[New progresses of studies on essence of meridian-collaterals of traditional Chinese medicine].

The meridian-collateral theory introduced in the classic book Huangdi Neijing (The Yellow Emperor's Canon of Internal Medicine,) has been being guiding the clinical diagnosis and treatment of diseases and health preservation by using traditional Chinese medicine (TCM) for thousands of years. However, despite of being the core theory of TCM, the meridian-colla-terals and their structural basis have not been scientifically clarified, which has become the "bottleneck" of the inheritance and innovation of TCM. It was reported in 2020 that the micro-channels formed by collagen fiber bundles in the skin and their contained components and the newly found interstitial cell, Telocyte, may be considered to be the ultra-micromorphological basis including their connection with the internal organs. In the present paper, we employed the Telocyte network and its relationships with other structures and cells to interpret, at the cellular level, various meridian hypotheses including 1) neurotheory, 2) humoral circulation theory, 3) biological field hypothesis, 4) fascia theory, 5) immune theory, 6) mast cell theory, 7) meridian-qi, and 8) elusive phenomenon of meridian. The absence of meridian-collaterals in morphology may be related to the difficulty of laboratory sample preparations of Telocyte processes in the continuity and completeness. We also proposed that the future research strategies should be aimed at revealing the morphological structure (including in vitro studies of the isolated and cultured Telocytes), establishment of relevant disease model, and clarification of the interrelation between the Telocyte network and the systems of nerve, blood circulation, immune, endocrine, and connective tissue.