Cyclooxygenase-2 activity is important in craniofacial fracture repair

A Comparative Study of Engineered Dermal Templates for Skin Wound Repair in a Mouse Model

Engineered dermal templates have revolutionised the repair and reconstruction of skin defects. Their interaction with the wound microenvironment and linked molecular mediators of wound repair is still not clear. This study investigated the wound bed and acellular "off the shelf" dermal template interaction in a mouse model. Full-thickness wounds in nude mice were grafted with allogenic skin, and either collagen-based or fully synthetic dermal templates. Changes in the wound bed showed significantly higher vascularisation and fibroblast infiltration in synthetic grafts when compared to collagen-based grafts (P ≤ 0.05). Greater tissue growth was associated with higher prostaglandin-endoperoxide synthase 2 (Ptgs2) RNA and cyclooxygenase-2 (COX-2) protein levels in fully synthetic grafts. Collagen-based grafts had higher levels of collagen III and matrix metallopeptidase 2. To compare the capacity to form a double layer skin substitute, both templates were seeded with human fibroblasts and keratinocytes (so-called human skin equivalent or HSE). Mice were grafted with HSEs to test permanent wound closure with no further treatment required. We found the synthetic dermal template to have a significantly greater capacity to support human epidermal cells. In conclusion, the synthetic template showed advantages over the collagen-based template in a short-term mouse model of wound repair.

CREB/Wnt10b mediates the effect of COX-2 on promoting BMP9-induced osteogenic differentiation via reducing adipogenic differentiation in mesenchymal stem cells

Bone morphogenetic protein 9 (BMP9) is one of the most potent osteogenic factors, which may be a potential candidate for bone tissue engineering. However, the osteogenic capacity of BMP9 still need to be further enhanced. In this study, we determined the effect of Wnt10b on BMP9-induced osteogenic differentiation in mesenchymal stem cell (MSCs) and the possible mechanism underlying this process. We introduced the polymerase chain reaction (PCR), Western blot analysis, histochemical stain, ectopic bone formation, and microcomputed tomography analysis to evaluate the effect of Wnt10b on BMP9-induced osteogenic differentiation. Meanwhile, PCR, Western blot analysis, chromatin immunoprecipitation, and immunoprecipitation were used to analyze the possible relationship between BMP9 and Wnt10b. We found that BMP9 upregulates Wnt10b in C3H10T1/2 cells. Wnt10b increases the osteogenic markers and bone formation induced by BMP9 in C3H10T1/2 cells, and silencing Wnt10b decreases these effects of BMP9. Meanwhile, Wnt10b enhances the level of phosphorylated Smad1/5/8 (p-Smad1/5/8) induced by BMP9, which can be reduced by silencing Wnt10b. On the contrary, Wnt10b inhibits adipogenic markers induced by BMP9, which can be decreased by silencing Wnt10b. Further analysis indicated that BMP9 upregulates cyclooxygenase-2 (COX-2) and phosphorylation of cAMP-responsive element binding (p-CREB) simultaneously. COX-2 potentiates the effect of BMP9 on increasing p-CREB and Wnt10b, while silencing COX-2 decreases these effects. p-CREB interacts with p-Smad1/5/8 to bind the promoter of Wnt10b in C3H10T1/2 cells. Our findings suggested that Wnt10b can promote BMP9-induced osteogenic differentiation in MSCs, which may be mediated through enhancing BMP/Smad signal and reducing adipogenic differentiation; BMP9 may upregulate Wnt10b via the COX-2/p-CREB-dependent manner.

The effect of NSAIDs on spinal fusion: a cross-disciplinary review of biochemical, animal, and human studies

PURPOSE

Non-steroidal anti-inflammatory drugs (NSAIDs) play an important role in postoperative pain management. However, their use in the setting of spine fusion surgery setting has long been a topic of controversy. In this review we examined relevant research, including in vivo, animal, and clinical human studies, with the aim of understanding the effect of NSAIDs on spinal fusion.

STUDY DESIGN/SETTING

Systematic review of study designs of all types from randomized controlled trials and meta-analyses to single-institution retrospective reviews.

METHODS

A search of PubMed and Embase was conducted using the keywords: "spine," "spinal fracture," NSAIDs, anti-inflammatory non-steroidal agents, bone, bone healing, fracture, fracture healing, yielding a total of 110 studies. Other 28 studies were identified by cross-referencing, resulting in total 138 studies.

