Non-multipotent stroma inhibit the proliferation and differentiation of mesenchymal stromal cells in vitro.
OBJECTIVE
The ability to expand and maintain bone marrow (BM)-derived mesenchymal stem cells (MSC) in vitro is an important aspect of their therapeutic potential. Despite this, the exact composition of stromal cell types within these cultures and the potential effects of non-stem cells on the maintenance of MSC are poorly understood.


METHODS
C57BL/6J BM stroma was investigated as a model to determine the relationship between MSC and non-multipotent cells in vitro. Whole BM and single-cell derived cultures were characterized using flow cytometry and cell sorting combined with multipotent differentiation. Proliferation of individual stromal populations was evaluated using BrdU.


RESULTS
At a single-cell level, MSC were distinguished from committed progenitors, and cells lacking differentiation ability, by the expression of CD105 (CD105+). A 3-fold reduction in the percentage of CD105+ cells was detected after prolonged culture and correlated with loss of MSC. Depletion of CD105+ cells coincided with a 10-20% increase in the frequency of proliferating CD105(-) cells. Removal of CD105(-) stroma caused increased proliferation in CD105+ cells, which could be diminished by conditioned media from parent cultures. Comparison of the multipotent differentiation potential in purified and non-purified CD105+ cells determined that MSC were detectable for at least 3 weeks longer when cultured in the absence of CD105(-) cells.


CONCLUSIONS
This work identifies a simple model for characterizing the different cellular components present in BM stromal cultures and demonstrates that stromal cells lacking multipotent differentiating capacity greatly reduce the longevity of MSC.
Rosu-Myles
Michael
M
Centre for Biologics Research, Biologics and Genetic Therapies Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada. michael.rosu-myles@hc-sc.gc.ca
Fair
Joel
J
Pearce
Nelson
N
Mehic
Jelica
J
D000818:Animals; D001853:Bone Marrow / Q000473:pathology; D002450:Cell Communication; D002454:Cell Differentiation; D049109:Cell Proliferation; D002469:Cell Separation; D002478:Cells, Cultured; D018920:Coculture Techniques; D000071063:Endoglin; D005434:Flow Cytometry; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism*; D017154:Stromal Cells / Q000378:metabolism* / Q000473:pathology
D000071063:Endoglin; C502004:Eng protein, mouse; D047908:Intracellular Signaling Peptides and Proteins