Introduction: Hyaluronic acid (HA)-based fillers are used for various cosmetic procedures. However, due to filler migration and degradation, reinjections of the fillers are often required. Methacrylated HA (MA-HA) can be made into injectable shape-memorizing fillers (three-dimensional [3D] MA-HA) aimed to address these issues. In this study, shape retention, firmness, and biocompatibility of 3D MA-HA injected subcutaneously in mice were evaluated.
Materials and methods: Fifteen mice, each receiving two subcutaneous injections in their back, were divided into four groups receiving HA, MA-HA, 3D MA-HA, or saline, respectively. Digital imaging, scanning electron microscope (SEM) and in vivo imaging system (IVIS), durometry, and histology were utilized to evaluate in vitro/vivo degradation and migration, material firmness, and the angiogenic (CD31) and immunogenic (CD45) response of the host tissue toward the injected materials.
Results: Digital imaging, SEM, and IVIS revealed that 3D MA-HA fillers maintained their predetermined shape for at least 30 days in vitro and in vivo. Little volume effects were noted in the saline and other control groups. There were no differences in skin firmness between the groups or over time. Histology showed intact skin architecture in all groups. Three-dimensional MA-HA maintained its macroporous structure with significant angiogenesis at the 3D MA-HA/skin interfaces and throughout the 3D MA-HA. There was no significant inflammatory response to any of the injected materials.
Conclusion: 3D MA-HA showed remarkable tissue compatibility, compliance, and shape predictability, as well as retention, and thus might be suitable for various skin sculpting and soft tissue reconstruction purposes.
Keywords: filler; hyaluronic acid; injectable; plastic surgery; regeneration; scaffold; shape-memorizing; skin sculpturing; soft tissue reconstruction.