Recombinant porcine follicle stimulating hormone produced in baculovirus-insect cells induces rat ovulation in vivo and gene expression of tissue plasminogen activator in vitro

Cell cycle phase dependent productivity of a recombinant Chinese hamster ovary cell line

A Chinese Hamster Ovary cell line, CHO1-15(500), producing recombinant human tissue type plasminogen activator (tPA) via the dihydrofolate reductase (DHFR) amplification system, was studied in batch culture. In this system both DHFR and tPA are under the control of the strong constitutive viral SV40 early promoter. Employing the cumulative viable cell-hour approach, the specific productivity of tPA had maxima in the lag (0.065 pg cell(-1 )h(-1)) and early decline (0.040 pg cell(-1 )h(-1)) population growth phases. The viable population was assigned into four subpopulations (G1, S, G2/M phase, and Apoptotic cells) using flow cytometric analysis. As expected, intracellular DHFR was maximally expressed during the S cell cycle phase. The production of tPA, however, was found to be a direct linear function of the G1 phase, with a subpopulation specific productivity of 0.080 pg c-h(-1). Productivity maxima in the lag and early decline corroborate the flow cytometric data, indicative that this recombinant tPA production occurs primarily in the G1 cell cycle phase, not the S phase. This suggests that endogenous regulatory mechanisms are important controlling influences on the production of recombinant tPA in this ovarian cell line. Productivity from recombinant cell lines cannot be inferred from either the plasmid construct or the host cell alone. Elucidation of the relationship between expression of recombinant protein and the cell cycle phases of the host cell is a major component of the characterization of the animal cell production system. This information facilitates rational process design, including operating mode, modelling and control, and medium formulation.

Regulation of serine protease inhibitor-E2 and plasminogen activator expression and secretion by follicle stimulating hormone and growth factors in non-luteinizing bovine granulosa cells in vitro

During ovarian follicle growth, there is expansion of the basal lamina and changes in the follicular extracellular matrix (ECM) that are mediated in part by proteolytic enzyme cascades regulated by tissue-type plasminogen activator (tPA) and urokinase plasminogen activator (uPA). One PA inhibitor, serine protease inhibitor-E2 (SERPINE2) is expressed in granulosa but not theca cells, and expression changes with follicle development. In this study, we hypothesized that PA and SERPINE2 expression/secretion by granulosa cells are regulated by FSH and growth factors. SERPINE2 mRNA and protein levels, tPA gene expression and uPA secretion were stimulated by FSH. Insulin-like growth factor-I stimulated SERPINE2 secretion and uPA activity, and decreased secreted tPA activity and gene expression. Bone morphogenetic protein-7 increased SERPINE2 secretion and expression and tPA secretion. In contrast, fibroblast growth factor-2 inhibited tPA secretion and SERPINE2 secretion and expression. Epidermal growth factor inhibited SERPINE2 secretion and expression, but increased secreted tPA activity. Estradiol and SERPINE2 secretion were highly positively correlated, but estradiol did not alter SERPINE2 expression. These data demonstrate that SERPINE2 expression and protein secretion are regulated by FSH and growth factors in non-luteinizing bovine granulosa cells. As estradiol is a known marker of follicle health, and SERPINE2 is an anti-apoptotic factor, we propose that SERPINE2 is involved in the regulation of atresia in bovine follicles.

Oxytocin gene expression and action in goat testis

Gene expression, immunohistochemical localization, binding and effects of oxytocin (OT) on androgen production in the testis of adult goats were studied. Using polymerase chain reaction (PCR) analysis we were able to detect OT gene transcripts in the goat testis. Immunohistochemistry revealed that both OT and neurophysin epitopes were expressed together in the intratubular regions, especially in the Sertoli cells, suggesting the production of OT in these cells. However, enzyme immunoassay found no difference in OT concentration between testicular arterial and venous plasma. Saturable, specific [3H]-OT binding sites were present in membrane fractions of the goat testis. Scatchard analysis indicated an apparent affinity of 42 +/- 7 L/nmol and binding capacity of 24 +/- 4 fmol OT bound/mg DNA. In vitro treatment of goat testes for 6 h with 100 nM OT led to a 3.5-fold increase (P < 0.001) in 5 alpha-dihydrotestosterone (DHT) production in spite of the induced decrease in testosterone, suggesting that OT not only affects testosterone production but also modulates its conversion to DHT. These results indicate that the goat testis produces OT, which may be involved in the local control of androgen biosynthesis.