Enamel Matrix Derivative Promotes Healing of a Surgical Wound in the Rat Oral Mucosa

Authors

Tal Maymon-Gil, Evgeny Weinberg, Carlos Nemcovsky, Miron Weinreb

Abstract

Background: Enamel Matrix Proteins (EMPs) play a role in enamel formation and the development of the periodontium. Sporadic clinical observations of periodontal regeneration treatments with Enamel Matrix Derivative (EMD), a commercial formulation of EMPs, suggest it also promotes post-surgical healing of soft tissues. In vitro studies showed that EMD stimulates various cellular effects, which could potentially enhance wound healing. This study examined the in-vivo effects of EMD on healing of an oral mucosa surgical wound in rats.

Methods: A bilateral oral mucosa wound was created via a crestal incision at the anterior edentulous maxilla of Sprague-Dawley rats. Full thickness flaps were raised and following suturing, EMD was injected underneath the soft tissues on one side while the EMD vehicle was injected in the contralateral side. Animals were sacrificed after 5 or 9 days and the wound area was subjected to histological and immunohistochemical analysis of epithelial gap, number of macrophages, blood vessels, proliferating cells and collagen content in the connective tissue. Gene expression analysis was also conducted 2 days after surgery.

Results: EMD had no effect on epithelial gap of the wound. On both days 5 and 9 EMD treatment increased significantly the number of blood vessels and the collagen content. EMD also enhanced (by 20-40%) the expression of transforming growth factor (TGF) β1 and TGFβ2, vascular endothelial growth factor (vEGF), interleukin-1β (IL-1β), matrix metalloproteinase-1 (MMP-1), Versican and Fibronectin.

Conclusions: EMD improves oral mucosa incisional wound healing by promoting formation of blood vessels and collagen fibers in the connective tissue.

Link to Article

http://dx.doi.org/10.1902/jop.2016.150567

Conditional Deletion of Murine Fgf23: Interruption of the Normal Skeletal Responses to Phosphate Challenge and Rescue of Genetic Hypophosphatemia

Authors

Erica L. Clinkenbeard, Taryn A. Cass, Pu Ni, Julia M. Hum, Teresita Bellido, Matthew R. Allen and Kenneth E. White

Abstract

The transgenic and knock out (KO) animals involving Fgf23 have been highly informative in defining novel aspects of mineral metabolism, but are limited by shortened life span, inability of spatial/temporal FGF23 control, and infertility of the global KO. To more finely test the role of systemic and genetic influences in FGF23 production, a mouse was developed that carried a floxed (‘f’)-Fgf23 allele (exon 2 floxed) which demonstrated in vivo recombination when bred to global-Cre transgenic mice (eIIa-cre). Mice homozygous for the recombined allele (‘Δ’) had undetectable serum intact FGF23, elevated serum phosphate (p < 0.05), and increased kidney Cyp27b1 mRNA (p < 0.05) similar to global Fgf23-KO mice. To isolate cellular FGF23 responses during phosphate challenge Fgf23Δ/f mice were mated with early osteoblast type Iα1 collagen 2.3kb promoter-cre mice (Col2.3-cre) and the late osteoblast/early osteocyte Dentin matrix protein-1-cre (Dmp1-cre). Fgf23Δ/f/Col2.3-cre+ and Fgf23Δ/f/Dmp1-cre+ exhibited reduced baseline serum intact FGF23 versus controls. After challenge with high phosphate diet Cre- mice had 2.1-2.5 fold increased serum FGF23 (p < 0.01), but Col2.3-cre+ mice had no significant increase, and Dmp1-cre+ mice had only a 37% increase (p < 0.01) despite prevailing hyperphosphatemia in both models. The Fgf23Δ/f/Col2.3-cre was bred onto the Hyp (murine XLH model) genetic background to test the contribution of osteoblasts and osteocytes to elevated FGF23 and Hyp disease phenotypes. Whereas Hyp mice maintained inappropriately elevated FGF23 considering their marked hypophosphatemia, Hyp/Fgf23Δ/f/Col2.3-cre+ mice had serum FGF23 <4% of Hyp (p < 0.01), and this targeted restriction normalized serum phosphorus and ricketic bone disease. In summary, deleting FGF23 within early osteoblasts and osteocytes demonstrated that both cell types contribute to baseline circulating FGF23 concentrations, and that targeting osteoblasts/osteocytes for FGF23 production can modify systemic responses to changes in serum phosphate concentrations and rescue the Hyp genetic syndrome.

Link to Article

http://dx.doi.org/10.1002/jbmr.2792

Gata2 is a Rheostat for Mesenchymal Stem Cell Fate in Male Mice

Authors

Xiaoxiao Li, HoangDinh Huynh, Hao Zuo, Marjo Salminen, and Yihong Wan

Abstract

Gata2 is a zinc finger transcription factor that is important in hematopoiesis and neuronal development. However, the roles of Gata2 in the mesenchymal lineages are poorly understood. In vitro studies suggest that Gata2 modulates adipocyte differentiation and mesenchymal stem cells (MSC) proliferation. To systematically determine the in vivo functions of Gata2 in MSC lineage commitment and development, we have generated three mouse models where Gata2 is specifically deleted in MSC, adipocyte or osteoblast. During MSC expansion stage, Gata2 promotes proliferation and attenuates differentiation; thereby Gata2 loss in MSC results in enhanced differentiation of both adipocyte and osteoblast. During differentiation stage, Gata2 also plays MSC-independent roles to impede lineage commitment; hence Gata2 loss in adipocyte or osteoblast lineages also augments adipogenesis and osteoblastogenesis, respectively. These findings reveal Gata2 as a crucial rheostat of MSC fate to control osteoblast and adipocyte lineage development.

