What’s up with Stem Cells?

First of all, what is a stem cell and why are they now so popular?  One of the essential wonders of mankind is that all human beings are derived from two cells – one egg and one sperm cell.  These two cells and their DNA become a single cell which divides and subsequently differentiates into all of the individual cells which comprise the human organism.  As the early cells divide to reproduce themselves some of them begin to differentiate into the cell lines that form different parts of the body as well as the blood flowing in our veins.  These cells which are only partially differentiated and still have the potential to become more than one type of cell are called stem cells.  If these cells are liberated during the embryonic phase of development they are called embryonic stem cells.   If the embryo is allowed to grow and the cells differentiate further the cell lines become more specific to each body part.  As these cell lines develop into their structures (skin, muscle, fat, blood) they lose their ability to reverse course and again become “pluripotential” stem cells.  Once they differentiate down their pluripotent lines they become more and specific as to their ultimate destination (i.e. skin, blood, brain, muscle, fat).  These slightly more differentiated cells are called multipotential stem cells and include our now famous adipose (fat) derived stem cells.   Think of this process as a gently flowing river – if one puts in and is slowly taken downstream there will come a point where it is not possible to paddle back upstream to the starting point.  As we travel further downstream, our momentum increases so that it becomes less possible to reverse course.  At this point where reversal, or in the cellular world – re-programming, becomes impossible, you have multipotent stem cells.  A little further downstream you have more specific adipose derived stem cells which after transversing a white water rapid becomes the fat cells and fatty tissue.  The fat tissue itself is the end of the river as it flows into the sea.  Luckily each part of our body retains a few less differentiated multipotent stem cells so that the end tissue (fat in this case) can keep renewing itself as cells live and are programmed to die (apoptosis) and be regenerated by fat cell division and adipose stem cell differentiation.  As much as we wish our excessive fatty tissue would die off, it would be catastrophic to our health as fat cells have been shown to be highly active and responsive to many chemical, protein or hormonal stimuli.  So, some fat is good and too much is not so good!

The coolest discovery occurred when adipose derived stem cells (ADSC) where discovered as a precursor to fat and were available and relatively easy to isolate from our fat and have all the necessary growth factor proteins to stimulate these cells to grow into the fatty tissue we all love so.  These growth factors, primarily platelet derived growth factor (PDGF) and transforming growth factor – Beta (TGF-B) among other proteins and cytokines stimulate the growth and vascularization of adipose tissue especially if used as a “fat graft.”  An unintended consequence of augmenting fat grafts with ADSC is that many of the stimulated cellular products have a trophic and rejuvenating effect on the adjacent skin.  This effect is particularly noticeable on facial skin which is aged, sun damaged, and environmentally damaged.  It has been shown that the ADSC augmented fat graft induces neoangiogenesis (blood vessel growth) causing an improved blood supply and “take” of the fat grafts (protein and growth factor modulated), increased collagen and extracellular matrix synthesis (macrocryptin and pre-adipocyte modulated) as well as the simulation of the ADSCs to transform (multipotent) into fibroblasts which further augment the damaged
skin.  The rejuvenation and thickening of the skin is primarily due to the increased collagen synthesis.  The possible addition of activated platelet rich plasma (a-PRP) may help to enhance even further the tissue response to fat grafting.

If I lost you at the river metaphor, I can summarize that the addition of science to the art of facial rejuvenation will yield some miraculous rejuvenating effects simply by understanding the biology (science) behind the plastic surgical art.

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