Recombinant human bone morphogenetic protein-type 2 (rhBMP-2) enhances local bone formation in the lumbar spine of osteoporotic sheep

Femoral µCT Analysis, Mechanical Testing and Immunolocalization of Bone Proteins in β-Hydroxy β-Methylbutyrate (HMB) Supplemented Spiny Mouse in a Model of Pregnancy and Lactation-Associated Osteoporosis

A metabolite of leucine, ß-hydroxy-ß-methylbutyrate (HMB), used as a dietary supplement effects muscle tissue gain and bone tissue quality. Since there are no studies on the effects of HMB during pregnancy yet, the aim of the current study was to determine the effects of HMB supplementation during pregnancy on osteoporotic bone quality postpartum and post-lactation using spiny mice (Acomys cahirinus) as the animal models. The six-month-old dams were divided into four groups: pregnant and lactating controls, and pregnant and lactating HMB-treated (during the second trimester of pregnancy) females. The intensity of the immunoreaction of osteocalcin (OC), osteoprotegerin (OPG), bone morphogenetic protein 2 (BMP-2), tissue inhibitor of metalloproteinases 2 (TIMP-2), matrix metalloproteinase 8 and 13 (MMP-8 and MMP-13) and proteins involved in bone turnover, was measured in femoral trabecular and compact bone, as well as in the hyaline and epiphyseal cartilage of the femora. The analysis of the trabecular bone microarchitecture showed that the administration of HMB to pregnant females, by influencing the proteins responsible for bone cell activity and collagen remodeling, can provide protection from bone loss. Based on the results of the current study it can be assumed that HMB administration to pregnant females has a more positive impact on trabecular than compact bone.

Utilization Trends of Recombinant Human Bone Morphogenetic Protein in the United States

STUDY DESIGN

Retrospective.

OBJECTIVE

The aim of this study was to explore the utilization trends of recombinant human bone morphogenetic protein (rh-BMP) in the United States using the largest inpatient administrative database.

SUMMARY OF BACKGROUND DATA

Since 2002, the rh-BMP has been widely used by the surgical spine community in fusion surgery. In light of the rising evidence regarding the safety and efficacy of this novel and expensive bone biological technology, a comprehensive examination of its utilization in the American population is warranted.

METHODS

We queried the 2002-Q3 2015 National Inpatient Sample for patients that underwent spinal fusion with rh-BMP. We calculated population-level estimates of rh-BMP utilization trends per 100,000 spinal fusions. Trends were estimated for the overall use as well as broken down by primary versus revision fusion, fusion type, number of levels, age category, US region, and hospital type.

RESULTS

A total of 5,563,282 fusions were performed, of which 19.9% (n = 1,108,984) utilized rh-BMP. We detected an increase in rh-BMP use in spinal fusion surgery from 0.7% in 2002 to a peak of 29.5% in 2010, followed by a gradual decline till Q3 2015, where it represented 14.7% of all fusion surgeries. These trends paralleled all fusion types. It was most commonly used in fusions spanning two to three levels. The South remained the most common region, whereas West has recently surpassed the Midwest. Its use is becoming more pervasive among older patients, particularly in the 65- to 74 years' age group.

CONCLUSION

Further studies are needed to provide insights into the correlation of these trends with the technology's safety and efficacy profile in contemporary series.Level of Evidence: 3.

In ovariectomy-induced osteoporotic rat models, BMP-2 substantially reversed an impaired alveolar bone regeneration whereas PDGF-BB failed

OBJECTIVES

We previously suggested an ovariectomy (OVX)-induced osteoporotic rat model showing an impaired alveolar bone defect healing. This study aimed to evaluate and compare the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human platelet-derived growth factor-BB (rhPDGF-BB) on alveolar bone defect healing in OVX-induced osteoporotic rats.

MATERIALS AND METHODS

A total of forty-one female rats were divided into four groups: a collagen group (n=10), a PDGF-BB group (n=11), a BMP-2 group (n=10), and a control group (n=10). Four months after OVX, alveolar bone drill-hole defects were created and grafted with collagen gel, rhPDGF-BB/collagen gel, or rhBMP-2/collagen gel. The defects in the control group were not grafted with any material. Defect healing was evaluated by histological, histomorphometric, and microcomputed tomographic (micro-CT) analyses at 2 and 4 weeks.

RESULTS

According to the micro-CT analysis, the BMP-2 group exhibited the greatest bone volume fraction among all groups, while the PDGF-BB group did not show significant differences compared with the collagen group. The histomorphometric analysis showed a significantly larger amount of new bone area in the BMP-2 group than in the control and collagen groups at 4 weeks; however, the PDGF-BB group did not reach significant superiority compared with the other groups.

CONCLUSIONS

Alveolar bone regeneration was significantly enhanced by the local use of rhBMP-2/collagen gel compared with the use of rhPDGF-BB/collagen gel in OVX-induced osteoporotic rats.

