Summary
We provide a method for isolating and culturing pure populations of heart valve endothelial cells (VEC). VEC can be isolated from either side of the cusp or leaflet and immediately following, underlying interstitial cell (VIC) isolation is straightforward.
Abstract
Heart valves are solely responsible for maintaining unidirectional blood flow through the cardiovascular system. These thin, fibrous tissues are subjected to significant mechanical stresses as they open and close several billion times over a lifespan. The incredible endurance of these tissues is due to the resident valvular endothelial (VEC) and interstitial cells (VIC) that constantly repair and remodel in response to local mechanical and biological signals. Only recently have we begun to understand the unique behaviors of these cells, for which in vitro experimentation has played a key role. Particularly challenging is the isolation and culture of VEC. Special care must be used from the moment the tissue is removed from the host through final plating. Here we present protocols for direct isolation, side specific isolation, culture, and verification of pure populations of VEC. We use enzymatic digestion followed by a gentle swab scraping technique to dislodge only surface cells. These cells are then collected into a tube and centrifuged into a pellet. The pellet is then resuspended and plated into culture flasks pre-coated with collagen I matrix. VEC phenotype is confirmed by contact inhibited growth and the expression of endothelial specific markers such as PECAM1 (CD31), Von Willebrand Factor (vWF), and negative expression of alpha-smooth muscle actin (α-SMA). The functional characteristics of VEC are associated with high levels of acetylated LDL. Unlike vascular endothelial cells, VEC have the unique capacity to transform into mesenchyme, which normally occurs during embryonic valve formation1. This can also occur during significantly prolonged post confluent in vitro culture, so care should be made to passage at or near confluence. After VEC isolation, pure populations of VIC can then be easily acquired.
Protocol
Discussion
An understanding of valvular biology has been impaired by technical difficulties isolating and culturing pure populations of valvular endothelial cells. Typical isolation techniques involve enzymatic digestion of the underlying basal matrix or chemical dissociation of endothelial adhesive bonds2,3. Preliminary isolation experiments were qualitatively assessed by varying dissociation agents and incubation periods. The results of these experiments showed that EDTA (or Trypsin-EDTA) incubation for up to 60 min…
Divulgations
The authors have nothing to disclose.
Acknowledgements
This research is supported by the NSF CAREER award, the Hartwell Foundation, and the American Heart Association (#0830384N).
Materials
| Material Name | Type | Company | Catalogue Number | Comment |
|---|---|---|---|---|
| Dulbecco’s Modified Eagle Medium | Mediatech | 50-103-PB | ||
| Fetal Bovine Serum | Gibco | 26140 | ||
| Penicillin Streptomycin | Gibco | 15140-122 | ||
| 0.25% Trypsin-EDTA | Gibco | 25200 | ||
| Heparin Sodium Salt | Sigma-Aldrich | H4784-1G | ||
| Collagenase Type 2 | Worthington Biochemical | LS004176 | ||
| DPBS | Gibco | 21300-058 | ||
| Rat Tail Collagen | BD Biosciences | 354236 | ||
| Critical Swabs | VWR | 89031-270 | ||
| Sodium Bicarbonate | Sigma-Aldrich | 55761 | ||
| T25 Flasks | BD Biosciences | 353018 | ||
| T75 Flasks | BD Biosciences | 353136 | ||
| 24 Well Plate | Falcon | 353047 | ||
| 60×15 mm Dishes | VWR | 25384-092 | ||
| 60×15 Glass Dishes | VWR | 89000-310 | ||
| Paraffin Embedding Wax | Electron Microscopy Sciences | 19304-01 | ||
| Precision Glide Needles | BD Biosciences | 305165 | ||
| 500 mL Nalgene Filters | VWR | 73520-985 | ||
| 1L Nalgene Filters | VWR | 73520-986 | ||
| Tissue Forceps | Fine Science Tools | 11023-15 | ||
| FSC Tweezers #5 | Fine Science Tools | 11295-00 |
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