Generazione di cellule staminali adiposo umano attraverso dedifferenziazione di adipociti maturi in Culture soffitto
Summary
Mature adipocytes may represent an abundant source of stem cells through dedifferentiation, which leads to a homogenous population of fibroblast-like cells. Collagenase digestion is used to isolate mature adipocytes from human fat. The goal of our protocol is to obtain multipotent, dedifferentiated fat cells from human mature adipocytes.
Abstract
Mature adipocytes have been shown to reverse their phenotype into fibroblast-like cells in vitro through a technique called ceiling culture. Mature adipocytes can also be isolated from fresh adipose tissue for depot-specific characterization of their function and metabolic properties. Here, we describe a well-established protocol to isolate mature adipocytes from adipose tissues using collagenase digestion, and subsequent steps to perform ceiling cultures. Briefly, adipose tissues are incubated in a Krebs-Ringer-Henseleit buffer containing collagenase to disrupt tissue matrix. Floating mature adipocytes are collected on the top surface of the buffer. Mature cells are plated in a T25-flask completely filled with media and incubated upside down for a week. An alternative 6-well plate culture approach allows the characterization of adipocytes undergoing dedifferentiation. Adipocyte morphology drastically changes over time of culture. Immunofluorescence can be easily performed on slides cultivated in 6-well plates as demonstrated by FABP4 immunofluorescence staining. FABP4 protein is present in mature adipocytes but down-regulated through dedifferentiation of fat cells. Mature adipocyte dedifferentiation may represent a new avenue for cell therapy and tissue engineering.
Introduction
In vitro dedifferentiation of mature adipocytes is achieved through a technique called ceiling culture1. Because of their natural tendency to float in aqueous solutions, isolated mature adipocytes adhere to the surface of an inverted flask fully filled with culture medium. Over a few days, cells modify their spherical morphology and become fibroblast-like cells. The resulting cells, called dedifferentiated fat (DFAT) cells, are multipotent2. Research articles on adipocyte dedifferentiation, especially on human cells, are limited. However, they have already provided interesting information regarding multipotency, cell phenotype and replicative capacity of DFAT cells2. Mature adipocytes originating from various fat compartments have been successfully dedifferentiated including those originating from human visceral and subcutaneous adipose tissues2-4. In addition to these depots, Kishimoto and collaborators sampled adipose tissue from the buccal fat pads and dedifferentiated adipocytes into DFAT cells5. Matsumoto and collaborators successfully generated subcutaneous DFAT cells from patients covering a wide range of ages, and the majority of cells had a high proliferative rate and less than 6% of senescence even after 10 passages in culture2.
DFAT cells have been successfully re-differentiated into several lineages, including adipogenic, osteogenic, chondrogenic and neurogenic lineages2,3,6. These cells express several embryonic stem cell markers such as Nanog and the four identified pluripotent factors Oct4, c-myc, Klf4 and Sox23. They also express markers specific to each of the three germ layers7. In addition, DFAT cells are similar to Bone Marrow-derived Mesenchymal Stem Cells (BM-derived MSC) based on their epigenetic signature3. Exploiting the stem cell capacity of DFAT cells, many groups have investigated their potential to treat or improve various diseases8,9. Improvements of pathologic conditions, such as infracted cardiac tissue, spinal cord injury and urethral sphincter dysfunction, have been observed with DFAT cell injections in rat models of disease10-12.
In addition to the stem cell properties of DFAT cells, they may represent a new cellular model for adipocyte physiology studies. The 3T3-L1 cell line is often used for this purpose as these cells differentiate into adherent, lipid-storing adipocytes under adipogenic stimulation13. However, these cells originate from mouse embryo tissue13. Also, depot-specificity cannot be investigated with this model and it may not fully reflect human adipocyte physiology14. Other laboratories work with isolated adipose cells from murine fat depots, but fat distribution is not dimorphic in mice and anatomical configuration of the rodent’s abdominal cavity prevents from extrapolating directly to humans15. In order to study adipocytes in the context of the physiopathology of human obesity, consideration of body fat distribution and fat depot-specific differences has become essential16. Some limitations of primary preadipocyte cultures, including cell quantities obtained from adipose tissue biopsy samples and their senescence after a few passages in culture, created the need for alternate models. Perrini and collaborators investigated depot-specificity in gene expression of DFAT cells originating from visceral and subcutaneous fat and compared them to adipose-derived stem cells (ASC) from the same fat depot. They demonstrated that differences in gene expression and function where mainly found between depots than between cell types, suggesting that DFAT cells are physiologically close to ASC from the same depot. DFAT cells may represent an interesting alternative to available models for studies on fat distribution in the pathophysiology of human obesity. Moreover, ceiling culture is a promising method to obtain adult stem cells for tissue engineering purposes.
