Comparative Evaluation of Hyaluronic Acid and Agarose Gel as Dermal Fillers: An Experimental Study on Volume Retention and Histological Response.

[BACKGROUNDS] Facial fillers are among the most commonly performed procedures in aesthetic surgery practice. Currently, hyaluronic acid-based products (HA) are the most widely used dermal fillers worldwide. Agarose gel (AG), on the other hand, is another filler material with a three-dimensional structure resembling that of the extracellular matrix. This experimental study aims to evaluate and compare the permanence and structural integrity of two different filler materials injected subcutaneously over time.

[METHODS] The AG group served as the experimental group, while HA and saline served as the positive and negative controls, respectively. The saline group was included to distinguish true filler persistence from normal tissue resorption. Equal doses of cross-linked HA, saline, and AG were subcutaneously injected into the dorsal regions of male Wilstar albino rats. After the injection, volume measurements were performed via ultrasonography (US) and magnetic resonance imaging (MRI). After repeating volume measurements on days 7, 28, and 63, skin biopsies were taken from the subjects. The presence or absence of capsule formation, the integrity of the capsule, the capsule thickness, the cell count, the number of blood vessels, and the subcutis thickness were examined histologically.

[RESULTS] Compared to the HA group, the AG group exhibited a significantly higher rate of intact capsule formation (p = 0.029) and a greater number of cells (p < 0.001). MRI and US-based measurements revealed that HA achieved the highest early volumes but resorbed progressively, whereas AG volumes remained relatively stable. The saline group showed complete resorption by day 7, confirming its validity as a negative control. Statistically significant differences were observed between groups at all time points (p < 0.001).

[CONCLUSION] AG demonstrated greater structural stability and a more robust cellular response compared to HA. These results suggest that AG may offer a more durable and biologically active alternative to HA in subcutaneous filler applications.

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