Population Council Research that makes a difference

Abstract

Regulation of a2-macroglobulin expression in Sertoli cells and hepatocytes in vitro by germ cells 
Braghiroli,L.; Silvestrini,Bruno; Sorrentino,J.; Grima,Josephine; Mruk,Dolores D.; Cheng,Chuen-yan
Biology of Reproduction 59 111-123
Publication date: 1998


Germ cells isolated from rat testes by trypsinization have beenshown to yield unwanted artifacts in biological assays, sinceconditioned media derived from these germ cells (germ cell-conditionedmedia [GCCM]) can modulate Sertoli cell secretory function becauseof the presence of residual trypsin. To determine whether germcells themselves can modulate Sertoli cell function, we isolatedgerm cells from tubules by a mechanical procedure and assessedthe effect of these cells on Sertoli cell -macroglobulin (-MG)steady-state mRNA level. It was found that germ cells indeedcould stimulate Sertoli cell -MG expression. This effect isprobably mediated by a soluble factor(s) released from germcells, since GCCM fractionated by HPLC contained multiple fractionsthat can stimulate Sertoli cell -MG expression dose-dependently.These results illustrate that germ cells play a role in regulatingtesticular -MG expression. Since Sertoli cells synthesize andsecrete many of the serum proteins behind the blood-testis barrierthat are also produced by hepatocytes, we sought to ascertainwhether germ cells can affect hepatic -MG expression. Whengerm cells were cocultured with hepatocytes isolated from adultrats, the hepatocyte -MG steady-state mRNA level was shownto be stimulated by germ cells dose-dependently. Using differentpools of fractions derived from GCCM after their fractionationby a preparative anion-exchange HPLC column, GCCM was foundto contain a factor(s) that stimulated hepatocyte -MG expressiondose-dependently. More importantly, the fractions that stimulatedhepatocyte -MG expression had a retention time different fromthat of the factor(s) that affected Sertoli cell -MG expression.These data illustrate that germ cells secrete multiple biologicalfactors capable of regulating -MG expression in the testisand the liver. In summary, this study reveals a possible physiologicallink between the testis and the liver in that germ cells mayrelease a factor(s) capable of modulating -MG expression inboth organs.