Biology tests based on the use of cells

Hi and welcome to this lesson on the use of cell  tests. You know that all plants and animals are  made of cells, and humans are no exception. Our  cells are not so different from those of other  organisms. Cells are very small and would not survive alone,   but in controlled conditions they live and proliferate, consume nutrients and O2,   produce CO2, mature and function somehow how they do inside our body. The job to keep   cells living and growing is called cell culture. The majority of cells that we use need a solid   surface to attach and grow. For this reason, cells are maintained in plastic dishes, to which cells   adhere happily.

Then we need to supply cells with a culture media, a red solution containing  

what they need: water, amino acids, vitamins, lipids and their favorite food: glucose 

Cells are kept in devices called incubators,  which provide the optimal conditions: the right  temperature, the right humidity, the  right concentration of oxygen and CO2.   It is essential to prevent their contamination with bacteria,   fungi or other microorganisms. For this reason, we need to manipulate cells in vertical flow hoods,   using sterile tools and instruments. Don’t miss the visit to the laboratory in next activities. 

Finally, we need special equipment to  evaluate the results of our experiments.  The most important thing for cell culture is -  of course… the cells! Clean and healthy cells can  be bought from specialized companies that store,  control and then sell many cell types…such  as neurons, or …adipocytes…or  thyroid cells, and many more.  It is very important to choose the right type of  cell for each experiment. Notably, some type of  cell, such as stromal cells, are easy to work  to with, while other types, like neurons,   are more delicate!  Oh Hi, Joe! Nice to see you.  Do you have a question for me?  Yes!

What basic tests can  we do with cells in culture?  Well, we can routinely measure many things,  like viability, proliferation, toxicity, cell  responses, accumulation of lipid  droplets, messanger RNAs and proteins.  So, here we are, a typical experiment. We have  the chosen cells in plastic dishes, in this  example these cells are pre-adipocytes. Then  we induce our pre-adipocytes to become mature  fat cells, and at the same time, we treat cells  with a chemical that we suspect to be obesogenic.  We give varying doses of this chemical – from  zero to high – and after some time.… we can  examine the cells, either visually with  a microscope, or with biochemical assays. 

In this case, we have stained cells with a dye  that colors lipids in red: so we can count lipid  droplets in the microscope. We repeat the  experiments, we plot the results in a table, we  calculate some statistics.  Sometimes we get a negative result,   that means no difference, which is good for us.  A similar approach can be applied for  other endocrine-related responses,   such as estrogenic and androgenic responses, thyroid stimulation,   insulin stimulation, lactogenic stimulation. Hi Joe, I guess you have another question, right?  Yes! Are there more advanced  questions that you can ask cells?  Yes, we can investigate  other biological processes,   like cell migration, cell metabolism, cell maturation and aging. 

Let’s move one step further: cultured cells can  be engineered to provide a fluorescent readout.  In this case GFP is a protein that is bright  green. We engineer a DNA that contains GFP and…  we inject this gene inside our  cells, a process called transfection.   In this way, cell will start producing GFP and will turn green. But we   link the GFP with a piece of DNA that responds to something. In this case, responds to estrogen.   Well, the cell will turn green but only when estrogens or simil-estrogens are present.   The same for androgen, we build a DNA with the red fluorescence, and the cells will turn red only   when androgens are around.

This is very nice indeed, as fluorescence can be   measured precisely and quickly. In this other example we use a neuron response   linked with GFP. You can clearly see the neuronal extensions bright green.  Some experiments go much further. In the analyses  called omics instead of one parameter at a  time (1 gene, 1 protein, 1 analyte) we try  to examine all parameters, if possible. These  experiments are very expensive, require  special equipment and lots of computer work to  analyze the big data. But they are highly  informative and soon will also become cheaper and  routine. Here we see our colleague  using one such instrument. 

To conclude, cell tests have advanced a lot,  are realistic for many laboratories, useful and  quick. Is this a solution for everything?  Clearly not, remember from week 2 that we are not  simply a bunch of cells. We are society of cells  that talk, interact and regulate each other.  There are things that cannot be measured, those  that require cell-cell interaction or organism  regulation, homeostasis, hormones, cells  don’t develop, don’t cooperate, don’t think….  Cultured cells escape testing  these integrated aspects.  All these free cells in dishes, added together   don’t make my friend Eddy. He is much more sophisticated than that. Do you agree?