Microneedling: Advances and widening horizons
Microneedling: Advances and widening horizons
Microneedling is a very simple, safe, effective, and minimally invasive therapeutic technique. It was initially introduced for skin rejuvenation, however, now it is being used for a very wide range of indications including acne scar, acne, post-traumatic/burn scar, alopecia, skin rejuvenation, drug delivery, hyperhidrosis, stretch marks, and many more. Moreover, during the last 10 years, many new innovations have been made to the initial instrument, which was used for microneedling. This technique can be combined with other surgical techniques to provide better results. In particular, it is a very safe technique for dark skin types, where risk of postinflammatory pigmentation is very high with other techniques that damage the epidermis. In this review article, we are updating on the different instruments now available for this procedure, and its efficacy when performed alone or in combination with other techniques for various indications.
Microneedling is a relatively new minimally invasive procedure involving superficial and controlled puncturing of the skin by rolling with miniature fine needles. Over a short period of time, it has gained mass popularity and acceptance as it is a simple, cheap, safe, and effective technique requiring minimal training. Traditionally used as a collagen induction therapy for facial scars and skin rejuvenation, it is also widely used now as a transdermal delivery system for therapeutic drugs and vaccines. In this review, we highlight the constantly evolving research and developments in microneedling techniques, instruments, and its applications in dermatology.
The advent of the concept of microneedling dates back to 1995 when Orentreich and Orentreich described dermal needling in the form of subcision for scar treatment and then independently in 1997 by a plastic surgeon Camirand who used tattoo guns without ink to take-off tension from postsurgical scars.[1,2] Microneedling technique was given further shape by a German inventor Liebl in 2000 and a plastic surgeon Fernandes in 2006 who self-designed a drum-shaped device with multiple fine protruding needles and used it for percutaneous collagen induction.[3,4]
The standard medical dermaroller [Figure 1] has a 12 cm long handle with a 2 × 2 cm wide drum-shaped cylinder at one end studded with 8 rows and 24 circular arrays of 192 fine microneedles, usually 0.5–3 mm in length and 0.1–0.25 mm in diameter. These single use microneedles are synthesized by reactive ion etching techniques on silicon or medical-grade stainless steel. The instrument is presterilized by gamma irradiation. Rolling with a standard dermaroller containing 192 needles of 2 mm length and 0.07 mm diameter over an area of skin for 15 times results in approximately 250 holes per square cm upto the papillary dermis depending on the pressure applied. Each pass produces 16 micropunctures in the stratum corneum per square cm without damaging the epidermis significantly.
Principle and mechanism of action
Micropunctures are created using microneedles which produce a controlled skin injury without actually damaging the epidermis. These microinjuries lead to minimal superficial bleeding and set up a wound healing cascade with release of various growth factors such as platelet derived growth factor (PGF), transforming growth factor alpha and beta (TGF-α and TGF-β), connective tissue activating protein, connective tissue growth factor, and fibroblast growth factor (FGF). The needles also breakdown the old hardened scar strands and allow it to revascularize. Neovascularization and neocollagenesis is initiated by migration and proliferation of fibroblasts and laying down of intercellular matrix.[8,9] A fibronectin matrix forms after 5 days of injury that determines the deposition of collagen resulting in skin tightening persisting for 5–7 years in the form of collagen III. The depth of neocollagenesis has been found to be 5–600 μm with a 1.5 mm length needle. Histological examination of the skin treated with 4 microneedling sessions 1 month apart shows upto 400% increase in collagen and elastin deposition at 6 months postoperatively, with a thickened stratum spinosum and normal rete ridges at 1 year postoperatively. Collagen fibre bundles appear to have a normal lattice pattern rather than parallel bundles as in scar tissue.
Liebl et al. have proposed another hypothesis to explain how microneedling works. Resting electrical membrane potential of cells is approximately ?70 mV, and when needles come near the membrane, the inner electrical potential increases quickly to ?100 mV. This triggers increased cell activity and the release of various proteins, potassium, and growth factors from the cells into the exterior leading to the migration of fibroblasts to the site of injury, and hence, collagen induction. Thus, the needles do not create a wound in a real sense, but rather body cells are fooled into believing that the injury has occurred.[9,11,12,13]
The expression of matrix metalloproteinases induced by microneedling is speculated in reduction of hyperpigmentation. In addition, the hyperproliferation of keratinocytes is downregulated by microneedling in acne patients because it overall balances out the cell equilibrium. However, more research needs to be done to elucidate the chain of events clearly.
Microneedling enhances the delivery of various drugs across the skin barrier as it bypasses the stratum corneum and deposits the drug directly up to the vascularized dermis. It has also been shown to cause significant widening of the follicular infundibulum by 47%, which may partly explain the increased penetration of the medication across the skin barrier. In addition, it removes the scales and sebum residues in the neighbourhood of the infundibulum.
Hence, this procedure extrapolates the body’s own physiology of wound healing and the new collagen deposition results in skin tightening and filling-up of atrophic scars with an overall better aesthetic appeal since overlying epidermis is not ablated.