1. Scope

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Rationale

Approved treatments with hematopoietic stem cells (HSCs) approach 70,000 worldwide each year; and both HSCs and mesenchymal stem cells (MSCs) are the focus of hundreds of clinical trials evaluating both stem cell therapies and gene therapies that utilize HSCs. Currently, all these important treatments are administered to patients without a method to determine the specific dosage, or differential count, of the critical tissue-stable, homeostatic, tissue cell-renewing stem cells in treatment samples that are essential for curative therapies. In the case of HSC transplantation therapies, the flow cytometry-based CD34+ cell count is used for the dosage basis. However, the CD34 cell count is known to be inaccurate for HSC quantification, because it also includes the number of more-abundant, non-curative, committed progenitor cells, which are also present in treatment samples. A similar cell specificity problem occurs with the use of other cellular biomarkers for other tissue stem cell types like MSCs (e.g., CD90, CD105, CD73). A standard test method for differential tissue stem cell counting is also lacking in the fields that are the foundations and extensions of tissue stem cell transplantation medicine. Presently, experimental cell and tissue research, including tissue stem cell research per se, lacks a practical standard test method for accurately and precisely counting tissue stem cells in experiments and analyses. The same need exists in the related fields of drug development, tissue cell production and supply, and cell and tissue biomanufacturing, including research and development for the emerging cultured food cell industry. New technologies are now available for quantifying the differential count of tissue stem cells, including hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). As these new methods are adopted and come into wider usage, their standardization is important for ensuring their proper use for accuracy and precision.