Cell expansion
Thermoresponsive hydrogels for chondrocyte expansion
Only small numbers of cells can be taken from the patient, and these must be expanded using tissue culture techniques to produce clinically useful amounts of material. Conventionally this expansion is carried out on tissue culture plastic, as most cell types die if not presented with a suitable solid support on which to develop. After a period of expansion the cells must be removed from the substrate, a process that requires the use of potentially harmful enzymes.
As a consequence, we are investigating the use of thermoresponsive hydrogels as replacements for tissue culture polystyrene for cell expansion. These materials undergo a physical and chemical phase change at about 37 C, causing them to release cells from their surface in response to a small drop in temperature.
See polymer and biomaterials chemistry laboratories website for more details.
Cell culture viability
Tissue engineering takes a small number of healthy cells from the patient and grows these into larger replacement tissues in vitro, after which they are re-implanted into the patient to replace damaged or diseased tissues.
The longer cell cultures can be kept viable, the smaller the original sample of cells need be to generate enough cells for re-implantation. Over time, however, it is found that cells de-differentiate, and may not be able to re-integrate with the patient's tissues.
Hyaluronic acid receptors on the cell are responsible for it adhering to the extracellular matrix in a tissue, fundamental to the re-integration process. The presence of hyaluronic acid receptors is controlled by the CD44 gene, the expression of which can be monitored in cells as a measure of their continuing utility for clinical treatments.
Researchers engaged in this work are Dr Aileen Crawford, Linda Elowsson, Greg Parker, Prof. Paul Hatton, Dr. Adrian Jowett, James Lapworth and Dr Steve Rimmer (Department of Chemistry)
Above right: Human cartilage cells stained green for CD44 activity. The upper micrograph shows cells fresh after collection, below are cells at the same scale after six passages. The older cells stain less intensely, but still show the desired activity.