Improved Bone Formation Research Articles

Effect of platelet‐rich plasma on bone healing of autogenous bone grafts in critical‐size defects

This study histologically analysed the effect of autogenous platelet-rich plasma (PRP), prepared according to a new semiautomatic system, on healing of autogenous bone (AB) grafts placed in surgically created critical-size defects (CSD) in rabbit calvaria. Sixty rabbits were divided into three groups: C, AB and AB/PRP. A CSD was created in the calvarium of each animal. In Group C (control), the defect was filled by blood clot only. In Group AB (autogenous bone graft), the defect was filled with particulate autogenous bone. In Group AB/PRP (autogenous bone graft with platelet-rich plasma), it was filled with particulate autogenous bone combined with PRP. All groups were divided into subgroups (n=10) and euthanized at 4 or 12 weeks post-operatively. Histometric and histologic analyses were performed. Data were statistically analysed (anova, t-test, p<0.05). Group C presented significantly less bone formation compared with Group AB and AB/PRP in both periods of analysis (p<0.001). At 4 weeks, Group AB/PRP showed a statistically greater amount of bone formation than Group AB (64.44 +/- 15.0%versus 46.88 +/- 14.15%; p=0.0181). At 12 weeks, no statistically significant differences were observed between Groups AB and AB/PRP (75.0 +/- 8.11%versus 77.90 +/- 8.13%; p>0.05). It is notable that the amount of new bone formation in Group AB/PRP at 4 weeks was similar to that of Group AB at 12 weeks (p>0.05). Within its limitation, the present study has indicated that (i) AB and AB/PRP significantly improved bone formation and (ii) a beneficial effect of PRP was limited to an initial healing period of 4 weeks.

Differential Effects of Growth Hormone and Alfa Calcidol on Trabecular and Cortical Bones in Hypophysectomized Rats

Growth hormone (GH) deficiency in children causes severe growth retardation, vitamin D deficiency, and osteopenia. We investigated whether alfacalcidol (1OHD) alone or in combination with GH can improve bone formation. Forty hypophysectomized female rats (HX) at the age of 8 wk were divided into HX, HX + 1OHD (oral 0.25 microg/kg daily), HX+GH (0.666 mg/0.2 mL SC daily) and HX+GH + 1OHD groups for a 4-wk study. Results showed that GH increased body weight, bone area, bone mineral content (BMC), and bone mineral density (BMD), whereas 1OHD only increased BMC and BMD. In cortical bone, GH increased both periosteal and endocortical bone formation resulting in a significant increase in cortical size and area in percentage, whereas 1OHD suppressed endocortical erosion surface per bone surface (ES/BS) without a significant effect on bone formation rate per bone surface (BFR/BS). In trabecular bone, GH mitigated the bone loss by increasing BFR/BS, whereas the 1OHD effect was by suppression of trabecular bone turnover in the HX rats. The combination of GH and 1OHD had no additive effect on increasing trabecular bone mass. In conclusion, GH activates new bone formation and increases bone turnover whereas 1OHD suppresses bone turnover. The combination intervention does not seem to provide any additive benefit.

The effect of an rhBMP-2 absorbable collagen sponge-targeted system on bone formation in vivo

Reparation of bone defects remains a major clinical and economic concern, with more than 3 million bone grafts performed annually only in the United States and the EU. The search for alternatives to autologous bone grafting led to the approval by the FDA of an absorbable collagen carrier combined with rhBMP-2 for the treatment of certain bone diseases and fractures. The present work is focused on the production of a collagen-targeted rhBMP-2 based system to improve bone formation. We produced a modified rhBMP-2 with only an additional collagen-binding decapeptide derived from the von Willebrand factor and tested its affinity to collagen and its ability to induce ectopic bone formation in vivo when implanted in combination with absorbable collagen sponges or hydroxyapatite. The results showed not only that the rhBMP2–CBD had an increased affinity to collagen, but also that this binding was very stable during a prolonged period of time. In vivo experiments demonstrated that this rhBMP2–CBD maintained its osteoinductive activity, being capable of inducing new bone formation even at lower concentrations than native rhBMP-2. These results indicate that the combination of the fusion protein with absorbable collagen may be a suitable and safer alternative to rhBMP-2 for bone repair purposes.

