Islet vascularization is regulated by primary endothelial cilia via VEGF-A-dependent signaling

Islet vascularization is essential for intact islet function and glucose homeostasis. We have previously shown that primary cilia directly regulate insulin secretion. However, it remains unclear whether they are also implicated in islet vascularization. At eight weeks, murine Bbs4^-/-islets show significantly lower intra-islet capillary density with enlarged diameters. Transplanted Bbs4^-/- islets exhibit delayed re-vascularization and reduced vascular fenestration after engraftment, partially impairing vascular permeability and glucose delivery to β-cells. We identified primary cilia on endothelial cells as the underlying cause of this regulation, via the vascular endothelial growth factor-A (VEGF-A)/VEGF receptor 2 (VEGFR2) pathway. In vitro silencing of ciliary genes in endothelial cells disrupts VEGF-A/VEGFR2 internalization and downstream signaling. Consequently, key features of angiogenesis including proliferation and migration are attenuated in human BBS4 silenced endothelial cells. We conclude that endothelial cell primary cilia regulate islet vascularization and vascular barrier function via the VEGF-A/VEGFR2 signaling pathway.

Pitchfork and Gprasp2 Target Smoothened to the Primary Cilium for Hedgehog Pathway Activation

The seven-transmembrane receptor Smoothened (Smo) activates all Hedgehog (Hh) signaling by translocation into the primary cilia (PC), but how this is regulated is not well understood. Here we show that Pitchfork (Pifo) and the G protein-coupled receptor associated sorting protein 2 (Gprasp2) are essential components of an Hh induced ciliary targeting complex able to regulate Smo translocation to the PC. Depletion of Pifo or Gprasp2 leads to failure of Smo translocation to the PC and lack of Hh target gene activation. Together, our results identify a novel protein complex that is regulated by Hh signaling and required for Smo ciliary trafficking and Hh pathway activation.

Revising the embryonic origin of thyroid C cells in mice and humans

Current understanding infers a neural crest origin of thyroid C cells, the major source of calcitonin in mammals and ancestors to neuroendocrine thyroid tumors. The concept is primarily based on investigations in quail–chick chimeras involving fate mapping of neural crest cells to the ultimobranchial glands that regulate Ca²⁺ homeostasis in birds, reptiles, amphibians and fishes, but whether mammalian C cell development involves a homologous ontogenetic trajectory has not been experimentally verified. With lineage tracing, we now provide direct evidence that Sox17+ anterior endoderm is the only source of differentiated C cells and their progenitors in mice. Like many gut endoderm derivatives, embryonic C cells were found to coexpress pioneer factors forkhead box (Fox) a1 and Foxa2 before neuroendocrine differentiation takes place. In the ultimobranchial body epithelium emerging from pharyngeal pouch endoderm in early organogenesis, differential Foxa1/Foxa2 expression distinguished two spatially separated pools of C cell precursors with different growth properties. A similar expression pattern was recapitulated in medullary thyroid carcinoma cells in vivo, consistent with a growth-promoting role of Foxa1. In contrast to embryonic precursor cells, C cell-derived tumor cells invading the stromal compartment downregulated Foxa2, foregoing epithelial-to-mesenchymal transition designated by loss of E-cadherin; both Foxa2 and E-cadherin were re-expressed at metastatic sites. These findings revise mammalian C cell ontogeny, expand the neuroendocrine repertoire of endoderm and redefine the boundaries of neural crest diversification. The data further underpin distinct functions of Foxa1 and Foxa2 in both embryonic and tumor development.

Highlighted article: Mouse thyroid C cell precursors arise in foregut endoderm, and not the neural crest, disproving the current concept of a neural crest origin of thyroid neuroendocrine cells.

