growing and isolating cells in culture

• Intact tissues contain complex mixtures of cell types and extracellular matrix. Biochemical preparations from tissues can obtain proteins but do not isolate specific cell types.
• Cultured cells provide homogeneous populations for easier biochemical analysis. Microscopy and testing effects of molecules is possible.
• To isolate cells, tissues are treated with proteolytic enzymes like trypsin and collagenase to digest extracellular matrix proteins. EDTA chelates calcium needed for cell adhesion. Gentle agitation then separates cells.
• Cells require a solid surface to grow, usually plastic culture dishes. Coating dishes with matrix components is often necessary.
• Primary cultures come directly from tissues, with or without initial separation of cell types. Cells from primary cultures can be repeatedly subcultured into secondary cultures.
• Cultured cells often maintain differentiated properties of their tissue of origin. Examples are fibroblast collagen secretion, muscle cell contraction, neuron electrical signaling and synapses. This allows study of cell properties.
•  Embryonic stem cells are pluripotent. They can differentiate into many cell types with appropriate signals. Organoids mimic 3D structure and function of organs.
• Vertebrate cells undergo replicative senescence after a finite number of divisions, due to telomere shortening. Telomerase immortalizes some cells. Others need oncogenes to avoid culture shock.
• Transformed cell lines from cancers differ from normal cells but are useful for large uniform populations. Normal cells can be transformed with viruses or chemicals. 
• Hybridomas produced by fusing B cells and transformed cells generate monoclonal antibodies. These are important research and therapeutic tools due to uniform specificity and large quantities.