Human cord blood lin-cd45- cells are capable of both hematopoietic and chondrocytic function

Human cord blood (CB) is an enriched source of pluripotent hemalopoietic stem cells present in rare numbers among a large heterogeneous collection of functional hematopoietic progenitors. With the exception of mature erythrocytes, cells within the human hematopoietic system are characterized by the cell surface expression of the pan-leukocyte receptor CD45. In adult bone marrow however, recent studies have provided evidence for the existence of CD45- mesenchymal stem cells capable of cartilage, bone and adipose differentiation potential. Here, we identify a novel subset among mononuclear cells depleted of lineage committed markers (Lin-) that is devoid of CD45 expression within full term umbilical cord blood. The majority of these Lin-CD45- cells lack the CD34 surface protein, a molecule currently used as a diagnostic tool for the identification of hematopoietic stem cells. Surprisingly, functional examination of Lin-CD45-CD34- cells revealed that this population is capable of giving rise to multipotential hematopoietic progenitors at a frequency of 1 in 100. In addition, co-culture of Lin-CD45-CD34- cells with mouse embryonic limb bud cells demonstrated that this population is capable of seeding early cartilage condensations and differentiating into human chondrocytes. Our study illustrates the existence of a novel population of Lin-CD45-CD34- cells capable of commitment into both hematopoietic and chondrocytic lineages. Moreover, since this population can be derived from easily procurable human cord blood tissue, isolation of such cells may provide a novel cell regenerative strategy for osteogenic disorders.