To differentiate or proliferate? The interaction between PI3K/PTEN and Cdx2

1α,25-Dihydroxyvitamin D3 accelerates skin wound re-epithelialization by promoting epidermal stem cell proliferation and differentiation through PI3K activation: an in vitro and in vivo study

1α,25-Dihydroxyvitamin D3 (VD3), the active form of vitamin D, plays a crucial role in wound healing. In this study, we aimed to investigate the effect of VD3 on the proliferation and differentiation of epidermal stem cells (EpSCs) and monitor its impact on re-epithelialization. We established a murine full-thickness skin defect model and applied four doses of VD3 (0, 5, 50, and 250 ng/mouse/day) to the wounds topically for three days. Immunostaining and flow cytometry confirmed the effect of VD3 on the proliferation and differentiation of EpSCs in wounds. This effect of VD3 (0, 1, 10, and 50 nM) on EpSCs and its possible mechanism were further confirmed in vitro by CCK8, westen blot, immunostaining, and flow cytometry. We found that on day five post-wounding, the means±SD length of the neo-epidermis was 195.88±11.57, 231.84±16.45, 385.80±17.50, and 268.00±8.22 μm in the control, 5, 50, and 250 ng groups, respectively, with a significant difference from the control (all P<0.05). Immunostaining and flow cytometry showed that VD3 improved the proliferation and differentiation of K15+ EpSC (vs control, all P<0.05), K14+ epidermal progenitor cells (vs control, all P<0.05), and K10+ epidermal terminal cells (vs control, all P<0.05) in vivo and in vitro. The PI3K signaling pathway appeared to underlie this response because significant inhibition of the response was found when inhibitors were used to inhibit PI3K. Our study demonstrated that VD3 is a potent promoter of cutaneous wound healing by stimulating EpSC proliferation and differentiation through PI3K activation.

Effects of Titanium Implant Surface Topology on Bone Cell Attachment and Proliferation in vitro

Purpose

Titanium is commonly used for implants because of its corrosion resistance and osseointegration capability. It is well known that surface topology affects the response of bone tissue towards implants. In vivo studies have shown that in weeks or months, bone tissue bonds more efficiently to titanium implants with rough surfaces compared to smooth surfaces. In addition, stimulating early endosseous integration increases the long-term stability of bone-implants and hence their clinical outcome. Here, we evaluated the response of human MG-63 osteoblast-like cells to flat and solid, compared to rough and porous surface topologies in vitro 1–6 days post seeding. We compared the morphology, proliferation, and attachment of cells onto three smooth surfaces: tissue culture (TC) plastic or microscope cover glasses, machined polyether-ether-ketone (PEEK), and machined solid titanium, to cells on a highly porous (average R_a 22.94 μm) plasma-sprayed titanium surface (composite Ti-PEEK spine implants).

Methods

We used immuno-fluorescence (IF) and scanning electron microscopy (SEM), as well as Live/Dead and WST-1 cell proliferation assays.

Results

SEM analyses confirmed the rough topology of the titanium implant surface, compared to the smooth surface of PEEK, solid titanium, TC plastic and cover glasses. In addition, SEM analyses revealed that MG-63 cells seeded onto smooth surfaces (solid titanium, PEEK) adopted a flat, planar morphology, while cells on the rough titanium surface adopted an elongated morphology with numerous filopodial and lamellipodial extensions interacting with the substrate. Finally, IF analyses of focal adhesions (vinculin, focal adhesion kinase), as well as proliferation assays indicate that MG-63 cells adhere less and proliferate at a slower rate on the rough than on a smooth titanium surface.

Conclusion

These observations suggest that bone-forming osteoblasts adhere less strongly and proliferate slower on rough compared to smooth titanium surfaces, likely promoting cell differentiation, which is in agreement with other porous implant materials.

CDX2 Is a Useful Marker of Intestinal-Type Differentiation: A Tissue Microarray–Based Study of 629 Tumors From Various Sites

Context.—CDX2, a critical nuclear transcription factor for intestinal development, is expressed in intestinal epithelium and adenocarcinomas.

Objectives.—To determine if CDX2 is a useful marker for intestinal-type differentiation and to correlate tumor histology with CDX2 staining in colorectal adenocarcinomas.

