Recombinant human bone morphogenetic protein-2 stimulates bone formation during interfrontal suture expansion in rabbits

Bone-targeted bortezomib increases bone formation within Calvarial trans-sutural distraction osteogenesis

The high rate of relapse in craniofacial disharmony treatment via trans-sutural distraction osteogenesis (TSDO) is due to the failure to form a stable bone bridge in the suture gap. Bisphosphonates (BP) have a high propensity to localize to hydroxyapatite in the bone matrix and are commonly used as targeting ligands for local delivery of therapeutics into bone microenvironment. Bone-targeted Bortezomib (BP-Btz) is chemosynthetic by linking Btz (Bortezomib) to a BP residue and could target bone tissue to promote osteoblast differentiation and inhibit osteoclastogenesis. Here, suture-derived mesenchymal stem cells (SuSCs) and osteoclasts were treated with Btz and BP-Btz. Aforesaid drugs were injected locally into the sagittal sutures to explore their effects in TSDO. Further, pharmacological properties of BP-Btz in the suture expansion model were assessed by fluorescent BP analogs and levels of total ubiquitinated (Ub)-proteins. The results showed that BP-Btz could stimulate osteogenic differentiation of SuSCs, bind to bone matrix and inhibit osteoclastogenesis. Biological effects of BP-Btz were similar with those of Btz in osteoblast differentiation and osteoclastogenesis inhibition in vitro. Activated bone metabolism were detected after 14 days in the sagittal suture expansion model. Increased osteoid area, remarkably decreased osteoclast surface and enhanced osteogenesis were detected in vivo after treatment with BP-Btz. Green fluorescence signal detection and pharmacodynamic studies revealed that BP-Btz bound to suture edge, released Btz in remodeling conditions, had a higher local concentration and sustained longer than free Btz. This study delineated the clinical potential of bone-targeted Btz conjugate as an efficacious strategy to promote trans-sutural distraction osteogenesis.

The mechanism underlying the remodeling effect of lactoferrin on midpalatal sutures during maxillary expansion and relapse in rats

INTRODUCTION

The remodeling effects of intragastric administration and intramaxillary injection of lactoferrin (LF) on midpalatal sutures (MPS) during maxillary expansion and relapse in rats were studied to explore the underlying bone remodeling mechanism.

METHODS

Using a rat model of maxillary expansion and relapse, rats were treated with LF by intragastric administration (1 g·kg^-1·d^-1) or intramaxillary injection (5 mg·25 μl^-1·d^-1). The effects of LF on the osteogenic and osteoclast activities of MPS were observed by microcomputed tomography, histologic staining, and immunohistochemical staining, and the expressions of key factors in the extracellular regulated protein kinase 1/2 (ERK1/2) pathway and osteoprotegerin (OPG)-receptor activator of nuclear factor-KB ligand (RANKL)-receptor activator of nuclear factor-KB (RANK) axis were detected.

RESULTS

Compared with the group with maxillary expansion alone, osteogenic activity was relatively enhanced, whereas osteoclast activity was relatively weakened in the groups administered LF, and the phosphorylated-ERK1/2: ERK1/2 and OPG: RANKL expression ratios increased significantly. The difference was more significant in the group administered LF intramaxillary.

CONCLUSIONS

Administration of LF promoted osteogenic activity at MPS and inhibited osteoclast activity during maxillary expansion and relapse in rats, which may have occurred through regulation of the ERK1/2 pathway and the OPG-RANKL-RANK axis. The efficiency of intramaxillary LF injection was greater than that of intragastric LF administration.

Gavage-administered lactoferrin promotes palatal expansion stability in a dose-dependent manner

OBJECTIVE

To investigate the effects of different lactoferrin concentrations on mid-palatal suture bone remodeling during palatal expansion and relapse in rats.

MATERIALS AND METHODS

Thirty-two 5-week-old male Wistar rats were randomly divided into four groups: EO (expansion only), E+LF1 (expansion plus 10 mg/kg/day daily LF), E+LF2 (expansion plus 100 mg/kg/day daily LF), and E+LF3 (expansion plus 1 g/kg/day daily LF). Thereafter, micro-computed tomography and micro-morphology of the mid-palatal suture were analyzed on day 7 and day 14, respectively.

