Hyaluronan as a novel marker for rapid selection of connective tissue progenitors.

Connective Tissue Progenitors (CTPs) in bone and marrow tissue are an important therapeutic target for bone regeneration. Concentration and selection of CTPs from the heterogenous population of cells in bone marrow remains a challenge due to their low prevalence. This study identifies surface-bound hyaluronan (HA), a component of the in vivo niche for CTPs, and evaluates HA as a useful surface marker for positive selection of CTPs. Mononuclear cells from bone marrow were labeled and magnetically separated on the basis of hyaluronan binding. HA(+++), HA(+) and HA(-) fractions were cultured and assayed for colony formation using a quantitative image-processing system. A mean of 2.7% of cells were retained in the HA(+++) fraction and were enriched by 3.4-fold (range of 95% CI: 2.3-4.8) in CTP prevalence when compared to the unselected buffy-coated bone marrow aspirate (BCM). In addition, colonies formed by HA(+++) CTPs demonstrated greater proliferation (more cells per colony) and greater alkaline phosphatase activity than CTP colonies derived from unselected BCM. These data demonstrate that one or more subsets of human marrow-derived CTPs retain a HA rich matrix on their surface at the time of harvest. HA(+++) CTPs may offer a useful cell population for regenerative therapies.