Can a low dosage of recombinant human bone morphogenetic protein-2 loaded on collagen sponge induce ectopic bone?

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is one of the growth factors that may induce the formation of new bone. The aim was to determine the efficacy of low doses of rhBMP-2 for bone regeneration using a collagen sponge as a carrier. Three doses of rhBMP-2 (1.167, 0.117, and 0.039 mg/mL) were combined with an absorbable collagen sponge (ACS) as a delivery vehicle. The rhBMP-2/ACS implants were placed in the subcutaneous tissues of rat backs. X-ray microcomputed tomography (micro-CT) and histological analysis were used to evaluate bone formation. The samples treated with 1.167 mg/mL of rhBMP-2 showed greater bone formation than the samples treated with 0.117 mg/mL of rhBMP-2 four weeks after surgery. However, there was no evidence of bone formation in the samples that were treated with 0.039 mg/mL of rhBMP-2. It was found that rhBMP-2 was osteogenic even at one-tenth of its manufacturer's recommended concentration (1.167 mg/mL), indicating its potential for clinical use at lower concentrations.

Phosphorylated pullulan promotes calcification during bone regeneration in the bone defects of rat tibiae.

The current study aimed to evaluate bone tissue regeneration using a combination of ß-tricalcium phosphate (ßTCP) and phosphorylated pullulan (PPL, a phosphate-rich polysaccharide polymer consisting of maltotriose units). Round defects of 2 mm diameter were created in the arterial center of rat tibiae, which were further treated with vehicle (control group), ßTCP (ßTCP group), or ßTCP + PPL (ßTCP + PPL group) grafts. The control specimens without bone grafts exhibited rapid bone formation after 1 week; however, the regenerated bone was not resorbed until 4 weeks. In contrast, ßTCP-grafted specimens exhibited fewer but thicker trabeculae, whereas the ßTCP + PPL group displayed many fine trabeculae at 4 weeks. In the ßTCP + PPL group, new bone was associated with the ßTCP granules and PPL. Similarly, PHOSPHO1-positive osteoblasts were localized on the ßTCP granules as well as the PPL. On the other hand, TRAP-reactive osteoclasts predominantly localized on newly-formed bone and ßTCP granules rather than on the PPL. No significant differences were observed in the expression of Alp, Integrin αv, Osteopontin, Osteocalcin, and Dmp-1 in PPL-treated MC3T3-E1 osteoblastic cells, suggesting that PPL did not facilitate osteoblastic differentiation. However, von Kossa staining identified abundant needle-like calcified structures extending inside the PPL. Furthermore, transmission electron microscopy (TEM) revealed many globular structures identical to calcified nodules. In addition, calcified collagen fibrils were observed in the superficial layer of the PPL. Thus, PPL may serve as a scaffold for osteoblastic bone formation and promotes calcification on its surface. In conclusion, we speculated that ßTCP and PPL might promote bone regeneration and could be integrated into promising osteoconductive materials.

Comparative immunolocalization of tissue nonspecific alkaline phosphatase and ectonucleotide pyrophosphatase/phosphodiesterase 1 in murine bone.

OBJECTIVE: This study aimed to demonstrate the immunolocalization and gene expression of tissue nonspecific alkaline phosphatase (TNALP) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) in osteoblasts, preosteoblasts, and osteocytes of murine bone to provide clues for a better understanding of the supply of phosphate ions (Pi) during bone mineralization. METHODS: Six-week-old male C57BL/6J mice (n = 6) were fixed with a paraformaldehyde solution, and the right femora were extracted for immunodetection of TNALP and ENPP1, while the left tibiae were used for reverse transcription polymerase chain reaction to evaluate Tnalp and Enpp1 gene expression. RESULTS: TNALP was intensely localized on the basolateral cell membranes of mature osteoblasts and preosteoblastic cells. There was little immunoreactivity of TNALP on the secretory surface of the osteoblasts and no TNALP reactivity in the osteocytes. In contrast, ENPP1 was observed throughout the cytoplasm of mature osteoblasts and osteocytes embedded in bone but was not observed in preosteoblasts. Together, despite the fact that the osteoid is a site of matrix vesicle-mediated mineralization, ENPP1, which inhibits mineralization by providing pyrophosphates, was localized in close proximity of the osteoid, whereas TNALP, which facilitates mineralization by providing Pi, was relatively distant from the osteoid. CONCLUSION: It seems likely that the differential localization of TNALP and ENPP1 around the osteoid observed at the microscopic level may provide preferential micro-circumstance for a balanced concentration of Pi and pyrophosphate for bone mineralization.