RESULTS

The arch widths were increased in all the four groups after expansion, and there was no significant difference among them on day 7. After relapse, however, the arch width in the E+LF3 group was significantly larger compared with EO group. In E+LF3 group and E+LF2 group, new bone formation and osteoblast number were enhanced with up-regulated expression of osteocalcin and collagen type I, while the expression of cathepsin K-positive cells was downregulated in E+LF3 group.

CONCLUSION

Lactoferrin gavage administration might increase the stability of palatal expansion and reduce relapse in a concentration-dependent manner by enhancing bone formation and inhibiting resorption. LF administration may be promising for optimizing the maxillary expansion outcome.

Hydroxyapatite Nanoparticles Facilitate Osteoblast Differentiation and Bone Formation Within Sagittal Suture During Expansion in Rats

Background

The potential of relapse of craniofacial disharmony after trans-sutural distraction osteogenesis is high due to the failure to produce a stable bone bridge in the suture gap. The aim of this study is to evaluate whether hydroxyapatite nanoparticles (nHAP) have the effect of promoting osteoblast differentiation of suture-derived stem cells (SuSCs) and bone formation in sagittal suture during expansion.

Methods

SuSCs were isolated from sagittal sutures and exposed to various concentrations of nHAP (0, 25, 50, and 100 μg mL⁻¹) to determine the optimal concentration of nHAP in osteoblast differentiation via performing Western Blotting and RT-qPCR. Twenty 4-week-old male Sprague–Dawley rats were randomly assigned into 4 groups: SHAM (sham-surgery), distraction, ACS (absorbable collagen sponge) and ACS+nHAP groups. In the ACS and ACS+nHAP groups, saline solution and nHAP suspended in a saline solution were delivered by ACS placed across the sagittal suture, respectively. In the latter three groups, the suture was expanded for 14 days by 50 g of constant force via a W shape expansion device. Suture gap area, bone volume fraction (BV/TV) and bone mineral density (BMD) of sagittal sutures were assessed via micro-CT, while the mechanical properties of sagittal sutures were evaluated via nanoindentation test. The efficacy of nHAP on bone formation in sagittal suture was also evaluated via BMP-2 immunohistochemistry staining.

Results

The expression of osteoblast related genes and proteins induced by 25μg mL⁻¹ nHAP were significantly higher than the other groups in vitro (p<0.05). Furthermore, treating with 25μg mL⁻¹ nHAP in vivo, the suture gap area was significantly reduced when compared with the distraction group. Correspondingly, the BV/TV, BMD, hardness and modulus of sagittal sutures were significantly increased in the ACS+nHAP group (p<0.05).

Conclusion

The 25μg mL⁻¹ dose of nHAP delivered by ACS can facilitate bone formation into the sagittal suture during expansion via inducing osteoblast differentiation of SuSCs.

Pyk2 deficiency enhances bone mass during midpalatal suture expansion

OBJECTIVE

To determine if Pyk2 deficiency increases midpalatal suture bone mass and preserves sutural integrity after maxillary expansion.

SETTING AND SAMPLE

Thirty-six male Pyk2 knockout (KO) and control (WT) mice at 6 weeks of age.

MATERIALS AND METHODS

Mice received nickel-titanium spring expanders delivering 0 g (no intervention control), 10 or 20 g force for 14 days. High-resolution micro-CT was used to determine bone volume/tissue volume (BV/TV), sutural width and intermolar width. Effects on osteoclasts, chondrocytes and suture morphology were determined by histomorphometry.

