Bone formation in rat calvaria ceases within a limited period regardless of completion of defect repair

Repair of critical-sized bone defects in rabbit femurs using graphitic carbon nitride (g-C3N4) and graphene oxide (GO) nanomaterials

Various biomaterials have been evaluated to enhance bone formation in critical-sized bone defects; however, the ideal scaffold is still missing. The objective of this study was to investigate the in vitro and in vivo regenerative capacity of graphitic carbon nitride (g-C₃N₄) and graphene oxide (GO) nanomaterials to stimulate critical-sized bone defect regeneration. The in vitro cytotoxicity and hemocompatibility of g-C₃N₄ and GO were evaluated, and their potential to induce the in vitro osteogenesis of human fetal osteoblast (hFOB) cells was assessed using qPCR. Then, bone defect in femoral condyles was created in rabbits and left empty as control or filled with either g-C₃N₄ or GO. The osteogenesis of the different implanted scaffolds was evaluated after 4, 8, and 12 weeks of surgery using X-ray, computed tomography (CT), macro/microscopic examinations, and qPCR analysis of osteocalcin (OC) and osteopontin (OP) expressions. Both materials displayed good cell viability and hemocompatibility with enhanced collagen type-I (Col-I), OC, and OP expressions of the hFOB cells. Compared to the control group, the bone healing process in g-C₃N₄ and GO groups was promoted in vivo. Moreover, complete healing of the bone defect was observed radiologically and grossly in g-C₃N₄ implanted group. Additionally, g-C₃N₄ implanted group showed higher percentages of osteoid tissue, mature collagen, biodegradation, and expressions of OC and OP. In conclusion, our results revealed that g-C₃N₄ and GO nanomaterials could induce osteogenesis in critical-sized bone defects.

The administration of bovine hydroxyapatite-alendronate implant accelerates bone defect healing in an osteoporotic rat

BACKGROUND

Bone fracture is the main consequence of osteoporosis, which may become a neglected disease.

OBJECTIVE

This study aims to fabricate bovine hydroxyapatite-gelatine (BHA-GEL) based bone-implant with alendronate (ALE) in vivo.

METHODS

Wistar rats were used for an osteoporotic animal model induced by ovariectomy. There were three groups: negative control, BHA-GEL implant, and BHA-GEL-ALE implant. Each group performed a defect by drilling the femur (diameter of 2.2 mm and depth of 2 mm). Observations on the closure of bone defects were performed by X-ray radiography at the second and sixth week after surgery. The mechanism of bone healing was observed by using hematoxylin-eosin (HE) staining and immunohistochemical technique with anti-vascular endothelial growth factor (VEGF) and anti-alkaline phosphatase (ALP) antibodies.

RESULTS

The radiograph examination showed the implanted group had accelerated bone growth. In addition, the osteoblast, osteoclast and osteocyte had accelerated migration to the defect area. Moreover, the immunoreactive score (IRS) of VEGF at the sixth week in the BHA-GEL-ALE group was lower than the other groups. Meanwhile, the IRS of ALP in BHA-GEL-ALE was higher compared to other groups.

CONCLUSION

The BHA-GEL-ALE implant accelerates the healing of bone defect in the osteoporotic rat by increasing the ALP expression and the total number of cells.

Enhancement of critical-sized bone defect regeneration using UiO-66 nanomaterial in rabbit femurs

Background

Repair of large-sized bone defects is a challengeable obstacle in orthopedics and evoked the demand for the development of biomaterials that could induce bone repair in such defects. Recently, UiO-66 has emerged as an attractive metal–organic framework (MOF) nanostructure that is incorporated in biomedical applications due to its biocompatibility, porosity, and stability. In addition, its osteogenic properties have earned a great interest as a promising field of research. Thus, the UiO-66 was prepared in this study and assessed for its potential to stimulate and support osteogenesis in vitro and in vivo in a rabbit femoral condyle defect model. The nanomaterial was fabricated and characterized using x-ray diffraction (XRD) and transmission electron microscopy (TEM). Afterward, in vitro cytotoxicity and hemolysis assays were performed to investigate UiO-66 biocompatibility. Furthermore, the material in vitro capability to upregulate osteoblast marker genes was assessed using qPCR. Next, the in vivo new bone formation potential of the UiO-66 nanomaterial was evaluated after induction of bone defects in rabbit femoral condyles. These defects were left empty or filled with UiO-66 nanomaterial and monitored at weeks 4, 8, and 12 after bone defect induction using x-ray, computed tomography (CT), histological examinations, and qPCR analysis of osteocalcin (OC) and osteopontin (OP) expressions.

