Hair regeneration depends on a complex interplay between the activation of hair follicle stem cells (HFSCs), maintenance of inductive capacity in the dermal papilla (DP), and the re-establishment of immune microenvironmental homeostasis. Collectively, this interplay underlies a fundamental 'restart' of a multicellular regenerative network. In their role as post-transcriptional regulators, micro-RNAs (miRNAs) exert network-level control over cell fate transitions, paracrine signaling, inflammatory thresholds, and fibrotic processes via the RNA-induced silencing complex (RISC). For this reason, miRNAs have emerged in recent years as key targets for hair regenerative therapies. Recent studies indicate that miRNAs enhance HFSC entry into the active growth phase (i.e., anagen) through pro-regenerative signaling pathways such as Wnt/β-catenin and Sonic hedgehog (Shh), while also mediating the initiation of catagen phase via TGF-β/BMP signaling, extracellular matrix remodeling, and androgen receptor (AR)-associated regressive signaling. In some immune-mediated alopecias (e.g., alopecia areata), miRNA regulation of inflammatory axes, including IFN-γ/JAK-STAT and NF-κB, provides additional therapeutic targets that could potentially be exploited to restore hair follicle immune privilege. In this context, miRNA mimics and inhibitors (e.g., antagomirs and locked nucleic acids, LNAs) enable gain-of-function or blockade, respectively, providing tools that can be used individually or as combined regimens to stimulate regeneration simultaneous with anti-regression/immune remodeling. Recent developments using chemical modifications (e.g., 2'-O modifications, 2'-F, and LNA) improve nucleic-acid stability and modulate RISC loading. From a delivery standpoint, lipid nanoparticles, polymeric nanocarriers, exosome mimetics, and physical enhancement strategies such as microneedles and iontophoresis may help overcome the skin barrier and exploit the follicular "reservoir effect" for localized targeting. Major barriers to clinical translation remain, however, including off-target and network side effects arising from miRNAs' multi-cellular roles in vivo, risk of local immunogenicity and inflammation, alignment of dose-schedule with the hair cycle, and batch consistency with CMC/quality-control requirements for delivery systems. This review summarizes recent developments in understanding the mechanisms, delivery platforms, and translational challenges of miRNAs and their mimics in hair regeneration. It further proposes a translational roadmap centered on modular pathway-guided combinatorial nucleic-acid strategies, follicle-targeted delivery, and standardization of efficacy endpoints to inform future clinical development in this area.