RESULTS

Pyk2-KO controls (0 g) had 7% higher BV/TV compared with WT controls. Expanded Pyk2-KO maxillae also exhibited 12% (10 g) and 18% (20 g) higher BV/TV than WT mice. Although bone loss following expansion occurred in both genotypes, BV/TV was decreased to a greater extent in WT maxillae (-10% at 10g; -22% at 20 g) compared with Pyk2-KO maxillae (-11% only at 20 g). Expanded WT maxillae also showed a greater increase in sutural width, intermolar width and fibrous connective tissue width compared with expanded Pyk2-KO maxillae. Moreover, osteoclast number was increased 77% (10 g) and 132% (20 g) in expanded WT maxillae, but remained unchanged in expanded Pyk2-KO, compared to their respective controls. Cartilage area and chondrocyte number were increased to the same extent in expanded WT and Pyk2-KO sutures.

CONCLUSIONS

These findings suggest that midpalatal suture expansion increases osteoclast formation in WT but not Pyk2-KO mice, leading to higher BV/TV in expanded Pyk2-KO maxillae. These studies suggest Pyk2-targeted strategies may be beneficial to increase bone density and preserve sutural integrity during maxillary expansion.

Influence of interdigitation and expander type in the mechanical response of the midpalatal suture during maxillary expansion

BACKGROUND AND OBJECTIVE

The orthopedic Maxillary Expansion (ME) procedure is used for treating the transverse maxillary deficiency. This pathology consists in a smaller transverse dimension in the maxilla and leads to malocclusion. The treatment takes advantage of the existence of the midpalatal suture (MPS), which corresponds to the junction at the palatine bones of its horizontal portions. The technique employs a device, conventionally a palatal expander attached to the posterior teeth, to separate the two maxillary bones in the MPS. The objective of this study was to analyze, using the Finite Element Method, the biomechanical behavior of the MPS when an expansion is applied.

METHODS

A Computer Tomography image of the maxilla was reconstructed, the suture geometry was modeled with different interdigitation levels and types of hyrax devices. A total of 12 geometric models (three levels for interdigitation and four types of hyrax devices) were prepared and analyzed taking into account the chewing forces and the expansion displacement. For each case, maximum principal stresses on the maxilla (bone), and equivalent stresses on the expander device (stainless steel) were observed. In the MPS, maximum principal stresses and directional displacement were evaluated.

RESULTS

The results showed that the interdigitation does not have an important influence on the deformation behavior of the maxilla but it affects the stress distribution. In addition, the type of expander device and anchorage have a direct relationship with the treatment effectiveness; larger deformation in the expansion direction was obtained with skeletal when compared to dental anchorage.

CONCLUSIONS

A study that allows a better understanding of the oral biomechanics during the application of ME was presented. To our knowledge, it is the first study based on computational simulations that takes into account bone structures, like maxilla and part of the skull, to analyze the interdigitation influence on the MPS behavior when exposed to a ME.

Histological evaluation of combined platelet-rich fibrin membrane and piezo-incision application in orthodontic tooth movement

The aim of this study was to evaluate the effect of platelet-rich fibrin (PRF) membrane on tooth movement in comparison with shunt control and piezoelectric surgery. Sixteen White Vienna rabbits were included in the study and divided into two groups. Reciprocal forces (20 g) were applied on the maxillary incisors by an orthodontic appliance. In group 1, PRF membrane was placed sub-periosteally on the distal alveolar bone surface of the right central incisors and the left side was kept as control. In group 2, piezo-incisions 3 mm in depth were performed and combined with PRF membrane on the distal alveolar bone surface of the right central incisors, while the left side was kept as control. All rabbits were euthanized on day 21 and bilateral alveolar bone segments from the distal regions were removed for histological evaluation. Isolated PRF membrane application increased the blood vessel (8.3 ± 1.0; P =  0.026), osteoblast (6 ± 0.8; P =  0.027), and osteoclast (2.3 ± 0.8; P =  0.026) counts significantly compared to shunt control. Combined application of PRF membrane + piezo-incision increased the blood vessel (15.3 ± 0.8; P =  0.027), osteoblast (9.8 ± 1.4; P =  0.026), and osteoclast (3.3 ± 0.8; P =  0.024) counts significantly compared to shunt control. The increases in blood vessel count and osteoblast cell count were more evident in the combined application group (both P =  0.002). PRF membrane application significantly increased bone turnover, and the combined application of PRF membrane + piezo-incision was found to be the best method for increasing bone turnover.