Results

The designed UiO-66 nanomaterial showed excellent cytocompatibility and hemocompatibility and stimulated the in vitro osteoblast functions. The in vivo osteogenesis was enhanced in the UiO-66 treated group compared to the control group, whereas evidence of healing of the treated bone defects was observed grossly and histologically. Interestingly, UiO-66 implanted defects displayed a significant osteoid tissue and collagen deposition compared to control defects. Moreover, the UiO-66 nanomaterial demonstrated the potential to upregulate OC and OP in vivo.

Conclusions

The UiO-66 nanomaterial implantation possesses a stimulatory impact on the healing process of critical-sized bone defects indicating that UiO-66 is a promising biomaterial for application in bone tissue engineering.

Poly-ε-Caprolactone/Fibrin-Alginate Scaffold: A New Pro-Angiogenic Composite Biomaterial for the Treatment of Bone Defects

We hypothesized that a composite of 3D porous melt-electrowritten poly-ɛ-caprolactone (PCL) coated throughout with a porous and slowly biodegradable fibrin/alginate (FA) matrix would accelerate bone repair due to its angiogenic potential. Scanning electron microscopy showed that the open pore structure of the FA matrix was maintained in the PCL/FA composites. Fourier transform infrared spectroscopy and differential scanning calorimetry showed complete coverage of the PCL fibres by FA, and the PCL/FA crystallinity was decreased compared with PCL. In vitro cell work with osteoprogenitor cells showed that they preferentially bound to the FA component and proliferated on all scaffolds over 28 days. A chorioallantoic membrane assay showed more blood vessel infiltration into FA and PCL/FA compared with PCL, and a significantly higher number of bifurcation points for PCL/FA compared with both FA and PCL. Implantation into a rat cranial defect model followed by microcomputed tomography, histology, and immunohistochemistry after 4- and 12-weeks post operation showed fast early bone formation at week 4, with significantly higher bone formation for FA and PCL/FA compared with PCL. However, this phenomenon was not extrapolated to week 12. Therefore, for long-term bone regeneration, tuning of FA degradation to ensure syncing with new bone formation is likely necessary.

Effects of fibrin sealant and bone fragments on defect regeneration performed on rat tibiae: An experimental study

Fibrin sealant (FS) is a biomaterial that exhibits hemostatic and repairing properties. It has been successfully used as scaffolds and adhesives to improve repair and regeneration of tissues. The objective of this study was to evaluate the effect of FS in the regeneration process of bone defects in male rat tibias through macroscopic, microscopic and mechanical analysis. A bone defect of 2.9 mm was performed on the medial face of the proximal third of the tibia of 40 rats and implanted FS and autologous bone graft (AG). The animals were divided into four groups: animals with bone defect without any treatment (CON), animals treated with fibrin sealant (TFS), animals treated with autologous graft (TAG) and animals treated with fibrin sealant and autologous graft (FSAG). The animals were euthanized 42 days after surgery. Macroscopic analysis showed no difference between the groups (p > 0.05) in relation to tibial weight, but a statistically significant difference (p = 0.005) was observed for their length. Micro-computed tomography (micro-CT) revealed tendentious values regarding bone microarchitecture and FS. Bone mineral densitometry (BMD) showed significance between the FSAG (p = 0.009) and TFS (p = 0.007) groups. The bone mineral content (BMC) presented a significant difference between all groups (p = 0.020). Maximum strength showed a significant difference between the FSAG group (p = 0.007) and the others. The results obtained in relation to the relative stiffness also present a significant difference (p = 0.023). Newly formed bone showed significant differences between groups (p = 0.035). We conclude that bone defect regeneration was directly influenced by the use of FS and AG.

