Activin A/BMP2 Chimera (AB204) Exhibits Better Spinal Bone Fusion Properties than rhBMP2

Comparison of the biocompatibility and osteogenesis potential of whitlockite and an activin A/BMP2 chimera using a rat calvarial defect model: a pilot study

PURPOSE

The aim of this study was to evaluate bone regeneration using whitlockite (WH) nanoparticles, collagenated bovine bone mineral, and an activin A/BMP2 chimera (AB204) on calvarial defects in rats.

METHODS

This study was conducted using 8 rats. Five-millimeter circular defects were formed on each side of the calvaria. The defects were randomly assigned to 3 groups (BO group: BioOss collagen, BO/WH group: BO + WH, and BO/WH/AB204 group: BO + WH + AB204). After healing periods of 2 and 4 weeks, histological and histomorphometric analyses were performed after sacrifice.

RESULTS

The BO/WH/AB204 group showed superior bone healing compared to the other 2 groups (BO and BO/WH). In the BO and BO/WH groups, new bone formation was found in the defect margin. However, in the BO/WH/AB204 group, new bone was observed on the upper and lower surfaces of the grafted area. The new bone area of the BO/WH/AB204 group at 4 weeks was significantly higher than that of the same group at 2 weeks. At 4 weeks, the total augmented area and material area in the BO/WH/AB204 group were significantly lower than the corresponding values at 2 weeks.

CONCLUSIONS

The BO/WH/AB204 group showed superior results of bone regeneration at 2 and 4 weeks compared to the BO and BO/WH groups. AB204 seems to play an important role in bone regeneration.

Bone regeneration using activin A/BMP2 chimera (AB204) with collagen membrane in rats with calvarial defects

PURPOSE

Collagen has long been recognized as an excellent carrier for growth factors, and membrane-type collagen has been widely applied in dentistry for guided bone regeneration. This study was conducted to examine the effects of an activin A/BMP2 chimera (AB204) combined with a collagen membrane (CM) on bone repair in a rat calvarial defect model.

METHODS

A unilateral calvarial defect measuring 5.0 mm was surgically created in 32 Sprague-Dawley rats. The rats were then randomly assigned to 1 of 4 groups, each consisting of 8 animals: control (untreated), CM (treated with a CM only), CM/bone morphogenetic protein 2 (BMP2) (treated with a CM and 1.0 μg of BMP2), and CM/AB204 (treated with a CM and 1.0 μg of AB204). Bone regeneration was evaluated using micro-computed tomography (CT) and histological analysis at 2 and 4 weeks following surgery.

RESULTS

Micro-CT analysis revealed that bone formation in the CM/BMP2 and CM/AB204 groups was superior to that observed in the control and CM groups at both 2 and 4 weeks postoperatively. BMP2 induced greater bone regeneration than AB204 at 2 weeks; however, AB204 resulted in a greater bone volume at 4 weeks, achieving the highest values recorded. No significant differences were found between the CM/BMP2 and CM/AB204 groups at either time point (P>0.05). On histological examination, new bone formation was evident in both CM/BMP2 and CM/AB204 groups.

CONCLUSIONS

Within the limitations of this study, the findings indicate that AB204 may enhance osteogenic potential when used in combination with CM for bone regeneration.

The activin/BMP-2 chimera AB204 promotes periodontal tissue regeneration in a buccal dehiscence model: a pilot study

PURPOSE

A combination of activin and bone morphogenetic protein-2 (BMP-2), termed AB204, has been shown to improve osteogenic potential with fewer side effects than BMP-2 alone. This study was performed to evaluate the effect of AB204 on periodontal tissue regeneration in a dog buccal dehiscence model.

METHODS

Buccal dehiscence defects were created on the maxillary premolars (P1, P2, and P3) of 6 mongrel dogs. After 5 weeks, the dogs were randomly assigned to 1 of 3 groups: the control, collagen matrix (CM), and CM/AB204 groups. Grafting procedures were then performed. The dogs were sacrificed 8 weeks after the grafting procedure, and volumetric and histological analyses were conducted.