RESULTS

There is no level I evidence from human studies regarding the use of NSAIDs on spinal fusion rates. The overall tone of the spine literature in the early 2000s was that NSAIDs increased the rate of non-union; however, nearly all human studies published after 2005 suggest that short-term (<2 weeks) postoperative use have no such effect. The dose dependency that is seen with a 2-week postoperative course is not present when NSAIDs are only used for 48 h after surgery.

CONCLUSIONS

NSAID appear to have dose-dependent and duration-dependent effects on fusion rates. The short-term use of low-dose NSAIDs around the time of spinal fusion surgery is reasonable. Spine surgeons can consider the incorporation of NSAIDs into pain control regimens for spinal fusion patients with the goal of improving pain control and reducing the costs and complications associated with opioids.

Cyclooxygenase-2 deficiency impairs muscle-derived stem cell-mediated bone regeneration via cellular autonomous and non-autonomous mechanisms

This study investigated the role of cyclooxygenase-2 (COX-2) expression by donor and host cells in muscle-derived stem cell (MDSC)-mediated bone regeneration utilizing a critical size calvarial defect model. We found that BMP4/green fluorescent protein (GFP)-transduced MDSCs formed significantly less bone in COX-2 knock-out (Cox-2KO) than in COX-2 wild-type (WT) mice. BMP4/GFP-transduced Cox-2KO MDSCs also formed significantly less bone than transduced WT MDSCs when transplanted into calvarial defects created in CD-1 nude mice. The impaired bone regeneration in the Cox-2KO MDSCBMP4/GFP group is associated with downregulation of BMP4-pSMAD1/5 signaling, decreased osteogenic differentiation and lowered proliferation capacity after transplantation, compared with WT MDSCBMP4/GFP cells. The Cox-2KO MDSCBMP4/GFP group demonstrated a reduction in cell survival and direct osteogenic differentiation in vitro These effects were mediated in part by the downregulation of Igf1 and Igf2. In addition, the Cox-2KO MDSCBMP4/GFP cells recruited fewer macrophages than the WT MDSC/BMP4/GFP cells in the early phase after injury. We concluded that the bone regeneration capacity of Cox-2KO MDSCs was impaired because of a reduction in cell proliferation and survival capacities, reduction in osteogenic differentiation and a decrease in the ability of the cells to recruit host cells to the injury site.

Meloxicam temporally inhibits the expression of vascular endothelial growth factor receptor (VEGFR)-1 and VEGFR-2 during alveolar bone repair in rats

BACKGROUND

Vascular endothelial growth factor (VEGF) plays an important role during angiogenesis and bone repair. This study investigated whether the use of meloxicam alters bone repair via downregulation of VEGF and receptor expression.

METHODS

One hundred twenty male Wistar rats had their maxillary right incisor extracted. Animals were divided into a control group (CG; n = 60) and a meloxicam-treated group (TG; n = 60) that received either a single daily intraperitoneal injection of 0.9% NaCl or meloxicam 3 mg/kg, respectively, for 7 consecutive days. Alveolar bone repair was evaluated histomorphometrically, whereas VEGF and its receptors were analyzed by immunohistochemistry and quantitative polymerase chain reaction (qPCR). Data were submitted to two-way analysis of variance and Tukey post hoc test with P < 0.05.

RESULTS

Bone volume density increased significantly (P = 0.001) in both groups with a strong correlation between treatment and periods (P = 0.003). In the TG, a small amount of bone formation occurred compared with the CG between 3 and 21 days. No significant differences in the number of VEGF-positive cells per square millimeter (P = 0.07) and VEGF messenger RNA (mRNA) expression (P = 0.49) were found between groups. Immunostained cells per square millimeter and mRNA expression for VEGF receptor (VEGFR)-1 (P = 0.04 and P < 0.001) and VEGFR-2 (P < 0.001 for both analysis) showed a strong interaction between treatment groups and periods. In the TG, immunostained cells per square millimeter and mRNA expression for VEGFR-1 were, respectively, 89% and 37% lower from 3 to 10 days compared with the CG, whereas for VEGFR-2, these values were 252% and 60%, respectively, from 3 to 7 days.

CONCLUSION

In rat alveolar bone repair, meloxicam did not affect VEGF expression but downregulated VEGFR expression, which may cause a delay in the bone repair/remodeling process.

