Age-related osteogenic potential of mesenchymal stromal stem cells from human vertebral bone marrow

Mesenchymal stem cells (MSCs) residing in bone marrow (BM) are the progenit ors for osteoblasts and for several other cell types, In humans, the age-re lated decrease in bone mass could reflect decreased osteoblasts secondary t o an age-related loss of osteoprogenitors. To test this hypothesis, BM cell s mere isolated from vertebral bodies of thoracic and lumbar spine (T1-L5) from 41 donors (16 women and 25 men) of various ages (3-70 years old) after death from traumatic injury, Primary cultures were grown in alpha modified essential medium with fetal bovine serum for 13 days until adherent cells Formed colonies (CFU-Fs), Colonies that stained positive for alkaline phosp hatase activity (CFU-F/ALP(+)) were considered to have osteogenic potential . BM nucleated cells were plated (0.5, 1, 2.5, 5, or 10 x 10(6) cells/10-cm dish) and grown in dexamethasone (Dex), which promotes osteoblastic differ entiation. The optimal plating efficiency using BM-derived cells from donor s of various ages was 5 x 10(6) cells/10-cm dish. BM-derived cells were als o grown in the absence of Dex at this plating density, At the optimal plati ng density, in the presence of Dex, the number of CFU-F/ALP(+) present in t he BM of the younger donors (3-36 years old) was 66.2 +/- 9.6 per 10(6) cel ls (mean +/- SEM), but only 14.7 +/- 2.6 per 10(6) cells in the older donor s (41-70 Sears old), With longer-term culture (4-5 weeks) of these BM cells in medium containing 10 mh I beta-glycerophosphate and 100 mu g/ml ascorbi c acid, the extracellular matrix: mineralized, a result consistent with mat ure osteoblastic function, These results demonstrate that the number of MSC s with osteogenic potential (CFU-F/ALP(+)) decreases early during aging in humans and may be responsible for the age-related reduction in osteoblast n umber, Our results are particularly important in that the vertebrae are a s ite of high turnover osteoporosis and, possibly, the earliest site of bone loss in age-related osteoporosis.