A glass polyalkenoate cement carrier for bone morphogenetic proteins.

This work considers a glass polyalkenoate cement (GPC)-based carrier for the effective delivery of bone morphogenetic proteins (BMPs) at an implantation site. A 0.12 CaO-0.04 SrO-0.36 ZnO-0.48 SiO2 based glass and poly(acrylic acid) (PAA, Mw 213,000) were employed for the fabrication of the GPC. The media used for the water source in the GPC reaction was altered to produce a series of GPCs. The GPC liquid media was either 100 % distilled water with additions of albumin at 0, 2, 5 and 8 wt% of the glass content, 100 % formulation buffer (IFB), and 100 % BMP (150 µg rhBMP-2/ml IFB). Rheological properties, compressive strength, ion release profiles and BMP release were evaluated. Working times (Tw) of the formulated GPCs significantly increased with the addition of 2 % albumin and remained constant with further increases in albumin content or IFB solutions. Setting time (Ts) experienced an increase with 2 and 5 % albumin content, but a decrease with 8 % albumin. Changing the liquid source to IFB containing 5 % albumin had no significant effect on Ts compared to the 8 % albumin-containing BT101. Replacing the albumin with IFB/BMP-2 did not significantly affect Tw. However, Ts increased for the BT101_BMP-2 containing GPCs, compared to all other samples. The compressive strength evaluated 1 day post cement mixing was not affected significantly by the incorporation of BMPs, but the ion release did increase from the cements, particularly for Zn and Sr. The GPCs released BMP after the first day, which decreased in content during the following 6 days. This study has proven that BMPs can be immobilized into GPCs and may result in novel materials for clinical applications.

Mutation of a cleavage site adjacent to the mature domain leads to increase in secreted mature BMP-2 with reduced activity.

Proteolytic cleavage of precursor bone morphogenetic protein (proBMP) is an important step in generating the active mature BMP. ProBMP-2 contains two proprotein convertase (PC) recognition sites (S1 and S2) and is postulated to be cleaved by PCs at those sites. Cell lines expressing proBMP-2, with a silenced S1 site (mS1) that inhibited PC cleavage, secreted the 20-kDa form BMP-2, while cells expressing wild type (wt) BMP-2 secreted 18- and 20-kDa mature BMP-2 N-terminal isoforms. The mS1 cells secreted 15-fold more mature BMP-2 than the wt, despite their similar mRNA levels. Mutant-secreted BMP-2 demonstrated biological activity in vitro; however, its activity was reduced compared with wt. These data demonstrate that proBMP-2 can be cleaved at an alternative cleavage site without prior S1 site cleavage in cell lines overexpressing BMP-2 and more importantly suggest that the presence of the 2-kDa linker peptide can affect activity and secretion of the mature protein.

Polyarginine peptide IND-1 enhances recombinant human bone morphogenetic protein-2 yield in mammalian cells.

To improve recombinant human bone morphogenetic protein-2 (rhBMP-2) yield, cell lines stably expressing hBMP2 were cultured in the presence of polyarginine peptide IND-1 and showed up to 6-fold increase in the yield of mature BMP-2. Repeated addition of IND-1 to cell cultures consistently improved BMP-2 yields over 53 days without affecting cell growth and viability. Investigation of its mechanism of action showed that IND-1 inhibited pro-protein convertase (PC) activity when incubated with cell lysates. However, when intact cells were cultured with IND-1, no change in cellular PC activity was observed. Furthermore, knockdown of furin (a prototypical member of the PCs) in cells did not affect their BMP-2 yields, suggesting furin/PC inhibition is unlikely the mechanism by which IND-1 enhances BMP-2 yields. IND-1 as a medium additive thus enhances BMP-2 production in mammalian cell expression systems.

Effect of hydrophilicity of carbon nanotube arrays on the release rate and activity of recombinant human bone morphogenetic protein-2.

