The Short Version
This glossary defines the terms you will meet across adipose tissue banking and regenerative medicine, written for a general reader rather than a specialist. It covers the cell types found in fat, including adipose-derived cells, stromal vascular fraction, and mesenchymal stromal cells, along with the science of how these cells are thought to signal, such as paracrine activity and extracellular vesicles. It also defines the FDA classifications that decide how a product is regulated, the difference between autologous and allogeneic sources, the meaning of minimal manipulation and homologous use, and the research terms that govern clinical studies. Where a cell type or product is investigational rather than approved, the entry says so plainly. Definitions are educational and are not medical advice.
Important: This glossary is educational. Defining a cell type, product, or mechanism here is not an endorsement of it as a treatment. Most adipose-derived cell products and all exosome products are investigational and are not FDA-approved to diagnose, treat, cure, or prevent any disease. SaveMyFat is a connector that links patients and providers with a United States based tissue bank for adipose tissue banking; it does not provide therapies. Talk with a licensed clinician about any medical decision.
How to Use This Glossary
Regenerative medicine is full of technical language, and that language is often used loosely in marketing. A term can sound like proof when it is really just a description. This glossary gives each term a plain definition, notes where the science is established and where it is still being studied, and points to a deeper article when one exists. The goal is not to make anyone an expert overnight. It is to help you read a research summary or a clinic’s website and tell the difference between a careful claim and an overstated one.
Terms are grouped loosely from cells, to how cells may work, to the FDA classifications, to the research vocabulary. If you are new to the topic, the companion overview of how adipose tissue banking works and the FDA regulation hub give the wider context. This page is reviewed quarterly.
Glossary of Terms
Adipose-Derived Stem Cells (ADSCs)
Adipose-derived stem cells, or ADSCs, are a population of cells found in fat tissue that can be isolated in the laboratory and are studied for their ability to become several connective-tissue cell types. Fat is a convenient source because it is abundant and can be collected through a relatively minor procedure. In careful writing, these are often called adipose-derived stromal or stromal-vascular cells, because they do not reliably meet the strict biological definition of a stem cell. ADSCs are an active research subject and are being investigated in clinical trials for a range of applications. They are not an FDA-approved treatment for orthopedic, aesthetic, or anti-aging uses. When banking preserves intact adipose tissue, it preserves the tissue that contains these cells; it does not isolate or expand them.
Stromal Vascular Fraction (SVF)
Stromal vascular fraction, or SVF, is the mixed population of cells left after fat tissue is processed to remove mature fat cells. It contains adipose-derived stromal cells along with immune cells, blood-vessel cells, and others. SVF matters for regulation as much as for science: isolating it typically requires enzymatic digestion, which the FDA generally considers more than minimal manipulation. That processing pushes an SVF product out of the lighter Section 361 tissue pathway and into the Section 351 biologic pathway, where it is investigational and requires an Investigational New Drug application to study. In plain terms, intact banked fat is one thing; enzyme-isolated SVF injected to treat a condition is another, and the second is not FDA-approved.
Mesenchymal Stromal Cells (MSCs)
Mesenchymal stromal cells, commonly abbreviated MSCs, are connective-tissue cells found in fat, bone marrow, and other tissues. The abbreviation is often expanded as mesenchymal stem cells, but the International Society for Cell and Gene Therapy recommends stromal rather than stem, because most of these cells do not meet the full definition of a stem cell. The distinction is not pedantic. It changes what can honestly be claimed and how the product is regulated. MSCs are among the most studied cells in regenerative medicine, yet for most uses they remain investigational. For the difference between the terms, see what mesenchymal stromal cells are and how they compare, and for the first approved product in this family, the first FDA-approved mesenchymal stem cell product.
Paracrine Signaling
Paracrine signaling describes how a cell may influence nearby cells by releasing signaling molecules, rather than by physically becoming new tissue itself. It is one leading hypothesis for how mesenchymal stromal cells might act in research settings: not by engrafting and rebuilding, but by secreting factors that affect the local environment. This is an area of genuine scientific interest, and it is still being studied. Describing a mechanism is not the same as proving a benefit. A product can have a plausible paracrine rationale and still fail to show effectiveness in controlled trials. Our deeper explainer covers what paracrine signaling is in more detail.
