The selection between the stromal vascular fraction (SVF) and adipose-derived stromal cells (ADSC) is dictated by the specific research objective. A primary consideration is whether the experimental goal requires clean, comparable readouts for metabolic processes, such as lipid handling and insulin signalling. This contrasts with objectives requiring the inclusion of stromal crosstalk, capillary networks, and innate immune components within the microtissue. The choice of SVF or ADSC fundamentally determines the subsequent experimental outcomes. Definitions, isolation methods, and comparative benefits and drawbacks of each source must be weighed. Specific model examples demonstrate these different applications in practice.

SVF represents the heterogeneous single-cell pellet released from adipose tissue after enzymatic collagenase digestion. It is not a single cell type but rather a complex population. This mixture includes endothelial cells, pericytes, adipocyte progenitors, fibroblasts, mast cells, and macrophages. For flow cytometry, the stromal progenitor gate is typically enriched by excluding hematopoietic and endothelial markers (CD45⁻, CD235a⁻, CD31⁻) and selecting CD34⁺ cells. The isolation protocol involves mincing lipoaspirate or surgical fat. This is followed by collagenase digestion, neutralization, and centrifugation. Mature adipocytes become buoyant, while the cell pellet at the bottom constitutes the SVF.

ADSCs are functionally distinct from SVF. They are defined as the plastic-adherent, culture-expanded stromal cell population that is derived from SVF. The methodology involves plating the fresh SVF and then removing non-adherent cells by rinsing. The remaining adherent, spindle-shaped population is subsequently expanded. After several passages, a reproducible, MSC-like immunophenotype emerges. This is characterized by positivity for CD13, CD29, CD44, CD73, CD90, and CD105, while remaining negative for hematopoietic and endothelial markers. A useful distinction is CD34 positivity at early passages, which wanes with time in culture. This population serves as a consistent, bankable cell source for engineered 3D systems.

The heterogeneous composition of SVF allows for self-organization within 3D constructs. This mixture enables the formation of endothelial strands, which are subsequently wrapped by perivascular cells. Resident immune cells also contribute to the cytokine milieu. Adipocyte progenitors then differentiate within this shared microenvironment. If the research objective involves vascular remodelling, chronic low-grade inflammation, oxygen tension, or emergent multicellular behaviours, SVF provides a more comprehensive starting population. SVF is well-suited for organoid models that are designed to preserve this heterogeneity. This approach is advantageous for complex disease modelling where the endogenous niche is required to contribute to the phenotype.

ADSCs are preferable when study parameters prioritize standardization, repeatability, and scalability. This population can be readily expanded, cryopreserved, and applied in multi-donor panels. They can be used to generate spheroids or hydrogel constructs with high uniformity. If the primary endpoints are quantitative metabolic metrics, ADSCs represent the more practical selection. This allows for achieving comparable data across numerous conditions, such as measuring lipid accumulation, adipokine secretion, lipolysis, or insulin signalling. They also integrate predictably into microphysiological systems and decellularized adipose hydrogels, making them suitable for screening workflows.

The defining strength of SVF, its native heterogeneity, also presents challenges. Donor variability is often wider in SVF preparations compared to cultured ADSCs. This can complicate comparisons between experiments. The presence of immune components within the mixed population complicates allogeneic applications, where cells from one donor are used in a different recipient system. Furthermore, the enzymatic isolation protocol itself may be subject to stricter regulatory categories. This is a consideration for clinical translation unless closed devices or alternative mechanical methods are used. These alternative mechanical methods, however, may sacrifice the total cell yield obtained from the tissue.

The primary advantages of ADSC are standardization and logistical ease, as they demonstrate reliable expansion and are amenable to cryobanking. However, limitations relate to biological fidelity. Extended time in culture can induce phenotypic shifts in the cells. Monocultures of ADSCs inherently under-represent the complex tissue microenvironment. They specifically lack the immune and endothelial compartments. These populations must be exogenously added back into the culture if their interactions are being studied. A major difficulty for both SVF and ADSC sources is that achieving mature, long-lived unilocular adipocytes (fat cells with a single large lipid droplet) in vitro remains a considerable challenge.

For studies centred on quantitative metabolic readouts, ADSCs are the logical first choice. This is especially true in screening workflows. These readouts include triglyceride handling, adiponectin or leptin output, lipolysis (FFA flux), and insulin-pathway responsiveness. ADSCs form uniform spheroids or organoids and populate hydrogels consistently. This provides stable endocrine and metabolic data across time and different donors. The uniformity allows the mapping of dose-response curves for compounds, such as PPARγ agonists. It also supports tracking insulin-stimulated endpoints at higher throughput. Several studies provide frameworks for these ADSC-based models, often using scaffold-free pipelines like hanging drops or agar support.

If the biological signal being studied is dependent on intercellular crosstalk, SVF is the appropriate starting material. This applies to interactions involving capillaries, perivascular cells, or resident immune cells. The organoids that result from SVF preserve these cellular interactions. This is the preferred route for models of inflammation-modulated insulin resistance. It is also used for studies of angiogenesis and barrier function, or investigations into how oxygen supply dictates lipid storage and survival under stress. Perfusion systems are a natural application for these complex models. Some studies show SVF organoids develop visible CD31⁺ vascular strands and αSMA⁺ perivascular coverage that persist through adipogenesis.

Yes, SVF and ADSC should not be viewed as rival methodologies. They are distinct tools for different experimental objectives. One pattern gaining traction is a two-step approach: discovery with SVF, followed by measurement with ADSC. An SVF organoid is first employed to capture a complex phenomenon and identify the required cellular players. Once the critical mechanisms are known, a minimal system can be reconstructed. This new system uses ADSCs plus the specific endothelial or immune partners identified earlier. This allows for a more controlled, higher-throughput screen. Many research programmes use both: SVF for discovery of complex phenomena, and ADSC to measure the mechanisms with high control.