Novel nanostructures such as vertically aligned carbon nanotube (CNT) arrays have received increasing interest as drug delivery carriers. In the present study, two CNT arrays with extreme surface wettabilities are fabricated and their effects on the release of recombinant human bone morphogenetic protein-2 (rhBMP-2) are investigated. It is found that the superhydrophilic arrays retained a larger amount of rhBMP-2 than the superhydrophobic ones. Further use of a poloxamer diffusion layer delayed the initial burst and resulted in a greater total amount of rhBMP-2 released from both surfaces. In addition, rhBMP-2 bound to the superhydrophilic CNT arrays remained bioactive while they denatured on the superhydrophobic surfaces. These results are related to the combined effects of rhBMP-2 molecules interacting with poloxamer and the surface, which could be essential in the development of advanced carriers with tailored surface functionalities.

Augmentation of the maxillary sinus: comparison of bioimplants containing bone morphogenetic protein and autogenous bone in a rabbit model.

OBJECTIVE: To evaluate the effectiveness of various bioimplants used for augmentation of the maxillary sinus floor by means of a rabbit model. MATERIALS AND METHODS: Bone was harvested from the posterior iliac crest of 40 adult New Zealand white rabbits to allow bilateral augmentation of the floor of the maxillary sinus with autogenous bone or other materials. One of the following was grafted to the maxillary sinus of each rabbit: particulated autogenous bone, demineralized bone matrix (DBM), DBM combined with purified bone morphogenetic protein (BMP-DBM bioimplants) and bioimplants consisting of a poloxamer gel with BMP in 1 of 2 different doses. Animals were sacrificed at 2 or 8 weeks. Histologic examination was used to assess biologic healing in the various samples. Histomorphometry was used to demonstrate and quantify bone formation. RESULTS: After 2 weeks, the BMP-containing bioimplants had produced more new bone than any of the other materials. Particulated autogenous bone grafts produced less new bone initially (after 2 weeks), but the amount of bone produced by these grafts gradually increased, to levels comparable to the BMP-containing bioimplants by 8 weeks. For groups in which the poloxamer gel was used as a carrier for BMP or where BMP was used in combination with DBM, the amount of bone generated by 8 weeks was similar to that produced by autogenous bone. CONCLUSION: The rabbit maxillary sinus model allowed evaluation of multiple types of bioimplants that could be suitable for peri-implant maxillary reconstruction. BMP-containing bioimplants demonstrated promise as alternatives to autogenous bone grafts for sinus-augmentation procedures. These bioimplants had more rapid initial bone production than all other materials, including autogenous bone. In the future, such biomaterials may enable earlier placement of dental implants into augmented maxillary sinuses.

Comparison of platelet-rich plasma, bovine BMP, and rhBMP-4 on bone matrix protein expression in vitro.

This study investigated the potential use of platelet-rich plasma (PRP) in conjunction with mRNA expression of bone matrix proteins using bioassay and RT-PCR comparing bovine bone morphogenetic proteins (BMP), recombinant human BMP-4 (rhBMP-4) during rat bone marrow stromal cell (Mesenchymal Stem Cell) differentiation at 14 days. The results showed that all three growth factors were associated with significantly elevated alkaline phosphatase activity. PRP and bovine BMP resulted in increased protein content. The mRNA of type I collagen was expressed with all three growth factors and remained consistently elevated. Osteopontin was observed with PRP from days 1 to 7; bone sialoprotein expression was detected on days 1 and 3. PRP, bovine BMP and rhBMP-4 enhanced the steady-state expression of PDGF-A as time-dependent to day 14 and in PRP was the strongest. PTHr was expressed at days 1 and 5. Vascular endothelial growth factor expression was the most highly expressed after day 3. These findings suggest that PRP increases mRNA expression of bone matrix protein, enchances osteogenesis and angiogenesis in vitro.

Induction of bone matrix protein expression by native bone matrix proteins in C2C12 culture.