CLINICAL RELEVANCE

A treatment modality using rhBMP-2 may be a promising approach to promote alveolar bone regeneration in patients suffering from postmenopausal osteoporosis.

Combination therapy with BMP-2 and psoralen enhances fracture healing in ovariectomized mice

The advantages of combining local delivery of bone morphogenetic protein (BMP)-2 with systemic or local anti-osteoporosis treatments have also been studied for enhancing osteoporotic fracture healing. The aim of the present study was to evaluate the effect of combination therapy with BMP-2 and psoralen on fracture repair in ovariectomized mice. At 6 weeks after bilateral ovariectomy, mice (n=30) underwent unilateral transverse osteotomy on the femur and were divided into 3 groups. In the model group (n=10), animals were implanted with an absorbable collagen sponge (ACS) alone and administered physiological saline intragastrically (i.g.). In the recombinant human (rh)BMP-2 group (n=10), animals were implanted with an ACS loaded with 2.5 µg rhBMP-2 and administered physiological saline i.g. In the psoralen + rhBMP-2 group (n=10) animals were implanted with an ACS loaded with 2.5 µg rhBMP-2 and administered psoralen i.g. The mice were euthanized after 21 days and their fractured femurs were assessed by micro computed tomography, histological analysis and biomechanical testing. Furthermore, the serum of the animals was analyzed. Psoralen + rhBMP-2 exerted more beneficial effects on callus consolidation and biomechanical strength. In addition, increased bone-specific alkaline phosphatase levels and decreased C-terminal telopeptide of type-1 collagen were observed in the Psoralen + rhBMP-2 group. However, no difference in estrogen levels was detected between the groups. In conclusion, the present study demonstrated that in ovariectomized mice, combination of locally delivered BMP-2 and systemically administered psoralen improved bone healing compared with BMP-2 alone.

Bone regeneration in osteoporosis by delivery BMP-2 and PRGF from tetronic-alginate composite thermogel

As the life expectancy of the world population increases, osteoporotic (OP) fracture risk increase. Therefore in the present study a novel injectable thermo-responsive hydrogel loaded with microspheres of 17β-estradiol, microspheres of bone morphogenetic protein-2 (BMP-2) and plasma rich in growth factors (PRGF) was applied locally to regenerate a calvaria critical bone defect in OP female rats. Three systems were characterized: Tetronic® 1307 (T-1307) reinforced with alginate (T-A), T-A with PRGF and T-A-PRGF with microspheres. The addition of the microspheres increased the viscosity but the temperature for the maximum viscosity did not change (22-24 °C). The drugs were released during 6 weeks in one fast phase (three days) followed by a long slow phase. In vivo evaluation was made in non-OP and OP rats treated with T-A, T-A with microspheres of 17β-estradiol (T-A-βE), T-A-βE prepared with PRGF (T-A-PRGF-βE), T-A-βE with microspheres of BMP-2 (T-A-βE-BMP-2) and the combination of the three (T-A-PRGF-βE-BMP). After 12 weeks, histological and histomorphometric analyzes showed a synergic effect due to the addition of BMP-2 to the T-A-βE formulation. The PRGF did not increased the bone repair. The new bone filling the OP defect was less mineralized than in the non-OP groups.

Cyst-Like Osteolytic Formations in Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) Augmented Sheep Spinal Fusion

Multiple case reports using recombinant human bone morphogenetic protein-2 (rhBMP-2) have reported complications. However, the local adverse effects of rhBMP-2 application are not well documented. In this report we show that, in addition to promoting lumbar spinal fusion through potent osteogenic effects, rhBMP-2 augmentation promotes local cyst-like osteolytic formations in sheep trabecular bones that have undergone anterior lumbar interbody fusion. Three months after operation, conventional computed tomography showed that the trabecular bones of the rhBMP-2 application groups could fuse, whereas no fusion was observed in the control group. Micro-computed tomography analysis revealed that the core implant area's bone volume fraction and bone mineral density increased proportionately with rhBMP-2 dose. Multiple cyst-like bone voids were observed in peri-implant areas when using rhBMP-2 applications, and these sites showed significant bone mineral density decreases in relation to the unaffected regions. Biomechanically, these areas decreased in strength by 32% in comparison with noncystic areas. Histologically, rhBMP-2-affected void sites had an increased amount of fatty marrow, thinner trabecular bones, and significantly more adiponectin- and cathepsin K-positive cells. Despite promoting successful fusion, rhBMP-2 use in clinical applications may result in local adverse structural alterations and compromised biomechanical changes to the bone.