Vertical Alveolar Augmentation Using BMP-2/ACS/Allograft with Printed Titanium Shells to Establish an Early Vascular Scaffold

Traditional reconstruction of major alveolar ridge deficiency has required autogenous cortical cancellous particulate bone grafts, often augmented with particulate allogeneic components. Now there is a new concept to consider, that of orthoalveolar form. This paradigm shift involves components of the tissue engineering triad of inductive growth factors combined with a matrix and stem cells, together with osteotomies or devices designed for space maintenance. Reported here is early experience with computer technology used to redesign deficient alveolar ridges deriving ideal alveolar-shaped bone-forms made from powdered titanium, sintered by laser at high temperature using rapid prototype technology.

Osteogenesis of Crouzon-Mutated Cells in an Experimental Model

Crouzon syndrome is an autosomal-dominant congenital disease due to a mutation in the fibroblast growth factor receptor 2 protein. The purpose of this study is to evaluate wound-healing potential of Crouzon osteoblasts and adipose-derived stem cells (ADSCs) in a murine model. Parietal skull defects were created in Crouzon and mature wild-type (WT) CD-1 mice. One group of WT and Crouzon mice were left untreated. Another group was transplanted with both WT and Crouzon adipose-derived stem cells. Additional groups compared the use of a fibrin glue scaffold and periosteum removal. Skulls were harvested from each group and evaluated histologically at 8-week and/or 16-week periods. Mean areas of defect were quantified and compared via ANOVA F-test. The average area of defect after 8 and 16 weeks in untreated Crouzon mice was 15.37 ± 1.08 cm and 16.69 ± 1.51 cm, respectively. The average area of the defect in untreated WT mice after 8 and 16 weeks averaged 14.17 ± 1.88 cm and 14.96 ± 2.26 cm, respectively. WT mice with autologous ADSCs yielded an average area of 15.35 ± 1.34 cm after 16 weeks while Crouzon mice with WT ADSCs healed to an average size of 12.98 ± 1.89 cm. Crouzon ADSCs transplanted into WT mice yielded an average area of 15.47 ± 1.29 cm while autologous Crouzon ADSCs yielded an area of 14.22 ± 3.32 cm. ANOVA F-test yielded P = .415. The fibroblast growth factor receptor 2 mutation in Crouzon syndrome does not promote reossification of critical-sized defects in mature WT and Crouzon mice. Furthermore, Crouzon ADSCs do not possess osteogenic advantage over WT ADSCs.

Calcification during bone healing in a standardised rat calvarial defect assessed by micro-CT and SEM-EDX

OBJECTIVE

The study was designed to investigate the process of calcification during bone healing in a standardized rat calvarial bone defect model, measured by bone mineral density and the concentrations and distributions of calcium, phosphorus and carbon in the bone matrix.

MATERIALS AND METHODS

A standard defect was made on the parietal bone of 12-week-old rats under anaesthesia. The rats were fixed in weeks 1, 2, 4 and 8,and the calvaria were resected and examined with microcomputed tomography, then frozen and sectioned for histology and analysed with energy-dispersive X-ray spectroscopy (EDX). Parietal bone of 12-week-old control rats was processed similarly.

RESULTS

The mineral density of healing bone increased with time. The healing bone became thicker and denser with time in histology. The distributions of Ca and P expanded over the bone matrix, whereas that of C became localised and complemented that of C and P. The Ca/P concentration ratio increased, whereas the C/Ca and C/P ratios decreased in the healing bone matrix.

CONCLUSION

Healing bone is immaturely calcified initially and proceeds calcification gradually, that is, as the bone volume increases, mineral increases in density and matures in quality, while organic components decrease.

