ASPIRATION TO OBTAIN OSTEOBLAST PROGENITOR CELLS FROM HUMAN BONE-MARROW - THE INFLUENCE OF ASPIRATION VOLUME

Bone marrow contains osteoblast progenitor cells that can be obtained with aspiration and appear to arise from a population of pluripotentia l connective-tissue stem cells. When cultured in vitro under condition s that promote an osteoblastic phenotype, osteoblast progenitor cells proliferate to form colonies of cells that express alkaline phosphatas e and, subsequently, a mature osteoblastic phenotype. We evaluated the number of nucleated cells in bone-marrow samples obtained with aspira tion from the anterior iliac crest of thirty-two patients without syst emic disease. There were nineteen male patients and thirteen female pa tients; the mean age was forty-one years (range, fourteen to seventy-s even years). The prevalence and concentration of the osteoblast progen itor cells also were determined, by placing the bone-marrow-derived ce lls into tissue-culture medium and counting the number of alkaline pho sphatase-positive colony-forming units. In order to assess the effect of aspiration volume, two sequential experiments were performed. In th e first experiment, aspiration volumes of one and two milliliters were compared. In the second experiment, aspiration volumes of two and fou r milliliters were compared. The mean prevalence of alkaline phosphata se-positive colony-forming units in the bone-marrow samples was thirty -six per one million nucleated cells (95 per cent confidence interval, 28 to 47); a mean of 2400 alkaline phosphatase-positive colony-formin g units was obtained from a two-milliliter aspirate. There was a signi ficant difference among the patients with respect to the number of alk aline phosphatase-positive colony-forming units in these bone-marrow s amples (p < 0.001). Seventy per cent of this variation in the prevalen ce was due to variation among patients, and 20 per cent was due to var iation among aspirates.The number of alkaline phosphatase-positive col ony-forming units in the aspirate increased as the aspiration volume i ncreased. However, contamination by peripheral blood also increased as the aspiration volume increased. An increase in the aspiration volume from one to four milliliters caused a decrease of approximately 50 pe r cent in the final concentration of alkaline phosphatase-positive col ony-forming units in an average sample. CLINICAL RELEVANCE: On the bas is of these data, we recommend that, when bone marrow is obtained with aspiration for use as a bone graft, the volume of aspiration from any one site should not be greater than two milliliters. A larger volume decreases the concentration of osteoblast progenitor cells because of dilution of the bone-marrow sample with peripheral blood. We estimate that four one-milliliter aspirates will provide almost twice the numbe r of alkaline phosphatase-positive colony-forming units as will one fo ur-milliliter aspirate. In addition, these data confirm that humans di ffer significantly from one another with respect to the cellularity of bone marrow and the prevalence of osteoblast progenitor cells. Additi onal studies are necessary to determine if the number or prevalence of alkaline phosphatase-positive colony-forming units in bone marrow is a determining factor in the efficacy of an autogenous bone or bone-mar row graft and to ascertain how the number and function of alkaline pho sphatase-positive colony-forming units may change as a function of fac tors such as age, menopausal status, and selected diseases.