The Immunologic Spectrum of Biostimulators and Its Clinical Importance.

Background: Biostimulators have become important tools in aesthetic medicine to address age-related volume loss and tissue changes. They stimulate the body's natural processes to produce collagen and other components that contribute to a youthful appearance. Understanding the immunologic mechanisms underlying these processes is crucial for achieving optimal clinical outcomes. We thus sought to review the immunologic mechanisms underlying the action of biostimulators and their implications in clinical practice in aesthetic medicine. Methods: A comprehensive literature review was conducted to examine the diverse immunologic mechanisms triggered by commonly used biostimulators, including poly-l-lactic acid, polycaprolactone, and calcium hydroxylapatite, with a particular focus on their physicochemical properties and clinical effects. Results: Biostimulators elicit variable wound-healing immune responses based on their physicochemical properties. Injecting a biomaterial recognized immunologically as nonself will follow a foreign body pathway, producing outcomes that can vary from those of an immunologically familiar biomaterial. The extent of tissue regeneration is influenced primarily by the injected biomaterial's physicochemical properties, and particle size and shape. Other factors (eg, injection technique and contamination) can also influence outcomes. Biostimulator choice depends on specific clinical goals and patient characteristics. All of these factors require consideration when formulating treatment strategies for tissue regeneration. Conclusions: Biostimulators elicit a spectrum of immunologic responses dependent on their physicochemical properties, ultimately producing clinical outcomes tending toward replacement or regeneration of native tissue. Understanding their immunologic mechanisms allows for optimal selection and use to achieve desired outcomes. Further research is needed to elucidate the complex immune responses to different biostimulators.