Mouse model of selective cryolipolysis.

BACKGROUND: Cryolipolysis is a noninvasive method of destroying adipocytes using controlled cooling, thereby enabling localized and targeted fat reduction. Due to their greater vulnerability to cold injury, adipocytes are selectively targeted, while other cell types are spared. OBJECTIVES: This study aims to develop a mouse model of cryolipolysis to offer a reliable and convenient alternative to human models, providing a methodology to validate clinical hypotheses in-depth with relative ease, low cost, and efficiency. This further facilitates comprehensive studies of the molecular mechanisms involved in cryolipolysis. MATERIALS AND METHODS: Mice (C57BL/6J) were placed under general anesthesia and were treated using our custom, miniaturized cryolipolysis system. A thermoelectric cooling probe was applied to the inguinal (ING) area for either a cold exposure of -10°C, or for a room temperature exposure for 10 minutes. The thickness of the subcutaneous fat of the mice was quantified using an optical coherence tomography (OCT) imaging system before and after the treatment. Histological analyses were performed before and after cryolipolysis at multiple time points. RESULTS: OCT analysis showed that mice that underwent cold cryolipolysis treatment induced a significantly greater reduction of subcutaneous fat thickness 1 month after treatment than the control mice. The mice that received cold treatment had no skin injuries. The selective damage of adipocytes stimulated cold panniculitis that was characterized histologically by infiltration of immune cells 2 and 3 days after treatment. CONCLUSION: This study shows that cryolipolysis performed in mice yields reproducible and measurable subcutaneous fat reduction, consistent with previous studies conducted in humans and pigs. Future studies can utilize the model of selective cryolipolysis developed by our group to further elucidate the cellular and molecular mechanisms of fat cell loss and improve clinical outcomes in humans.

First Assessment of a Carbon Monoxide Laser and a Thulium Fiber Laser for Fractional Ablation of Skin.

BACKGROUND AND OBJECTIVES: A recent generation of 5,500 nm wavelength carbon monoxide (CO) lasers could serve as a novel tool for applications in medicine and surgery. At this wavelength, the optical penetration depth is about three times higher than that of the 10,600 nm wavelength carbon dioxide (CO2 ) laser. As the amount of ablation and coagulation is strongly influenced by the wavelength, we anticipated that CO lasers would provide extended coagulation zones, which could be beneficial for several medical applications, such as tissue tightening effects after laser skin resurfacing. Until now, the 1,940 nm wavelength thulium fiber (Tm:fiber) laser is primarily known as a non-ablative laser with an optical penetration depth that is eight times higher than that of the CO2 laser. The advantage of lasers with shorter wavelengths is the ability to create smaller spot sizes, which has a determining influence on the ablation outcome. In this study, the ablation and coagulation characteristics of a novel CO laser and a high power Tm:fiber laser were investigated to evaluate their potential application for fractional ablation of the skin. STUDY DESIGN/MATERIALS AND METHODS: Laser-tissue exposures were performed using a novel CO laser, a modified, pulse-width-modulated CO2 laser, and a Tm:fiber laser. We used discarded ex vivo human skin obtained from abdominoplasty as tissue samples. Similar exposure parameters, such as spot size (108-120 µm), pulse duration (2 milliseconds), and pulse energy (~10-200 mJ) were adjusted for the different laser systems with comparable temporal pulse structures. Laser effects were quantified by histology. RESULTS: At radiant exposures 10-fold higher than the ablation threshold, the CO laser ablation depth was almost two times deeper than that of the CO2 laser. At 40-fold of the ablation threshold, the CO laser ablation was 47% deeper. The ablation craters produced by the CO laser exhibited about two times larger coagulation zones when compared with the CO2 laser. In contrast, the Tm:fiber laser exhibited superficial ablation craters with massive thermal damage. CONCLUSIONS: The tissue ablation using the Tm:fiber laser was very superficial in contrast to the CO laser and the CO2 laser. However, higher etch depths should be obtainable when the radiant exposure is increased by using higher pulse energies and/or smaller spot sizes. At radiant exposures normalized to the ablation threshold, the CO laser was capable of generating deeper ablation craters with extended coagulation zones compared with the CO2 laser, which is possibly desirable depending on the clinical goal. The effect of deep ablation combined with additional thermal damage on dermal remodeling needs to be further confirmed with in vivo studies. Lasers Surg. Med. © 2020 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.