Fibroblasts Polar or Bipolar? The Brain Institute of America

I just wanted to post a random science post, as I wanted to clarify a vernacular issue that I come up against a lot in my teaching. While I do not expect students, or the public to understand these terms, I do think it is important for everyone to know why we use certain terms in science.

I was recently doing some research for our Autism support corner and found an amazing paper by Brick et. al., where the authors could take fibroblasts from patients with different autism spectrum disorders and convert them to induced pluripotent stem cells (iPSCs)¹. Basically, these are cells that are very close to stem cells and can be expanded and differentiated down certain paths to grow all different types of cells in the body. The hope with this type of research is that, in culture we can correct the faulty gene or mutation we think is causing the problem in the first place, and then transplant those engineered cells back into the patient to correct the disease. While this is a very complicated process, I want to focus first on one particular point within this experiment. The use of the fibroblasts.

Fibroblasts are found everywhere in the body. They part of the stromal tissue, just beneath the epidermis. Think of your skin. When you get accidentally scraped or scratched, you’re really just losing some of those top layer epidermal cells. Now think of when you get a paper cut, or a really nasty bruise when falling off your bike. Hurts, right? Well that’s because you’ve lost those protective epidermal cells, as well as some of the dermal layer of tissue. The dermal tissue layer has all of your fast cells, and vasculature tissue, and yes neurons. So, when you get a scrape or get cut down to the dermis (like with those really tiny paper cuts) your damaging those neurons, which is why it hurts!

Luckily fibroblasts are really good during would repair. And some of the more primitive fibroblasts can be replicative. So, they can make copies of themselves to help repair the wound site until properly differentiated cells can fill in the area that got damaged from when you fell off your bike, for instance.

Fibroblasts are also really motile, and malleable². So, fibroblasts tend take on different shapes depending on the environment they are in. And here is my big issue regarding the vernacular. Fibroblasts (at least when in culture) are mostly bipolar in orientation. Yes, I said bipolar. And no not the mental illness type of bipolar.

See Figure below or fibroblasts in culture.

Figure 1.

CCL-10 hamster fibroblast cells. Polar is defined as a straight line or intersection between two points. Think of North pole, South pole. Or a magnet with a (+) pole and (-) pole. Now look at these fibroblasts in culture. Most of them seem polar (see cell type A). However, look a cell type B. How many points? Seems like 3. So, by definition that’s multipolar. So now we have to talk vernacular…. Technically uni-polar = 1 point of contact, however most cells make two points of contact, so we say cells are bi-polar = 2 poles (think of when you get a pay check every two weeks), and then we have multipolar (more than 2), like those Y or V shaped cells in the figure.

Figure 2.

Here fibroblasts are grown on different substrates. In the top panel you can see how the cells look either polar a bipolar. Panel B, shows how fibroblasts can be round or polygonal in shape when placed on a different substrate⁶.

So that’s where we get these terms from. It’s not like fibroblasts have a mental illness or anything . It’s really that we as biologists ascribe a term or set of terms to a particular phenotype we observe, and then we have to be consistent with our terminology. So here we described the cells in culture by the number of poles (or focal adhesions or points of contact the cells have to the dish).

Also, similar terms mean different things in different areas of science, which is also why we sometimes get overlapping definitions and mixtures of vernacular.

So overall, fibroblasts are very cool cells, and can be used for lots of applications. I will post more on the uses of these cells in ASD research in later posts. I also want to reference the studies by Dr. Weiss, where the description of fibroblasts and use of bi-polar first began in the late 1950s…

Finally, wanted to mention that all the examples and citations provided derived from original yet freely available sources. Most of which were stored in the national archives (pub med central, which is a repository for federally funded projects). Thanks America!

References

Brick DJ, Nethercott HE, Montesano S, et al: The Autism Spectrum Disorders Stem Cell Resource at Children’s Hospital of Orange County: Implications for Disease Modeling and Drug Discovery. Stem Cells Transl Med 3:1275–1286, 2014

Rhee S, Jiang H, Ho C-H, et al: Microtubule function in fibroblast spreading is modulated according to the tension state of cell-matrix interactions. Proc Natl Acad Sci U S A 104:5425–30, 2007