How Does Rejuran Work:
The Science Behind the Treatment

What Happens
at the Injection Site

A fine needle delivers the polynucleotide solution into the mid-dermis, the layer where collagen and elastin are actually produced. What happens next is better documented than most clinic descriptions suggest. Endogenous nucleases break the injected chains down into individual deoxyribonucleotides, and those bind to adenosine A2A receptors on fibroblasts. That binding, together with the salvage pathway that lets cells reuse the nucleotides rather than synthesising new ones from scratch, is what shifts fibroblasts toward producing matrix. The injected material also holds water and forms a physical scaffold in the dermis while it degrades, which is a separate effect from the receptor signalling and part of why hydration changes are often noticed before texture changes are. Practitioners typically use a grid of serial punctures across the treatment area rather than concentrating the solution in one spot.

How This Differs
From Other Mechanisms

The comparison below focuses on how three common approaches actually trigger change in the skin, since the mechanism is what determines the timeline and the type of result.

Why Results
Take Weeks to Show

Because the mechanism depends on fibroblasts increasing output rather than on an immediate physical change, initial texture improvement is commonly reported around two to four weeks after a session, and a 2026 review comparing polynucleotides with fillers describes the effect building over four to six weeks as new matrix accumulates. That is also why courses are usually planned as three to four sessions rather than one. Published protocols line up with that timeline: across the clinical studies collected in a systematic review published in December 2024, sessions were most often spaced two to four weeks apart and follow-up ran as long as 28 weeks, with texture changes generally documented within three months. This is a fundamentally different timeline from treatments that produce a visible change on the day, and it is the single most common source of disappointment when expectations are set by before-and-after photographs rather than by the mechanism.

For what a full treatment course looks like from booking to follow-up, see our Rejuran treatment process guide, and for the broader picture of what this treatment is used for, our Rejuran Healer overview covers who tends to benefit most.

PN and PDRN
Why the Label Matters

You will see two abbreviations used almost interchangeably in clinic marketing, and they are not the same thing. A 2025 paper in Biomolecules proposed a working cutoff at 1,500 kDa: chains below that threshold are classed as polydeoxyribonucleotides (PDRN), chains at or above it as polynucleotides (PN). Rejuran sits in the PN category, which is the relevant one for injectables.

The distinction is not about mechanism. Both break down into the same deoxyribonucleotides and both act on the same adenosine A2A receptors on fibroblasts. What differs is how long that takes. Longer PN chains need more enzymatic work to degrade, so the stimulation is spread over a longer period, and the material forms a viscous scaffold in the dermis rather than dispersing quickly. Shorter PDRN chains degrade faster. PDRN is sold as injectables as well as in gels, creams, serums and masks, and its lower molecular weight is what makes it workable in topical products, where getting into the skin matters more than how long the material stays there.

In practical terms this is why an injectable PN product is dosed in sessions weeks apart rather than applied daily, and why the periorbital area, where a stable, slow-releasing material is preferable to a fast-acting one, is a common indication.

Frequently Asked
Questions

Why doesn’t Rejuran work immediately like a filler?

Filler adds physical volume the moment it’s placed, while Rejuran works by signaling your own cells to produce more collagen, a biological process that takes weeks rather than minutes.

Does the injection depth matter?

Yes, considerably. The solution needs to reach the mid-dermis where fibroblasts are active; too shallow or too deep can reduce how effectively the treatment works.

How long does one session take?

The injections themselves usually take about 20 to 40 minutes, depending on the area. Numbing cream goes on first and generally needs 20 to 30 minutes to work, so plan for the visit to take noticeably longer than the injection time alone.

Does the mechanism change with more sessions?

The mechanism stays the same, but cumulative sessions build on each other since fibroblast activity and collagen deposits from earlier sessions compound over the course.

Is the polynucleotide solution the same at every clinic?

Formulations can vary by manufacturer and concentration, so it’s worth asking a specific clinic which product they use if you want to compare options.