Stem Cell Niche Concept: Search for Current Expert Consensus.

Postnatal stem cells are crucial for tissue homeostasis and repair and are regulated by specialized microenvironmental microterritories known as "stem cell niches". Proposed by R. Schofield in 1978 for hematopoietic stem cells, niches maintain self-renewal, guide differentiation and maturation, and can even revert progenitor cells to an undifferentiated state. Niches respond to injury, oxygen levels, mechanical cues, and signaling molecules. While the niche concept has advanced regenerative medicine, bioengineering, and 3D bioprinting, further progress is hindered by inconsistent interpretations of its core principles. To address this, we proposed a consensus-building initiative among experts in regenerative medicine and bioengineering. We have developed a questionnaire covering the niche topography, hierarchy, dimension, geometry, composition, regulatory mechanisms, and specifically the mesenchymal stem cell niches. This pilot survey, being conducted under the auspices of the National Society for Regenerative Medicine in the Russian Federation, aims to establish a standardized framework on the eve of the 50th anniversary of Schofield's hypothesis. The resulting consensus will guide future research and innovation in this pivotal field.