Design.—Tissue microarrays from 71 colorectal adenocarcinomas, 31 hepatocellular carcinomas, 47 lung adenocarcinomas, 55 squamous cell carcinomas of the lung, 69 neuroendocrine carcinomas of the lung and 43 of the pancreas, 57 pancreatic adenocarcinomas, and 256 endometrial adenocarcinomas were stained with antibody against CDX2.

Results.—CDX2 staining was positive in 51 (71.8%) of 71 colorectal cancers, including 38 (74.5%) of 51 well- or moderately differentiated tumors and 13 (65.0%) of 20 high-grade tumors. Of the high-grade tumors, 5 (71.4%) of 7 mucinous, 3 (100%) of 3 signet ring cell, and 5 (50.0%) of 10 poorly differentiated tumors were positive. Other tumors showing occasional CDX2 staining included 1 of 30 well- or moderately differentiated neuroendocrine carcinomas of the lung and 2 of 43 from the pancreas, 1 of 47 lung adenocarcinomas, 3 of 57 pancreatic adenocarcinomas, and 15 of 256 endometrial carcinomas. Hepatocellular, poorly differentiated neuroendocrine carcinoma of the lung and squamous cell carcinomas of the lung were not immunoreactive for CDX2.

Conclusions.—CDX2 is a useful marker for intestinal-type differentiation, is rarely seen in tumors from the other sites evaluated, and may be useful in determining the site of origin for some metastatic tumors. However, CDX2 is not a sensitive marker for poorly differentiated colorectal carcinoma.

Molecular alterations during development of esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma has risen significantly over the last decades. During esophageal carcinogenesis many molecular alterations occur that disrupt essential cellular processes, directing the cell to a rapidly proliferating, immortal state. The chronic inflammation that is present in Barrett's esophagus creates an environment in which such molecular alterations are both induced and tolerated. Here, the novel insights in the molecular mechanisms that underlie the development of esophageal adenocarcinoma are reviewed, focusing on the role of inflammation, angiogenesis, apoptosis inhibition, loss of cell cycle control, and loss of cell-cell adhesion. These novel developments will open new perspectives for diagnosis, treatment, and prevention of esophageal adenocarcinoma.

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Opposing effects of PI3 kinase pathway activation on human myeloid and erythroid progenitor cell proliferation and differentiation in vitro

OBJECTIVE

To investigate 1) the effects of lineage-specific cytokines (G-CSF and EPO) combined with ligands for different classes of cytokine receptors (common beta chain, gp130, and tyrosine kinase) on proliferation by human myeloid and erythroid progenitor cells; and 2) the signal transduction pathways associated with combinatorial cytokine actions.

PATIENTS AND METHODS

CFU-GM and BFU-E were cloned in vitro. Secondary colony formation by replated CFU-GM and subcolony formation by BFU-E provided measures of progenitor cell proliferation. Studies were performed in the presence of cytokine combinations with and without signal transduction inhibitors.

RESULTS

Proliferation by CFU-GM and BFU-E was enhanced synergistically when common beta chain receptor cytokines (IL-3 or GM-CSF) were combined with G-CSF or EPO, but not with gp130 receptor cytokines (LIF or IL-6) or tyrosine kinase receptor cytokines (SCF, HGF, Flt-3 ligand, or PDGF). Delayed addition studies with G-CSF+IL-3 and EPO+IL-3 demonstrated that synergy required the presence of both cytokines from the initiation of the culture. The Jak2-specific inhibitor, AG490, abrogated the effect of combining IL-3 with EPO but had no effect on the enhanced CFU-GM proliferation stimulated by IL-3+G-CSF. The PI3 kinase inhibitors LY294002 and wortmannin substituted for G-CSF in combination with IL-3 since proliferation in the presence of LY294002/wortmannin+IL-3 was enhanced to the same extent as in the presence of G-CSF+IL-3. In contrast, LY294002 and wortmannin inhibited proliferation in the presence of EPO and in the presence of EPO+IL-3.

CONCLUSION

1) IL-3 may activate different signal transduction pathways when combined with G-CSF and when combined with EPO; 2) different signal transducing intermediates regulate erythroid and myeloid progenitor cell proliferation; and 3) inhibition of the PI3 kinase pathway suppresses myeloid progenitor cell differentiation and thereby increases proliferation.