Ferret/Mink Midkine (MK) is a heparin-binding growth factor and cytokine that plays important roles in cell growth, survival, and tissue repair in ferrets (Mustela putorius furo) and mink (Neogale vison). The midkine protein is identical at the amino acid level in these two species, reflecting strong evolutionary conservation of this growth factor within mustelids. Midkine is highly expressed during embryonic development and can also be induced in adult tissues in response to injury, inflammation, or physiological stress. Ferret and mink midkine interact with several cell surface receptors, including receptor-type protein tyrosine phosphatase ζ (PTPRZ1), low-density lipoprotein receptor–related proteins (LRPs), and integrins, activating intracellular signaling pathways such as MAPK, PI3K–AKT, and NF-κB that regulate cell proliferation, migration, and survival. Through these mechanisms, midkine contributes to processes including tissue regeneration, angiogenesis, immune cell recruitment, and inflammatory regulation. In cell culture, recombinant ferret/mink midkine is commonly used to stimulate cell proliferation and migration and to study growth factor–mediated signaling pathways involved in tissue repair and inflammatory responses. Ferrets and mink are also used in infectious disease research models, making midkine relevant for studies investigating tissue injury, immune regulation, and host responses during viral infection.