MIXED PHOSPHOLIPID LIPOSOME CALCIFICATION

Synthetic lipid vesicle (liposome) suspensions have been used to experimentally model many of the calcium phosphate precipitation steps observed in matrix vesicle (MV) calcification. In particular, precipitate development in liposomes can be made to preferentially follow the progression seen in MV, i.e. to occur initially in intraliposomal spaces and then to expand into the surrounding suspending medium. This paper reviews results from studies by us which show that certain phospholipid (PL) constituents of the liposomal membrane can modulate this progression. Of greatest relevance to MV calcification is the observation that phosphatidylserine and sphingomyelin, two lipids selectively enriched in MV, slow the expansion of the precipitation from inside to outside the liposome.