Nuclear factor erythroid 2–related factor 2 (Nrf2) is a crucial transcription factor to maintain cellular redox homeostasis, but is also affecting bone metabolism. As the association between Nrf2 and osteoporosis in elderly females is not fully elucidated, our aim was to shed light on the potential contribution of Nrf2 to the development of age-dependent osteoporosis using a mouse model. Female wild-type (WT, n=18) and Nrf2-knockout (KO, n=12) mice were sacrificed at different ages (12 weeks=young mature adult, and 90 weeks=old), morphological cortical and trabecular properties of femoral bone analyzed by micro-computed tomography (µCT), and compared to histochemistry. Mechanical properties were derived from quasi-static compression tests and digital image correlation (DIC) used to analyze full-field strain distribution. Bone resorbing cells and aromatase expression by osteocytes were evaluated immunohistochemically and empty osteocyte lacunae counted in cortical bone. Wilcoxon rank sum test was used for data comparison and differences considered statistically significant at p<0.05. When compared to old WT mice, old Nrf2-KO mice revealed a significantly reduced trabecular bone mineral density (BMD), cortical thickness (Ct.Th), cortical area (Ct.Ar), and cortical bone fraction (Ct.Ar/Tt.Ar). Surprisingly, these parameters were not different in skeletally mature young adult mice. Metaphyseal trabeculae were thin but present in all old WT mice, while no trabecular bone was detectable in 60% of old KO mice. Occurrence of empty osteocyte lacunae did not differ between both groups, but a significantly higher number of osteoclast-like cells and fewer aromatase-positive osteocytes were found in old KO mice. Furthermore, female Nrf2-KO mice showed an age-dependently reduced fracture resilience when compared to age-matched WT mice. Our results confirmed lower bone quantity and quality as well as an increased number of bone resorbing cells in old female Nrf2-KO mice. Additionally, aromatase expression in osteocytes of old Nrf2-KO mice was compromised, which may indicate a chronic lack of estrogen in bones of old Nrf2-deficient mice. Thus, chronic Nrf2 loss seems to contribute to age-dependent progression of female osteoporosis.
The large bone defects with high risk of delayed bone union and pseudoarthrosis remain significant clinical challenge. Aim of the present study was the investigation of the critical size fracture healing process in transgenic mice using a novel beta-TCP scaffold. The luciferase transgenic mice strains (BALB/C-Tg(NF-kappaB-RE-luc)-Xen) and FVB/N-Tg(Vegfr2-luc)-Xen were used. Critical size fracture on femur was performed and stabilized using external fixation (RISystem). The fracture was bridged with a synthetic scaffold with and without Strontium. In consequence, the expression levels of NF-kappaB and VEGFR2 could be monitored in a longitudinal fashion using the Xenogen imaging system for two months. Animals were euthanized, serial section of femur were prepared, and the fracture sites were histologically examined. Sr reduced inflammation in the early phase of healing (15th days), but it was increased in the late healing stage. The level of VEGFR2 activity increases in the Sr doped beta-TCP group at the 15th day, the luciferase activity starts to decrease in this group and show significantly less activity compared to other groups in the second half. In the group without scaffold a connective tissue formation were observed. In both, beta-TCP and beta-TCP+Sr, the connection of newly formed tissue within integrated canals in scaffold was visible. Tissue formation in beta-TCP+Sr group was significantly higher than in the beta-TCP group, whereas the percentage of osseous tissue in relation to the newly formed tissue was in beta-TCP scaffold much more than in beta-TCP+ Sr groups. This study presents the first data regarding VEGFR2 and NF-kappB and angiogenesis activity profiles during fracture healing. The collected longitudinal data reduces the number of experimental animals in the study. Addition of strontium in scaffolds influenced the inflammation in different stage of the healing. This effect might influence the healing process and may prove to be advantageous for osteoporosis fracture healing.
Large bone defects still challenge the orthopaedic surgeon. Local vascularity at the site of the fracture has an important influence on the healing procedure. Vascular endothelial growth factor (VEGF) and it's receptor (VEGFR2) are potent inducer of angiogenesis during the fracture healing. Aim of the present study was the investigation of critical size fracture (CSF) healing in VEGFR2-luc mice using tailored scaffolds. CSFs were performed and stabilised in mouse femur using an external fixator. The fracture was bridged using a synthetic 3D printed scaffold with a defined porosity to promote regeneration. The ß-tricalciumphosphate (ßTCP) and strontium doped ß-tricalciumphosphate (ßTCP+Sr) scaffolds were investigated for their regenerative potential. The expression levels of VEGFR2 could be monitored non-invasively via in vivo bioluminescence imaging for 2 months. After the longitudinal measurements the animals were euthanised for an in depth histological endpoint analysis. The different scaffold induced tissue regeneration was quantified for both, the ßTCP and the ßTCP+Sr group.Background
Methods
Aim of the study was to evaluate if abrasion-arthroplasty (AAP) and abrasion-chondroplasty (ACP) leads to a release of mesenchymal stem cell (MSC) like cells from the bone marrow to the joint cavity where they probably differentiate into a chondrogenic phenotype. Cartilage demage is a sever problem in our aging society. About 5 million people only in Germany are affected. Osteoathritis is a degeneration of cartilage caused by aging or traumata 50 % of the people over 40 have signs of osteoarthritis. But the ability of self-regeneration of cartilage is strongly limited. There are different approaches to therapy osteoathritic lesions. Arthroscopic treatment of OA includes bone marrow stimulation technique such as abrasion arthroplasty (AAP) and microfracturing (MF). Beside the support of chondrocyte progenitor cells the environment is also important for the commitment to chondrocytes. Therefore insulin-like growth factor-1 (IGF-1) and transforming growth factor beta-1 (TGF-β1) are important factors during the regeneration process. In the present study we characterised the heamarthrosis and the released cells after AAP and its ability to differentiate into the chondrocyte lineage. Postoperative haemarthrosis was taken 5, 22 or 44 hours after surgery. 7.5 mg Dexamethasone (Corticosteroid) was administered into the knee joint to prevent postoperative inflammation. Mononuclear cells were isolated from haemarthrosis from the drainage bottle by ficoll density gradient centrifugation. The isolated cells were characterised using fluorescence-activated cell-sorting (FACS) analysis for characteristic markers of MSC such as CD 44, 73, 90, 105. After expanding cells were cultured in a pellet culture. After 3 weeks, histochemistry and immunohistochemistry against Sox9, collagen II and proteoglycan were performed. The release of IGF1, BMP4 and BMP7 was analysed in haemarthrosis serum by ELISA and Luminex technology.Introduction
Material and Methods
