Production of recombinant human type I procollagen trimers using a four-gene expression system in the yeast Saccharomyces cerevisiae.

The expression of stable recombinant human collagen requires an expression system capable of post-translational modifications and assembly of the procollagen polypeptides. Two genes were expressed in the yeast Saccharomyces cerevisiae to produce both propeptide chains that constitute human type I procollagen. Two additional genes were expressed coding for the subunits of prolyl hydroxylase, an enzyme that post-translationally modifies procollagen and that confers heat (thermal) stability to the triple helical conformation of the collagen molecule. Type I procollagen was produced as a stable heterotrimeric helix similar to type I procollagen produced in tissue culture. A key requirement for glutamate was identified as a medium supplement to obtain high expression levels of type I procollagen as heat-stable heterotrimers in Saccharomyces. Expression of these four genes was sufficient for correct assembly and processing of type I procollagen in a eucaryotic system that does not produce collagen.

Acute periodontal abscess associated with an immediate implant site in the maintenance phase: a case report.

This article describes a complication that occurred with root-form implants: an acute periodontal abscess associated with an implant during the maintenance phase. The clinical treatment is outlined, as are the results achieved.