Link to Article

http://dx.doi.org/10.1210/en.2015-1827

Sclerostin antibody (Scl-Ab) improves osteomalacia phenotype in dentin matrix protein 1(Dmp1) knockout mice with little impact on serum levels of phosphorus and FGF23

Authors

Yinshi Rena, Xianglong Hana, Yan Jinga, Baozhi Yuanc, Huazhu Ked, Min Liud, Jian Q. Feng

Abstract

Unlike treatments for most rickets, the treatment using 1,25-(OH)2 vitamin D3 has little efficacy on patients with hypophosphatemic rickets, a set of rare genetic diseases. Thus, understanding the local cause for osteomalacia in hypophosphatemic rickets and developing an effective treatment to restore mineralization in this rare disease has been a longstanding goal in medicine. Here, we used Dmp1 knockout (KO) mice (whose mutations led to the same type of autosomal recessive hypophosphatemic rickets in humans) as the model in which the monoclonal antibody of sclerostin (Scl-Ab) was tested in two age groups for 8 weeks: the prevention group (starting at age 4 weeks) and the treatment group (starting at age 12 weeks). Applications of Scl-Ab greatly improved the osteomalacia phenotype (> 15%) and the biomechanical properties (3-point bending, ~ 60%) in the treated long-bone group. Our studies not only showed improvement of the osteomalacia in the alveolar bone, which has the highest bone metabolism rate, as well as the long bone phenotypes in treated mice. All these improvements attributed to the use of Scl-Ab are independent of the change in serum levels of phosphorus and FGF23, since Scl-Ab had little efficacy on those parameters. Finally, we propose a model to explain how Scl-Ab can improve the Dmp1 KO osteomalacia phenotype, in which the sclerostin level is already low.

Link to Article

http://dx.doi.org/10.1016/j.matbio.2015.12.009

Dihydroartemisinin, an Anti-Malaria Drug, Suppresses Estrogen Deficiency-Induced Osteoporosis, Osteoclast Formation, and RANKL-Induced Signaling Pathways

Authors

Lin Zhou, Qian Liu, Mingli Yang, Tao Wang, Jun Yao, Jianwen Cheng, Jinbo Yuan, Xixi Lin, Jinmin Zhao, Jennifer Tickner and Jiake Xu

Abstract

Osteoporosis is an osteolytic disease that features enhanced osteoclast formation and bone resorption. Identification of agents that can inhibit osteoclast formation and function is important for the treatment of osteoporosis. Dihydroartemisinin is a natural compound used to treat malaria but its role in osteoporosis is not known. Here, we found that dihydroartemisinin can suppress RANKL-induced osteoclastogenesis and bone resorption in a dose-dependent manner. Dihydroartemisinin inhibited the expression of osteoclast marker genes such as cathepsin K, calcitonin receptor, and tartrate-resistant acid phosphatase (TRAcP). Furthermore, dihydroartemisinin inhibited RANKL-induced NF-κB and NFAT activity. In addition, using an in vivo ovariectomized mouse model, we show that dihydroartemisinin is able to reverse the bone loss caused by ovariectomy. Together, this study shows that dihydroartemisinin attenuates bone loss in ovariectomized mice through inhibiting RANKL-induced osteoclast formation and function. This indicates that dihydroartemisinin, the first physiology or medicine nobel prize discovery of China, is a potential treatment option against osteolytic bone disease.

Sclerostin Antibody Treatment Improves the Bone Phenotype of Crtap-/- Mice, a Model of Recessive Osteogenesis Imperfecta

Authors

Ingo Grafe, Stefanie Alexander, Tao Yang, Caressa Lietman, Erica P Homan, Elda Munivez, Yuqing Chen, Ming Ming Jiang, Terry Bertin, Brian Dawson, Franklin Asuncion, Hua Zhu Ke, Michael S Ominsky and Brendan Lee

Abstract

Osteogenesis Imperfecta (OI) is characterized by low bone mass, poor bone quality and fractures. Standard treatment for OI patients is limited to bisphosphonates, which only incompletely correct the bone phenotype, and seem to be less effective in adults. Sclerostin neutralizing antibodies (Scl-Ab) have been shown to be beneficial in animal models of osteoporosis, and dominant OI resulting from mutations in the genes encoding type I collagen. However, Scl-Ab treatment has not been studied in models of recessive OI. Cartilage associated protein (CRTAP) is involved in posttranslational type I collagen modification, and its loss of function results in recessive OI. In this study, we treated 1 and 6 week old Crtap-/- mice with Scl-Ab for 6 weeks (25 mg/kg, s.c., twice per week), to determine the effects on the bone phenotype in models of “pediatric” and “young adult” recessive OI. Vehicle treated Crtap-/- and wildtype (WT) mice served as controls. Compared with control Crtap-/- mice, microCT analyses showed significant increases in bone volume and improved trabecular microarchitecture in Scl-Ab treated Crtap-/- mice in both age cohorts, in both vertebrae and femurs. Additionally, Scl-Ab improved femoral cortical parameters in both age cohorts. Biomechanical testing showed that Scl-Ab improved parameters of whole bone strength in Crtap-/- mice, with more robust effects in the week 6-12 cohort, but did not affect the increased bone brittleness. Additionally, Scl-Ab normalized the increased osteoclast numbers, stimulated bone formation rate (week 6-12 cohort only), but did not affect osteocyte density. Overall, our findings suggest that Scl-Ab treatment may be beneficial in the treatment of recessive OI caused by defects in collagen post-translational modification.

Link to Article

http://dx.doi.org/10.1002/jbmr.2776