Effects of lactoferrin on bone resorption of midpalatal suture during rapid expansion in rats

INTRODUCTION

The aim of this study was to investigate the effect of lactoferrin (LF) on bone resorption of rats' midpalatal sutures during rapid palatal expansion.

METHODS

Sixty male 5-week-old Wistar rats were randomly divided into 3 groups: expansion only (EO), expansion plus LF (E + LF), and sham device (control).

RESULTS

Microcomputed tomography showed that the bone volume/tissue volume ratio and the relative bone mineral density of the suture bone were significantly increased in the E + LF group compared with the EO group. Histochemical staining suggested that the activity of osteoblast-like cells and the amount of new bone formation were stimulated in the E + LF group whereas the activity of osteoclasts showed no obvious difference between groups. On the other hand, the immunohistochemical and the real-time polymerase chain reaction results showed that the expressions of receptor activator of nuclear factor kappa B ligand and osteoprotegerin had no significant difference between the EO and E + LF groups.

CONCLUSIONS

These findings demonstrated that LF could stimulate bone volume and bone density in midpalatal sutures during the suture remodeling process under tensile force. However, this enhancement effect was not caused by the reduction of bone resorption.

Rapid Maxillary Expansion after Alveolar Bone Grafting with rhBMP-2 in UCLP Evaluated by Means of CBCT

Objective

To demonstrate the feasibility of rapid maxillary expansion (RME) after alveolar bone grafting (ABG) in complete unilateral cleft lip, alveolus and palate (UCLP) without damage to the grafted area.

Setting

Hospital for Rehabilitation of Craniofacial Anomalies (HRAC), University of São Paulo, Department of Orthodontics.

Patient

A case report of a 10-year-old boy with a complete UCLP who was treated with RME after secondary ABG procedure. RME was performed 1.3 years after the bone grafting with rhBMP-2 in collagen membrane.

Result

Postexpansion cone-beam computed tomography (CBCT) axial and coronal sections demonstrated the opening of the midpalatal suture in the premaxilla without damages to the alveolar bone grafting region. Postretention CBCT images showed bone formation at the split midsuture of the premaxilla.

Conclusion

Rapid maxillary expansion performed after ABG with rH-BMP2 led to complete opening of the premaxillary midline suture without compromising the integrity of the grafted alveolar cleft.

Effect of longitudinal flutes on miniscrew implant stability and 3-dimensional bone formation

INTRODUCTION

The purpose of this study was to evaluate the effects of longitudinal flutes on miniscrew implant (MSI) stability and bone healing.

METHODS

Using 11 skeletally mature New Zealand white rabbits, we placed 31 longitudinally fluted and 31 nonfluted, 3-mm-long MSIs in standardized positions in their calvaria and immediately loaded them with 100 g using nickel-titanium coil springs. Insertion torque values were obtained for each MSI placed; removal torque values were obtained for 28 MSIs that had been in place for 6 weeks and 20 MSIs that had been in place for 2 weeks. The bone volume fractions at 6 to 24, 24 to 42, and 42 to 60 μm from the MSI surfaces were evaluated using microcomputed tomography with an isotropic resolution of 6 μm.

RESULTS

The success rate was 97% for both the fluted and nonfluted MSIs. The difference in insertion torque between the fluted and nonfluted MSIs was not statistically significant (P = 0.930). After 2 weeks, there was no statistically significant (P = 0.702) difference in removal torque between the fluted and nonfluted MSIs. After 6 weeks, removal torque values were significantly (P = 0.008) higher for the fluted (3.42 ± 0.26 N.cm) than the nonfluted (2.49 ± 0.20 N.cm) MSIs. Bone volume fractions of the 6-to-24-, 24-to-42-, and 42-to-60-μm layers were significantly (P <0.05) greater for the nonfluted than the fluted MSIs.

CONCLUSIONS

Loaded 3-mm-long MSIs with and without flutes have high success rates. Longitudinal flutes placed in 3-mm MSIs increased their removal torque by 37% and decreased the amount of bone immediately surrounding them.