Concept of Hematopoietic and Stromal Niches for Cell-Based Diagnostics and Regenerative Medicine (a Review)

Background: R. Schofield (1978) proposed a hypothesis of hematopoietic stem cells (HSCs) niche (specialized cell microenvironment). An existence of osteoblastic and vascular niches for HSCs has been postulated since 2003. At the same time, the discussion about the existence and functioning of niche for multipotent mesenchymal stromal cells (MMSCs) is just beginning to develop. The design of artificial materials capable of biomimetical reproduction of the cellular and tissue microenvironment based on ideas and main elements borrowed from wildlife is an experimental approach in search of the stem cell niches. Results: Recent attempts to model the microterritories (niches) for HSCs have been undertaken and the behavior of cells in such structures has been investigated. However, the main quantitative factors involved in the original design of stem cell microterritories remain unknown. At the modern stage, the topography, hierarchy, and the size of the niches have to be determined, because the definition of the niches as morphological (structural and functional) units (microterritories), which provides the conditions for vital activity of stem cells, implies finite values of its parameters. The aim of this review was the critical review of key milestones of the niche concept for HSCs and MMSCs as we understood it. Conclusion: We speculated our definition of the stem cell niche, proposed and described certain stages (postulation; morphofunctional; topographical; quantitative; bioengineering) of the niche theory development. Prospective directions of the niche designing for cell-based diagnostics and regenerative medicine were noted.