The characterization of preterm newborn saliva by top-down proteomic as a stimulus for the study of human development. A review of the results obtained over the past 25 years

Abstract

Around the first years of 2000, our teams, at the Cagliari and Catholic-Policlinico Gemelli (Rome) Universities, started an investigation of the in­tact proteins of human saliva by a top-down pipeline. Since one of the most interesting topics of our research was the study of molecular events occurring during fetal development, we carried out the top-down proteomic analysis on whole saliva of human preterm newborns, induced by the non-invasive specimen collection. The results obtained showed a proteome profile of human preterm newborns sensibly different from that of adults, and they were a stimulus for the study of the variation of several proteins during development, with the support of immunohistochemical methods on tissues obtained at autopsy. This review describes the main results obtained over around 25 years of research. The results on the main protein families of adult saliva, i.e., acidic, basic, and glycosylated proline-rich proteins, amylase, histatins, statherin, P-B peptide, and salivary cystatins, are described in the first section. The results obtained on the salivary proteome of preterm newborns are then reported. A section was devoted to the description of the great heterogeneity of basic proline-rich proteins and of their variable structure in the salivary evolutionary pathway from Homo Neanderthalensis to Homo Sapiens. The chapter on thymosins β₄ and β₁₀ peptides highlights how the results obtained on saliva from preterm newborns stimulated studies on other fetal organs, the latter suggesting some potential role for these peptides during human development. The small proline-rich proteins, cystatins, and S100 proteins are next described. The studies also showed that some enzymes, i.e., the Fam20C kinase recently characterized by another research group, are almost inactive during the last months of fetal development, while other enzymes, i.e., various proteinases and convertases, are much more active in the last fetal period of development than in adults.