/ 01 · Capsule one · The cell ecosystem

Fundamentals of stromal vascular fraction.

SVF is not a single cell. It is a heterogeneous pool drawn from adipose tissue — a working microenvironment of progenitors, pericytes, endothelial precursors, and immune-modulating cells. The pool, not any one cell, is what does the work.

/ 01What it is

A heterogeneous cell pool, not a stem cell product.

The stromal vascular fraction is the cellular residue that remains after enzymatic or mechanical processing of adipose tissue removes the mature adipocytes and connective scaffolding. What remains is a working ecosystem — adipose-derived stem cells, endothelial progenitors, pericytes, macrophages, regulatory T cells, fibroblasts, and a sparse population of haematopoietic cells.

The clinical literature has historically conflated SVF with "adipose stem cells", but the two are distinct. Cultured, expanded adipose stem cells (ASCs) are a single-lineage product that meets the definition of an advanced therapy medicinal product in most jurisdictions. SVF, prepared by minimal manipulation at point of care, retains the full cellular and signalling architecture of the tissue niche.

This distinction is not pedantic. The regulatory pathway, the clinical mechanism, and the commercial model all turn on it. SVF behaves like a tissue, not a drug.

ASC~10–30%
Adipose stem cellsMesenchymal progenitors
Multipotent stromal progenitors capable of osteogenic, chondrogenic, and adipogenic differentiation. Secrete the dominant paracrine signal in SVF — VEGF, HGF, IGF-1, TGF-β.
EPC~10–20%
Endothelial progenitorsVasculogenic precursors
Contribute directly to new vessel formation. Express CD31 and CD34. The vascular surface of SVF — without them, the angiogenic effect collapses.
PCT~3–10%
PericytesVessel-wall stabilisers
Stabilise nascent capillaries, regulate vessel permeability, and serve as a reservoir of mesenchymal progenitors in their own right.
MAC~10–25%
MacrophagesImmune modulators
M2-polarised macrophages dominate the SVF immune fraction, driving the anti-inflammatory tone and clearing apoptotic debris in the injection field.
Treg< 5%
Regulatory T cellsTolerance signal
Small in number, large in effect. Suppress local inflammatory cascades and protect the engrafting niche from rejection-like responses.
Stromalbalance
Fibroblasts & matrixStructural carriers
Remnant stromal cells and matrix fragments that serve as a biological carrier — a scaffold-like context that distinguishes SVF from a clean cell suspension.
/ 02Where it comes from

Adipose tissue. By design, not by convenience.

Adipose tissue is the richest accessible source of mesenchymal progenitors in the adult human body — by an order of magnitude over bone marrow. A litre of lipoaspirate routinely yields cell counts that would require multiple bone marrow harvests to match, with significantly less donor-site morbidity.

That density is not the only reason adipose was chosen. Adipose is a vascularised, innervated, immunologically active organ — not the passive fat depot of older textbooks. Its stromal compartment evolved to support tissue expansion, vessel formation, and wound response. The biological context the cells came from is part of what they bring with them.

The collection procedure is a standard tumescent lipoaspiration — well established in plastic surgery for decades, with a known safety profile and minimal patient burden. Processing to SVF is then completed within 60 to 90 minutes at point of care, allowing same-day intervention.

/ 03How it works

Three mechanisms. One coordinated response.

SVF does not "replace" damaged tissue. It is not a cellular transplant in the classical sense. The therapeutic effect is mediated through three interlocking mechanisms, each carried by a different cell fraction, each acting on the local tissue environment over weeks rather than minutes.

/ 01

Angiogenesis

Endothelial progenitors and pericytes integrate into local microvasculature, while ASC-derived VEGF and HGF stimulate sprouting from existing capillaries. The result is an expanded perfusion field around the injection site within four to six weeks.

/ 02

Anti-inflammatory tone

M2 macrophages and regulatory T cells shift the local cytokine balance — suppressing IL-1β, TNF-α, and IL-6 while elevating IL-10 and TGF-β. The inflamed catabolic environment of chronic injury is dampened, creating space for repair.

/ 03

Trophic regeneration

ASC-secreted growth factors — IGF-1, FGF-2, PDGF, BDNF — activate resident progenitors and modulate matrix turnover. The effect is on the host tissue, not on the injected cells themselves: SVF resets the niche so the patient's own biology resumes repair.

"The injected cells are the signal, not the substrate. SVF works by changing the environment, not by becoming the tissue."
/ 04Comparative frame

SVF, PRP, BMAC. Three orthobiologics. One platform.

