Microneedling

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.

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).[7]

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.[10] Collagen fibre bundles appear to have a normal lattice pattern rather than parallel bundles as in scar tissue.[6]

Liebl et al. have proposed another hypothesis to explain how microneedling works.[ 11 ] 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.[11] In addition, the hyperproliferation of keratinocytes is downregulated by microneedling in acne patients because it overall balances out the cell equilibrium.[11] However, more research needs to be done to elucidate the chain of events clearly.

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.[ 14 ]

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.