Cellular and molecular mechanisms of accelerated fracture healing by COX2 gene therapy: studies in a mouse model of multiple fractures

This study sought to determine the cellular and molecular mechanisms of cyclooxygenase-2 (COX2) gene therapy to accelerate fracture repair in a mouse multiple tibial fractures model. The lenti-COX2 (or lenti-gfp control vector) was injected into fractures on day 1 post-fracture. At days 3-7, the COX2 treatment increased Sdf1-, Cxcr4-, Nes-, and Podxl-expressing mesenchymal stem cells (MSCs) within fracture calluses, suggesting an enhanced MSC recruitment or expansion. The COX2-treated mice formed smaller cartilaginous calluses that had less cartilage tissues than control mice. The expression of Sox9 mRNA was 7-fold less in COX2-treated than in control calluses at day 14, implying that COX2 reduces chondrocytic differentiation of MSCs. The therapy also enhanced angiogenesis as reflected by increased immunostaining of CD31, vWF, and α-SMA over controls in the cartilaginous callus at day 14-21. At which time, the COX2 gene therapy promoted bony remodeling of the cartilaginous callus to bridge the fracture gap that was accompanied by 2-fold increase in osteoclasts along the surface of the woven bone and an onset of osteogenesis. Blocking angiogenesis with daily injection of endostatin from day 4 to day 10 into fracture sites blocked the COX2-mediated reduction of callus size that was associated with an increase in hypertrophic chondrocytes and concomitant reduction in osteoclasts. In conclusion, COX2 accelerates fracture healing in part through three biological actions: 1) increased recruitment/expansion of MSCs; 2) decreased cartilaginous callus formation; and 3) increased angiogenesis-dependent cartilage remodeling. These effects were associated with an earlier onset of bony bridging of the fracture gap.

Targeting polymer therapeutics to bone

An aging population in the developing world has led to an increase in musculoskeletal diseases such as osteoporosis and bone metastases. Left untreated many bone diseases cause debilitating pain and in the case of cancer, death. Many potential drugs are effective in treating diseases but result in side effects preventing their efficacy in the clinic. Bone, however, provides a unique environment of inorganic solids, which can be exploited in order to effectively target drugs to diseased tissue. By integration of bone targeting moieties to drug-carrying water-soluble polymers, the payload to diseased area can be increased while side effects decreased. The realization of clinically relevant bone targeted polymer therapeutics depends on (1) understanding bone targeting moiety interactions, (2) development of controlled drug delivery systems, as well as (3) understanding drug interactions. The latter makes it possible to develop bone targeted synergistic drug delivery systems.

Perioperative glucocorticosteroid treatment delays early healing of a mandible wound by inhibiting osteogenic differentiation

AIM

The purpose of this study is to investigate the effects of dexamethasone on repair of a critical size defect of the mandible in male Sprague-Dawley rats.

MATERIALS AND METHODS

Fifty rats were divided into 2 groups: saline control and dexamethasone-treated groups. A 1 mm × 3 mm full-thickness bone defect was created at the inferior border of the mandible. Saline or dexamethasone was administered once a day for 5 days after postoperative palinesthesia. On days 1, 3, 6, 10 and 17, after cessation of drug administration, 5 samples from each group were analysed. The bone defect healing process was examined and analysed by stereology, radiology, histology and histochemical staining for total collagen, tartrate-resistant acid phosphatase staining for osteoclasts and immunohistochemical staining for the COX-2, RUNX2 and osteocalcin antigens.

RESULTS

The dexamethasone-treated rats exhibited significantly lower radiopacity properties compared to the control rats. Histological staining revealed that the osteogenic differentiation and maturation of a callus in the defect region was significantly delayed from day 1 to day 10 in the dexamethasone group after cessation of drug administration compared to the control group. Consistent with the histological data, the level of total collagen protein was significantly lower in the dexamethasone group than in the control group. However, there was no significant difference between the 2 groups at day 17. Immunohistochemical analysis of COX-2, RUNX2 and osteocalcin expression showed that, at day 1, COX-2 and RUNX2 expression in the dexamethasone group was significantly lower than in the control group. There was no significant difference in osteocalcin expression between the two groups at each time point. There was no significant difference in the number of osteoclasts between the two groups.

CONCLUSION

In a model of bone healing of a mandible defect, dexamethasone-treated rats exhibited impaired osteogenic differentiation and maturation due to the inhibition of COX-2, osteogenic gene, RUNX2 and collagen protein expression, which resulted in delayed bone repair. Although perioperative short-term therapy did not exhibit long-term effects on wound healing of the maxillofacial bone, the application of glucocorticoids should be cautiously considered in the clinic.