Enhancement of bone formation in hydroxyapatite implants by rhBMP‐2 coating

The combination of hydroxyapatite (HA) implants serving as osteoconductive scaffold with growth factors is an interesting approach for the improvement of bone defect healing. The purpose of this study was to test whether recombinant human bone morphogenetic protein-2 (rhBMP-2) coating of solid HA-implants improves bone formation in a cortical bone defect. Cylindrical trephine mill defects (diameter: 9.8 mm, depth: 10 mm) were created into the cortical tibia shaft of minipigs and subsequently filled either by plain HA cylinders (Endobon) or by rhBMP-2-coated HA cylinders. Fluorochrome labeling for the evaluation of time-dependent bone formation was done on days 8, 9, and 10 postsurgery with tetracyclin-100, at days 25 and 30 with alizarin-komplexon, and finally on days 32, 37, 73, and 79 with calcein green. Twelve weeks after implantation, the tibiae were harvested and were prepared for standard histological staining, fluorochrome analysis, and histomorphometry. Coating of HA implants with rhBMP-2 led to significant enhanced new bone formation of 84.7% (+/-4.6%) of the implant area with almost complete bony incorporation compared with only 27.7% (+/-8.5%) in the uncoated HA implants (p = 0.028). In both types of implants, osteoconduction of HA led to bone ingrowth of the surrounding host bone into the implants. However, only rhBMP-2-coated implants showed multitopic de novo bone formation reflecting the osteoinductive properties of rhBMP-2 in all areas of the HA implant. This study showed that the coating of HA ceramic implants with rhBMP-2 can significantly enhance new bone formation attributable to its osteoinductive effects.

Bortezomib-Thalidomide-Dexamethasone as Primary Induction Therapy for Newly Diagnosed Multiple Myeloma Significantly Decreases Bone Resorption While Sparing Bone Formation as Compared to Thalidomide-Dexamethasone

Bone disease occurs in approximately 80% of patients with newly diagnosed multiple myeloma (MM) and is caused by the interaction of the neoplastic clone with bone marrow microenvironment, ultimately resulting in an altered balance between bone resorption and bone formation. It has been previously reported that therapies aimed at eradicating the myeloma clone could contribute to decrease bone resorption, even though bone formation remains impaired even in responding patients, due to the use of high-dose steroids. It has been recently demonstrated, both in vitro and in animal models, that Bortezomib improves bone formation by stimulating osteoblasts. In order to test whether this activity was retained also in vivo, we evaluated markers of bone resorption (serum crosslaps) and bone formation (serum osteocalcin-OC and bone alkaline phosphatase - BAP) in a series of patients who were enrolled in the “Bologna 2005” phase III clinical trial at our Center. By study design, after registration patients were randomized to receive three 21-days courses of induction therapy with either VTD (Bortezomib, 1.3 mg/sqm on d 1, 4, 8, and 11, plus Dexamethasone, 40 mg on each day of and after Bortezomib administration plus Thalidomide 200 mg/d from d 1 to 63.) or TD (Thalidomide as in VTD and Dexamethasone 40 mg/d on d 1–4 and 9–12 of every 21-d cycle), prior to stem cell collection and double autologous stem cell transplantation. As of January 2008, 27 patients (19 male and 8 female, median age = 57.5 yrs) entered the sub-study; of these, 15 and 12 patients were randomized in the VTD and TD arm, respectively. At diagnosis, both groups of patients showed a marked increase in serum crosslaps as compared to upper baseline limit (7321±1445pmol/L in the VTD arm and 11140±2576pmol/L in the TD arm) while both OC and BAP were reduced as compared to lower baseline limits. After completion of the induction therapy, serum crosslaps were significantly decreased in both treatment groups (2747±319pmol/L in VTD arm, p=0.007; 3686±1084pmol/L in the TD arm, p=0.0015). In the TD group a significant further reduction in bone formation markers was also observed (42% reduction in serum OC and 30% in BAP, p=0.03 and 0.04 as compared to pre-treatment values); on the contrary, in the VTD arm both OC and BAP were not significantly decreased as compared to baseline values (15% and 11% for OC and BAP, respectively). These data suggest that incorporation of Bortezomib into induction therapy counteracts the inhibitory effects of high-dose steroids on osteoblastogenesis, thus sparing bone formation.

