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SUMMARY POINTS
What’s Important?
Adipocytes, or fat cells, are a major component of the subcutaneous tissue in the human body. In addition to playing roles in thermogenesis and metabolism, these cells perform various nonmetabolic functions including antimicrobial defense, hair cycling, and wound healing.
Changes in the production, distribution, and degeneration of facial adipose tissue have significant aesthetic implications that can be targeted with cosmetic procedures.
What’s New?
Collagenase clostridium histolyticum injections have been shown to improve cellulite and were approved by the FDA in 2020.
Emerging biomechanical studies have improved the clinical understanding of the sex- and age-related pathogenesis of cellulite and other adipose-related disease processes.
Newly uncovered mechanisms of adipocyte plasticity are promising avenues of research in the prevention of cutaneous disease and advancement of regenerative medicine.
What’s Coming?
Further study is needed to characterize macro- and micro-characteristics of facial adipose tissue and their age-related changes across different anatomic compartments.
Large-scale, standardized, and prospective clinical studies are necessary to evaluate various harvesting, processing, and delivery methods for autologous fat transfer. The risks and benefits of supplementation strategies including platelet-rich plasma, progenitor cells, and functional growth factors should be similarly evaluated.
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Subcutaneous tissue, or the hypodermis, is one of the largest tissues in the human body. The major components of this layer are adipocytes, fibrous tissue, and blood vessels. It is estimated that this layer represents 9% to 18% of body weight in normal-weight men and 14% to 20% in women of normal weight.1 In severe obesity, fat mass can increase by up to four times and represent 60% to 70% of total body weight.2 Though gaining fat in the body is undesirable for many, losing fat in the face has cosmetic implications as well. Adipose tissue gains and losses and volume changes contribute to the aged appearance of the face and body. This chapter will review the importance of the subcutaneous tissue and its various functions.
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The subcutaneous tissue is usually not given as much attention as the dermis and epidermis because pathology at superficial layers is easier to detect or diagnose by a shave or small punch biopsy. Subcutaneous tissue usually must have an extensive defect before it is noticed, and an incision or large punch biopsy (e.g., 6 mm) is required to biopsy this area. During histologic tissue processing of biopsy tissue, the triglyceride component, which is the major component of adipocytes, is removed by alcohol and xylol. For this reason, subcutaneous tissue has long been ignored. However, with advances in diagnostic methods and new treatments, much more has been learned about the subcutaneous layer (Box 3-1). It is important for dermatologists and cosmetically oriented physicians to pay close attention to this tissue because it plays multiple roles in cosmetic dermatology and general appearance.
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BOX 3-1 Functions of the Subcutaneous Tissue
The largest repository of energy in the body.
Stores fat-soluble vitamins (A, D, E, ...