The effects of combined low level laser therapy and mesenchymal stem cells on bone regeneration in rabbit calvarial defects

Abstract: This study evaluated the effect of Low Level Laser Therapy (LLLT) and Mesenchymal Stem Cells (MSCs) on bone regeneration. Background data: Although several studies evaluated the effects of MSCs and LLLT, there is little information available regarding in vivo application of LLLT in conjunction with MSCs. Methods: Forty-eight circular bone defects (6 mm in diameter) were prepared in the calvaria of 12 New- Zealand white rabbits. The defects of each animal were randomly assigned to 4 groups: (C) no treatment; (L) applying LLLT; (SC) filled with MSCs; (SCL) application of both MSCs and LLLT. LLL was applied on alternate days at wavelength of 810 nm, power density of 0.2 W/cm2 and a fluency of 4 J/cm2 using a Gallium–Aluminum–Arsenide (GaAlAs) diode laser. The animals were sacrificed after 3 weeks and then histological samples were evaluated to determine the amount of new bone formation and the remaining scaffold and inflammation. Results: The histological evaluation showed a statistically significant increase in new bone formation of LLLT group relative to the control and the other two experimental groups (p < 0.05). There was no significant difference in bone formation of the control group compared to experimental groups filled with MSCs. Laser irradiation had no significant effect on resorption of the scaffold material. In addition, inflammation was significantly reduced in LLLT group compared to the control defects and the other two experimental groups. Conclusion: Low level laser therapy could be effective in bone regeneration but there is no evidence of a synergistic effect when applied in conjunction with MSCs

Thermodynamic Modeling of the Competition between Cancer and Normal Cells

One of the recognized differences between normal and cancer cells is in their metabolic profile. Tumor cells tend to produce energy through glycolysis rather than the much more efficient oxidative phosphorylation pathway, which healthy cells generally prefer. This phenomenon is identified as the Warburg effect. Although several functional explanations have been proposed for the Warburg effect, the competitive advantage of it is still subject of debate. Here we present a thermodynamic model to simulate the competition of cancer and normal cells in terms of bioenergetics. Our model shows that the Warburg effect has an advantage because the entropy production rate is increased and metabolic efficiency is decreased for cancer cells. Although inefficiency is generally considered a competitive disadvantage for living organisms, the thermodynamic model shows that it is not always the case. Indeed, when the energy resources are abundant and the system has a limited ability to export entropy, the organism with a higher rate of entropy production will have a higher chance of survival despite its lower metabolic efficiency. This thermodynamic model predicts that as long as there are enough nutrients in circulating blood, there are two thermodynamic strategies to control cancer cell populations, i. e., (i) decreasing the entropy production rate of cancer cells and (ii) increasing normal cells' entropy production rate. © 2019 Walter de Gruyter GmbH, Berlin/Boston 2019

Comment on: The cancer Warburg effect may be a testable example of the minimum entropy production rate principle

This comment argues against the view that cancer cells produce less entropy than normal cells as stated in a recent paper by Marin and Sabater. The basic principle of estimation of entropy production rate in a living cell is discussed, emphasizing the fact that entropy production depends on both the amount of heat exchange during the metabolism and the entropy difference between products and substrates. © 2018 IOP Publishing Ltd