Reducing Limping by Tibial Lengthening Along Nails in Adult Unilateral Developmental Dysplasia of the Hip with High Dislocation

Background/Purpose Treatment of adult neglected developmental dysplasia of the hip (DDH) with high dislocation is still not established. The main concern of young patients is leg-length discrepancy (LLD), which leads to limping gait and impaired body image. Such patients usually ask for a minimally invasive treatment that can improve the LLD. Methods Between 1993 and 2003, 17 patients with neglected DDH with high dislocation (mean age, 22.8 years) were treated by tibial lengthening using the Ilizarov external fixator over an intramedullary nail. The inclusion criteria were unmarried young adults, unilateral lesion, significant limping or unsightly gait with psychologic discomfort, marked shortening > 4 cm with the block test, and benefit from a shoe-lift. Exclusion criteria were patients older than 30 years, hip pain as the chief complaint, and compensated low hip dislocation without significant limping. Results All 17 patients had eventual bone consolidation without further operation. The mean external fixation index was 14.2 day/cm. Bone formation was good in all patients with a mean consolidation index of 57.7 day/cm. At an average follow-up period of 7.8 years, the limping was much improved from a moderate or severe degree to a mild degree in all patients. No patients had equinus contracture. All patients were satisfied with their treatment results. There were two complications: transient loss of big toe extension and mild wound infection. Conclusion Tibial lengthening can improve limping in adult patients with neglected DDH and high dislocation with a low morbidity. Lengthening along intramedullary nails can effectively reduce the external fixation time, improve bone formation, and prevent complications.

Healing patterns of critical size bony defects in rat following bone graft

The aim of the present study was to evaluate the healing patterns of critical size calvarial bony defects treated with different bone substitutes and to compare them to an autogenous graft and an ungrafted control group. Thirty-six Sprague-Dawley rats (200-230 g) were used. A periosteal flap was raised and an 8 mm defect was trephined. Rats were divided into six groups and treated as follows: group 1 was treated with a deproteinized bovine xenograft (XO), group 2 was treated with a bovine xenograft and covered with a resorbable membrane (XOCM), defects in group 3 were filled with a decalcified freeze-dried bone allograft (DFDBA), group 4 was treated with a composite bone substitute made of bovine xenograft and collagen (XOC), group 5 was filled with autogenous bone (AUTO), and group 6 was left untreated (control). The animals were euthanized at 2 months. Mean bone formation was 2.97 +/- 1.82 mm2 in group 5 (AUTO) followed by 2.93 +/- 1.93 mm2 in group 3 (DFDBA) and 2.25 +/- 1.94 mm2 in group 4 (XOC). Groups 1, 2, and 6 (XO, XOCM, and control, respectively) were not significantly different (p > 0.05) with a mean bone formation of 1.97 +/- 1.64, 1.87 +/- 1.07, and 1.85 +/- 1.04 mm2, respectively. This work confirmed the superiority of autogenous bone when it comes to bone grafting. Nevertheless, some bone substitutes can improve bone formation when compared to the control. New bone substitutes with growth factors to improve their abilities to induce bone formation should be experimented.

Mesenchymal stem cells and platelet‐rich plasma enhance bone formation in sinus grafting: a histomorphometric study in minipigs

Autologous, allogenic, and alloplastic materials for sinus augmentation have specific drawbacks, which has stimulated an ongoing search for new materials and tissue-engineering constructs. We investigated whether mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) seeded on a fluorohydroxyapatite (FH) scaffold can improve bone formation and bone-to-implant contact (BIC) in maxillary sinus grafting. Bilateral sinus augmentation procedures were performed in eight minipigs. MSCs, PRP, and FH scaffold (test site) or FH alone (control site) were grafted in each maxillary sinus. Distal to the osteotomy, one dental implant per sinus was placed in the grafting material through the facial sinus wall. The animals were killed 3 months after grafting, and block sections of the implant sites were harvested and prepared for histomorphometric analysis. After 12 weeks, a significant increase in bone formation occurred in the test sites compared with the control sites (42.51%versus 18.98%; p=0.001). In addition, BIC was significantly greater in the test sites compared with the control sites in the regenerated area (23.71%versus 6.63%; p=0.028). These findings show that sinus augmentation with MSCs-PRP, combined with FH may enhance bone formation and osseointegration of dental implants compared with FH alone in minipigs.

