The claimed mechanism, step by step

2.1.1The chain as it is usually told

It is worth writing the account out in full and in its strongest form, because a weak version of an argument is not worth examining. Here it is, as a competent practitioner would explain it.

1. Fragmented, purified DNA is placed into the dermis or immediately beneath it.
2. The long chains bind and hold water in the tissue, producing local hydration.
3. Nucleases present in the tissue degrade the chains progressively into shorter fragments and eventually into individual nucleotides.
4. Cells in the vicinity take up nucleotides through salvage pathways, which is the ordinary mechanism by which cells reuse nucleotide building blocks rather than synthesising them afresh.
5. Adenosine, one of the products of this degradation, acts on adenosine receptors on cell surfaces, and activity at one receptor subtype in particular is associated with reduced inflammatory signalling and with tissue repair behaviour.
6. Fibroblasts, the cells responsible for producing collagen and other matrix components, respond by increasing their production.
7. The dermal matrix is altered in a way that is visible at the surface as improved skin quality, and because the change is in the tissue rather than in the injected material, it persists after the material has gone.

2.1.2Where the account is solid

Steps one to four are not controversial. Nucleases exist everywhere in the body and degrade nucleic acid as a matter of routine. Salvage pathways are textbook cell biology and were characterised long before anyone thought of injecting DNA into a face. Long chain polymers in solution hold water. None of this requires any special pleading and none of it is in doubt.

Step five is where the account draws on the PDRN literature. Adenosine receptor activity is a real and studied phenomenon with a substantial body of work behind it in other contexts. The question is not whether adenosine receptors exist and do things. It is whether injecting a polynucleotide preparation into human dermis produces enough local adenosine, for long enough, in the right place, to change what the cells there do to a degree anyone could see.

2.1.3Where it becomes speculative

Steps six and seven carry almost the entire commercial proposition, and they are the least supported. To believe them, you need three things to be true at once: that fibroblast behaviour changes measurably in living human dermis after this treatment, that the change produces a matrix alteration large enough to be visible, and that the alteration persists after the trigger has been cleared.

Each of those is testable. Fibroblast activity can be examined in tissue. Matrix change can be examined histologically and, less directly, by imaging. Persistence can be examined by measuring outcomes late enough that the material cannot still be present. The reason these questions remain open is not that they are hard to frame. It is that the studies which frame them that way, in people, with controls and adequate follow up, are not what the field has mostly produced.

2.1.4The hydration confound

There is a simpler explanation available for a good deal of what patients notice, and it deserves to be stated because it is rarely stated in clinics. Injecting a water binding polymer into the dermis makes the dermis hold more water. Skin that holds more water looks and feels different: plumper, smoother, more reflective. That is a real effect, patients are not imagining it, and it requires no biological mechanism at all beyond physical chemistry.

The trouble is that this explanation predicts the same short term appearance as the regenerative account, and distinguishing them requires measuring late rather than early. A study that photographs a face two weeks after the last of a course of injections cannot separate the two. A study that photographs it several months after the material must have cleared, against a control, can. The distribution of study designs in this field is therefore not a neutral technical detail.

2.1.5Why the mechanism is worth taking seriously anyway

It would be easy to write this article as debunking, and that would be a distortion. The proposed mechanism is not implausible. Nucleotide salvage is real. Adenosine receptor signalling is real and is a legitimate target of pharmacological interest. Fibroblasts do respond to their chemical environment. A researcher proposing this mechanism as a hypothesis would be proposing something reasonable.

The gap is between a reasonable hypothesis and a marketed treatment. In a medicine, that gap is crossed by a trial programme that a regulator scrutinises. In a device sold for cosmetic use, there is no obligation to cross it at all, and so it often has not been crossed. The correct attitude is neither dismissal nor enthusiasm but the recognition that we are being sold the hypothesis.

2.1.6How to use this in a consultation

You do not need to argue about receptors. One question does the work: how would we know, in a few months, whether this did anything beyond hydrating my skin for a while?

A thoughtful practitioner will engage with that. They may say that they photograph under standardised conditions and review at a set interval. They may say candidly that separating the two is difficult and that they judge by patient reported change over time. They may say that they are not certain and that the treatment is worth trying on that basis. All of those are respectable answers.

An answer that restates the mechanism more emphatically is not an answer to the question that was asked, and noticing that is the whole skill.

2.1.7Summary of the chain

Injected material binds water: established. Material is degraded by nucleases: established. Nucleotides are salvaged by cells: established as general biology. Local adenosine signalling changes cell behaviour in treated human skin: plausible, not demonstrated in this setting. Fibroblast output increases measurably in people: not demonstrated to a standard the claim requires. The change persists after clearance: not demonstrated, and this is the claim on which the value of the treatment ultimately rests.