Skin needling stimulates the production of collagen to promote skin rejuvenation, and can be performed with either a manual or automatic device.
One of the limitations of a manual device is that the entire skin surface is not treated or with the same pressure, and the technique can be very painful for the patient.
Automatic needling devices are now available that attempt to overcome these limitations, and active ingredients can be directly supplied to the deeper layers of the skin.
Hyaluronic acid-based products may also be beneficial to apply in the post-needling phase.
Percutaneous collagen induction (PCI) via skin needling has also been used for treatment of acne scarring.
This novel technique may offer a simple and safe modality to improve the appearance of acne scars without the risk of dyspigmentation in patients with all skin types. 
Another novel technique that can be associated with needling is the use of platelet-rich plasma (PRP) as it contains autologous growth factors, which could act synergistically with growth factors induced by skin needling to enhance the wound-healing response. 
The combination of treatments, carried out by using skin needling and PRP application, have the potential to enhance the efficacy of both treatments.
Studies have indeed shown that both skin needling and PRP is more effective than skin needling alone in improving acne scars.
The application of topical retinoids is of interest as histochemical and ultrastructural studies have demonstrated that topical all-trans retinoic acid (RA) stimulates the deposition of a subepidermal band of collagen.
Early studies demonstrated that RA-iontophoresis is an effective, non-invasive treatment for atrophic acne scars without undesirable side effects. 
Overall, topical RA therapy appears to be well tolerated.
Four variables appear to be associated with RA tolerability: retinoid concentration, formulation vehicle, skin sensitivity and individual retinoid. 
Lower retinoid concentrations are associated with less irritation.
Vehicle influence tolerability, but whether a gel or cream is better tolerated varies from retinoid to retinoid.
Tolerability is better on normal skin vs sensitive skin.
Topical RA can be used throughout the year and on all types of skin colours.
Fabbrocini G, De Vita V, Monfrecola A, et al. Percutaneous collagen induction: an effective and safe treatment for post-acne scarring in different skin phototypes. J Dermatolog Treat. 2014 Apr;25(2):147-52.
Presented by: Prof. Kristian Reich, Translational Research in Inflammatory Skin Diseases, Institute for Health Services Research in Dermatology and Nursing, University Medical Center Hamburg-Eppendorf, and Skinflammation® Center, Hamburg, Germany