Osteogenic differentiation of human dental pulp stem cells in decellularised adipose tissue solid foams

3D cell culture systems based on biological scaffold materials obtainable from both animal and human tissues constitute very interesting tools for cell therapy and personalised medicine applications. The white adipose tissue (AT) extracellular matrix (ECM) is a very promising biomaterial for tissue engineering due to its easy accessibility, malleability and proven biological activity. In the present study, human dental pulp stem cells (hDPSCs) were combined in vitro with ECM scaffolds from porcine and human decellularised adipose tissues (pDAT, hDAT) processed as 3D solid foams, to investigate their effects on the osteogenic differentiation capacity and bone matrix production of hDPSCs, compared to single-protein-based 3D solid foams of collagen type I and conventional 2D tissue-culture-treated polystyrene plates. pDAT solid foams supported the osteogenic differentiation of hDPSCs to similar levels to collagen type I, as assessed by alkaline phosphatase and alizarin red stainings, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) and osteocalcin/bone gamma-carboxyglutamate protein (BGLAP) immunostaining. Interestingly, hDAT solid foams showed a markedly lower capacity to sustain hDPSC osteogenic differentiation and matrix calcification and a higher capacity to support adipogenesis, as assessed by RT-qPCR and oil red O staining. White ATs from both human and porcine origins are relatively abundant and available sources of raw material to obtain high quality ECM-derived biomedical products. These biomaterials could have promising applications in tissue engineering and personalised clinical therapy for the healing and regeneration of lesions involving not only a loss of calcified bone but also its associated soft non-calcified tissues.

Adhesion, integration and osteogenesis of human dental pulp stem cells on biomimetic implant surfaces combined with plasma derived products

Dental implants are the usual therapy of choice in the dental clinic to replace a loss of natural teeth. Over recent decades there has been an important progress in the design and manufacturing of titanium implant surfaces with the goal of improving their osteointegration. In the present work, the aim was to evaluate the usefulness of hDPSCs (human dental pulp stem cells), in combination with autologous plasma components, for in vitro bone generation on biomimetic titanium dental implant materials. In this context, the combination of hDPSCs stimulated by PRGF or PRF and cultured on standard Ti6A14V and biomimetic BAS™ (Avinent Implant System) titanium surfaces were studied in order to evaluate possible enhancements in the osteoblastic differentiation process out of human mesenchymal cells, as well as bone matrix secretion on the implant surface. The results obtained in this in vitro model of osteogenesis suggested a combination of biomimetic rough titanium surfaces, such as BAS™, with autologous plasma-derived fibrin-clot membranes such as PRF and/or insoluble PRGF formulations, but not with an addition of water-soluble supplements of plasma-derived growth factors, to maximise osteoblastic cell differentiation, bone generation, anchorage and osteointegration of titanium-made dental implants.

Correction to: Similarities and differences in tissue distribution of DLK1 and DLK2 during E16.5 mouse embryogenesis

In the original publication of the article, some symbols in Figure 3 were not correctly aligned with the image.

Notch/Wnt cross-signalling regulates stemness of dental pulp stem cells through expression of neural crest and core pluripotency factors

Dental pulp stem cells (DPSCs) from adult teeth express neural crest (NC) markers together with core transcriptional factors associated with stem cell pluripotency, such as Oct4a, Sox2, c-Myc, Rex1, Stella/Dppa3, Ssea1/Fut4, Lin28 and Nanog. The possibility to boost the natural stemness features of DPSCs by mild methods, that do not involve gene and/or chromatin modification or gene transfection, is highly desirable for cell therapy. Canonical Wnt and Notch are two highly conserved developmental signalling pathways that are involved in NC emergence and stem cell self-renewal. We determined that both pathways coordinate to regulate the expression of core pluripotency and NC factors in DPSCs. Pharmacological inhibition of the Notch pathway for 48 h, by the γ-secretase inhibitor N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), abolished the expression of NC and core factors. In addition, it induced a silencing of the canonical Wnt signalling and a clear reduction in the stemness potential of DPSCs, as shown by a reduced ability to generate mature, fully differentiated osteoblasts and adipocytes. Conversely, pharmacological activation of the Wnt pathway for 48 h, by either the glycogen synthase kinase 3 beta (GSK3-β) inhibitor 6-bromoindirubin-3´-oxime (BIO) or the human recombinant protein Wnt-3a, not only largely increased the expression of NC and core factors, but also increased the efficiency of DPSCs to differentiate into mature osteoblasts and adipocytes. These results showed that a short preconditioning activation of Wnt/Notch signalling by small molecules and/or recombinant proteins enhanced the stemness and potency of DPSCs in culture, which could be useful for optimising the therapeutic use of these and other tissue-specific stem cells.