Doses effects of zoledronic acid on mineral apatite and collagen quality of newly-formed bone in the rat's calvaria defect

Due to their inhibitory effects on resorption, bisphosphonates are widely used in the treatment of diseases associated to an extensive bone loss. Yet, little is known about bisphosphonates effects on newly-formed bone quality. In the present study, adult male Sprague-Dawley rats (n=80) with a bone defect calvaria area were used and short-term effects of zoledronic acid (ZA) were studied on the healing bone area. Three ZA treatments were tested by using either: 1°) a low single dose (120μgZA/kg, n=10; equivalent to human osteoporosis treatment), 2°) a low fractionated doses (20μgZA/kg daily for 6days either a total of 120μg/kg, n=15), and 3°) a high fractionated doses, (100μgZA/kg weekly for 6weeks, n=15; equivalent to 6months of human bone metastasis treatment). For each treatment, a control "vehicle" treatment was performed (with an identical number of rats). After ZA administration, the intrinsic bone material properties were evaluated by quantitative backscattered electron imaging (qBEI) and Raman microspectroscopy. Neither single nor fractionated low ZA doses modify the intrinsic bone material properties of the newly-formed bone compared to their respective control animals. On the opposite, the high ZA treatment resulted in a significant decrease of the crystallinity (-25%, P< 0.05) and of the hydroxyproline-to-proline ratio (-30%, P<0.05) in newly-formed bones. Moreover, with the high ZA treatment, the crystallinity was positively correlated with the hydroxyproline-to-proline ratio (ρ=0.78, P<0.0001). The present data highlight new properties for ZA on bone formation in a craniofacial defect model. As such, ZA at high doses disrupted the apatite crystal organization. In addition, we report here for the first time that high ZA doses decreased the hydroxyproline-to-proline ratio suggesting that ZA may affect the early collagen organization during the bone healing.

Comparison of Effects of Pulsed Electromagnetic Field Stimulation on Platelet-Rich Plasma and Bone Marrow Stromal Stem Cell Using Rat Zygomatic Bone Defect Model

BACKGROUND

Reconstruction of bone defects that occur because of certain reasons has an important place in plastic and reconstructive surgery. The objective of the treatments of these defects was to reinstate the continuity of tissues placed in the area in which the defect has occurred. In this experimental study, the effect of pulsed electromagnetic field stimulation on platelet-rich plasma (PRP) and bone marrow stromal cell, which propounded that they have positive impact on bone regeneration, was evaluated with the bone healing rate in the zygomatic bone defect model enwrapped with superficial temporal fascia.

METHODS

After creating a 4-mm defect on the zygomatic bone of the experiments, the defect was encompassed with a superficial temporal fascial flap and a nonunion model was created. After surgery, different combinations of the PRP, bone marrow stromal cell, and electromagnetic field applications were implemented on the defective area. All the experiments were subjected to bone density measurement.

RESULTS

The result revealed that the PRP and pulsed electromagnetic field implementation were rather a beneficial and an effective combination in terms of bone regeneration.

CONCLUSIONS

It was observed that the superficial temporal fascial flap used in the experiment was a good scaffold choice, providing an ideal bone regeneration area because of its autogenous, vascular, and 3-dimensional structures. As a result, it is presumed that this combination in the nonhealing bone defects is a rather useful treatment choice and can be used in a reliable way in clinical applications.

Application of a novel resorbable membrane in the treatment of calvarial defects in rats

