The utilization of minimally invasive techniques has brought about a transformative shift in the approach to face rejuvenation, potentially representing one of the most notable advancements in facial plastic surgery in recent times. Originally employed to address the presence of fine lines and wrinkles, the application of fillers has now evolved to encompass the remediation of volume depletion and the enhancement of the aging visage.

KOS® L in the dermis regulates water balance, osmotic pressure and ion flow and functions as a sieve, excluding certain molecules, enhancing the extracellular domain of cell surfaces and stabilizes skin structures by electrostatic interactions.

The Research Question of the present study is the following: to collect sufficient clinical data to demonstrate compliance with the General Safety and Performance Requirements of KOS® L when used as intended.

Inclusion Criteria:

• Signed informed consent by the subject
• Men and women with ≥ 22 years of age
• Two fully visible bilateral nasolabial folds, each with a Wrinkle Severity Rating Scale Score of moderate (3) or severe (4) based on the 5-point WSRS
• Ability to follow study instructions and likely to complete all required visits
• Reliable methods of contraception which result in a low failure rate (i.e. less than 1 % per year) for women of childbearing potential, e.g. implants, injectables, combined oral contraceptives, some intrauterine-devices, sexual abstinence or vasectomized partner) for the entire study duration.

Exclusion Criteria:

1. Subject having received at any time injection with a slowly resorbable filling product (polylactic acid, calcium hydroxyapatite, combinations of hyaluronic acid (HA) and hypromellose, HA and dextran microbeads or HA and TriCalcium Phosphate (TCP), …) or with a non-resorbable permanent filling product (polyacrylamide, silicone, combination of methacrylic polymers and collagen, polymer particles, …)
2. Subject who received oral surgery (e.g. tooth extraction, orthodontia or implantation) within 6 weeks prior to screening visit or who plans to undergo any of these procedures during the study
3. Severe midface volume loss or severity of wrinkles or folds requiring other treatments
4. Previous tissue revitalization with neurotoxin, laser or light, mesotherapy, chemical peeling, or dermabrasion below the zygomatic arch within 6 months
5. Previous tissue augmenting therapy or, contouring, or fat injection in the facial area
6. Subject with a tattoo, a scar, moles or anything on the studied zones which might interfere with the evaluation
7. Subject having received injection with a resorbable filling product (eg, hyaluronic acid, collagen) below the inferior orbital rim within the past 12 months prior to screening visit
8. History of allergy to lidocaine or local anaesthesia of amide compounds
9. Suffering from inflammatory and/or infectious cutaneous disorders in or near the studied zones (herpes, acne, mycosis, papilloma…)
10. Body mass index BMI<18 or >30 kg/m2
11. Smoker with >10 pack-year history within the past year
12. Using any new over-the-counter or prescription oral or topical, anti-wrinkle products within 30 days before enrolment or is planning to begin using such products during the study. (Subjects who have been on a regimen of such products for at least 30 days are eligible for the study if they intend to continue their regimen throughout the study)
13. History of or active autoimmune disease/immune deficiency
14. Prone to hypertrophic scars
15. History of allergy to hyaluronic acid or any of the product's components
16. Known case of porphyria
17. Pregnancy or lactation
18. Taking medications and/or substances known to increase coagulation time (e.g., aspirin, ibuprofen, or herbal supplements) 10 days prior to treatment
19. Have a condition or be in a situation that, in the physician's opinion, may put the subject at significant risk, may confound the study results, or may interfere significantly with the subject's participation in the study
20. Untreated epilepsy
21. Hypersensitivity to gram positive bacterial proteins as hyaluronic acid is produced by Streptococcus type bacteria.