Comparison of adipose-derived stromal vascular fraction with biodegradable poly-4-hydroxybutyrate and polycaprolactone scaffolds on fat graft viability

Aim: Bioresorbable scaffolds have recently gained attention in aesthetic and reconstructive surgery due to their potential to minimize fat graft resorption and enhance regenerative capacity. This study aimed to compare the effects of poly-4-hydroxybutyrate (P4HB) and polycaprolactone (PCL) scaffolds, combined with adipose-derived stromal vascular fraction (ADSVF), on fat graft viability and tissue regeneration. Materials and Methods: A total of 26 adult female Sprague Dawley rats were used. Bilateral subcutaneous dorsal pockets were created in each animal. Group 1: Right side: P4HB + fat graft; Left side—P4HB only. Group 2: Right side: PCL + fat graft; Left side—PCL only. Group 3: Right side: PCL + fat graft + ADSVF; Left side—P4HB + fat graft + ADSVF. The scaffolds were prepared in circular shapes (2 cm diameter), trimmed at a 90° angle, and shaped into cones using 4-0 PDS sutures (Ethicon, USA). Fat grafts were obtained from the bilateral inguinal regions of three rats, and ADSVF was isolated according to our previously defined protocol. Under general anesthesia and sterile conditions, 2 cm skin incisions were made 1.5 cm inferior to the designated sites, and subcutaneous pockets were bluntly dissected over the panniculus carnosus. The scaffolds, fat grafts, and ADSVF were placed according to group designations. Macroscopic, volumetric, histopathological (H&E, Trichrome), and immunohistochemical (Perilipin, CD31) analyses were performed at 4, 8, and 12 weeks postoperatively. In one rat, additional ultrasonographic elastography, computed tomography (CT), and magnetic resonance imaging (MRI) were performed under sedation for demonstrative evaluation. Results: In specimens with PCL scaffolds, the constructs were significantly larger in size and volume compared with those containing P4HB scaffolds (p<0.05). In the overall histopathological comparison, scaffold type, fat grafting, and ADSVF application did not produce a statistically significant difference in the amount of newly formed adipose tissue (p>0.05). However, subgroup analysis revealed that the PCL + fat graft + ADSVF group had a significantly greater adipose tissue volume than the P4HB + fat graft + ADSVF group (p=0.022). Inflammation scores were significantly higher in the groups receiving fat graft and ADSVF (p<0.05). In terms of vascularization, vessel formation was significantly greater in the PCL group compared with the P4HB group (p=0.019). Moreover, vascularization levels increased significantly within the PCL subgroups (PCL, PCL + fat, PCL + fat + ADSVF) (p=0.017). CD31 immunostaining revealed that neovascularization was significantly higher in the fat-grafted groups (p=0.020). No statistically significant differences were observed between the groups regarding fibrosis or perilipin expression (p>0.05). Conclusion: This experimental study demonstrated that combining bioresorbable P4HB and PCL scaffolds with fat grafts can enhance tissue volume maintenance and vascularization. The stiffer and more porous structure of PCL scaffolds likely provides a more favorable microenvironment for cell proliferation and angiogenesis. Both materials exhibited excellent biocompatibility and low fibrosis potential. These findings support the potential clinical applicability of PCL and P4HB scaffolds in combination with fat grafts for breast reconstruction and soft-tissue augmentation.