OBJECTIVE: To study the expression of bone matrix protein (BMP) induced by bovine bone morphogenetic proteins (BMPs) in vitro. METHODS: Type I collagen, osteopontin (OPN), osteonectin (ON), osteocalcin (OC), and bone sialoprotein (BSP) were detected by immunohistochemistry in C2C12 cultured from day 1 to day 28. RESULTS: The signaling of bone matrix protein expression became weaker except for type I collagen, OC and BSP after 5 days. Fourteen days after culture, the positive signaling of type I collagen, OPN, ON, OC, and BSP was gradually declined, and could be detected significantly as compared with that of the negative control on day 28. BMP assay showed that the alkaline phosphatase (ALP) activity was higher in C2C12 culture than in the control during the 14-day culture. Also, total protein and DNA significantly increased during the 14-day culture. High levels of ALP were seen in preosteoblasts and osteoblasts in vivo and in differentiating osteoblasts in vitro. ALP was well recognized as a marker reflecting osteoblastic activity. CONCLUSION: Native bovine BMP induces conversion of myoblasts into osteoblasts, produces type I collagen, and plays significantly role in osteoinduction and bone matrix mineralization of C2C12 in vitro.

An Injectable Glass Polyalkenoate Cement Engineered for Fracture Fixation and Stabilization.

Glass polyalkenoate cements (GPCs) have potential as bio-adhesives due to their ease of application, appropriate mechanical properties, radiopacity and chemical adhesion to bone. Aluminium (Al)-free GPCs have been discussed in the literature, but have proven difficult to balance injectability with mechanical integrity. For example, zinc-based, Al-free GPCs reported compressive strengths of 63 MPa, but set in under 2 min. Here, the authors design injectable GPCs (IGPCs) based on zinc-containing, Al-free silicate compositions containing GeO2, substituted for ZnO at 3% increments through the series. The setting reactions, injectability and mechanical properties of these GPCs were evaluated using both a hand-mix (h) technique, using a spatula for sample preparation and application and an injection (i) technique, using a 16-gauge needle, post mixing, for application. GPCs ability to act as a carrier for bovine serum albumin (BSA) was also evaluated. Germanium (Ge) and BSA containing IGPCs were produced and reported to have working times between 26 and 44 min and setting times between 37 and 55 min; the extended handling properties being as a result of less Ge. The incorporation of BSA into the cement had no effect on the handling and mechanical properties, but the latter were found to have increased compression strength with the addition of Ge from between 27 and 37 MPa after 30 days maturation.

Controlled bone formation using ultrasound-triggered release of BMP-2 from liposomes.

Recombinant human bone morphogenetic protein 2 (rhBMP-2) is used clinically to enhance implant-mediated bone regeneration. However, there are risks associated with the high rhBMP-2 dose that is required in the implant to mitigate diffusional loss over the therapeutic timespan. On-demand, localized control over delivery of rhBMP-2, days after implantation, would therefore be an attractive solution in the area of bone repair and reconstruction, yet this has posed a significant challenge, with little data to support in vivo efficacy to date. To address this, we have developed novel liposome-rhBMP-2 nanocomplexes that release rhBMP-2 in response to non-thermogenic, clinical diagnostic ultrasound exposure. In vitro validation shows that rhBMP-2 release is in proportion to applied ultrasound pressure and duration of exposure. Moreover, here we show in vivo validation of this ultrasound-triggered rhBMP-2 delivery system in a standard mouse bone regeneration model. Implanted into hindleg muscles, the liposome-rhBMP-2 nanocomplexes induced local bone formation only after ultrasound exposure. Such post-implantation control of delivery has potential to improve the safety, efficacy and cost of rhBMP-2 use in bone reconstruction. Furthermore, this first proof-of-concept demonstration of in vivo efficacy for ultrasound-triggered liposomal delivery of rhBMP-2 has broader implications for tunable delivery of a variety of drugs and biologics in medicine and tissue engineering.

Osteoinductivity assay of the variability of repeated extractions of bone morphogenetic proteins from bovine bone at different times.