Diplen-Gam (DG) is a novel absorbable guided bone regeneration (GBR) membrane. This study was designed to evaluate the capacity of bone repair of DG compared with that of Bio-Gide (BG). Critical size defects were created in both sides of the calcarium of 36 Sprague-Dawley rats. Defects were assigned to six groups and each group was subjected to one of the following treatments: (A1) unfilled defects, (A2) Bio-Oss (BO) grafts, (B1) DG membrane, (B2) BG membrane, (C1) DG membrane + BO grafts and (C2) BG membrane + BO grafts. The animals were killed at 2, 4, 8 and 12 weeks after the operation. The defects and surrounding tissues were examined by gross observation and X-ray examination. The paraffin sections were subjected to HE (hematoxylin and eosin) staining and IHC (immunohistochemistry) for bone morphogenetic protein-2 (BMP-2). The X-rays showed that, at 12 weeks, the DG and BG group exhibited more new bone formation than CSD blank group did; the BG group exhibited more new bone formation than the DG group did (t = 5.240, P = 0.035), the BG + BO group showed no significant differences in bone formation compared with the DG + BO group (t = 1.246, P = 0.339). By IHC staining, BMP-2-positive results could be seen inside the DG membrane, on the surface of the new bone, and inside the new bone. It can be suggested that BG membrane achieved better effects in guided bone regeneration compared with DG membrane. No significant differences were found between the two membranes in their bone healing ability when they are used with BO. Therefore, DG membrane shows clinical effectiveness, but should be used in combination with bone substitute.

Evaluation of Amniotic Multipotential Tissue Matrix to Augment Healing of Demineralized Bone Matrix in an Animal Calvarial Model

Amniotic multipotential tissue matrix (AmnioMTM) is a membrane material derived from placental tissues and rich in growth factors that have been reported to have potential in healing bone. This study hypothesized that demineralized bone matrix (DBM) supplemented with AmnioMTM would accelerate healing and bone formation as compared with DBM alone in a critical size (10 mm) rat calvarial bone defect model. Five DBM grafts and 5 DBM supplemented with AmnioMTM grafts were implanted in a 10-mm critical sized defect in 10 rats (1 implant per rat). After 4 weeks, animals were euthanized and defects evaluated by microCT and histology. There were no statistical differences in microCT data for mineral density, percent bone fill, or bone surface to volume ratios between groups, though the bone surface to volume ratio for the amnio-supplemented group suggested increased osteoid activity as compared with the DBM alone group. Histological data also indicated active osteoid activity and induced bone formation in the center of defects implanted with AmnioMTM supplemented graft as compared with DBM graft alone suggesting some potential osteoinductive potential. However, there was no significant difference at the mean percent of newly mineralized bone in the DBM group defect as compared with the AmnioMTM supplemented graft material. These data suggest that while bone formation was not increased at this early time point, the increased osteoid activity and the induction of new bone in the middle of the defect by the AmnioMTM indicates that further study is needed to assess its potential benefit to bone healing and regeneration.

Transplantation of human-induced pluripotent stem cells carried by self-assembling peptide nanofiber hydrogel improves bone regeneration in rat calvarial bone defects

Objectives/Aims

The requisite conditions for successful bone tissue engineering are efficient stem cell differentiation into osteogenic cells and a suitable scaffold. In this study, we investigated in vivo bone regeneration from transplanted induced pluripotent stem cells (iPSCs).

Materials and Methods

Two critical-sized calvarial bone defects were created in 36 rats. The surgical sites were randomly assigned to one of three treatments to test the healing effectiveness of the scaffold alone, scaffold with iPSCs or a salt solution as a control. The effectiveness of the treatments was evaluated after 2 or 4 weeks using radiographic and histological analyses of bone regeneration in the six groups.

Results

Micro-computed tomography (CT) analysis of the bone defects found minimal bone regeneration with the salt solution and nanofiber scaffold and increased bone regeneration in defects repaired with iPSCs delivered in the nanofiber scaffold.

Conclusion

Transplanted iPSCs encapsulated in a nanofiber scaffold can regenerate bone in critical-sized defects.

