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March 11, 2009


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A few things:

"He went on to point out that keratinocytes are divided faster in retinoid treated skin which is the main reason to use a retinoid."

Faster dividing keratinocytes are only of use to the extent that they cause transient smoothing and reduce cellular atypia. Partially because of the next point ...

"There is also a general misconception that retinoids thin the skin. In a study that was conducted by Dr. Kang, skin biopsies show that the skin doubled in thickness.""

Of course it "doubled in thickness" over the course of the 6 month study Kang did. Longer term studies reinforce again and again that epidermal hyperplasia takes place in the first 6-12 months. After that initial period, the epidermis retreats to baseline, actually a little thinner, around the same time the stratum corneum becomes looser again.

In contrast, the dermal repair zone of collagen seems to thicken around month 10-12, gradually increasing thereafer to about double tickness around month 24. Whether this thicekning of the DRZ offsets the eventual thinning of the epidermis for a net thickening is an open question.

In addition, retinoids inhibit/destroy certain structural components of the epidermis, desmosomes. Studies on this have been short term, and thus I don't know how this plays out long term.

In short, every treatment on retioids, even/especially from the Michigan docs, who have done some really interesting research, seems to indicate that the treatment is a universal good. In biology there are seldom free rides. If someone wants to prove retinoids as an anti-aging panacea, one would need to gauge net skin thickness past 12 months of treatment, as well as determine what structural components of the skin are down-regulated as collagen I and III are up-regulated again past 12 months).

Kevin Katechis

Wow, don't know how I missed this post, but would certainly like to address some of the questions you raised (sorry its late).

I need some help though to address your assertions to better to comment "the epidermis retreats to baseline, actually a little thinner" I have not seen this statement made in any of the studies I have read. Though I would agree studies over 12 months would be very beneficial. Therefore, I can only submit to you 20+ of observational data would contradict that statement.

I think your statement of destroy desmosomes is a bit overboard...inhibit is open for debate. Again, if you can supply the citation, I would be happy to review it.

I agree there are no free rides in biology, but I must also point out that there are alot of things we don't fully understand about how retinoids work from a scientific standpoint...all we have to go on is what is known (from a clinical standpoint) and what is observed over a twenty year time frame. My goal is to one day supply the data we need to help answer these questions.

Thank you for your observations and input.

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