In vivo evaluation of bioactive glass foams associated with platelet-rich plasma in bone defects

The objective of this study was to evaluate the use of bioactive glass foams produced by the sol-gel process, associated or not with platelet-rich plasma (PRP), in the regeneration of bone defects. Mongrel dogs (n = 14) were divided into two groups after having their superior first premolar removed. A small piece of vestibular bone from the alveolus was intentionally removed. The area was filled with bioactive glass foam produced by the sol-gel method. Two groups were tested: group A was the glass foam; group B was the same material associated with PRP, prepared from each animal. The other side of alveolar bone was used as a control group, in which the bone defect did not receive any biomaterial. The thickness of the bone area was measured before and after the intervention. After a period of 60 days implantation, the right and left bones were measured again, and a bone biopsy on both regions was conducted for histological analysis. The findings show an increase of bone thickness for both materials implanted compared to the control group. Group B, implanted with bioactive glass foam associated with PRP, showed a thicker bone area compared to Group A. Histological results indicate bone formation for both materials used. However, the bioactive glass associated with PRP gave rise to a more mature bone formation. These results show that bioactive glass foams processed by a sol-gel method is effective in maintaining the thickness of the alveolar ridge, and the use of PRP associated with the foams improve bone formation.

Prospective In Vivo Identification of Osteogenic Stem/Progenitor Cells from Bone Marrow-Derived Lin−/Sca-1+/CD45− Cells.

We previously developed an in vivo prospective assay for identification of non-cultured cells with MSC potential. Using this assay we identified a population of cells that were slowly cycling and of low density that were capable of multilineage differentiation both in vitro and in vivo (Z. Wang et al, Stem Cells. 2006 24(6):1573). Further characterization of these cells suggested that they resemble a homogenous population of rare Lin−/Sca-1+/CD45− cells that have the morphology and express several markers of undifferentiated embryonic-like stem cells. In vitro the Lin−/Sca-1+/CD45− cells may differentiate into cells from all three germ-layers (M. Kucia et al, Leukemia. 2007 21(2):297). To determine the in vivo fate of this population, we transplanted 500 or 5,000 Lin−/Sca-1+/CD45− cells from a GFP mouse into SCID mice in each group (n=3) immediately after cell sorting to evaluate tissue generation in vivo. At 4 weeks the regenerative potential of these populations was evaluated by micro-CT and histology, and cells were tracked by gross examination of the harvested tissues by fluorescent microscopy. The results showed that a large number of GFP+ cells are located in the implants, indicating that the transplanted cells maintain the ability to contribute to the generation of new tissue. Bone-like tissue was observed in the Lin−/Sca-1+/CD45− group with as low as 500-cells/implant, while 5,000 Lin−/Sca-1+/CD45− cells generated significantly larger mineralized tissue volume, which was confirmed by micro-CT. Lin−/Sca-1+/CD45+ cell only implantation did not form any mineralized tissue, however, while mixed with 2x106 whole bone morrow cells, positive mineralized tissue occurred. Whole bone marrow mixture also improve bone formation in Lin−/Sca-1+/CD45− cell implants compared the actual bone volumes measured by micro-CT. This study demonstrates that non-cultured BM-derived Lin−/Sca-1+/CD45− cells exhibit the capacity to form bone in vivo with as low as 500 cells/implant. Whole bone marrow mixtures can enhance the bone formation, presumably through the interaction of other populations cells. Based on these findings, it is proposed that non-cultured BM-derived Lin−/Sca-1+/CD45− cells are enriched osteogenic cells that can be applied to bone regeneration in vivo.

