Does the number or quality of pluripotent bone marrow stem cells decrease with age?

In the next 25 years, as the 37 million baby boomers age, we can expect a 400% increase in total joint arthroplasties that will challenge surgeons, the healthcare system, and the scientific community. The burden may be eased if we are able to manipulate side population stem cells and enhance peri-prosthetic bone remodeling thereby reducing the incidence of revisions. Therefore, as a preliminary question, we asked if the number and quality of side population stem cells, with the ability to proliferate into multiple cell lineages for long periods, correlates with age and can be evaluated in peripheral blood. Using flow cytometry we analyzed the quantity and quality of side population stem cells from bone marrow and peripheral blood in 54 patients (20 under 60 years of age, 34 over) undergoing THA. The total side population of stem cells decreased with age, but their long-term repopulating ability (quality) remained constant. The total count of side population stem cells in marrow correlated with the number found in peripheral blood. If these populations can be manipulated, periprosthetic remodeling may be beneficially enhanced.