Sequential delivery of BMP-2 and BMP-7 for bone regeneration using a heparinized collagen membrane

To investigate the effect of the sequential delivery of bone morphogenetic proteins BMP-2 and BMP-7 on bone regeneration in rat calvarial defects (40 Sprague-Dawley rats, 8mm defect size), all animals were treated with a hydroxyapatite (HA)/tricalcium phosphate (TCP) bone graft covered with a collagen membrane. The experimental groups were as follows: (1) control group: unmodified collagen (no treatment); (2) BMP-2 group: 5 μg of BMP-2; (3) hep-BMP-7 group: 5 μg BMP-7 chemically bound to heparinized collagen; and (4) BMP-2/hep-BMP-7 group: 2.5 μg BMP-7 bound to heparinized collagen and subsequently treated with 2.5 μg BMP-2. Defect healing was examined at 2 and 8 weeks after surgery. The BMP-2 group showed the largest new bone area at week 2 (29.3 ± 7.3%; P = 0.009); new bone areas in the hep-BMP-7 and BMP-2/hep-BMP-7 groups were similar (11.8 ± 3.4% and 12.9 ± 5.71%, respectively; P = 0.917). After 8 weeks, the BMP-2/hep-BMP-7 group showed the largest new bone area (43.3 ± 6.2%), followed by the BMP-2 and hep-BMP-7 groups (P = 0.013). Accordingly, in comparison with single deliveries of BMP-2 and BMP-7, sequential delivery of BMP-2 and BMP-7 using a heparinized collagen membrane significantly induced new bone formation with a smaller quantity of BMP-2 in rat calvarial defects.

Treatment of critical defects produced in calvaria of mice with mesenchymal stem cells

Mesenchymal stem cells (MSC) are present in specialized niches in perivascular regions of adult tissues and are able to differentiate into various cell types, such as those committed to repairing. Bone marrow derived MSC from eight young mice C57BL/ 6 gfp(+) were expanded in culture for repairing critical defects in calvarial bone produced in twenty-four young isogenic adult C57BL/6 mice. The animals were subjected to a cranial defect of 6.0mm diameter and divided into two equal experimental groups. Control group did not receive any treatment and the treated group received a MSC pellet containing 1.0 x 10(7) cells/mL into the defects. The group treated with MSC showed increased angiogenesis and amount of new bone deposited on the defect limits than that observed in the control group. The results demonstrated that transplantation of bone marrow-derived MSC of C57BL/6 gfp(+) mice to bone critical defects produced in mice calvarial contributes positively to the bone repair process. MSC presets ability to influence the correct functioning of osteoblasts, increases the amount of mobilized cells for the repairing process, speeds up growth, and increases deposition of bone matrix.

Association of mesenchymal stem cells with platelet rich plasma on the repair of critical calvarial defects in mice

PURPOSE

To evaluate the effects of mesenchymal stem cells (MSC) from eight mice C57BL/6 gfp(+) bone marrows expanded in cultures associated with platelets rich plasma (PRP) deriving from another eight mice, in the repair of critical defects in calvarial bone produced in twenty-four adult isogenic mice C57BL/6.

METHODS

The animals were submitted to a cranial defect of 6.0mm in diameter and divided into two equal experimental groups. Control group did not receive treatment and the treated group received a MSC pellet containing 1.0 x 10(7) cells/mL associated with 50.0 µL of plasma gel containing 1.0 x 10(9) autologous platelets within the defect.

RESULTS

In the treated group was observed process of angiogenesis and bone repair better than control group.

CONCLUSION

Mesenchymal stem cells derived from bone marrow of C57BL/6 gfp(+) mice associated with PRP gel applied in bone critical defects produced in calvarial contributes positively to the process of bone repair.

Micro-CT observation of angiogenesis in bone regeneration

OBJECTIVES

Restoration of an adequate blood supply is essential for the bone healing process and is key to the success of bone augmentation procedures. In this study, we evaluated angiogenesis in rat calvarial flat bone defects using in vivo microfocus computed tomography (micro-CT).

MATERIALS AND METHODS

Twenty rats were used. The calvarium was exposed and calvarial bone defects of critical (5-mm diameter) and non-critical (2.7-mm diameter) sizes were prepared. Bone regeneration and angiogenesis were evaluated by image analysis using micro-CT and histological examination.