OBJECTIVE: To observe the activity of repeated extracts of bone matrix and the production of purified bone morphogenetic proteins (BMPs). METHODS: BMPs were extracted 1- 4 times from fresh bovine cortical bone by the modified Urist's method, with each collected precipitate separated and lyophilized as partially purified BMPs. Another fresh bovine bone was extracted three times and the precipitates were mixed and lyophilized. Meanwhile,the alkaline phosphatase (ALP) activity was measured by an in vitro assay employing cultured C2C12 mouse myoblast cells through the osteoinductivity of bovine BMPs extracted four times at days 1, 4, 7, and 14, and the correlation between BMPs quantities and costing during extraction processes was analyzed. RESULTS: The BMPs purified and the cost showed a positive correlation (r=0.969). To separate and lyophilize each collected precipitate as partially purified BMPs raised the cost, and mixed precipitates also cost much. ALP activities of the 1st and mixed extractions of BMPs were shown to be highly osteoinductive and keep a significantly high level (P<0.05-0.01) 4 days after culturing, compared with the 2nd, 3rd and 4th extractions, especially the control group. However, the more times the extraction was done, the less activity of BMPs was shown and more costing was. The x-ray and histological analysis also showed that the 1st extraction of BMPs induced more ossicles and new bone formation. CONCLUSIONS: The results indicated that BMPs enhanced the abilities of osteoinductivity in C2C12 culture in vitro. The first extraction of BMPs from bone is fitfull, the second extraction should be enough, while, the 3rd and 4th extractions are unnecessary for they cost more and waste more time, say nothing of mixed extractions.

Serum levels of BMP-2, 4, 7 and AHSG in patients with degenerative joint disease requiring total arthroplasty of the hip and temporomandibular joints.

To date, there is no objective or reliable means of assessing the severity of degenerative joint disease (DJD) and need for joint replacement surgery. Hence, it is difficult to know when an individual with DJD has reached a point where total arthroplasty is indicated. The purpose of the present study is to determine whether serum levels of Alpha-2 HS-glycoprotein (AHSG) as well as bone morphogenetic proteins (BMP-2, 4, 7) can be used to predict the presence of severe DJD of the hip and/or temporomandibular joint (TMJ) (specifically: joints that require replacement). A total of 30 patients scheduled for arthroplasty (diseased) (15 HIP, 15 TMJ) and 120 age-matched controls (healthy/non-diseased) were included. Blood samples were collected from all patients ≥8 weeks after the last arthroplasty. Concentrations of serum analytes were measured using enzyme-linked immunosorbent assays, and these were compared between the Diseased and Healthy groups, utilizing the Mann-Whitney U-test. Patients with disease had significantly higher levels of BMP-2 and BMP-4 and lower levels of AHSG in serum compared to non-diseased humans (p < 0.01). Higher levels of BMP-2, 4 and reduced levels of AHSG appear to characterize patients who have DJD that is severe enough to require total joint replacement. Perhaps measurements of these proteins can be used to make objective decisions regarding the need for total arthroplasty as opposed to the current subjective approaches.

Osteoinductivity of partially purified bovine, ostrich and emu bone morphogenetic proteins in vitro.

The aim of this study was to observe the osteogenic activity of native bone morphogenetic proteins (BMPs) obtained from different species including bovine, ostrich and emu sources in order to compare mammalian and avian BMPs. Rat mesenchymal progenitor marrow stromal cells and pre-osteoblastic C2C12 cell cultures, were exposed to the native BMPs and alkaline phosphatase (ALP) and creatine kinase (CK) levels were determined by assay. The results showed that the ALP activity in C2C12 cultures was elevated by bovine BMP by 2- to 10-fold (p < 0.05-0.001) from day 3 during 14 days. There were no significant differences in avian BMP related elevations of ALP activity except with ostrich BMPs at day 14 (p < 0.05). However, exposure of MSCs cultures to BMPs derived from bovine, ostrich or emu sources resulted in elevated ALP from day 3 (p < 0.05). Bovine BMP resulted in more ALP elevation than with either of the avian BMPs. All of BMPs elevated Creatine kinase (CK) activity from day 1 and climbed until peaking at day 7. Compared with control cultures, CK was elevated more with exposure to emu BMP and was more elevated with greater statistical significance than with bovine and ostrich BMP before day 5. These higher levels remained until day 14 (p < 0.05). The results of this study suggest that both bovine and avian BMPs are able to stimulate osteogenesis in mature osteoblasts in vitro. The strongest synergistic effect on osteogenesis was detected in cells stimulated with bovine BMP. Avian BMPs had lower effects on ALP and CK activity, emu BMP being more effective than ostrich BMP.