Probing the interaction forces of prostate cancer cells with collagen I and bone marrow derived stem cells on the single cell level

Adhesion of metastasizing prostate carcinoma cells was quantified for two carcinoma model cell lines LNCaP (lymph node-specific) and PC3 (bone marrow-specific). By time-lapse microscopy and force spectroscopy we found PC3 cells to preferentially adhere to bone marrow-derived mesenchymal stem cells (SCP1 cell line). Using atomic force microscopy (AFM) based force spectroscopy, the mechanical pattern of the adhesion to SCP1 cells was characterized for both prostate cancer cell lines and compared to a substrate consisting of pure collagen type I. PC3 cells dissipated more energy (27.6 aJ) during the forced de-adhesion AFM experiments and showed significantly more adhesive and stronger bonds compared to LNCaP cells (20.1 aJ). The characteristic signatures of the detachment force traces revealed that, in contrast to the LNCaP cells, PC3 cells seem to utilize their filopodia in addition to establish adhesive bonds. Taken together, our study clearly demonstrates that PC3 cells have a superior adhesive affinity to bone marrow mesenchymal stem cells, compared to LNCaP. Semi-quantitative PCR on both prostate carcinoma cell lines revealed the expression of two Col-I binding integrin receptors, α1β1 and α2β1 in PC3 cells, suggesting their possible involvement in the specific interaction to the substrates. Further understanding of the exact mechanisms behind this phenomenon might lead to optimized therapeutic applications targeting the metastatic behavior of certain prostate cancer cells towards bone tissue.

Establishment of immortalized periodontal ligament progenitor cell line and its behavioural analysis on smooth and rough titanium surface

Periodontal ligament (PDL) can be obtained from patients undergoing orthodontic treatment. PDL contains progenitor cells that can be expanded and differentiated towards several mesenchymal lineages in vitro. Furthermore, PDL-derived cells have been shown to generate bone- and PDL-like structures in vivo. Thus, PDL cells, combined with suitable biomaterials, represent a promising tool for periodontitis-related research and PDL engineering. Here, a new PDL cell line using lentiviral gene transfer of human telomerase reverse transcriptase (hTERT) was created. HTERT-expressing PDL cells showed similar morphology and population doubling time but an extended lifespan compared to the primary cells. In addition, PDL-hTERT cells expressed several characteristic genes and upon osteogenic stimulation produced a calcified matrix in vitro. When cultivated on two topographically different titanium scaffolds (MA and SLA), PDL-hTERT cells exhibited augmented spreading, survival and differentiation on smooth (MA) compared to rough (SLA) surfaces. These findings differ from previously reported osteoblast behaviour, but they are in agreement with the behaviour of chondrocytes and gingival fibroblasts, suggesting a very cell type-specific response to different surface textures. In summary, we report the testing of titanium biomaterials using a new PDL-hTERT cell line and propose this cell line as a useful model system for periodontitis research and development of novel strategies for PDL engineering.

Researching into the cellular shape, volume and elasticity of mesenchymal stem cells, osteoblasts and osteosarcoma cells by atomic force microscopy

Within the bone lie several different cell types, including osteoblasts (OBs) and mesenchymal stem cells (MSCs). The MSCs are ideal targets for regenerative medicine of bone due to their differentiation potential towards OBs. Human MSCs exhibit two distinct morphologies: rapidly self-renewing cells (RS) and flat cells (FC) with very low proliferation rates. Another cell type found in pathological bone conditions is osteosarcoma. In this study, we compared the topographic and morphometric features of RS and FC cells, human OBs and MG63 osteosarcoma cells by atomic force microscopy (AFM). The results demonstrated clear differences: FC and hOB cells showed similar ruffled topography, whereas RS and MG63 cells exhibited smoother surfaces. Furthermore, we investigated how selected substrates influence cell morphometry. We found that RS and MG63 cells were flatter on fibrous substrates such as polystyrene and collagen I, but much more rounded on glass, the smoothest surface. In contrast, cells with large area, namely FC and hOB cells, did not exhibit pronounced changes in flatness with regards to the different substrates. They were, however, remarkably flatter in comparison to RS and MG63 cells. We could explain the differences in flatness by the extent of adhesion. Indeed, FC and hOB cells showed much higher content of focal adhesions. Finally, we used the AFM to determine the cellular Young's modulus. RS, FC and hOB cells showed comparable stiffness on the three different substrates, while MG63 cells demonstrated the unique feature of increased elasticity on collagen I. In summary, our results show, for the first time, a direct comparison between the morphometric and biophysical features of different human cell types derived from normal and pathological bone. Our study manifests the opinion that along with RNA, proteomic and functional research, morphological and biomechanical characterization of cells also reveals novel cell features and interrelationships.

