Stem cells possess inherent properties of self-renewal and differentiation, and thus hold significant promise for regenerating damaged tissues or replacing lost cells. Unless their therapeutic effects are solely mediated by paracrine, transplanted stem cells need to be highly plastic to adapt to the host tissue environment and differentiate into constituent tissue-specific cells for tissue repair. Stem cells used in current cell-based therapies either have limited differentiation potential or are pluripotent but must be strictly restricted to avoid tumorigenicity risk in vivo. Here, we describe the derivation of human adult high-plasticity stem cells, which we call guide-integrated adult stem cells (giaSCs), from the interaction of blood-derived guide cells and umbilical cord tissue-derived mesenchymal stromal cells (UC-MSCs). The guide cells are a cell population derived from the peripheral blood of human adults. Unidirectional transfer through nanotube-like structures of granular substances from the guide cells into the recipient UC-MSCs gave rise to giaSCs. Topical application of human giaSCs into full-layer excisional wounds of wild-type mice led to reconstitution of skin tissue. Systemically administered human giaSCs migrated to and reside in mouse small intestinal tissue damaged by lipopolysaccharides and then differentiated into small intestinal epithelial cells for tissue repair. These transplantation experiments demonstrated that giaSCs have in vivo high plasticity. Additional in vivo and in vitro data showed that giaSCs have low immunogenicity and are nontumorigenic. These data indicate that giaSCs offer a highly promising approach to stem cell therapy.