Semaphorin 3A contributes to distal pulmonary epithelial cell differentiation and lung morphogenesis.

RATIONALE: Semaphorin 3A (Sema3A) is a neural guidance cue that also mediates cell migration, proliferation and apoptosis, and inhibits branching morphogenesis. Because we have shown that genetic deletion of neuropilin-1, which encodes an obligatory Sema3A co-receptor, influences airspace remodeling in the smoke-exposed adult lung, we sought to determine whether genetic deletion of Sema3A altered distal lung structure. METHODS: To determine whether loss of Sema3A signaling influenced distal lung morphology, we compared pulmonary histology, distal epithelial cell morphology and maturation, and the balance between lung cell proliferation and death, in lungs from mice with a targeted genetic deletion of Sema3A (Sema3A(-/-)) and wild-type (Sema3A(+/+)) littermate controls. RESULTS: Genetic deletion of Sema3A resulted in significant perinatal lethality. At E17.5, lungs from Sema3A(-/-) mice had thickened septae and reduced airspace size. Distal lung epithelial cells had increased intracellular glycogen pools and small multivesicular and lamellar bodies with atypical ultrastructure, as well as reduced expression of type I alveolar epithelial cell markers. Alveolarization was markedly attenuated in lungs from the rare Sema3A(-/-) mice that survived the immediate perinatal period. Furthermore, Sema3A deletion was linked with enhanced postnatal alveolar septal cell death. CONCLUSIONS: These data suggest that Sema3A modulates distal pulmonary epithelial cell development and alveolar septation. Defining how Sema3A influences structural plasticity of the developing lung is a critical first step for determining if this pathway can be exploited to develop innovative strategies for repair after acute or chronic lung injury.

B lymphocyte activation by human papillomavirus-like particles directly induces Ig class switch recombination via TLR4-MyD88.

Vaccination with human papillomavirus type 16 (HPV16) L1 virus-like particles (VLP) induces both high titer neutralizing IgG and protective immunity. Because protection from experimental infection by papillomavirus is mediated by neutralizing IgG, we sought the mechanisms that trigger humoral immunity to HPV16 L1 VLP. We find that HPV16 L1 VLP bind to murine B lymphocytes thereby inducing activation-induced cytidine deaminase expression and Ig class switch recombination to cause the generation of IgG. HPV16 L1 VLP also activate production of proinflammatory factors IFN-alpha, IL-6, MIP-1alpha, RANTES, and KC, up-regulate the expression of costimulatory molecules by naive B cells, and increase the B1 B cell subpopulation. These B cell responses to HPV16 L1 VLP are dependent upon MyD88. Although MyD88(-/-) B cells produce only mu transcript after exposure to HPV16 L1 VLP, MyD88(+/+) B cells express alpha, gamma, and mu Ig H chain and activation-induced cytidine deaminase transcripts. Notably, TLR4 mutant C3H/HeJ mice exhibited significantly reduced HPV16 VLP-specific IgG1, IgG2a, IgG2b, and IgG3 titers after vaccination as compared with the control C3H/HeOuJ mice. HPV16 L1 VLP directly activated class switch recombination and costimulatory molecule expression by B cells of C3H/HeOuJ mice but not C3H/HeJ mice. Thus HPV16 L1 VLP directly activate B cells to induce CD4(+) T cell independent humoral immune responses via TLR4- and MyD88-dependent signaling.

Telomere shortening is an early somatic DNA alteration in human prostate tumorigenesis.

Chromosomal instability appears to be key to the pathogenesis of malignant transformation in human cancers, yet the precise molecular mechanisms underlying chromosomal rearrangements remain largely unknown. Telomeres stabilize and protect the ends of chromosomes, but shorten because of cell division and/or oxidative damage. Critically short telomeres, in the setting of abrogated DNA damage checkpoints, have been shown to cause chromosomal instability in vitro and in animal models, leading to an increased cancer incidence as a result of chromosome fusions, subsequent breakage, and rearrangement. We present results from a quantitative, high-resolution, in situ method for telomere length assessment used to test the hypothesis that telomere shortening is an early contributor to human tumorigenesis. High-grade prostatic intraepithelial neoplasia (HGPIN) is a putative preinvasive precursor of prostatic adenocarcinoma, the most common noncutaneous malignancy in Western men. The telomere lengths of epithelial cells within HGPIN lesions were strikingly shorter than those of adjacent normal appearing epithelial cells in 93% (28 of 30) of lesions examined. This shortening is similar to what has been shown in fully invasive prostate adenocarcinomas. Interestingly, telomere shortening was restricted to the luminal epithelial cells of HGPIN and was not present in the underlying basal epithelial cells; this provides strong evidence that basal cells are most likely not the direct targets of neoplastic transformation. These findings reveal that telomere shortening is a defining somatic DNA alteration characterizing HGPIN. The implications of this are that the earliest phase of human prostate carcinogenesis may proceed as a consequence of chromosomal instability mediated by shortened, dysfunctional telomeres.