Self organizing vascularized cardiac scaffolds from human atrial appendages

We investigated human left atrial appendages (LAA) as a promising new cell source for vascularized cardiac tissue scaffolds. LAAs were minced and cells harvested after outgrowth and MACS sorted for CD31. Cell populations (whole cellmix, CD31- and CD31 + ) were characterized by immunofluorescence and FACS. CD31+ endothelial cells (haaEC) were tested in compressed collagen I scaffolds primed with I) human dermal fibroblasts or II) LAA whole cell mix creating a completely autologous construct. After 24 h of incubation and removal of a central needle placeholder, the resulting core channel was seeded with haaEC and continuous perfusion was initiated with 1 ml/min. Patches were examined over 14 days regarding morphology and cell viability/proliferation. EC marker expression and synthesizing activity were investigated immunohistochemically. Whole cell mix (WCM) and CD31- cell immunofluorescence showed mostly alpha-SMA positive cells as well as an overall Connexin43 positivity and CD105 positive subpopulations. HaaEC were positive for VE-Cadherin, TIE2, VEGFR2, Connexin43, CD105 and showed broad Ki67 staining matching 2D culture proliferation in contrast to WCM and CD31- poorly expressing Ki67. HaaEC inside the core channel showed good attachment, survival and proliferation during the whole investigation period, regardless of scaffold cell priming. WCM in II) showed interstitial proliferation of all subpopulations under 3D conditions unlike in cell culture flasks. Strikingly, embedded haaEC showed self-organization potential and built vessel like structures as confirmed by immunostainings. Human atrial appendages are a new cell source of cardiac primed cells providing both endothelial and interstitial cellular components within autologous prevascularized scaffolds for cardiac tissue engineering.