Extracellular Vesicles and Exosomes
Extracellular vesicles are tiny membrane-bound particles that cells release, and exosomes are one well-studied class of them. They carry proteins and genetic material and are thought to play a role in how cells communicate, which is why they are an active research topic in regenerative medicine. Regulation here is strict for a reason. The FDA has issued a public safety notification about exosome products after reports of serious adverse events, and there are no FDA-approved exosome products for any use. Any clinic marketing exosomes as a treatment is operating outside approved pathways. See extracellular vesicles and exosomes from adipose cells for the science and the caution.
MISEV Guidelines
MISEV stands for Minimal Information for Studies of Extracellular Vesicles, a set of research standards published by the International Society for Extracellular Vesicles. The guidelines tell scientists what they must characterize and report so that a study of vesicles or exosomes can be trusted and reproduced. MISEV is a marker of rigor: research that follows it is easier to evaluate, and claims about exosomes that ignore it deserve extra scrutiny. For a patient or provider, the practical point is simple. Serious extracellular-vesicle science is careful and standardized, so marketing that leans on the mystique of exosomes without any reference to standards like MISEV is a signal to slow down and ask questions.
Minimal Manipulation
Minimal manipulation is one of the four criteria the FDA uses to decide whether a human tissue product falls under the lighter Section 361 pathway. For structural tissue such as fat, it means the processing does not alter the original characteristics relevant to the tissue’s basic functions, such as cushioning and support. FDA guidance treats cryopreservation and storage of intact tissue as generally meeting this criterion, while enzymatic digestion or laboratory expansion of cells is more than minimal manipulation. This single term often decides whether a product is a lawful preservation service or an investigational biologic. See what minimally manipulated really means under 1271.
Homologous Use
Homologous use is another of the four Section 361 criteria. It means the tissue performs the same basic function in the person receiving it that it performed in the donor. For adipose tissue, the basic functions are cushioning, support, and insulation, so using banked fat for structural purposes can be homologous. Using adipose-derived cells to treat arthritis, a neurological disease, or an autoimmune condition is generally non-homologous, which moves the product into the Section 351 biologic pathway that requires FDA approval. Homologous use is one of the most common places a product quietly crosses from tissue into drug territory. See homologous use, the 361 criterion physicians cannot ignore.
HCT/P Classification (361 versus 351)
HCT/P stands for human cells, tissues, and cellular and tissue-based products, the FDA’s umbrella term for products made from human tissue. The FDA sorts them into two pathways under 21 CFR Part 1271. A Section 361 HCT/P meets all four criteria, including minimal manipulation and homologous use, and needs registration and good tissue practices but not clinical trials. A Section 351 product fails one or more criteria and is regulated as a drug or biologic, requiring an Investigational New Drug application to study and a Biologics License Application to market. This classification is the backbone of the entire field. See what 21 CFR Part 1271 is and why it governs tissue and the FDA regulation hub.
Cryopreservation and Post-Thaw Viability
Cryopreservation is the controlled freezing of tissue or cells to very low temperatures so that biological material can be stored for long periods. Done with validated protocols and cryoprotectant agents, it aims to limit the ice damage that freezing can cause. Post-thaw viability is the measure of how many cells remain intact and functional after the tissue is warmed again, and it is the honest test of whether a freezing method worked. A responsible tissue bank documents pre-freeze baselines and post-thaw viability rather than simply promising that frozen tissue lasts forever. Viability is a laboratory measurement, not a guarantee of any future clinical use. See adipose tissue cryopreservation and viability.
Autologous versus Allogeneic
Autologous means the tissue or cells come from the same person who will later receive them. Allogeneic means they come from a donor. The distinction affects both immunology and regulation. Autologous use avoids donor-matching concerns and is treated differently under some of the Section 361 criteria, which is one reason personal banking of your own adipose tissue is framed as autologous preservation. Allogeneic products raise additional screening and testing requirements. Neither label, on its own, makes a product approved or effective; it describes the source, not the evidence. Banking your own fat is autologous preservation, which is distinct from receiving a donor-derived investigational product.
IND and IRB
These two abbreviations appear whenever an investigational product is studied in people. An IND, or Investigational New Drug application, is the FDA submission a sponsor must have in place before an unapproved biologic can be given to human subjects in a study. An IRB, or Institutional Review Board, is the independent committee that reviews a trial’s ethics and protects participants, including through informed consent. Together they are the guardrails of legitimate research. A registered clinical trial has both; a clinic offering an unapproved injection for cash usually has neither. See IRB approval versus investigational status and the clinical trials directory.