Histological observation on the initial stage of vascular invasion into the secondary ossification of murine femoral epiphyseal cartilage.

It remains unknown whether the histology of vascular invasion during secondary ossification of epiphyseal cartilage is the same as that seen in primary ossification; we examined the initial processes of vascular invasion of secondary ossification in the murine femora. Many endomucin-immunoreactive blood vessels gathered at the central region of the articular surface, and buds of soft tissue, including glomerular loops of endomucin-immunoreactive blood vessels and TNALPase- immunopositive osteoblastic cells accompanied by TRAP-positive osteoclasts, had begun to invade the epiphyseal cartilage. The invading soft tissues formed cartilage canals displaying MMP9 immunoreactivity in the tip region, and cartilaginous collagen fibrils were not visible in the vicinity of the vascular wall of the blood vessels. Thus, the histological profile marked by invading glomerular vasculature and the erosion of the cartilage matrix near the vascular walls during secondary ossification differs from that seen during primary ossification.

Histochemical characteristics on minimodeling-based bone formation induced by anabolic drugs for osteoporotic treatment.

Modeling, the changes of bone size and shape, often takes place at the developmental stages, whereas bone remodeling-replacing old bone with new bone-predominantly occurs in adults. Unlike bone remodeling, bone formation induced by modeling i.e., minimodeling (microscopic modeling in cancellous bone) is independent of osteoclastic bone resorption. Although recently-developed drugs for osteoporotic treatment could induce minimodeling-based bone formation in addition to remodeling-based bone formation, few reports have demonstrated the histological aspects of minimodeling-based bone formation. After administration of eldecalcitol or romosozumab, unlike teriparatide treatment, mature osteoblasts formed new bone by minimodeling, without developing thick preosteoblastic layers. The histological characteristics of minimodeling-based bone formation is quite different from remodeling, as it is not related to osteoclastic bone resorption, resulting in convex-shaped new bone and smooth cement lines called arrest lines. In this review, we will show histological properties of minimodeling-based bone formation by osteoporotic drugs.

Picosecond master-oscillator, power-amplifier system based on a mixed vanadate phase conjugate bounce amplifier.

We demonstrate a high average power approximately 4 ps output from a phase conjugate laser system based on a diode-side-pumped Nd:Gd(0.6)Y(0.4)VO(4) bounce amplifier. An average output power of 16.2 W with a peak power of 210 kW was achieved. A corresponding extraction efficiency of 23% was measured.

[Effect of body fat percentage on estimated propofol concentrations at awakening from anesthesia using target controlled infusion].

BACKGROUND: Target controlled infusion (TCI) for propofol allows anesthesiologists to target constant blood concentrations of propofol. However, the pharmacokinetic parameters in TCI system do not take account of the patient's age, make up and gender. We evaluated the relationship between body fat percentage and the estimated effect site propofol concentrations at awakening. METHODS: Anesthesia was induced in 37 patients with fentanyl and propofol by TCI. Patients's percentage of fat was evaluated by measuring the thickness of the three parts of the skin fat with Skyndex (Caldwell Justiss, USA). After surgery and discontinuation of anesthesia, the estimated effect site propofol concentrations (EPEC) were determined when the patient could respond to verbal command. RESULTS: The EPECs at awakening were 1.5 +/- 0.2 micrograms.ml-1 in male and 1.5 +/- 0.3 micrograms.ml-1 in female. In male, the percentage of fat and body mass index (BMI) correlated significantly with EPEC (r = 0.79 and 0.49 respectively). In female, the percentage of fat and BMI did not correlate with EPEC. The estimated fentanyl effect site concentrations at awakening did not correlate with the EPEC. CONCLUSIONS: Male patients who have high percentage of fat have a tendency to delayed of awakening from propofol anesthesia. In female, however, no correlation was seen between percentage of fat and awakening time from propofol anesthesia. Measuring the percentage of fat might bring a new insight into pharmacokinetics of propofol.