Effects of local delivery of BMP2, zoledronate and their combination on bone microarchitecture, biomechanics and bone turnover in osteoporotic rabbits

The hip fracture is one major clinical challenge associated with osteoporosis, resulting in heavy socioeconomic burdens and high mortality. Systemic therapies of anti-osteoporosis drugs are expensive, time-consuming and also evoke substantial side effects, which fails to provide early protection from fractures. Accumulating evidence demonstrates the high bioavailability and therapeutic efficacy of local drug delivery in accelerating facture healing and bone defect repair. This study aims at investigating the effects of local delivery of BMP2 and zoledronate (two promising anabolic/anti-catobolic reagents) encapsulated by fibrin sealants into femoral necks on regulating bone quality and remodeling in osteoporotic rabbits subjected to combined ovariectomy and glucocorticoid injection. We show that 6-week BMP2 delivery exhibited more prominent effect on mitigating trabecular bone microarchitecture deterioration and mechanical strength reduction of femoral necks than local zoledronate treatment. BMP2 plus zoledronate showed more significant improvement of bone microstructure, mechanical strength and bone formation rate at 12 weeks post injection than single BMP2 or zoledronate delivery via μCT, biomechanical, histomorphometric and serum biochemical analyses. This study enriches our knowledge for understanding the availability of local drug delivery for improving bone quantity and quality, which may lead to earlier, safer and more efficient protection from osteoporosis-induced fractures in clinics.

Effects of Ovariectomy and Corticosteroid-Induced Osteoporosis on the Osteoinductivity of rhBMP-2 in a Segmental Long-Bone Defect Model

This study used the segmental long-bone defect model to assess the effects of osteoporosis on the formation of new bones and the osteoinductivity of recombinant human bone morphogenetic protein-2 (rhBMP-2). Seventy-two female Sprague-Dawley rats were divided into two groups: an osteoporosis group with ovariectomies and dexamathasone intramuscular injections and a sham group. When they reached 22 weeks in age, each group was further divided into two groups and a 5-mm defect was made in both fibular mid-shafts of each rat. One fibula in each rat was picked randomly and was injected with 0.05 mL of hydrogel carrier; the opposite fibula was injected with the same carrier mixed with rhBMP-2 (10 μg). After rearing for a further 5 and 9 weeks, the ratios of the lengths of the newly formed bones in the fibular defects were determined using micro-CT and undecalcified histology. The sham rhBMP-2-injected group-in all of the 5- and 9-week-kept groups-showed a significantly higher bridging bone formation ratio than the other three groups. The osteoporosis rhBMP-2-injected group showed a significantly higher ratio than both the non-rhBMP-2-injected sham hydrogel and the osteoporosis hydrogel groups. The comparison of the micro-CT parameters of the newly formed bones showed that the sham rhBMP-2 group at both 5 and 9 weeks compared with the osteoporosis rhBMP-2 group had significantly higher percentage bone volumes, trabecular thicknesses, and trabecular numbers, in addition to significantly lower specific surfaces, trabecular pattern factors, and structural model indices. The histology results showed that the sham-rhBMP-2 group began forming bridging bones in the defect areas at 5 weeks, and at 9 weeks, trabeculae and marrow spaces were observed. However, the osteoporosis rhBMP-2 group exhibited a relatively minor level of new bone and trabecula formation. Consequently, the rhBMP-2 group showed significantly increased bone formation in the osteoporosis rat fibular defect model compared with the hydrogel group, whereas the new bone quantities, qualities, and remodeling in the osteoporosis rhBMP-2 group were less effective than those in the sham-rhBMP-2 group, signaling that ovariectomy and corticosteroid-induced osteoporosis significantly undermines rhBMP-2 osteoinductivity.

Local drug delivery for enhancing fracture healing in osteoporotic bone

Fragility fractures can cause significant morbidity and mortality in patients with osteoporosis and inflict a considerable medical and socioeconomic burden. Moreover, treatment of an osteoporotic fracture is challenging due to the decreased strength of the surrounding bone and suboptimal healing capacity, predisposing both to fixation failure and non-union. Whereas a systemic osteoporosis treatment acts slowly, local release of osteogenic agents in osteoporotic fracture would act rapidly to increase bone strength and quality, as well as to reduce the bone healing period and prevent development of a problematic non-union. The identification of agents with potential to stimulate bone formation and improve implant fixation strength in osteoporotic bone has raised hope for the fast augmentation of osteoporotic fractures. Stimulation of bone formation by local delivery of growth factors is an approach already in clinical use for the treatment of non-unions, and could be utilized for osteoporotic fractures as well. Small molecules have also gained ground as stable and inexpensive compounds to enhance bone formation and tackle osteoporosis. The aim of this paper is to present the state of the art on local drug delivery in osteoporotic fractures. Advantages, disadvantages and underlying molecular mechanisms of different active species for local bone healing in osteoporotic bone are discussed. This review also identifies promising new candidate molecules and innovative approaches for the local drug delivery in osteoporotic bone.