The Colony-Forming Unit - Fibroblast was introduced by Friedenstein and coworkers in 1971. It is considered a Mesenchymal Progenitor Cell present in the bone marrow. The cells are adherent in nature and despite their low frequency, estimated at about 1 in 100,000 bone marrow cells, they can be grown and expanded in culture and still retain their ability to differentiate into a number of different cell types under the correct culture conditions.
The CFU-F assay is shown diagrammatically below. Mononuclear cells are separated from the whole bone marrow and used as target cells. They are usually plated into 100mm Petri dishs with medium that can support the production of MSC and incubated initially for 14 days at 37°C in 5% CO2. After this time, "colonies" of adherent fibroblasts can be observed under the microscope. It should be pointed out that such "colonies" are only observed under the correct cell density and time contraints, since the cells will continue to proliferate and divide to confluency. To observe and count these colonies, it is usually necessary to stain the cells in situ by first fixing the cells with methanol and staining with Wright's Giemsa solution.
It follows that this, like the traditional colony-forming assay is an extremely laborious and tedious method. Since the CFU-F population is a proliferating and expanding population, it can be easily measured using an ATP-based bioluminescence proliferation assay. HemoGenix® has therefore developed the LUMENESC™ to detect MSC and the CFU-F population.