Ultrastructural and histochemical study on the interrenal cells of the male stickleback (Gasterosteus aculeatus, Teleostea), in relation to the reproductive annual cycle

The steroidogenic interrenal cells in the adrenal homologue of the male stickleback (Gasterosteus aculeatus) were studied in relation to the reproductive cycle by means of histological and ultrastructural observations, and using histochemical methods for the localisation of 3beta-hydroxysteroid dehydrogenase (3betaHSD) and 17beta-hydroxysteroid dehydrogenase (17betaHSD). To determine the various stages of the reproductive cycle, the testes were also examined by histological and histochemical methods (3betaHSD). The results indicate that in this teleost the interrenal cells can undergo a cycle in which phases characterised by different cytological aspects are observed. During this cycle there is a renewal of organelles, in particular mitochondria and SER. Periodic degenerative processes are also found. Organelle cytology showed that the cell cycle has at least 3 different aspects during the year. An analogy with some cytological aspects of the adrenal zonation in mammals is possible. It is postulated that the interrenal gland activity could substitute or supplement androgen production by the testes.

Influence of maternal CD4 levels on the predictive value of virus load over mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1). Study Group for Vertical Transmission

Forty-four anti-HIV seropositive pregnant women were enrolled in a study of maternal factors related to mother-to-infant human immunodeficiency virus type 1 (HIV-1) transmission. HIV-1 infection was documented in 11 of 45 infants (24.4%). Obstetric factors, maternal CD4 counts, and disease stage were not related to the risk of transmission. HIV-1 RNA levels at delivery were significantly higher in mothers who transmitted the infection (P = .024). A strong relationship between viral load and risk of transmission was observed in women with stage A1 (P= .006), but not in those with stages A2-A3. These results suggest that vertical transmission of HIV-1 is multifactorial and that viral load plays a major role in mothers with early-stage HIV-1 infection.

Prospective study of mother-to-infant transmission of hepatitis C virus (HCV) infection. Study Group for Vertical Transmission

Seventy-five women with anti-hepatitis C virus (HCV) antibody were enrolled prospectively during pregnancy or at delivery for study of mother-to-child transmission of HCV. Twenty-three women were coinfected with the human immunodeficiency virus (HIV). Seventy babies were monitored for at least 6 months. HCV infection was diagnosed in six infants (8.6%), four of whom were born to anti-HIV-positive mothers. HCV RNA was first detected between 2 and 6 months, and the genotypes of infected babies matched those of their mothers (type 1: n = 4; type 3: n = 2). Identical master sequences of the hypervariable region (HVR1) were detected in a mother-infant pair. In three babies coinfected with HCV and HIV, anti-HCV disappeared between 2 and 7 months, being persistently negative in two cases monitored for 11 and 26 months. Transmitting mothers did not differ significantly from those who did not transmit the infection with anti-HIV, HCV genotypes, and viral load at delivery, but had lower rate of reactivity to C100 by the recombinant immunoblot assay (RIBA) (P < .01). This prospective study confirms transmission of HCV from anti-HIV-negative mothers (4.4% in this series). Absence of anti-C100 antibodies at delivery is apparently related to increased risk of vertical transmission. Seronegative HCV infection can be observed in children coinfected with HIV.

Prevention of perinatally transmitted hepatitis B virus infection by hepatitis B immunoglobulin immunoprophylaxis: an account of 201 newborn babies of hepatitis Bs antigen carrier mothers

Of 5,327 pregnant women who were screened between July 1981 and July 1983, 5.2% were found to be hepatitis Bs antigen (HBsAg) carriers. This high percentage of carriers accentuates the importance of vertical transmission of hepatitis B virus in our area. In view of this we sought to verify the effectiveness of hyperimmune immunoglobulins in the prevention of infection. We studied 201 babies born to HBsAg-positive mothers. These babies had regular checkups until 12 months of age. One hundred forty-nine received prophylactic hyperimmune globulin (two to seven doses according to risk ranking), while 52 did not. A higher percentage of infection was found in the babies who had no prophylaxis (25%) than in the babies who had prophylaxis (7.4%). Furthermore, hepatitis appeared earlier (from the 2nd to the 6th month) in the babies who had no prophylaxis than in the babies who had prophylaxis (from the 9th to the 12th month). No infection was observed during prophylaxis or up to 6 months.