Evaluation of Rosa damascena mouthwash in the treatment of recurrent aphthous stomatitis: a randomized, double-blinded, placebo-controlled clinical trial.

OBJECTIVE: As the exact etiology of recurrent aphthous stomatitis remains unknown, its treatment has primarily been palliative to relieve the pain, associated inflammation, and duration of the lesions by using antibacterial mouthrinses, analgesics, and immunomodulators. Nevertheless, no treatment has been universally effective in management of recurrent aphthous stomatitis, which necessitates the search for novel therapeutic agents. The aim of this study was to assess the clinical efficacy of the aqueous extract of Rosa damascena, which has reported anti-inflammatory and antinociceptive properties, in the treatment of recurrent aphthous stomatitis. METHOD AND MATERIALS: This was a randomized, double-blind, placebo-controlled investigation. Fifty patients were enrolled in this 2-week study; the clinical efficacy of the mouthwash on pain, size, and number of ulcers in the test group was compared with that of the placebo group on days 4, 7, 11, and 14. RESULTS: There were no statistically significant differences between baseline parameters. However, statistical analysis indicated a significant difference on days 4 and 7 between the placebo and test groups for all parameters. CONCLUSION: This study showed that mouthwash containing Rosa damascena extract was more effective than the placebo in the treatment of recurrent aphthous stomatitis.

Calvarial bone wound healing: a comparison between carbide and diamond drills, Er:YAG and Femtosecond lasers with or without BMP-7.

OBJECTIVE: This study compared the healing of 2 laser ablation units, erbium YAG and femtosecond lasers versus conventional mechanical cutting with carbide and diamond drills to explore future applications for bone surgery. The effects of laser or mechanical ablation combined with rhBMP-7 were also investigated. METHODS AND MATERIALS: Following defect standardization, a full-thickness circular defect was created on the parietal bones of 160 mice divided into 4 groups: carbide drill, diamond drill, erbium YAG laser, and femtosecond laser. Each of the 4 ablation groups was treated with and without BMP 7. Hard tissue healing was assessed using microcomputerized tomography at 3 and 12 weeks postsurgical time points. RESULTS: The femtosecond laser created wounds that showed slightly delayed bone healing during the observation period when compared with mechanical drilling, although the difference was not statistically significant. The Er:YAG laser showed a healing rate similar to that of the mechanically ablated groups. When BMP 7 was added to the surgical sites, bone wound closure occurred at a similar rate in all test groups. CONCLUSIONS: The femtosecond and Er:YAG lasers are 2 laser modalities suitable for bone ablation that are comparable to mechanical instrumentation in terms of bone healing. This study suggested that BMP-7 may be used to enhance bone healing with success regardless of the ablative modality used, whether laser or mechanical drilling.

The expression of bone matrix proteins induced by different bioimplants in a rabbit sinus lift model.

This study aimed to analyze the expression of bone matrix proteins and CD31 by immunohistochemistry after maxillary sinus grafting with different bioimplants in a rabbit model. Rabbit demineralized bone matrix (DBM), partially purified bovine bone morphogenetic proteins (BMP), a mixture of BMP with DBM (BMP/DBM), or particulated autogenous bone was grafted into the maxillary sinuses of 42 rabbits. Animals were sacrificed at 2 and 8 weeks. Immunohistochemistry was used to investigate the expression of type 1 collagen (COL1), osteonectin (ON), osteocalcin (OC), bone sialoprotein (BSP), osteopontin (OPN), and CD31. Sinuses grafted with BMP were filled with trabeculae of woven bone that was strongly immunoreactive for COL1, OC, ON, and BSP. BMP/DBM showed strongly positive immunoreactivity for these proteins within the newly formed bone, but weak immunoreactivity in the DBM particles. Immunoreactivity for COL1, OC, ON, and BSP in DBM sinuses was only seen in the osteoblasts rimming the grafted bone particles. The staining of autogenous bone graft sinuses was similar to those grafted with DBM. OPN staining was detected in autogenous bone graft, BMP/DBM, and BMP bioimplants. CD31 staining was strongest in BMP and BMP/noncollagenous matrix proteins sinuses. These results suggest that exogenous BMP enhances not only osteogenesis but also angiogenesis, an important part of bone repair.

