A positive effect of low-level laser irradiation (LLLI) on the proliferation of some cell types has been observed, but little is known about its effect on dental pulp stem cells (DPSCs). The aim of this study was to identify the lowest energy density able to promote the proliferation of DPSCs and to maintain cell viability. Human DPSCs were isolated from two healthy third molars. In the third passage, the cells were irradiated or not (control) with an InGaAlP diode laser at 0 and 48 h using two different energy densities (0.5 and 1.0 J/cm²). Cell proliferation and viability and mitochondrial activity were evaluated at intervals of 24, 48, 72, and 96 h after the first laser application. Apoptosis- and cell cycle-related events were analyzed by flow cytometry. The group irradiated with an energy density of 1.0 J/cm² exhibited an increase of cell proliferation, with a statistically significant difference (p < 0.05) compared to the control group at 72 and 96 h. No significant changes in cell viability were observed throughout the experiment. The distribution of cells in the cell cycle phases was consistent with proliferating cells in all three groups. We concluded that LLLI, particularly a dose of 1.0 J/cm², contributed to the growth of DPSCs and maintenance of its viability. This fact indicates this therapy to be an important future tool for tissue engineering and regenerative medicine involving stem cells.

This study aimed to verify the efficacy of low‐level laser irradiation (LLLI) on the proliferation of MC3T3‐E1 preosteoblasts cultured on poly(lactic acid) (PLA) films. The produced films were characterized by contact angle tests, scanning electron microscopy (SEM), atomic force microscopy, differential scanning calorimetry, and X‐ray diffraction. The MC3T3‐E1 cells were cultured as three different groups: Control—cultured on polystyrene plastic surfaces; PLA—cultured on PLA films; and PLA + Laser—cultured on PLA films and submitted to laser irradiation (660 nm; 30 mW; 4 J/cm2). Cell proliferation was analyzed by Trypan blue and Alamar blue assays at 24, 48, and 72 h after irradiation. Cell viability was assessed by Live/Dead assay, apoptosis‐related events were evaluated by Annexin V/propidium iodide (PI) expression, and cell cycle events were analyzed by flow cytometry. Cell morphology on the surface of films was assessed by SEM. Cell counting and biochemical assay results indicate that the PLA + Laser group exhibited higher proliferation (p < 0.01) when compared with the Control and PLA groups. The Live/Dead and Annexin/PI assays indicate increased cell viability in the PLA + Laser group that also presented a higher percentage of cells in the proliferative cell cycle phases (S and G2/M). These findings were also confirmed by the higher cell density observed in the irradiated group through SEM images. The evidence from this study supports the idea that LLLI increases the proliferation of MC3T3‐E1 cells on PLA surfaces, suggesting that it can be potentially applied in bone tissue engineering.

Tissue engineering aims at the development of biological substitutes that can restore, maintain, or improve the functionality of damaged tissue or organs. To this end, molecular and cellular interactions may influence the tissue reactions to biomaterials. In order to be effective and integrated to the receiving area, the bone graft is required to allow a strong cell adhesion, interacting with several molecules to induce migration, differentiation, and thus the mineralization of the new bone on the graft. These cell adhesion molecules (CAM) will mediate the contact between two cells or between cells and the extracellular matrix, an essential process to the success of the implant. Objective: This paper is a systematic review of the literature on the mechanisms of cell adhesion to bone grafts associated to nanotechnology, describing the importance and the role of those molecules in the adhesion and thus in tissue regeneration. Literature review: After the use of search strategies, 18 articles that describe processes of cell adhesion to bone grafts were selected. Results: The main reported mechanisms involve cell adhesion molecules (CAMs) and extracellular matrix components. Conclusion: Several molecules are involved in the process of cell adhesion to bone grafts, highlighting the role of integrins, the focal adhesion mechanism, the influence of the collagen matrix, and the activity of alkaline phosphatase in bone matrix formation. Accurate identification of these mechanisms of cell adhesion is essential for further advancement in tissue engineering, such as the production of biological bone substitutes that achieve a better clinical outcome.

SUMMARY:Bone remodeling is a process regulated by the interaction between cells and various molecules such as parathyroid hormone (PTH). The aim of the study was to evaluate the effect of different doses of PTH on osteoclast activity in a culture model of bone organs. Six-day-old male C57BL/6 mice (n=14) were euthanized and the calvariae were dissected and sectioned in the middle, keeping the periosteal and endosteal. The bone fragments were divided into three groups: Group I (control -without adding PTH), Group II (addition of 3 nM PTH) and Group III (30 nM PTH), all cultured in aMEM for up to 72 h osteoclast activity was evaluated by biochemical quantification of calcium released in the culture medium at intervals of 24, 48, and 72 h and by histomorphometric analysis of bone resorption lacunae at 72 h our results show that group II exhibited significantly higher values of calcium levels in the medium compared to group I (p<0.05) in all intervals, also being higher for group III at 24 hours (p<0.05). Group II promoted a greater demineralization area (22068 ± 2193 mm 2 ) than those found in group I (2084 ± 38 mm 2 ) and group III (8952 ± 246 mm 2 ), with statistically significant difference (p<0.001) among all groups. We concluded that in culture model of bone organs PTH promotes higher bone resorption when administered in lower doses.