RESULTS

The thickness of the buccal gingiva in the CM/AB204 group was greater than those in the other groups at 2 weeks (P<0.05). The ridge width in the AB204/CM group exceeded the width in the other groups at 4 and 8 weeks; however, the difference was not statistically significant. Histological analysis revealed that the CM/AB204 group demonstrated the formation of new bone surrounded by newly formed periodontal ligament and cementum (P=0.035).

CONCLUSIONS

The combined application of CM and AB204 shows promise in facilitating the regeneration of periodontal attachment, including the formation of new bone, cementum, and periodontal ligament.

Murine models of posterolateral spinal fusion: A systematic review

BACKGROUND

Rodent models are commonly used experimentally to assess treatment effectiveness in spinal fusion. Certain factors are associated with better fusion rates. The objectives of the present study were to report the protocols most frequently used, to evaluate factors known to positively influence fusion rate, and to identify new factors.

METHOD

A systematic literature search of PubMed and Web of Science found 139 experimental studies of posterolateral lumbar spinal fusion in rodent models. Data for level and location of fusion, animal strain, sex, weight and age, graft, decortication, fusion assessment and fusion and mortality rates were collected and analyzed.

RESULTS

The standard murine model for spinal fusion was male Sprague Dawley rats of 295g weight and 13 weeks' age, using decortication, with L4-L5 as fusion level. The last two criteria were associated with significantly better fusion rates. On manual palpation, the overall mean fusion rate in rats was 58% and the autograft mean fusion rate was 61%. Most studies evaluated fusion as a binary on manual palpation, and only a few used CT and histology. Average mortality was 3.03% in rats and 1.56% in mice.

CONCLUSIONS

These results suggest using a rat model, younger than 10 weeks and weighing more than 300 grams on the day of surgery, to optimize fusion rates, with decortication before grafting and fusing the L4-L5 level.

A novel rat model of interbody fusion based on anterior lumbar corpectomy and fusion (ALCF)

BACKGROUND

Rats have been widely used as experimental animals when performing fundamental research because they are economical, rapidly reproducing, and heal quickly. While the rat interbody fusion model has been applied in basic studies, existing rat models generally have shortcomings, such as insufficiently simulating clinical surgery. The purpose of this study was to develop a novel rat model of interbody fusion which more closely represents clinical surgery.

METHODS

The internal fixation was designed based on physical measurements of the rats' lumbar spine. Then, ten rats divided into two groups (A and B) underwent anterior lumbar corpectomy and fusion of the L5 vertebrae. Groups A and B were sacrificed four and 8 weeks post-surgery, respectively. Micro-CT and histological examination were used to evaluate the model. Fusion rate, bone volume fraction (BV/TV), trabecular bone number (Tb.N), trabecular bone thickness (Tb.Th), and the area ratio of newly formed bone (NB) were calculated for quantitative analysis.

RESULTS

Based on the L5 body dimensions of individual rats, 3D-printed titanium cage of the appropriate size were printed. The operations were successfully completed in all ten rats, and X-ray confirmed that internal fixation was good without migration. Micro-CT suggested that fusion rates in group B (100%) were greater than group A (40%, P < 0.05). The BV/TV (B: 42.20 ± 10.50 vs. A: 29.02 ± 3.25, P < 0.05) and Tb.N (B: 4.66 ± 1.23 vs. A: 1.97 ± 0.40, P < 0.05) were greater in group B than A, and the Tb.Th in group B was lower than group A (B: 0.10 ± 0.04 vs. A: 0.15 ± 0.02, P < 0.05). Histomorphometry results demonstrated that the area ratio of NB in group B were greater than group A (B: 35.72 ± 12.80 vs. A: 12.36 ± 16.93, P < 0.05).

CONCLUSION

A rat interbody fusion model based on anterior lumbar corpectomy and fusion has successfully been constructed and verified. It could provide a new choice for fundamental research using animal models of spinal fusion.