Each of these three orthobiologics works through a different mechanism, requires a different harvest, and fits a different clinical context. The most common error in practice is to substitute one for another based on availability rather than indication.

SVF PRP BMAC
Source Adipose tissue, lipoaspirate Peripheral blood, venous draw Bone marrow, posterior iliac crest
Active fraction Heterogeneous cell pool — ASCs, EPCs, pericytes, M2 macrophages Concentrated platelets and plasma growth factors. Cell-free of nucleated cells. Mesenchymal stromal cells, HSCs, platelets. Lower MSC density than SVF.
Primary mechanism Multicellular: angiogenesis, anti-inflammatory, trophic Paracrine signalling from platelet α-granules. Short-acting. Mixed cellular and paracrine. Closer to SVF than to PRP, but at lower cell density.
Yield per harvest ~250–500 × 10⁶ nucleated cells per 100 mL lipoaspirate ~5–10× baseline platelet concentration, no cellular regenerative load ~5–15 × 10⁶ nucleated cells per 60 mL aspirate
Harvest morbidity Low — outpatient lipoaspiration, local anaesthesia Minimal — standard venepuncture Moderate — iliac crest aspiration, often under sedation
Best clinical fit Knee OA KL II–III Chronic tendinopathy Discogenic pain Soft-tissue defects Mild knee OA Acute tendinopathy Augment to surgery Cartilage defects Non-union fractures AVN of the hip
Regulatory frame Tissue, point-of-care, minimally manipulated — generally outside ATMP definition in most jurisdictions when prepared by mechanical methods. Autologous blood product. Lowest regulatory burden of the three. Tissue, point-of-care. Similar framing to SVF but lower cell yield drives different commercial model.
Cost frame Mid — single harvest, single intervention, equipment-dependent Low — minimal equipment, repeatable Mid-high — harvest morbidity drives up procedure cost

The platform treats these as complementary, not competing. The Knee and Sports capsules each specify when PRP is the appropriate first-line option, when SVF is justified as escalation, and when BMAC fits a specific cartilage or osseous indication. A buyer running a multi-product orthobiologics line can deploy the platform across all three.

/ 05Evidence base

The shape of the evidence. Where it's strong. Where it's still emerging.

SVF is one of the most actively studied orthobiologics of the past decade. The literature is now substantial enough that systematic reviews converge on a coherent picture — particularly for knee osteoarthritis, where the evidence is densest. The platform synthesises three principal sources, each summarised below.

Lana et al. — 2022
Adipose-derived therapies for knee OA — pooled improvement across pain and function scores at 12 months, with a favourable safety profile.
Type Systematic review Studies 17 N ~1,200
Goncharov et al. — 2023
Adipose-derived cell therapies in orthopaedics — meta-analysis confirming pain reduction signal in KL II–III knees, mixed signal at KL IV.
Type Meta-analysis Studies 23 N ~1,800
Hohmann et al. — 2025
SVF versus expanded ASCs — comparable clinical outcomes at 24 months, with shorter intervention path favouring point-of-care SVF.
Type Comparative review Studies 14 N ~900

Where the evidence is strong: Knee osteoarthritis KL II–III, chronic tendinopathy of the rotator cuff and lateral elbow, and selected discogenic low back pain pathways. Where it's still emerging: Spinal facet and radicular pain, ligament repair as adjunct to surgery, and cartilage defect filling without scaffold. Where it is not supported: Bone-on-bone end-stage osteoarthritis, post-fusion spinal pain, and acute trauma in the first six weeks.

Each clinical capsule that follows is built on this evidence map, and each makes its evidence boundary explicit at the patient-selection stage.

/ 06What to read next

Fundamentals sets the grammar. The clinical capsules apply it.

If Fundamentals is the cell biology, the next three capsules are the clinical translation. Each takes the same heterogeneous cell pool and applies it to a specific anatomy, with its own evidence base, its own patient-selection algorithm, and its own counselling script.

/ 02 · NEXT
Knee ClinicalOsteoarthritis pathway
KL-graded selection, contraindications, the procedure skeleton, and the counselling script for patients considering SVF for knee OA.
Read capsule →
/ 03
SpineDiscogenic & facet logic
Conservative-first triage, the multidisciplinary positioning, and the mechanistic rationale for intradiscal and facet injection.
Read capsule →
/ 04
Sports & Soft TissueTendon · muscle · repair
Chronic tendinopathy, muscle injury, and the role of SVF as an adjunct to meniscal and ligament reconstruction.
Read capsule →