Monolignol ferulate transferase introduces chemically labile linkages into the lignin backbone

Redesigning lignin, the aromatic polymer fortifying plant cell walls, to be more amenable to chemical depolymerization can lower the energy required for industrial processing. We have engineered poplar trees to introduce ester linkages into the lignin polymer backbone by augmenting the monomer pool with monolignol ferulate conjugates. Herein, we describe the isolation of a transferase gene capable of forming these conjugates and its xylem-specific introduction into poplar. Enzyme kinetics, in planta expression, lignin structural analysis, and improved cell wall digestibility after mild alkaline pretreatment demonstrate that these trees produce the monolignol ferulate conjugates, export them to the wall, and use them during lignification. Tailoring plants to use such conjugates during cell wall biosynthesis is a promising way to produce plants that are designed for deconstruction.

Bone marrow cells can give rise to ameloblast-like cells

Post-eruptive loss of ameloblasts requires identification of alternative sources for these cells to realize tooth-tissue-engineering strategies. Recent reports showed that bone-marrow-derived cells can give rise to different types of epithelial cells, suggesting their potential to serve as a source for ameloblasts. To investigate this potential, we mixed c-Kit(+)-enriched bone marrow cells with embryonic dental epithelial cells and cultured them in re-association with dental mesenchyme. Non-dividing, polarized, and secretory ameloblast-like cells were achieved without cell fusion. Before basement membrane reconstitution, some bone marrow cells migrated to the mesenchyme, where they exhibited morphological, molecular, and functional characteristics of odontoblasts. These results show, for the first time, that bone-marrow-derived cells can be reprogrammed to give rise to ameloblast-like cells, offering novel possibilities for tooth-tissue engineering and the study of the simultaneous differentiation of one bone marrow cell subpopulation into cells of two different embryonic lineages.

Basement membrane alterations in psoriasis are accompanied by epidermal overexpression of MMP-2 and its inhibitor TIMP-2

Psoriasis is most probably an inherited disease characterized by cell proliferation, angiogenesis, and an inflammatory process. The pathophysiology remains unknown, although an alteration in cell-cell and cell-matrix adhesion versus an autoimmune process has been proposed as the primary defect. Here, we show evidence of a new mechanism involving basement membrane alterations accompanied by keratinocyte overexpression of matrix metalloproteinase (MMP) 2 and tissue inhibitor of MMP-2 (TIMP-2) in both uninvolved and involved psoriatic skin. Immunocytochemistry with antibodies against collagen IV (alpha1, alpha2 chains) and laminins (alpha2, alpha5, beta1, gamma1 chains) revealed gaps, folding, and reduplication of the epidermo-dermal basement membrane. There was overexpression of MMP-2 in the cytoplasm of suprabasal keratinocytes. Gelatin zymography revealed pro-MMP-2 and its activated form, a-MMP-2, in both uninvolved and involved psoriatic skin, whereas pro-MMP-9 was only present in involved skin. TIMP-2 was expressed at the cell surface of psoriatic involved suprabasal keratinocytes whereas it was restricted to basal keratinocytes in uninvolved areas. Western blots showed a marked increase in a-MMP-2 and TIMP-2 in uninvolved and involved psoriatic skin although it was more pronounced in the latter. MT1-MP, known to activate pro-MMP-2, was increased in involved areas. In situ hybridization revealed strong signals of MMP-2 mRNA in both uninvolved and involved psoriatic epidermis. The overexpression of MMP-2 in uninvolved and involved psoriatic epidermis supports the concept that the primary alteration may reside in the keratinocyte. In addition, the presence of the activated form of MMP-2 could be responsible for cell-cell and cell-matrix changes noted in psoriatic epidermis.

