Physiological Mechanisms and Therapeutic Applications of Microneedling: A Narrative Review.

Microneedling (MN), also known as percutaneous collagen induction therapy, is a minimally invasive dermatologic procedure that stimulates the skin's intrinsic wound repair cascade by creating controlled micro-injuries to the epidermis and dermis using multiple small-sized needles. This review aims to document and discuss the skin's physiological mechanisms activated through the MN process and its therapeutic applications and, where possible, to describe the impacts on changes in the skin's biophysical properties. Three databases, namely, PubMed, Web of Science, and Embase, were searched for relevant peer-reviewed articles published in English between 1990 and 2024. After eliminating duplicate and irrelevant articles, 70 studies were included in this review. The main physiological mechanisms associated with the MN process were collagen and elastin production, angiogenesis, transient increases in skin permeability, and improved epidermal barrier function post-treatment. Therapeutic applications targeted cosmetic improvements, scar healing, and drug delivery. As the wound repair process is initiated, fibroblasts migrate to the wounded area to initiate collagen and elastin production, contributing to the improved firmness and elasticity of the healed epidermis. The micropores created by MN increase skin permeability, allowing hydrophilic water-soluble molecules to transfer across the skin to enhance transdermal drug delivery and absorption. Multiple growth factors are secreted by monocytes upon injury and contribute to collagen production, epithelization, and angiogenesis, which increase epidermal thickness and epidermal barrier enhancement found post-procedure. Additionally, TGFM-1, a cross-linker of the protein filaggrin, and ki67, a marker of cell proliferation, are upregulated following the controlled tissue injury. These upregulated biomarkers contribute to the increase in filaggrin and the improvement of skin barrier function. Ceramides, which help retain moisture and prevent transepidermal water loss, are also increased when MN is combined with a solution containing human adipose tissue stem cell-derived exosomes. The cosmetic applications included improvements in skin texture, wrinkles, and scarring. As a minimally invasive procedure, MN is reported to have a low risk of post-procedural hyperpigmentation, scarring, or other adverse effects.