Freezing without surrounding cryomedium preserves the endothelium and its function in human internal mammary arteries.
OBJECTIVE
Cryopreserved human blood vessels may become important tools in bypass surgery. Optimal cryopreservation of an arterial graft should, therefore, preserve both histological and physiological characteristics of smooth muscle and endothelium comparable to the unfrozen artery.


METHODS
Rings from human internal mammary arteries (IMA) were investigated in vitro either unfrozen or after immersion into a cryomedium (RPMI 1640 containing 1.8M Me2SO and 0.1M sucrose) and cryostorage with and without surrounding medium.


RESULTS
In unfrozen IMA, neither contractile responses to noradrenaline (NA) nor endothelium-dependent relaxant responses to acetylcholine (ACH) was modified after exposure of the IMA to cryomedium or during activation of protein kinase C by phorbol-12,13-dibutyrate (PDBu). Exposure to cryomedium with gradually increasing Me2SO content before starting the cooling process did not improve the post-thaw functional activity of the artery. Optimal post-thaw recovery of contractile responses to NA and PGF(2alpha) was observed after freezing at a speed of -1.2 and -3 degrees C/min in arteries stored with and without surrounding cryomedium. Compared to unfrozen controls, the ACH-induced endothelium-dependent relaxation during active tone induced by 3 microM PGF(2alpha) reached 16 and 56% after freezing with and without surrounding medium. All functional data were reflected by electron microscopy images showing considerably better preservation of the endothelial layer after freezing without medium.


CONCLUSIONS
Freezing of human arteries at a mean cooling rate of -3 degrees C/min and storage without surrounding medium offers the prospect of optimal preservation of both smooth muscle and endothelial function in cryopreserved human IMA.
Müller-Schweinitzer
Else
E
Department of Thoracic and Cardiovascular Surgery, University Hospital, Basel, Switzerland. dremueller36@bluewin.ch
Grapow
Martin
M
Konerding
Moritz A
MA
Zerkowski
Hans-Reinhard
HR
D000109:Acetylcholine / Q000494:pharmacology; D002273:Carcinogens; D003080:Cold Temperature; D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000494:pharmacology*; D003470:Culture Media / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004727:Endothelium / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism; D004789:Enzyme Activation; D005615:Freezing; D006801:Humans; D008323:Mammary Arteries / Q000378:metabolism / Q000473:pathology*; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D009130:Muscle, Smooth / Q000166:cytology; D009638:Norepinephrine / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D013395:Sucrose / Q000494:pharmacology; D013696:Temperature; D014021:Tissue Preservation / Q000379:methods
D002273:Carcinogens; D003451:Cryoprotective Agents; D003470:Culture Media; D015240:Phorbol 12,13-Dibutyrate; D013395:Sucrose; D011493:Protein Kinase C; D000109:Acetylcholine; D009638:Norepinephrine; D004121:Dimethyl Sulfoxide