Noncanonical Wnt-4 Signaling Enhances Bone Regeneration of Mesenchymal Stem Cells in Craniofacial Defects through Activation of p38 MAPK

Mesenchymal stem cells (MSCs) are multipotent cells that can be differentiated into osteoblasts and provide an excellent cell source for bone regeneration and repair. Recently, the canonical Wnt/beta-catenin signaling pathway has been found to play a critical role in skeletal development and osteogenesis, implying that Wnts can be utilized to improve de novo bone formation mediated by MSCs. However, it is unknown whether noncanonical Wnt signaling regulates osteogenic differentiation. Here, we find that Wnt-4 enhanced in vitro osteogenic differentiation of MSCs isolated from human adult craniofacial tissues and promoted bone formation in vivo. Whereas Wnt-4 did not stabilize beta-catenin, it activated p38 MAPK in a novel noncanonical signaling pathway. The activation of p38 was dependent on Axin and was required for the enhancement of MSC differentiation by Wnt-4. Moreover, using two different models of craniofacial bone injury, we found that MSCs genetically engineered to express Wnt-4 enhanced osteogenesis and improved the repair of craniofacial defects in vivo. Taken together, our results reveal that noncanonical Wnt signaling could also play a role in osteogenic differentiation. Wnt-4 may have a potential use in improving bone regeneration and repair of craniofacial defects.

The Effect of Osteoclastic Activity on Tendon-to-Bone Healing

Healing of a tendon graft in a bone tunnel depends on bone ingrowth into the interface between tendon and bone. Excessive osteoclastic activity may contribute to bone resorption, tunnel widening, and impaired healing. We hypothesized that inhibition of osteoclastic activity by osteoprotegerin (OPG) would increase bone formation around a tendon graft in anterior cruciate ligament reconstruction in a rabbit model, while increased osteoclastic activity due to the application of receptor activator of nuclear factor-kappa B ligand (RANKL) would impair bone ingrowth. Sixty skeletally mature, male New Zealand White rabbits underwent bilateral anterior cruciate ligament reconstruction. OPG (100 microg per tunnel) or RANKL (10 microg per tunnel) was delivered to the tendon-bone interface with use of a synthetic calcium phosphate carrier vehicle. Twenty animals were killed at two, four, and eight weeks after surgery. Two rabbits from each group were prepared for histological evaluation, and the other rabbits were used for biomechanical testing. A significantly greater amount of bone surrounded the tendon at the healing tendon-bone interface in the OPG-treated limbs compared with the controls and the RANKL-treated limbs at all time-points (p < 0.05). There were significantly fewer osteoclasts in the OPG-treated limbs compared with the controls and the RANKL-treated limbs (p < 0.05). The average tunnel area in the OPG group was significantly smaller than that in the RANKL group (p = 0.003 at two weeks and p = 0.004 at four weeks). The femur-anterior cruciate ligament-tibia complex of the OPG-treated limbs had significantly increased stiffness compared with RANKL-treated limbs at eight weeks (p = 0.04). Osteoprotegerin significantly improves bone formation around the grafted tendon and improves the stiffness at the healing tendon-bone junction in a rabbit model.

Effects of Granule Size on the Osteoconductivity of Bovine and Synthetic Hydroxyapatite: A Histologic and Histometric Study in Dogs

Two bovine hydroxyapatites (BHAs), one with granule size of 150 to 200 microm and one with granule size of 300 to 329 micro, and 2 synthetic hydroxyapatites (SHAs), with granule size of 150 and 300 microm, respectively, were compared for effectiveness in repairing circumferential bone defects in dogs. The hydroxyapatites (HAs) were characterized through powder x-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Three trephined bone defects (5.0 mm wide x 4 mm long) were created in the humeruses of 8 dogs. In a random manner, the defects on each side were treated with either BHA with small granules (BHA[s]), BHA with large granules (BHA[L]), SHA with small granules (SHA[s]), SHA with large granules (SHA[L]), or left to heal unaided (bilateral control). Four dogs were sacrificed after 6 and 12 postoperative weeks, respectively. Ground sections of each defect were submitted to histologic and histomorphometric analysis (percentage of area occupied by bone, bone marrow, and biomaterial). As a rule, the HA granules exhibited direct bone contact, regardless of the origin and the size of the granules. Control sites were related and had an increased amount of connective tissue infiltration. At 12 weeks, BHA(s) exhibited improved bone formation compared with SHA(s) and SHA(L). The SHA(s) delivered reduced amounts of bone compared with the remaining groups (control included). The area of bone measured in BHA(s) sites was significantly higher at 12 weeks than 6 weeks. The XRD revealed the tested HA samples to be highly crystalline, while BHA appeared with rougher surface at SEM analysis. The BHA(s) performed better than the SHA(s) and SHA(L), as assessed by the amount of bone measured in both implantation sites at 12 weeks. The BHA's material characteristic itself rather than granules size accounted for the distinctive biological behavior. The increased roughness of the BHAs' surface, as assessed through SEM, seemed to benefit the osteoconduction process.

