Objectives: Although autologous vessels still remain the gold standard for coronary bypass surgery
not all patients can provide suitable arterial or venous graft material. We have developed
small caliber bioartificial bypass grafts made from bacterial nanocellulose (BNC).
Key factor for the long-term patency of these bypass grafts is a proper endothelialization.
Here, we have investigated different protein surface coatings to improve endothelialization.
Methods: BNC tubes (inner diameter of 5 mm) were produced in a bioreactor. The tubes were
then functionalized with a heparin/chitosan-, human albumin- or fibronectin-coating.
To investigate the endothelialization we used two different cell types: human saphenous
vein endothelial cells (hSVEC) and endothelial progenitor cells (hEPC). The effect
on endothelialization was approved under both static and dynamic conditions. The coated
BNC was either cut into discs and cells were cultivated under static conditions in
48 well plates or the BNC tubes were mounted on a customized bioreactor and perfused
with media under pulsatile conditions for five days. The same cell number per area
of the respective cell type was seeded in a well plate as control. Endothelialization
was monitored by proliferation assay, substrate balancing and fluorescence microscopy
(i.e., F-actin, core- and AcLDL staining).
Result: Although none of the BNC tubes reached confluency when compared with controls, striking
differences between coatings could be observed. Under static conditions, the seeding
efficiency on uncoated BNC was <2% for hSVEC and 27% for hEPC while fibronectin coating
improved the seeding efficiency to 19% for hSVEC and 40% for hEPC. Similar results
were observed under dynamic conditions. For hSVEC, fibronectin coated BNC tubes showed
a seeding efficiency of 59% while uncoated tubes showed lower results (<33%). For
hEPC the differences were even more decisive as fibronectin coated tubes reached a
mean seeding efficiency of 59% and uncoated tubes 0%. The histological analyzes confirmed
these findings with differences in cell counts, general appearance of the cytoskeleton
and AcLDL uptake.
Conclusion: Here, we have shown that uncoated bacterial nanocellulose is a challenging surface
for endothelial cells. Coating of BNC tubes with human fibronectin improves the ability
of endothelial cells to attach and grow on these grafts dramatically, indicating its
value for future applications in coronary artery bypass surgery.
