Histological Evaluation of Tissues Expanded Using Osmotic Hydrogel Expanders

Objective:  Tissue expansion is one of the most common procedures employed in plastic and reconstructive surgery. This procedure not only provides extra tissue but will also improve the aesthetic and functional outcome. Many studies have reported the microscopic changes in rapidly expanded tissues, however; data on the tissues expanded at slow rates is lacking. Therefore, the aim of this study was to investigate the histological changes in the expanded tissues at different swelling rates in comparison with non-expanded tissues. Method: Osmotic hydrogel expanders were implanted in 15 adult male Dorper sheeps subcutaneously at the lower limb region. The sheep were divided into three groups (n = 5):  (i) control (ii) rapid and (iii) slow expander.  The tissue expansion was monitored over a period of 4 weeks. At explantation, the tissues were harvested and fixed in 10% formalin solution.  The samples were stained with H&E and viewed using a 3D Histech Pannoramic Viewer (Budapest, Hungary). Result: No significant differences were observed between control and slow expander groups in term of skin appendages distribution and thickness of the epidermis and dermis layers. However, the rapid expander group showed a marked decrease in skin appendages distribution and dermis thickness and a considerable increase in epidermis thickness. No signs of inflammations were observed in control and slow expander groups. In contrast, intense infiltrations of inflammatory cells were evident in rapid expander group especially in the dermis layer. Formations of new blood vessels were noted in both slow and rapid expander groups. Conclusion: The results suggest a more favorable outcome when using slow expander for tissue expansion. Rapid osmotic expander was found to potentially cause tissue damage.