The Effect of Osteoclastic Activity on Tendon-to-Bone Healing

Background: Healing of a tendon graft in a bone tunnel depends on bone ingrowth into the interface between tendon and bone. Excessive osteoclastic activity may contribute to bone resorption, tunnel widening, and impaired healing. We hypothesized that inhibition of osteoclastic activity by osteoprotegerin (OPG) would increase bone formation around a tendon graft in anterior cruciate ligament reconstruction in a rabbit model, while increased osteoclastic activity due to the aplication of receptor activator of nuclear factor-kappa B ligand (RANKL) would impair bone ingrowth. Methods: Sixty skeletally mature, male New Zealand White rabbits underwent bilateral anterior cruciate ligament reconstruction. OPG (100 μg per tunnel) or RANKL (10 μg per tunnel) was delivered to the tendon-bone interface with use of a synthetic calcium phosphate carrier vehicle. Twenty animals were killed at two, four, and eight weeks after surgery. Two rabbits from each group were prepared for histological evaluation, and the other rabbits were used for biomechanical testing. Results: A significantly greater amount of bone surrounded the tendon at the healing tendon-bone interface in the OPG-treated limbs compared with the controls and the RANKL-treated limbs at all time-points (p < 0.05). There were significantly fewer osteoclasts in the OPG-treated limbs compared with the controls and the RANKL-treated limbs (p < 0.05). The average tunnel area in the OPG group was significantly smaller than that in the RANKL group (p = 0.003 at two weeks and p = 0.004 at four weeks). The femur-anterior cruciate ligament-tibia complex of the OPG-treated limbs had significantly increased stiffness compared with RANKL-treated limbs at eight weeks (p = 0.04). Conclusions: Osteoprotegerin significantly improves bone formation around the grafted tendon and improves the stiffness at the healing tendon-bone junction in a rabbit model. Clinical Relevance: Inhibition of excessive osteoclastic activity may improve tendon-to-bone healing.

Effect of local delivery of alendronate on bone formation in bioactive glass grafting in rats

The aim of this study was to investigate whether local delivery of alendronate could improve bone formation after bioactive glass grafting in rat mandible. Twenty-six male Sprague-Dawley rats were divided into control and experimental groups (13 rats/group). A surgical defect was created on the angle of mandible of each animal. In the experimental group, a bioactive glass soaked with the alendronate solution was placed in the bone defect, and in the control group the bioactive glass soaked with saline was used. All animals were killed after 4 weeks. The number of osteoclasts and the amount of new bone formation were evaluated and compared. Four weeks after surgery, the experimental group had significantly more bone formation than the control groups (P < .05). However, no statistically significant difference was found between the groups when the numbers of osteoclasts were compared. Histologic results showed that a single dose of local delivery of alendronate improves bone formation. However, further studies are required to elucidate the effect of local delivery of alendronate on bone formation in humans.

Locally administered low-dose alendronate increases bone mineral density during distraction osteogenesis in a rabbit model

We investigated the effect of locally administered bisphosphonate on distraction osteogenesis in a rabbit model and evaluated its systemic effect. An osteotomy on the right tibia followed by distraction for four weeks was performed on 47 immature rabbits. They were divided into seven equal groups, with each group receiving a different treatment regime. Saline and three types of dosage of alendronate (low, 0.75 microg/kg; mid, 7.5 microg/kg and high 75 microg/kg) were given by systemic injection in four groups, and saline and two dosages (low and mild) were delivered by local injection to the distraction gap in the remaining three groups. The injections were performed five times weekly during the period of distraction. After nine weeks the animals were killed and image analysis and mechanical testing were performed on the distracted right tibiae and the left tibiae which served as a control group. The local low-dose alendronate group showed a mean increase in bone mineral density of 124.3 mg/cm(3) over the local saline group (analysis of variance, p < 0.05) without any adverse effect on the left control tibiae. The findings indicate that the administration of local low-dose alendronate could be an effective pharmacological means of improving bone formation in distraction osteogenesis.