RESULTS

Critical- and non-critical-sized calvarial bone defects showed bone regeneration and angiogenesis around the midsagittal suture. Critical-sized calvarial bone defects showed approximately 1.2% reossification of the original surgical defect, whereas the non-critical-sized defects showed approximately 43.3% reossification at day 28. Furthermore, angiogenesis was observed later in the critical-sized calvarial bone defects (about 38.2%), whereas angiogenesis was observed early in the non-critical-sized calvarial bone defects (about 75.5%) at day 28. New blood vessel networks were observed around defects of both sizes.

CONCLUSIONS

Angiogenesis preceded bone regeneration around critical- and non-critical-sized calvarial bone defects. Angiogenesis led to full bone formation in non-critical-sized defects.

Involvement of sensory neurons in bone defect repair in rats

We investigated bone repair in sensory-denervated rats, compared with controls, to elucidate the involvement of sensory neurons. Nine-week-old male Wistar rats received subcutaneous injections of capsaicin to denervate sensory neurons. Rats treated with the same amount of vehicle served as controls. A standardized bone defect was created on the parietal bone. We measured the amount of repaired bone with quantitative radiographic analysis and the mRNA expressions of osteocalcin and cathepsin K with real-time polymerase chain reaction (PCR). Quantitative radiographic analysis showed that the standard deviations and coefficients of variation for the amount of repaired bone were much higher in the capsaicin-treated group than in the control group at any time point, which means that larger individual differences in the amount of repaired bone were found in capsaicin-treated rats than controls. Furthermore, radiographs showed radiolucency in pre-existing bone surrounding the standardized defect only in the capsaicin-treated group, and histological observation demonstrated some multinuclear cells corresponding to the radiolucent area. Real-time PCR indicated that there was no significant difference in the mRNA expression levels of osteocalcin and cathepsin K between the control group and the capsaicin-treated group. These results suggest that capsaicin-induced sensory denervation affects the bone defect repair.

Rodent models in bone-related research: the relevance of calvarial defects in the assessment of bone regeneration strategies

In vivo research with animal models has been a preferred experimental system in bone-related biomedical research since, by approximation, it allows relevant data gathering regarding physiological and pathological conditions that could be of use to establish more effective clinical interventions. Animal models, and more specifically rodent models, have been extensively used and have contributed greatly to the development and establishment of a wide range of translational approaches aiming to regenerate the bone tissue. In this regard, the calvarial defect model has found great application in basic and applied research, nonetheless the controversial rationalization for the use of critical size defects - defects that are unable to report spontaneous healing - or subcritical size defects in the proposed applications. Accordingly, this work aims to review the advantages and limitations of the use of rodent models in biomedical bone-related research, emphasizing the problematic issues of the use of calvarial critical and subcritical size defects. Additionally, surgical protocols for the establishment of both defects in rat calvarial bone, as well as the description and exemplification of the most frequently used techniques to access the bone tissue repair, are portrayed.

Biocompatibility of adhesive complex coacervates modeled after the sandcastle glue of Phragmatopoma californica for craniofacial reconstruction

Craniofacial reconstruction would benefit from a degradable adhesive capable of holding bone fragments in three-dimensional alignment and gradually being replaced by new bone without loss of alignment or volume changes. Modeled after a natural adhesive secreted by the sandcastle worm, we studied the biocompatibility of adhesive complex coacervates in vitro and in vivo with two different rat calvarial models. We found that the adhesive was non-cytotoxic and supported the attachment, spreading, and migration of a commonly used osteoblastic cell line over the course of several days. In animal studies we found that the adhesive was capable of maintaining three-dimensional bone alignment in freely moving rats over a 12 week indwelling period. Histological evidence indicated that the adhesive was gradually resorbed and replaced by new bone that became lamellar across the defect without loss of alignment, changes in volume, or changes in the adjacent uninjured bone. The presence of inflammatory cells was consistent with what has been reported with other craniofacial fixation methods including metal plates, screws, tacks, calcium phosphate cements and cyanoacrylate adhesives. Collectively, the results suggest that the new bioadhesive formulation is degradable, osteoconductive and appears suitable for use in the reconstruction of craniofacial fractures.