Background

Adipose tissue plays a crucial role in numerous medical applications, such as tissue reconstruction, cosmetic procedures, and the correction of soft tissue deformities. The first use of autologous adipose tissue in humans was described in 1889 by Van der Meulen [1]. While many subsequent studies have explored this technique to correct various defects, a significant advancement in fat transplantation occurred with the publication of Coleman’s studies in fat grafting [2]. The Coleman technique, which utilizes autologous adipose tissue, has gained widespread acceptance due to its effectiveness and safety [3]. This method involves harvesting adipose tissue via liposuction, processing it, and reinjecting it into various tissue depths. Studies have demonstrated its efficacy in yielding viable adipocytes and sustaining optimal cellular function within fat grafts, making it a valuable method for soft-tissue augmentation and tissue repair [4].

The use of adipose tissue has led to numerous advancements in the use of autologous fat grafts not only in aesthetic treatments but also in various medical specialties such as therapies for breast cancer [2,5]. The regenerative potential of adipose tissue is attributed to the presence of stem cells, which makes it an ideal filler due to its availability, low donor-site morbidity, cost-effectiveness, and biocompatibility [6]. Adipose-derived stromal cells can secrete various growth factors, such as VEGF, HGF, and TGF-β, which play a crucial role in tissue remodeling. These growth factors influence the differentiation of stem cells and promote angiogenesis, thereby enhancing the efficacy of adipose tissue in tissue engineering approaches [7]. Moreover, after transplantation, ischemic adipocytes attract macrophages, initiating revascularization through neoangiogenesis, suggesting thus that the foreign body response is associated with increased vascularization [6,8].

However, existing autologous adipose engraftment methods have several limitations that impact the success and consistency of clinical outcomes. In clinical practice, a major issue with adipose tissue autotransplantation is the absorption rate over time, which ranges from 25% to 70% of the total implanted volume [2,6,9]. In 1987, the American Society of Plastic and Reconstructive Surgeons reported that only 30% of the injected autologous fat was expected to survive for one year [9]. Additionally, it was observed that the transplanted tissue often became filled with connective tissue, indicating the death of the adipose tissue followed by its replacement with fibrous tissue or newly formed metaplastic fat [9]. In contrast, Peer proposed the cellular survival theory, which suggests that the final volume after an adipose tissue transplant depends on the number of living adipocytes at the time of transplantation [9,10]. These challenges underscore the need for better grafting techniques to improve the predictability and consistency of adipose grafting results.

Biomaterials are extensively utilized in tissue engineering for their capability to support cell adhesion, proliferation, and growth during the development of new tissues. For instance, porous scaffolds and hydrogels, both natural and synthetic, have shown promise in improving adipose tissue grafting procedures. These materials have been found to enhance cell viability, promote vascularization, and support the growth of adipocytes derived from progenitor cells. Collagen-based scaffolds, hyaluronan-heparin-collagen hydrogels, fibrinogen hydrogels, and decellularized extracellular-matrix scaffolds are among the natural materials that have demonstrated potential in creating a suitable microenvironment for adipose tissue regeneration [11–13]. On the other hand, synthetic materials such as poly(N-isopropylacrylamide) (PNIPAm), polyglycolic acid (PGA), polymeric nanocomposites, and poly(lactic-co-glycolic acid) (PLGA) have shown promise in tissue regeneration, contributing to adipose tissue grafting [14,15].

In this context, we propose a protocol to improve grafting outcomes using milled/pulverized electrospun PLGA fibers combined with lipoaspirated tissue to create a fibrous slurry for injection into recipient tissue. PLGA is a copolymer widely used in tissue engineering due to its excellent biocompatibility, biodegradability, and mechanical properties. PLGA degrades into lactic acid and glycolic acid, which are naturally metabolized by the body, minimizing its toxicity [16]. Additionally, the mechanical properties (e.g., degradation rate) can be adjustable by altering the ratio of lactic acid to glycolic acid monomers. Higher lactic acid content results in slower degradation, while higher glycolic acid content leads to faster degradation. The ability to control the degradation rate by adjusting the ratio is a unique feature of PLGA that sets it apart from other commonly used biodegradable polymers, such as PGA or polylactic acid (PLA) [17,18]. While PLGA can be easily electrospun into microscale fibers for scaffolding in cell culture, these fibers must be processed into small pieces to make them suitable for injection. Therefore, we pulverize the electrospun fiber mats using a mini mill to create small fibrous clusters with increased pore size and porosity, which are critical for influencing key cellular responses.

We present a detailed protocol for using milled electrospun PLGA fibers co-injected with adipose tissue, aimed at enhancing vascularity, perfusion, and graft volume retention. This approach offers the potential to improve the consistency and success of adipose grafting techniques, addressing the limitations of current methods.