Comparison of the osteoinductivity of bioimplants containing recombinant human bone morphogenetic proteins 2 (Infuse) and 7 (OP-1).

OBJECTIVES: Recent research has focused on application of growth factors such as bone morphogenetic proteins (BMPs) as alternatives to autogenous bone grafting. Two bone graft substitute bioimplants containing recombinant human BMPs (rhBMPs), Infuse (rhBMP-2) and OP-1 (rhBMP-7), are approved for human application but have never been compared side by side. The aim of this study was to provide a direct comparison of the osteoinductive activity of the 2 commercially available and approved rhBMP-containing bioimplants in their clinically available forms. STUDY DESIGN: The activity of rhBMP-2 and -7 in solution were compared in vitro using the C2C12 cell-based assay. The activity of Infuse and OP-1 bioimplants containing 52.5 microg of rhBMP-2 or rhBMP-7, respectively, were compared in vivo using a mouse muscle pouch assay and analyzed by microscopic CT (microCT) and histology. RESULTS: The in vitro results showed that rhBMP-2 stimulated greater alkaline phosphatase production than rhBMP-7 over various time points and concentrations. The in vivo results showed that OP-1 induced greater bone volume than Infuse. Both implants induced bone of equivalent quality based on microCT and histologic evaluation. CONCLUSION: In their clinically available forms, the rhBMP-7-containing OP-1 induced greater bone volume than the rhBMP-2-containing Infuse in the mouse muscle pouch model.

Bone healing with an in situ-formed bioresorbable polyethylene glycol hydrogel membrane in rabbit calvarial defects.

OBJECTIVES: The aims of this study were to test whether or not the application of an in situ-formed synthetic polyethylene glycol hydrogel (PEG) used as a biodegradable membrane for guided bone regeneration with a variety of graft materials and ambient oxygen or hyperbaric oxygen (HBO) environments would result in enhanced bone regeneration, and to observe the histologic and histomorphometric aspects of bone healing of the calvarial defects with and without a PEG membrane. STUDY DESIGN: Thirty adult, skeletally mature, male New Zealand white rabbits were randomly divided into 3 groups of 10 animals each. Bilateral 15-mm-diameter critical-size defects were created in the parietal bones of each animal. Group 1 served as a control with unfilled bilateral calvarial defects, group 2 had bilateral calvarial defects filled with morcelized autogenous calvarial bone, and group 3 had bilateral calvarial defects filled with a biphasic calcium phosphate ceramic. One of the calvarial defects was randomly protected with a PEG resorbable liquid membrane in each animal. Five animals from each group underwent a course of HBO treatment (2.4 ATA 100% oxygen for 90 minutes 5 days a week for 4 weeks) and the other 5 served as control and did not receive any supplemental oxygen (normobaric). The animals were killed 6 weeks after their surgery, and their parietal bones were harvested. The specimens were analyzed with microscopic computerized tomography (microCT) scans and histomorphometrics. RESULTS: The unfilled normobaric control bony defects did not heal, proving the critical-size nature of these defects. The presence of autogenous bone or bone ceramic in the defects increased the bone volume fraction and bone mineral density of the defects (P < .001). The presence of a membrane in the ungrafted and autogenous bone grafted defects resulted in a decrease in the corrected bone volume fraction (P = .002) but not in the bone ceramic grafted defects (P = .580). Bony healing of defects where the membrane was unsupported was compromised; the membrane did not maintain the desired bone regeneration volume with the unfilled and autogenous bone grafted groups. The PEG resorbable liquid membrane worked best with the bone ceramic material. HBO did not ameliorate the healing of the autogenous bone graft or ceramic filled defects in the 6-week time period of this study. CONCLUSIONS: Although the PEG resorbable liquid membrane is easy to use and forms an occlusive layer, caution is recommended when using the membrane over an unsupported defect. HBO did not ameliorate bony healing with the membrane at the early 6-week time point. The authors recommend future assessment with HBO at the 12-week time point.

