics the clinical presentation of human frozen shoulder and recapitulates the changes in the gene expression pattern and the histology of frozen shoulder and joint contracture in humans and other larger animal models. The model is highly reproducible, without any major complications. Therefore, the present model may serve as a useful tool for investigating frozen shoulder etiology and for identifying its potential target genes. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1732–1738, 2015.     

Development of a mouse intestinal transplantation model

We have recently developed a mouse intestinal transplantation model. The proximal segment of donor jejunum is transplanted into the recipient in a heterotopic position. End-to-side anastomoses are performed between donor aorta and recipient aorta and between donor portal vein and recipient inferior vena cava. Mortality rates were initially high due to shock, arterial thrombosis, and postoperative sepsis. Refinements in surgical techniques reduced these complications, resulting in a high rate of success. Important technical factors included (1) minimizing ischemic injuries to the graft in both the donor and the recipient, (2) using an aortic patch and elliptical aortotomy for anastomosis, (3) administering large volumes of crystalloid to maintain normal blood pressure during the donor and recipient surgeries, and (4) using broad-spectrum antibiotics as postoperative prophylaxis. The mice with isografts had normal intestinal function and histology when they were sacrificed 1 month after surgery. This new model of small bowel transplantation will be a useful tool to study the immunology of intestinal grafting at the molecular level. © 1993 Wiley-Liss Inc.     

Development,validation and characterization of a novel mouse model of Adynamic Bone Disease (ABD)

The etiology of Adynamic Bone Disease (ABD) is poorly understood but the hallmark of ABD is a lack of bone turnover. ABD occurs in renal osteodystrophy (ROD) and is suspected to occur in elderly patients on long-term anti-resorptive therapy. A major clinical concern of ABD is diminished bone quality and an increased fracture risk. To our knowledge, experimental animal models for ABD other than ROD-ABD have not been developed or studied. The objectives of this study were to develop a mouse model of ABD without the complications of renal ablation, and to characterize changes in bone quality in ABD relative to controls.To re-create the adynamic bone condition, 4-month old female Col2.3Δtk mice were treated with ganciclovir to specifically ablate osteoblasts, and pamidronate was used to inhibit osteoclastic resorption. Four groups of animals were used to characterize bone quality in ABD: Normal bone controls, No Formation controls, No Resorption controls, and an Adynamic group. After a 6-week treatment period, the animals were sacrificed and the bones were harvested for analyses. Bone quality assessments were conducted using established techniques including bone histology, quantitative backscattered electron imaging (qBEI), dual energy X-ray absorptiometry (DXA), microcomputed tomography (microCT), and biomechanical testing.Histomorphometry confirmed osteoblast-related hallmarks of ABD in our mouse model. Bone formation was near complete suppression in the No Formation and Adynamic specimens. Inhibition of bone resorption in the Adynamic group was confirmed by tartrate-resistant acid phosphatase (TRAP) stain. Normal bone mineral density and architecture were maintained in the Adynamic group, whereas the No Formation group showed a reduction in bone mineral content and trabecular thickness relative to the Adynamic group. As expected, the No Formation group had a more hypomineralized profile and the Adynamic group had a higher mean mineralization profile that is similar to suppressed bone turnover in human. This data confirms successful replication of the adynamic bone condition in a mouse without the complication of renal ablation.Our approach is the first model of ABD that uses pharmacological manipulation in a transgenic mouse to mimic the bone cellular dynamics observed in the human ABD condition. We plan to use our mouse model to investigate the adynamic bone condition in aging and to study changes to bone quality and fracture risk as a consequence of over-suppressed bone turnover.     

Creation and characterization of a mouse model of mandibular distraction osteogenesis

While the histological and ultrastructural changes associated with distraction osteogenesis have been extensively characterized using various animal models, the molecular mechanisms governing this technique remain poorly understood. In the current study, for the first time, we describe a mouse mandibular distraction osteogenesis model. Development of this model will allow assessment of factors involved in normal vs. abnormal healing (especially in non-unions) of craniofacial skeletal elements. Complete osteotomies were created on the right hemimandibles of 51 adult male CD-1 mice and customized distraction devices attached. Thirty-three animals underwent gradual distraction (5 days latency, distraction at 0.2 mm BID × 8 days, 28 days consolidation), while the remaining 18 mice underwent acute lengthening (immediate distraction to 3.2 mm) at the time of surgery. Mandibles were harvested at time points corresponding to the latent (POD 5), distraction (POD 9, 13), and consolidation (POD 28, 41) periods and processed for histological or quantitative real-time RT-PCR analysis. Specimens from each group were processed for μCT analysis. Histological and radiological data demonstrated that all mandibles undergoing gradual distraction achieved complete bony union by the end of consolidation, while those undergoing acute lengthening formed a fibrous non-union. Quantitative real-time RT-PCR demonstrated upregulation of mRNA for VEGF, FGF-2, collagen I, and osteopontin during gradual distraction but not during acute lengthening. These data validate our novel mouse mandibular distraction model and demonstrate its utility in elucidating the molecular mechanisms regulating bone formation during distraction osteogenesis as compared to those that are expressed during the formation of fibrous non-unions.     

Development of a mouse limb transplantation model.

A tremendous amount of research has been dedicated to laying the groundwork that will eventually lead to successful limb transplantation in humans. Limb transplantation in animal models has also been widely used for evaluating composite tissue allografts and various immunosuppressive regimens. Currently, there is no mouse model of limb transplantation. Such a model is attractive because it would allow investigators to apply the well-defined genetic characteristics of the mouse to the challenging field of limb transplantation. In this study, 12 mice underwent orthotopic hind limb transplantations using end-to-end anastomoses of the femoral vessels. The success rate of this surgical procedure was 83%, with 10 of the 12 limbs surviving. Experimental devices, operative procedures, and the major elements of success are discussed.     

Development of a femoral non-union model in the mouse

OBJECTIVES: Advancements in our knowledge of fracture healing have occurred in large part by the understanding of this process on a microscopic level. The ability to develop experimental non-union models in animals will assist in the investigation of this problem and are likely to lead to novel treatments. We report on a technique for developing experimental non-unions in mice. METHODS: Femoral fractures were created in 48 CD1 mice, 24 mice underwent standard closed femoral fractures, and 24 mice underwent creation of a femoral non-union through an open osteotomy and fracture devascularisation method. All fractures were subsequently rodded. Histological examinations of the fractures were then conducted at eight time points post-operatively. RESULTS: The control group showed normal fracture healing with histological evidence of bony fracture bridging by 28 days and mature bony remodelling at 63 days. The non-union group showed delayed fracture healing at all time points and no evidence of bony healing at 63 days. CONCLUSION: This is the first report of a reliable method to develop fracture non-union in mice. We believe this technique will be critical to further the investigation of fracture non-union in normal mice and provides the great advantage of using the plethora of transgenic and knockout mouse models to analyse non-union at the cell and molecular level.