Here, we describe collagenase digestion, a widely-used technique to isolate mature adipocytes from the subcutaneous and/or visceral fat samples17, and the subsequent steps to perform ceiling culture and dedifferentiate these cells into multipotent, fibroblast-like cells.
Protocol
Representative Results
Discussion
Dedifferenziazione di adipociti maturi con la tecnica di coltura soffitto è un nuovo approccio per ottenere cellule staminali adipose da un piccolo campione di tessuto adiposo nativo. Sulla base della nostra esperienza e quella di altri 2, un grammo di tessuto è sufficiente al piatto un pallone da 25 cm 2 e per ottenere una popolazione di cellule DFAT per i quali l'omogeneità è stata dimostrata da Poloni e collaboratori 3. Adipociti dedifferentiation sembra possibile con le cellu…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
This study was supported by Natural Sciences and Engineering Research Council of Canada Discovery Grant (371697-2011, AT). The authors want to acknowledge the help of bariatric surgeons Drs S. Biron, F-S. Hould, S. Lebel, O. Lescelleur, P. Marceau as well as Christine Racine and Caroline Gagnon from the IUCPQ Tissue Bank. We thank Mr Jacques Cadorette from the IUCPQ’s audiovisual services for video shooting and editing.
Materials
| Bovine serum albumine | Sigma | A7906 | |
| Adenosine | Sigma | A4036 | |
| Ascorbic acid | Sigma | A0278 | |
| NaCl | Any brand can be used | ||
| KCl | Any brand can be used | ||
| CaCl2 | Any brand can be used | ||
| MgCl2 | Any brand can be used | ||
| KH2PO4 | Any brand can be used | ||
| HEPES | Any brand can be used | ||
| Glucose | Any brand can be used | ||
| Type I collagenase | Worthington Biochemical Corp | LS-004196 | |
| DMEM/F-12, HEPES, no phenol red | Gibco-Life Technologies | 11039-021 | Add to medium : 20% calf serum, gentamicin (50µg/ml) and fungizone (2.5µg/ml) |
| Calf Serum, iron supplemented, from formula-fed calves | Sigma | C8056-500ml | |
| 1/2 In plastic bushing | Iberville | 2704-CP | SKU:1000120918 (Home Depot) |
| Liquid nitrogen | Linde | ||
| Formalin soluton, neutral buffered, 10% | SIGMA | HT501128 | |
| Sterile tweezers | |||
| Sterile scissors | |||
| 60cc syringes | BD Syringe | ||
| Plastic tubing | |||
| Krebs-Ringer-Henseleit stock buffer (KRH) | Prepare stock buffer as following: 25mM HEPES pH7.6, 125mM NaCl, 3.73mM KCl, 5mM CaCl2.2H2O, 2.5mM MgCl2.6H2O, 1mM K2HPO4. Adjust pH to 7.4. | ||
| Krebs-Ringer-Henseleit-Working Buffer (KRH-WB) | Add the following components freshly to KRH buffer: 4% bovine serum albumin, 5mM glucose, 0.1µM adenosine, 560 µM ascorbic acid | ||
| KRH-WB supplemented with Type I collagenase | Add 350U/ml of Type I collagenase | ||
| T25 unvented cap tissue culture flask | Sarsted or other brand | ||
| 6-well tissue culture plate | BD Falcon or other brand | ||
| Microscope cover glass 22×22 | Fisherbrand | 12-542-B | |
| Sterile beakers |
Riferimenti
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