Human bone marrow mesenchymal stem cells in vivo.

Area of Science:

• Regenerative Medicine
• Cell Biology
• Stem Cell Research

Background:

• Significant confusion persists regarding the in vivo identity of human bone marrow mesenchymal stem cells (MSCs).
• Established methods for robust identification and purification of BM MSCs are available.
• Human BM MSCs exhibit a homogeneous phenotype, sharing characteristics with marrow adventitial reticular cells (ARCs) and pericytes.

Purpose of the Study:

• To clarify the in vivo identity and characteristics of human bone marrow mesenchymal stem cells (MSCs).
• To address the confusion surrounding MSC markers and their expression patterns.
• To establish a foundation for understanding MSCs in vivo for improved therapeutic development.

Main Methods:

• Extensive panel of markers used for BM MSC characterization.
• Rare cell phenotypical analysis.
• In vitro colony forming unit-fibroblast (CFU-F) assays.

Main Results:

• Diverse MSC markers reported in literature are expressed on the same cell population.
• No compelling evidence suggests BM MSCs circulate in healthy individuals.
• A definitive marker for MSC 'stemness' and multipotentiality remains undefined, as culture-expanded MSCs can retain multipotentiality despite marker loss.

Conclusions:

• Human BM MSCs are a phenotypically homogeneous population, identical to ARCs.
• Current evidence does not support the circulation of MSCs in healthy individuals.
• Understanding MSCs in vivo is crucial for advancing regenerative medicine and tissue engineering therapies.