Atopic Dermatitis: a Short Summary
Hyaluronic Acid And The Skin (Dermatoporosis) (For Professionals)
Structure of the presentation
-1. dermatoporosis
-2. hyaluronic acid (HA)
-3. hyalurosome
-4. fragments of hyaluronic acid. the 3 types of HA used in the skin.
- 1. dermatoporosis: due to the loss of volume in the dermis, mainly due to the loss of hyaluronic acid. It manifests clinically as thinning of the skin and purpura senilis.
- 2. hyaluronic acid (HA)
- consistance like honey
- consists of a polymer of disaccharides of glucuronic acid and N acetyl-glucosamine. Length of around 1 million kilodaltons (KD).
- name derived from grec “Hyalos” = vitrous
- function: volume filling and hydration
- 3. Hyalurosome
- is a small organelle intervening in the metabolism of HA
- function deficient in dermatoporosis
- can be modulated by intervention
- stages in the synthesis of HA:
-starter (Hyaluronic acid fragments)
-cd44
-hyaluronate synthases
-the hyluronidases inhibit the synthesis of HA by the hyalurosome
mucinosis = excess of deposits of HA due to the excess of the synthesis of mucines
- 4. fragments of hyaluronic acid (HA):
- intervenes directly in the physiological stimulation of HA.
- fragmentation of hyaluronic acid takes place during inflammation; the fragments then play a role in the signalling (and not a volume filling function): renewal, activation, angiogenesis, production of extracellular matrix.
- Local stimulation (topical application) of the hyalurosome:
-on the internet, there are more than 1000 products on sale which indicate “hyaluronic acid” but none of them can stimulate the hyalurosome, because the molecules are too big. Practically speaking hylaluronic acid can be divided in 2 categories:
-1million kilodaltons injectable form (=filler)(derived in-vitro from streptococcus), also used for hydration.
-smaller: these fragment of HA stimulate CD44 which also act on the loss of substance by inducing the synthesis of hyaluronic acid.
-If the fragments are of an intermediary size they are called HAFi (Hyaluronic acid fragments)(i=intermediate)
-young people (29-32 years old) have a functional hyalurosome and is therefore not modulable by HAFi whereas it can in elderly people (74-86 years old). Between these age classes, the degree of modulation is more variable.
-the action on the dermis and epidermis takes place through the “hyaluronic acid-binding protein”.
- Conclusions:
- the synthesis of hyaluronic acid in the epidermis and upper dermis takes place by stimulatory action of HAFi.
- injection: role of volume filling but not of signalling
- topical substance (cream made from HAFi): doesn’t have a volume filling function but a stimulatory effect acting on the signalling for HA synthesis. RAL (retinaladehyde) 0.05% and HAFi 1% have a synergistic effect in the final concentration in ug/l in the epidermis and dermis (KAYA and al, JID 2006). RAL 0.01% and HAFi 0.1% is also effective.
- In the future, cheaper products could be developped. Tacrolimus also seems to work, moreover it is reimbursed by the health insurance system in Switzerland but it has a repercussion on blood levels.
Source of information: HMDP visiting expert Professor JH Saurat -Singapore – January 2010
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