Effect of low-level laser irradiation on osteoblast proliferation and bone formation.

Applications of laser therapy in biostimulation and healing injured tissues are widely described in medical literature. The present study focuses on the effects of laser irradiation on the growth rate and differentiation of human osteoblast-like cells seeded on titanium or zirconia surfaces. Cells were laser irradiated with low therapeutical doses at different intervals and the effects of irradiation were evaluated at each time-point. After 3 hours lasered cells showed an enhanced mitogen activity compared to non-lasered control cells and a higher alkaline phosphatase activity, marker of bone formation. At the same time, the mRNA of RUNX2 and OSTERIX, two genes involved in osteoblast differentiation, showed a clear decrease in lasered cells. This reached the lowest value 6 to 12 hours after irradiation, after which the transcripts started to increase, indicating that the laser treatment did promote the osteogenic potential of growth-induced cells. These results indicate that Low Level Laser Treatment (LLLT) stimulates osteogenic cell proliferation.

Osteogenic properties of human dental pulp stem cells.

Stem cells are a promising tool for bone tissue regeneration. Dental pulp stem cells (DPSCs) can be easily obtained even in human young adults. In this study we investigated the capability of DPSCs, to express the osteoblastic phenotype when cultured with osteogenic medium. DPSCs isolated from the dental pulp of impacted third molar teeth were cultured with appropriate medium to induce osteoblast differentiation. Using Western-Blot, RT-PCR and microarray analysis, we studied the expression of osteoblastic parameter, and by Von Kossa staining we evaluated the production of mineralized matrix nodules. The results were compared with controls represented by undifferentiated DPSCs. DPSCs, differentiated into osteoblast-like cells, express large amount of alkaline phosphatase (ALP), collagen I (Coll I), osteopontin (OPN) and osteocalcin (OCN), all these parameters characterizing the osteoblastic phenotype. Differentiated DPSCs express Runx2 and JunB, a member of the AP-1 complex; both the transcription factors are associated with osteoblast differentiation and skeletal morphogenesis. Moreover, DPSCs express insulin growth factor-binding protein 5 (IGFBP-5), one of the regulating proteins of IGFs function. Finally, DPSCs can form mineralized matrix nodules that are a feature exclusive to osteoblasts. DPSCs could represent a potential source of osteoblasts to be used for bone regeneration.

Osteoblast apoptosis in periodontal disease: role of TNF-related apoptosis-inducing ligand.

Periodontal disease (Pd) is characterized by an increased osteoclast resorption and a decreased osteoblast (OB) bone formation. OBs obtained from alveolar bone of Periodontitis patients (Pp) undergo apoptosis in the presence of TNF-related apoptosis-inducing ligand (TRAIL). We studied the intracellular apoptotic pathway induced by TRAIL; TRAIL death (DR4, DR5) and decoy (DcR1, DcR2) receptors expression in Periodontitis patients OBs (PpOBs), and we measured the concentration of TRAIL in the serum of Pp. We demonstrated that DNA fragmentation and activation of caspase-8 and caspase-3 in PpOBs, following TRAIL stimulation, occurred in shorter time; moreover, a higher amount of both caspases was activated in order to direct OBs. Down-regulation of DcR2 in PpOBs was demonstrated and high TRAIL levels were detected in the serum of Pp. In conclusion, our data suggest that PpOBs are more sensitive to TRAIL-induced apoptosis when compared to the control group. The down-regulation of DcR2 possibly leads to an imbalanced ratio between death and decoy receptors. Our findings highlight a role of TRAIL in the pathogenesis of Pd.

[Avascular jaw osteonecrosis in a hemodialysis patient treated with bisphosphonates]. / Osteonecrosi avascolare mandibolare in un paziente in trattamento emodialitico sostitutivo trattato con bifosfonati.

Bisphosphonates are molecules derived from pyrophosphates,but, unlike pyrophosphates, they are resistant to enzymatic hydrolysis. Bisphosphonates are used in the treatment of Paget's disease, cancer-related osteolysis, myeloma, primary hyperparathyroidism, and osteoporosis. In dialysis patients bisphosphonates may be used to reduce bone pain due to renal osteodystrophy. We describe the case of a 60-year-old woman with a history of breast cancer who had been on dialysis for 8 years. She had been receiving clodronic acid at 100 mg per week intravenously for the last 2 years. A year ago, the patient underwent surgical extraction of the lower right second molar. Her jaw pain increased in the following days. An orthopanthograph and a CT scan of the head showed osteolysis, and a surgical osteotomy was performed. Histological examination led to a diagnosis of avascular osteonecrosis of the jaw. Avascular osteonecrosis is typically described in the jaw. In this case, prolonged bisphosphonate treatment may have worsened the osteonecrosis.

Alteration of activity and survival of osteoblasts obtained from human periodontitis patients: role of TRAIL.

Periodontal disease (Pd) is characterized by extensive alveolar bone loss, that occurs as a consequence of the impairment of the normal bone remodelling. Bone remodelling is regulated by the correct balance between osteoclast and osteoblast formation and activity. Alveolar bone loss could be due to an increased bone resorption by osteoclasts or a decreased bone formation by osteoblasts (OBs) or both. Although the role played by osteoclasts in increasing bone resorption in Pd is already known, the behaviour of OBs in this disease is poorly understood. In the present study we hypothesized that activity and survival of OBs, locally present in alveolar bone of Pd patients, are altered. Thus, we studied the activity and survival of OBs obtained from alveolar bone fragments of Pd patients. The results, obtained in OBs from the patients were compared with those from OBs obtained from healthy donors. We demonstrated that OBs from Pd patients weakly express OB phenotype in respect to the control cells. In particular, the alkaline phosphatase activity and the collagen type I production, as well as the formation of mineralized nodules, typical markers of differentiated OBs, were significantly lower in Pd patients. Interestingly, we also demonstrated that OBs from the patients were more sensitive to the apoptotic effect induced by TNF-related apoptosis-inducing ligand (TRAIL). TRAIL, a member of the TNF superfamily, induces apoptosis by interacting with its death receptors, (DR4, DR5). However, its activity can be modulated by two decoy receptors, DcR1 and DcR2. Thus, the sensitiveness of TRAIL induced apoptosis is determined by the ratio of death and decoy receptor. We demonstrated that OBs from Pd patients showed an imbalanced ratio between death and decoy TRAIL receptors due to the down-regulation of DcR2 expression. Furthermore, the levels of TRAIL in the serum of the same patients were significantly higher than those detected in the controls. In conclusion, we show for the first time that the alveolar bone loss in Pd patients could be due to the increased TRAIL-mediated apoptosis of OBs.