Platelet-rich plasma induces mRNA expression of VEGF and PDGF in rat bone marrow stromal cell differentiation.

OBJECTIVE: To investigate the potentially useful of platelet-rich plasma (PRP) on mRNA expression of angiogenesis. STUDY DESIGN: Adjunct assay and reverse-transcription polymerase chain reaction (RT-PCR) analysis of type I collagen, vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) in rat bone marrow stromal cells differentiation in 14 days' culture. RESULTS: The PRP significantly elevated alkaline phosphatase activity after day 5 (P < .05), and DNA and protein content increased at culture days 1, 3, and 5 (P < .01) with PRP compared with control. The RT-PCR demonstrated that type I collagen was expressed in all substrates and remained high with PRP during 14 days of culture, and that mRNA expression of VEGF and PDGF were higher over time. CONCLUSIONS: This study indicates a potential contribution of PRP as possibly starting the process of angiogenesis, recruiting the endothelial cells which line blood vessels, and beginning the initiation of bone regeneration.

Hyperbaric oxygen results in increased vascular endothelial growth factor (VEGF) protein expression in rabbit calvarial critical-sized defects.

BACKGROUND: Hyperbaric oxygen therapy (HBO) promotes osseous healing, however the mechanism by which this occurs has not been elucidated. HBO may promote angiogenesis, which is vital for bone healing. Vascular endothelial growth factor (VEGF) is one of the key factors that stimulates angiogenesis. OBJECTIVE: The objective of this study was to investigate whether HBO altered VEGF expression during bone healing. METHODS AND MATERIALS: Archived samples from calvarial defects of rabbits exposed to HBO (2.4 ATA, 90 minutes a day, 5 days a week for 4 weeks) and normobaric oxygen controls (NBO) were analyzed by immunohistochemistry. RESULTS: VEGF expression in 6-week HBO samples was elevated compared to NBO (P = .012). Staining of the 12-week HBO samples was reduced compared to 6-week HBO (P = .008) and was similar to 6- and 12-week NBO control samples. CONCLUSION: HBO therapy resulted in increased VEGF expression in the defects even 2 weeks after the termination of treatment (6 weeks postsurgery).

An evaluation of hydroxyapatite and biphasic calcium phosphate in combination with Pluronic F127 and BMP on bone repair.

Calcium phosphates like hydroxyapatite (HA), beta-tricalcium phosphate (beta-TCP), and their mixtures (biphasic calcium phosphates; BCP) are used clinically to repair bone defects. These materials can be difficult to handle and have no inherent biological activity. Handling properties of other bone substitute materials have been improved by combining them with an inert carrier such as Pluronic F-127 (Pluronic, BASF, Mt. Olive, NJ), while the addition of bone morphogenetic proteins (BMP) with such implants has also been shown to enhance bone repair. This study assessed the impact of adding Pluronic and BMPs to an HA (C-Graft) or a BCP (80/20 HA/beta-TCP ratio; Algisorb) implant's ability of promote bony repair in the rabbit calvarial defect model.Twenty-five New Zealand white rabbits were divided into 5 groups of 5 animals each. Bilateral calvarial defects were made in the parietal bones of each animal. HA or BCP alone or combined with Pluronic and/or BMP were implanted into the defect sites. Animals were euthanized at 6 weeks, postoperatively. Bone regeneration was evaluated quantitatively by histomorphometry. The amount of bone regeneration, which occurred in defects containing HA and BCP, was similar over the time period studied. Incorporating Pluronic increased handling and moldability without compromising osteoconductivity of either calcium phosphate. The addition of BMP significantly increased the amount of new bone formed with all calcium phosphates studied (P < 0.05). These results suggest that Pluronic can be added to calcium phosphates to enhance handling and moldability without any negative effects on their biocompatibility and that healing can be enhanced with the incorporation of BMPs.