We conclude that PRL is an important modulator of normal rat prostate biology and that different forms of PRL have specific functions. The molecular mimic of phosphorylated PRL, S179D PRL, is the most important in terms of epithelial cell differentiation.

Current clinical methods to treat articular cartilage lesions provide temporary relief of the symptoms but fail to permanently restore the damaged tissue. Tissue engineering, using mesenchymal stem cells (MSCs) combined with scaffolds and bioactive factors, is viewed as a promising method for repairing cartilage injuries. However, current tissue engineered constructs display inferior mechanical properties compared to native articular cartilage, which could be attributed to the lack of structural organization of the extracellular matrix (ECM) of these engineered constructs in comparison to the highly oriented structure of articular cartilage ECM. We previously showed that we can guide MSCs undergoing chondrogenesis to align using microscale guidance channels on the surface of a two-dimensional (2-D) collagen scaffold, which resulted in the deposition of aligned ECM within the channels and enhanced mechanical properties of the constructs. In this study, we developed a technique to roll 2-D collagen scaffolds containing MSCs within guidance channels in order to produce a large-scale, three-dimensional (3-D) tissue engineered cartilage constructs with enhanced mechanical properties compared to current constructs. After rolling the MSC-scaffold constructs into a 3-D cylindrical structure, the constructs were cultured for 21 days under chondrogenic culture conditions. The microstructure architecture and mechanical properties of the constructs were evaluated using imaging and compressive testing. Histology and immunohistochemistry of the constructs showed extensive glycosaminoglycan (GAG) and collagen type II deposition. Second harmonic generation imaging and Picrosirius red staining indicated alignment of neo-collagen fibers within the guidance channels of the constructs. Mechanical testing indicated that constructs containing the guidance channels displayed enhanced compressive properties compared to control constructs without these channels. In conclusion, using a novel roll-up method, we have developed large scale MSC based tissue-engineered cartilage that show microscale structural organization and enhanced compressive properties compared to current tissue engineered constructs.

Williams VL, DeGuzman A, Dang H, Kawaminami M, Ho TW, Carter DG, Walker AM. Common and specific effects of the two major forms of prolactin in the rat testis. Am J Physiol Endocrinol Metab 293: E1795-E1803, 2007. First published October 2, 2007; doi:10.1152/ajpendo.00541.2007.-Prolactin (PRL) has both stimulatory and inhibitory effects on testicular function, a finding we hypothesized may be related in some part to the form of the hormone present or administered. In the analysis of the pituitary secretion profiles of early pubescent vs. mature male rats, we found PRL released from early pubescent pituitaries had about twice the degree of phosphorylation. Treatment of mature males with either unmodified PRL (U-PRL) or phosphorylated PRL (via the molecular mimic S179D PRL) for a period of 4 wk (circulating level of ϳ50 ng/ml) showed serum testosterone decreased by ϳ35% only by treatment with the phospho-mimic S179D PRL. Given the specificity of this effect, it was initially surprising that both forms of PRL decreased testicular expression of 3␤-hydroxysteroid dehydrogenase and steroidogenic acute regulatory protein. Both forms also increased expression of the luteinizing hormone receptor, but only S179D PRL increased the ratio of short to long PRL receptors. Endogenous PRL and luteinizing hormone levels were unchanged in all groups in this time frame, suggesting that effects on steroidogenic gene expression were directly on the testis. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling analysis combined with staining for 3␤-hydroxysteroid dehydrogenase and morphometric analysis showed that S179D PRL, but not U-PRL, increased apoptosis of Leydig cells, a finding supported by increased staining for Fas and Fas ligand in the testicular interstitium, providing an explanation for the specific effect on testosterone. S179D PRL, but not U-PRL, also increased apoptosis of primary spermatogonia, and U-PRL, but not S179D PRL, decreased apoptosis of elongating spermatids. Thus, in mature males, hyperprolactinemic levels of both forms of PRL have common effects on steroidogenic proteins, but specific effects on the apoptosis of Leydig and germ cells. phosphorylated prolactin; S179D prolactin; apoptosis; Leydig cells; testosterone; 3␤-hydroxysteroid dehydrogenase; steroidogenic acute regulatory protein; luteinizing hormone receptor; luteinizing hormone; short prolactin receptor PROLACTIN (PRL) is a 23-kDa polypeptide hormone produced and secreted in largest quantity by lactotropes of the anterior pituitary (reviewed in Ref. 13). It has a broad range of functions in the male reproductive system, but its role in testes remains poorly understood and is somewhat species specific (reviewed in Ref. 1).In studies by other investigators, PRL has been shown to be responsible for the induction of Leydig cell proliferation and differentiation in prepubertal hypophysectomized rats (10) and the maintenance of Leydig cell morphology, upregulation of luteinizing hormone receptor (LHR) expression, and ...