Modeling and Assessing Osteoarthritis in Mice by Destabilization of the Medial Meniscus (DMM).

In this chapter, we describe an induced model of osteoarthritis in mice, frequently employed in the study of this disease. We outline in detail the surgical induction of disease and preparation of samples for histological assessment of disease.

Role of Ciliary Protein Intraflagellar Transport Protein 88 in the Regulation of Cartilage Thickness and Osteoarthritis Development in Mice.

OBJECTIVE: Mechanical and biologic cues drive cellular signaling in cartilage development, health, and disease. Primary cilia proteins, which are implicated in the transduction of biologic and physiochemical signals, control cartilage formation during skeletal development. This study was undertaken to assess the influence of the ciliary protein intraflagellar transport protein 88 (IFT88) on postnatal cartilage from mice with conditional knockout of the Ift88 gene (Ift88-KO). METHODS: Ift88fl/fl and aggrecanCreERT2 mice were crossed to create a strain of cartilage-specific Ift88-KO mice (aggrecanCreERT2 ;Ift88fl/fl ). In these Ift88-KO mice and Ift88fl/fl control mice, tibial articular cartilage thickness was assessed by histomorphometry, and the integrity of the cartilage was assessed using Osteoarthritis Research Society International (OARSI) damage scores, from adolescence through adulthood. In situ mechanisms of cartilage damage were investigated in the microdissected cartilage sections using immunohistochemistry, RNAScope analysis, and quantitative polymerase chain reaction. Osteoarthritis (OA) was induced in aggrecanCreERT2 ;Ift88fl/fl mice and Ift88fl/fl control mice using surgical destabilization of the medial meniscus (DMM). Following tamoxifen injection and DMM surgery, the mice were given free access to exercise on a wheel. RESULTS: Deletion of Ift88 resulted in progressive reduction in the thickness of the medial tibial cartilage in adolescent mice, as well as marked atrophy of the cartilage in mice during adulthood. In aggrecanCreERT2 ;Ift88fl/fl mice at age 34 weeks, the median thickness of the medial tibial cartilage was 89.42 µm (95% confidence interval [95% CI] 84.00-93.49), whereas in Ift88fl/fl controls at the same age, the median cartilage thickness was 104.00 µm (95% CI 100.30-110.50; P < 0.0001). At all time points, the median thickness of the calcified cartilage was reduced. In some mice, atrophy of the medial tibial cartilage was associated with complete, spontaneous degradation of the cartilage. Following DMM, aggrecanCreERT2 ;Ift88fl/fl mice were found to have increased OARSI scores of cartilage damage. In articular cartilage from maturing mice, atrophy was not associated with obvious increases in aggrecanase-mediated destruction or chondrocyte hypertrophy. Of the 44 candidate genes analyzed, only Tcf7l2 expression levels correlated with Ift88 expression levels in the microdissected cartilage. However, RNAScope analysis revealed that increased hedgehog (Hh) signaling (as indicated by increased expression of Gli1) was associated with the reductions in Ift88 expression in the tibial cartilage from Ift88-deficient mice. Wheel exercise restored both the articular cartilage thickness and levels of Hh signaling in these mice. CONCLUSION: Our results in a mouse model of OA demonstrate that IFT88 performs a chondroprotective role in articular cartilage by controlling the calcification of cartilage via maintenance of a threshold of Hh signaling during physiologic loading.

Overview of approved and upcoming vaccines for SARS-CoV-2: a living review.

The rapid design and implementation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines is testament to a successfully coordinated global research effort. While employing a variety of different technologies, some of which have been used for the first time, all approved vaccines demonstrate high levels of efficacy with excellent safety profiles. Despite this, there remains an urgent global demand for coronavirus disease 2019 vaccines that require further candidates to pass phase 3 clinical trials. In the expectation of SARS-CoV-2 becoming endemic, researchers are looking to adjust the vaccine constructs to tackle emerging variants. In this review, we outline different platforms used for approved vaccines and summarize latest research data with regards to immunogenicity, dosing regimens and efficiency against emerging variants.

Does Pain at an Earlier Stage of Chondropathy Protect Female Mice Against Structural Progression After Surgically Induced Osteoarthritis?

OBJECTIVE: Female C57BL/6 mice exhibit less severe chondropathy than male mice. This study was undertaken to test the robustness of this observation and explore underlying mechanisms. METHODS: Osteoarthritis was induced in male and female C57BL/6 or DBA/1 mice (n = 6-15 per group) by destabilization of the medial meniscus (DMM) or partial meniscectomy (PMX). Some mice were ovariectomized (OVX) (n = 30). In vivo repair after focal cartilage defect or joint immobilization (sciatic neurectomy) following DMM was assessed. Histologic analysis, evaluation of gene expression in whole knees, and behavioral analysis using Laboratory Animal Behavior Observation Registration and Analysis System (LABORAS) and Linton incapacitance testing (n = 7-10 mice per group) were performed. RESULTS: Female mice displayed less severe chondropathy (20-75% reduction) across both strains and after both surgeries. Activity levels after PMX were similar for male and female mice. Some repair-associated genes were increased in female mouse joints after surgery, but no repair differences were evident in vivo. Despite reduced chondropathy, female mice developed pain-like behavior at the same time as male mice. At the time of established pain-like behavior (10 weeks after PMX), pain-associated genes were significantly up-regulated in female mice, including Gdnf (mean ± SEM fold change 2.54 ± 0.30), Nrtn (6.71 ± 1.24), Ntf3 (1.92 ± 0.27), and Ntf5 (2.89 ± 0.48) (P < 0.01, P < 0.01, P < 0.05, and P < 0.001, respectively, versus male mice). Inflammatory genes were not regulated in painful joints in mice of either sex. CONCLUSION: We confirm strong structural joint protection in female mice that is not due to activity or intrinsic repair differences. Female mice develop pain at the same time as males, but induce a distinct set of neurotrophins. We speculate that heightened pain sensitivity in female mice protects the joint by preventing overuse.

HPA axis regulation and stress response is subject to intergenerational modification by paternal trauma and stress.

There is increasing evidence that one's risk for psychiatric disturbances and metabolic syndromes is influenced by their parents' own health history, lifestyle and living environment. For example, paternal high fat diet is strongly linked to neuroendocrine dysregulation in offspring and increased risk for diabetes. The potential intergenerational impact of paternal stress has only just begun to emerge, with the initial evidence suggestive of greater risk for anxiety-related disorders. The hypothalamic-pituitary-adrenal (HPA)-axis is a key neuroendocrine signalling system involved in physiological homeostasis and stress response. In individuals, dysregulation of this system is closely associated with behavioral deficits and mood disorders. Various preclinical models of paternal stress have demonstrated robust behavioral shifts but little is known about the intergenerational modification of HPA axis function. This review will present evidence drawn from a range of laboratory mouse and rat models that the intergenerational influence of paternal stress on offspring behavioral phenotypes involve some level of HPA axis dysregulation. It makes the case that further investigations to comprehensively profile HPA axis function in offspring generations is warranted.