Position statementStromal cells from the adipose tissue-derived stromal vascular fraction and culture expanded adipose tissue-derived stromal/stem cells: a joint statement of the International Federation for Adipose Therapeutics and Science (IFATS) and the International Society for Cellular Therapy (ISCT)
Introduction
The use of adipose tissue-derived progenitors as a therapeutic has grown substantially in the past decade and has sparked the growth of a new research field and industry worldwide. Nevertheless, there still remain some unclear aspects in the literature and in the medical community about the identity of adipose tissue-derived cell populations. This field is at a juncture similar to that faced a few years ago by the field of bone marrow mesenchymal stromal/stem cells (MSCs). Under the authority of the International Society for Cellular Therapy (ISCT), researchers in the MSC field issued a bold statement defining the identity of the MSC (1). Our intent in this paper is to build such a statement under the joint authorities of the International Federation of Adipose Therapeutics and Sciences (IFATS) and the ISCT describing both stromal cells from the stromal vascular fraction (SVF) of the adipose tissue and the adipose tissue-derived stromal cells. Recognizing that this is a dynamic field that will require further standardization, our goal is to establish a “living” document that will be modified in response to new data and findings from ongoing and future pre-clinical and clinical studies. This document does not intend to establish policies that may restrict future advances; rather, it is designed to provide guidance that promotes further biologic clarifications, best clinical practices and safety to improve efficacious adipose tissue-derived cell therapies that benefit society.
Section snippets
Definitions
The following definitions are pertinent to our discussion. Stromal cells are connective tissue cells of any organ. A progenitor is cell that has a limited proliferation potential and is able to differentiate into one or several specific cell types. A stem cell is here characterized by its ability to self-renew and its multipotency.
Status of adipose tissue for cell engineering and regenerative medicine
The medical community and general public perception of adipose tissue as an organ has changed dramatically over the past 4 decades. Within this period, the incidence of obesity has increased substantially, reaching levels of ≥30% of the population of many economically advantaged nations. Although obesity is less common in economically developing countries, numbers of overweight and obese citizens in these countries also have increased. Increased obesity has led to changes in medical practices,
Phenotyping SVF
Compared with the bone marrow mononucleated fraction generating MSCs, the SVF contains a higher percentage of stromal elements (Table I), although multiple other lineages, most notably those of endothelial, hematopoietic and pericytic origin, are also present 11, 12, 13, 23. Endothelial, hematopoietic and pericytic lineages represent 10–20%, 25–45% and 3–5%, respectively, of the total nucleated cells (Table II). The degree of heterogeneity depends, in part, on the adipose tissue depot site and
Fibroblastoid colony-forming unit evaluation
The fibroblastoid colony-forming unit (CFU-F) assay is the standard to define the number of progenitor cells. This assay, modified from the one performed for bone marrow MSCs (28), takes 11–14 days of culture (29). The cell suspension of SVF should be seeded at low density (40–400 cells/cm2) to allow each clone to grow separately in a medium carefully chosen to allow clone growth (29). After fixation and staining, clones with >50 cells are enumerated. In general, the frequency of stromal
Identification of ASCs after culture
We propose the following main features and optional properties.
Conclusions
The goal of this paper is to provide initial guidance to academia, industry and regulatory authorities regarding the minimal properties expected for adipose tissue-derived cells (summarized in Table III). The features described in this paper are designed to facilitate further progressive development of international standards based on reproducible parameters and endpoints that will possibly harmonize cellular products across boundaries and accelerate the delivery of safe and effective ASC-based
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