Presence of laminin and 67KDa laminin-receptor on endothelial surface of lung capillaries. An immunocytochemical study

The existence of cell surface-associated molecules has been claimed to play a major role in cellular recognition and interaction. In this respect, different tumor cell lines express laminin and its receptor, and this expression has been correlated with metastatic potential. In the present work, we have studied, by electron microscopic immunolabeling methods, the presence of laminin and 67KDa laminin-receptor on the surface of endothelial cells of lung blood capillaries. To label these molecules, we have developed an easy method in which the labeling is carried out "in situ", in previously excised lungs. The presence of both molecules was observed on the luminal surface of endothelial capillaries and, in many cases, gold particles were associated to small open vesicles of the endothelial cells. The results suggest that these molecules, traditionally associated to extracellular matrix, are also expressed in cellular surface of the lung vascular bed.

Apoptosis during retinoic acid-induced differentiation of F9 embryonal carcinoma cells

In this work we have characterized a process of cell death by apoptosis occurring in retinoic acid-induced differentiation of F9 embryonal carcinoma cells. Morphological changes corresponding to apoptosis were observed concomitantly with those of differentiated phenotype, in cell cultures treated for 48 h with physiological concentrations of all-trans-retinoic acid. Internucleosomal DNA fragmentation was also detected using agarose gels. These observations show that retinoic acid can induce both differentiation and apoptosis in an experimental system--the teratocarcinoma stem cell lines--widely used so far in the study of differentiation. We present this system as a tool for a better understanding of the role of retinoic acid in the regulation of cell differentiation and programmed cell death.

In vivo delivery of human alpha 1-antitrypsin gene to mouse hepatocytes by liposomes

The pTG7101 plasmid containing the full length human alpha 1-Antitrypsin was encapsulated in large (142 +/- 15 nm of diameter) and small (54 +/- 11 nm of diameter) liposomes and administered i.v. to mice (80 ng/mouse). Control animals were treated with empty (small and large) liposomes plus free DNA and with the liposome solvent buffer. The immunohistochemical results on liver cryosections and cytophotometric analysis of hepatocyte chromophore absorbance, after peroxidase reaction, indicated that significant presence of immunoreactive human alpha 1-antitrypsin was present 7 days after mice treatment with encapsulated DNA in small liposomes but not when large liposomes were used. This effect was observed in a great number of liver parenchymal cells. These results agree with the observation that only small liposomes have easy access to hepatocytes and support the idea that small liposomes are appropriate vehicles for in vivo delivery of specific genetic material to liver parenchymal cells, with high efficiency.

Differential distribution of B16F10 melanoma cells in the liver lobule

The distribution pattern and the number of tumor cells arrested in the liver were studied in mouse livers. Mice were perfused intravascularly with a suspension of B16F10 melanoma cells. The animals were sacrificed at 0, 1, 5, and 20 min after tumor cell perfusion. The pattern of tumor cell distribution was studied by morphological methods, and by a combined method of fluorescent-tumor cell labelling and histochemical succinate dehydrogenase activity on frozen sections, in order to define the localization of tumor cells arrested in the liver lobule. The results show that the tumor cells have an exclusive distribution in the periportal regions of the liver lobule (identified as the high succinate dehydrogenase activity areas), and that the cells are not arrested in the pericentral regions (identified as the low succinate dehydrogenase activity areas). In addition, indomethacin treatment (2 mg/kg/day) induced an increase in the number of melanoma cells arrested in the liver, but a different distribution with respect to controls was not observed. These results show that periportal regions of the liver lobule constitute a particular domain in which the B16F10 melanoma cells present a special retention ability that can be modulated by indomethacin treatment.