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Stem Cell and Progenitor (CFC) Assays
Highly sensitive and biologically relevant assays of hematopoietic and non-hematopoietic stem cells and progenitors have a valuable place in the drug development process. Drug screening has typically been performed with high throughput assays using immortalized cell lines and relatively simplistic end points like cell death or cell proliferation. However, use of cell lines to generate meaningful biological data in the drug screening process has many limitations. For instance, individual cell lines generally represent mature cell types from single lineages and they are often prone to genetic instability. They are an artificial biological state and are not necessarily representative of the natural situation in vivo. One way to potentially improve the efficiency of the drug pipeline (and therefore decrease the expense) is to introduce a biologically relevant
'high content' assay into the drug discovery process that overcomes these limitations. In contrast to cell lines, primary cells
- and in particular stem cells and progenitor cells
- have much more fastidious and normal growth and proliferation requirements, and better represent in vivo conditions. Use of primary cells in the drug screening process, therefore, can increase assay sensitivity and biological relevance. In addition, various primary cells may be cultured together, allowing the study of drug effects on cell-cell interactions that mirror the natural in vivo state and the effects of test compounds on these interactions to be assessed.
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Hematopoietic and non-hematopoietic stem cells and progenitors can be assessed using a variety of well characterized in vitro assays. Of these, the Colony Forming Cell (CFC) or Colony Forming Unit (CFU) assays are the most widely applicable. Conditions have been developed that support the in vitro formation of morphologically distinct colonies of hematopoietic cells (including red blood cells, granulocytes, macrophages, platelets, etc) and non-hematopoietic cells (e.g. mesenchymal) by the clonal growth and maturation of progenitor cells. Specific formulations of different growth factors and other nutrients within the assay medium determine which type of progenitor colony develops within the culture system.
Hematopoietic Progenitor Assays
Colony Forming Cell (CFC) assays
are well characterized assays
that can detect an increase or
decrease in the frequency of
hematopoietic progenitor
proliferation in response to
stimulatory or inhibitory (or
toxic) agents. The relatively
long incubation period (14 days)
increases the sensitivity of the
assay and allows the detection
of more long-term effects than
are detectable in a simple
proliferation assay. Since
cultures are assessed
morphologically, distinct
progenitor lineages can be
discriminated and lineage-specific effects of compounds
can be detected. This is in
sharp contrast to simple
proliferation assays, which only
provide an aggregate readout of
all proliferating cells and cell
types within a bulk culture. It
is also possible to detect
informative qualitative effects
on individual cell morphology
with CFC assays, even at
compound concentrations that do
not affect absolute colony
number or proliferative
potential. Furthermore, if
desired, colonies can be
individually removed from the
semi-solid growth matrix for
genotypic and/or phenotypic
analysis of the (clonal) cell
population. For information
about in vitro hematopoietic
progenitor assays provided by
ReachBio,
click here.
Non-hematopoietic Progenitor Assays
Like their hematopoietic counterparts, non-hematopoietic progenitors can be assessed using a Colony Forming Cell assay known as the CFU-F assay. The CFU-F assay is used to detect and quantify mesenchymal stem cells (MSC). This assay was first described in 1970 by Alex Friedenstein and colleagues and has been very well characterized. The 14 day CFU-F assay has been used to detect deleterious effects of toxic agents and ionizing radiation on the marrow microenvironment. Similar to the high content data provided by hematopoietic CFC assays, data provided by the CFU-F assay can be both quantitative (number of colonies) and qualitative (altered appearance and size of colonies). For full information about ReachBio's in vitro non-hematopoietic progenitor assays,
click here.
Value of CFC Assays in Drug Development
The data provided by CFC assays are often more predictive of the clinical situation than data derived using cell lines. Therefore, they are of particular utility when the goal is to identify toxic compounds and exclude them before costly clinical trials commence. It has been estimated that the average drug takes 10-15 years to get to market at a cost of approximately $800 million*. The use of exquisitely stringent tests such as CFC assays within the drug screening process can help to eliminate late drug failure and save much of the time and costs currently associated with drug development. However, despite the obvious value and utility of CFC assays in the drug development process, they are perceived by many to be time-consuming and technically challenging. ReachBio removes these obstacles and makes the power of sensitive CFC assays available to biopharma organizations of all sizes by providing fee-for-service access to highly trained and knowledgeable scientists with many years experience in performing reproducible CFC assays and interpreting the resulting data.
* Tufts Center for Study of Drug Development report, November 2001
ReachBio's Commitment to our Clients
ReachBio understands and appreciates the premium its clients put on the confidentiality of their research programs. We are also sensitive to the fact that often time is of the essence and waiting for results from outside service providers such as CROs can be frustrating and costly. We appreciate the overall time and financial commitments related to outsourced research and endeavor to provide the highest level of professional conduct to all our clients, regardless of size. At the same time, we strive to reduce the time taken in the entire process of working with us - from upfront contract and CDA negotiations and other paperwork, to performing the assays and delivering the results in a complete and thorough report. We operate under a strict fee-for-service model and have no affiliations with R&D programs that might result in conflicts of interest or other issues related to our clients' intellectual property.
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