Hybrid composites of calcium phosphate granules, fibrin glue, and bone marrow for skeletal repair

Synthetic bone substitutes, such as calcium phosphate ceramics, give good results in clinical applications. In order to adapt to surgical sites, bioceramics come in the form of blocks or granules, and are either dense or porous. Combining these bioceramics with fibrin glue provides a mouldable and self-hardening composite biomaterial with the biochemical properties of each component. Critical-sized defects in the femoral condyle of rabbits were filled with TricOs/fibrin glue/bone marrow hybrid/composite material. The TricOs granules (1-2 mm) were composed of hydroxyapatite and beta tricalcium phosphate (60/40 in weight). The fibrin glue was composed of fibrinogen, thrombin and other biological factors and mixed with MBCP granules either simultaneously or sequentially. Bone marrow was also added to the MBCP/fibrin composite prior to filling the defects. After 3, 6, 12, and 24 weeks of implantation, the newly-formed bone was analysed with histology, histomorphometry and mechanical tests. The newly-formed bone had grown centripetally. Simultaneous application of fibrin glue showed better results for mechanical properties than sequential application after 6 weeks. Around 40% of bone had formed after 24 weeks in the three groups. Although the addition of bone marrow did not improve bone formation, the MBCP/fibrin material could be used in clinical bone filling applications.

Prevention of osteoporosis by foods and dietary supplements. Magnesium and bone metabolism

About half the total magnesium (Mg) of the body is existed in bone. Bone is one of the main Mg pools in the body. Epidemiologic studies have demonstrated a positive correlation between Mg intake and bone mineral density. It is also reported that Mg deficiency induced a decrease in osteoblasts number, an increase in osteoclasts number and a decrease in bone strength in rats. In contrast, dietary Mg supplementation improved bone formation, bone resorption and bone strength in ovariectomized rats. Mg deficiency is known as a risk factor for osteoporosis, since Mg is essential mineral for normal bone growth. However, the detail of effects of Mg on bone metabolism remains unclear. Further studies should be developed to clarify the details.

Alginate Hydrogels as Biomaterials

[Image: see text] Alginate hydrogels are proving to have a wide applicability as biomaterials. They have been used as scaffolds for tissue engineering, as delivery vehicles for drugs, and as model extracellular matrices for basic biological studies. These applications require tight control of a number of material properties including mechanical stiffness, swelling, degradation, cell attachment, and binding or release of bioactive molecules. Control over these properties can be achieved by chemical or physical modifications of the polysaccharide itself or the gels formed from alginate. The utility of these modified alginate gels as biomaterials has been demonstrated in a number of in vitro and in vivo studies.Micro-CT images of bone-like constructs that result from transplantation of osteoblasts on gels that degrade over a time frame of several months leading to improved bone formation.

Heat‐treated BMP‐2 depots release BMP‐2 in its bioactive form

AbstractSmall depots of locally fixed bone morphogenetic protein‐2 (BMP‐2), which were dried onto biocompatible carriers and afterwards heat‐treated, induce a local differentiation of contacting osteoblastic cells. Here we investigate whether such depots may act via a release of bioactive BMP‐2. For in vivo experiments we employed a modified gap‐healing approach using dump bell‐shaped implants made from titanium plasma‐sprayed Ti‐6Al‐4V, which were coated with BMP‐2 at only one side. Four weeks after implantation into the cancellous bone of the lateral femur condylus of adult sheep we observed a polar formation of new trabecular bone close to the side where BMP‐2 had been immobilized. We also tested whether BMP‐2 depots stimulate remote cells under cell culture conditions and found that alkaline phosphatase (ALP) of MC3T3‐E1 cells was induced over a distance of several millimetres. Experiments show that BMP‐2 at least in part desorbs from air‐dried and heat‐treated BMP‐2 depots in its bioactive form. Local depots of BMP‐2 may therefore allow to improve bone formation next to metal implants at predefined sites.