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The olfactory epithelium (OE) of the mammal is uniquely suited as a model system for studying how neurogenesis and cell death interact to regulate neuron number during development and regeneration. To identify factors regulating neurogenesis and neuronal death in the OE, and to determine the mechanisms by which these factors act, investigators studied OE using two major experimental paradigms: tissue culture of OE; and ablation of the olfactory bulb or severing the olfactory nerve in adult animals, procedures that induce cell death and a subsequent surge of neurogenesis in the OE in vivo. These studies characterized the cellular stages in the olfactory receptor neuron (ORN) lineage, leading to the realization that at least three distinct stages of proliferating neuronal precursor cells are employed in generating ORNs. The identification of a number of factors that act to regulate proliferation and survival of ORNs and their precursors suggests that these multiple developmental stages may serve as control points at which cell number is regulated by extrinsic factors. In vivo surgical studies, which have shown that all cell types in the neuronal lineage of the OE undergo apoptotic cell death, support this idea. These studies, and the possible coregulation of neuronal birth and apoptosis in the OE, are discussed.

Background and Objectives Helium plasma skin regeneration (PSR) is a novel skin rejuvenation technology with significant differences compared with nitrogen PSR technology but that may exert similar skin tissue effects. Study objectives included a comparison of acute and chronic skin tissue changes among the two plasmas in a porcine animal model. Study Design/Materials and Methods In this study, both helium and nitrogen gas plasmas were used to treat the dorsal skin of Yorkshire cross mini pigs with 20% (8.6 J/cm2) and 40% (17.8 J/cm2) power helium plasma single pass treatment (4 liter gas flow, continuous energy delivery, and linear non‐overlapping passes) compared with high energy nitrogen plasma double pass treatment (PSR3 @ 14.1 J/cm2: 4.0 J, 2.5 Hz pulse rate, overlapping horizontal, and vertical passes). Acute and chronic skin contraction, maximum acute depth of injury and chronic reparative healing depth were assessed along with representative histopathology in each treatment paradigm. Results High‐energy nitrogen plasma treatment exhibited greatest mean depth of acute tissue injury 4 hours post‐treatment whereas helium plasma treatment exhibited greater acute skin tissue contraction. Then, 20% and 40% power helium plasma treatment results were each very similar among animals as a percentage of nitrogen plasma treatment results for both depths of acute tissue injury and acute skin tissue contraction. Mean depths of reparative tissue healing were similar among treatment paradigms 30 days after treatment with significant intra‐ and inter‐animal variability observed within each treatment paradigm. Thirty‐day mean skin tissue contraction was greater for helium plasma treatment; however, the data varied significantly between animals in all paradigms. Histopathologic tissue evaluation after 30 days showed similar findings among the treatment paradigms with epidermal hyperplasia, flattening of rete ridges and with regenerative granulation tissue expanding the superficial and papillary dermis. Conclusions This study demonstrates modestly reduced depth of the thermal effect, greater skin tissue contraction and similarity of acute and chronic histopathological findings for helium plasma when compared with nitrogen plasma in a porcine animal model. © 2019 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals, Inc.

The micropulsed 1444-nm neodymium-doped lipolysis laser exhibits favorable characteristics for novel application in facial contouring. The study described herein is the first clinical report of laser-assisted facial contouring (LAFC). We retrospectively reviewed records of 478 LAFC patients (mean age 52) who underwent contouring of 1278 individual mid- and lower facial treatment sites over 18 months. Along with clinical assessment, study parameters evaluated among "original" and "modified" (where protocol updates included deep dermal soft tissue coagulation as an optional step) protocol groups included laser power, pulse energy, and total energy delivery as well as lipoaspirate volume at each treatment site. Mean power and pulse energy were similar (within 5%) and total energy use was greater (70% higher for mid- and lower face) in the original protocol group. Lipoaspirate volume was similar for both groups for the midface (within 10%) but elevated in the modified protocol group for the lower face (40% higher). Treatment complications were observed in 47 of 363 treatment sites (13%) in the original and in 12 of 915 treatment sites (1%) in the modified protocol group with the majority (63%) of the complications comprising over- versus undercorrections of desired tissue contour. Clinical efficacy varied with improvements of mid- and/or lower facial contour ranging from marginal to subtle to very apparent. LAFC as detailed herein is a novel treatment modality that enables selective soft tissue removal for greater precision in three-dimensional contouring of the face. Protocol modifications based on laboratory and observed tissue photothermodynamics have improved LAFC safety.