Animal-Inspired Regenerative Systems: A Conceptual 3-7-12 Framework for Limb Regeneration Research – From Comparative Regeneration Biology to a Testable, Safety-Gated Translational Research Program

Complex tissue regeneration requires more than cell proliferation. Regenerative organisms coordinate injury sensing, immune resolution, extracellular-matrix remodeling, positional information, vascular support, neural interactions, and growth termination in space and time. Recent work in axolotl limb regeneration has clarified the importance of positional memory, connective-tissue signalling centres, retinoic-acid regulation, Hedgehog-dependent patterning, and vascular signalling. At the same time, human translation remains constrained by the limited regenerative competence of adult mammals, safety requirements for cell-based interventions, and the difficulty of reproducing large-scale pattern formation. This manuscript proposes the 3-7-12 framework as a systems-level hypothesis generator for regenerative medicine. Code 3 organizes regeneration around three coupled domains: neural, immune, and connective/structural. Code 7 represents a process sequence from injury and haemostasis through inflammatory resolution, progenitor activation, pattern formation, tissue growth, maturation, and functional integration. Code 12 is used as a candidate network layer covering twelve signalling families frequently implicated in regeneration and tissue repair; it is not asserted that exactly twelve pathways universally govern regeneration. The framework is deliberately designed for falsifiability. It proposes computational modelling, human-cell and organoid experiments, spatial transcriptomics/proteomics, and staged animal studies to test whether coordinated multi-domain control can improve tissue repair without inducing uncontrolled proliferation, fibrosis, ectopic tissue, or systemic toxicity. The manuscript also defines evidence gates, intellectual-property opportunities, partnership models, and a commercialization pathway. The resulting proposition is not a ready-to-use clinical treatment; it is a research platform intended to help laboratories, biotechnology companies, medical-device developers, and strategic investors evaluate a coherent route from comparative biology to regulated translational development.