Extrinsic ageing in the human skin is associated with alterations in the expression of hyaluronic acid and its metabolizing enzymes

Abstract: Extrinsic skin ageing or ‘photoageing’, as opposed to intrinsic skin ageing, is the result of exposure to external factors, mainly ultraviolet irradiation. Glycosaminoglycans (GAG) and particularly hyaluronic acid (HA) are major components of the cutaneous extracellular matrix involved in tissue repair. However, their involvement in extrinsic skin ageing remains elusive. In this study, we investigated the expression of HA and its metabolizing enzymes in photoexposed and photoprotected human skin tissue specimens, obtained from the same patient. Total GAG were isolated, characterized using specific GAG‐degrading enzymes and separated by electrophoresis on cellulose acetate membranes and polyacrylamide gels. Quantitation of HA in total GAG was performed using ELISA. Gene expression of hyaluronan synthases (HAS), hyaluronidases (HYAL) and HA receptors CD44 and receptor for HA‐mediated motility (RHAMM) was assessed by RT‐PCR. We detected a significant increase in the expression of HA, of lower molecular mass, in photoexposed skin as compared with photoprotected skin. This increase was associated with a significant decrease in the expression of HAS1 and an increase in the expression of HYAL1‐3. Furthermore, the expression of HA receptors CD44 and RHAMM was significantly downregulated in photoexposed as compared with photoprotected skin. These findings indicate that extrinsic skin ageing is characterized by distinct homoeostasis of HA. The elucidation of the role of HA homoeostasis in extrinsic skin ageing may offer an additional approach in handling cutaneous ageing.     

Case series of tongue necrosis from vascular complications after chin augmentation with hyaluronic acid: Potential pathophysiology and management

Background

Even though the chin is considered a safe injection area for facial filler augmentation, tongue necrosis is a rare complication in this area.

Objective

Our aim was to present case series of rare complications from chin filler augmentation with possible pathophysiology and management.

Methods

From our thorough literature search found only one case report of tongue necrosis from chin filler augmentation. We present case series of unilateral tongue necrosis from vascular occlusion following hyaluronic acid injection in the chin, which was successfully treated with a high-dose hyaluronidase injection resulting in complete recovery in all patients.

Results

Variation in vascular anastomosis leads to a possible cause of vascular occlusion. The lingual artery is the primary arterial supply for the tongue, which is an exclusive target for embolism. Two main responsible arteries and branches are the deep lingual and sublingual arteries. The submental artery variation was previously described as the cause of this event. We proposed potential pathophysiology of the occlusion, not only the variation of vasculature but bone. The midline lingual foramen, an anatomical bone variation on the surface of the midline inferior jaw, was found to be another possible cause. This foramen contains a branch of the submental and sublingual artery, which includes the perforating artery, median perforating artery, or both. Filler injection with a sharp needle on the bone can potentially increase the risk of this vascular incident. A high dose of hyaluronidase administered with multiplane injections was accomplished with complete recovery.

Conclusions

Tongue necrosis from vascular complications after hyaluronic acid filler injection can occur. Not only vessels but bone variation pathology were possible causes.