Rationale: In experimental models, lung fibrosis is dependent on transforming growth factor (TGF)-β signaling. TGF-β is secreted in a latent complex with its propeptide, and TGF-β activators release TGF-β from this complex. Because the integrin αvβ6 is a major TGF-β activator in the lung, inhibition of αvβ6-mediated TGF-β activation is a logical strategy to treat lung fibrosis. Objectives: To determine, by genetic and pharmacologic approaches, whether murine radiation-induced lung fibrosis is dependent on αvβ6. Methods: Wild-type mice, αvβ6-deficient (Itgb6−/−) mice, and mice heterozygous for a Tgfb1 mutation that eliminates integrin-mediated activation (Tgfb1+/RGE) were exposed to 14 Gy thoracic radiation. Some mice were treated with an anti-αvβ6 monoclonal antibody or a soluble TGF-β receptor fusion protein. αvβ6 expression was determined by immunohistochemistry. Fibrosis, inflammation, and gene expression patterns were assessed 20–32 weeks postirradiation. Measurements and Main Results: β6 Integrin expression increased within the alveolar epithelium 18 weeks postirradiation, just before onset of fibrosis. Itgb6−/− mice were completely protected from fibrosis, but not from late radiation-induced mortality. Anti-αvβ6 therapy (1–10 mg/kg/wk) prevented fibrosis, but only higher doses (6–10 mg/kg/wk) caused lung inflammation similar to that in Itgb6−/− mice. Tgfb1-haploinsufficient mice were also protected from fibrosis. Conclusions: αvβ6-Mediated TGF-β activation is required for radiation-induced lung fibrosis. Together with previous data, our results demonstrate a robust requirement for αvβ6 in distinct fibrosis models. Inhibition of αvβ6-mediated TGF-β activation is a promising new approach for antifibrosis therapy.

The TGF-βs are multifunctional proteins whose activities are believed to be controlled by interaction with the latent TGF-β binding proteins (LTBPs). In spite of substantial effort, the precise in vivo significance of this interaction remains unknown. To examine the role of the Ltbp-3, we made an Ltbp-3–null mutation in the mouse by gene targeting. Homozygous mutant animals develop cranio-facial malformations by day 10. At 2 mo, there is a pronounced rounding of the cranial vault, extension of the mandible beyond the maxilla, and kyphosis. Histological examination of the skulls from null animals revealed ossification of the synchondroses within 2 wk of birth, in contrast to the wild-type synchondroses, which never ossify. Between 6 and 9 mo of age, mutant animals also develop osteosclerosis and osteoarthritis. The pathological changes of the Ltbp-3–null mice are consistent with perturbed TGF-β signaling in the skull and long bones. These observations give support to the notion that LTBP-3 is important for the control of TGF-β action. Moreover, the results provide the first in vivo indication for a role of LTBP in modulating TGF-β bioavailability.

Mesenchymal stem cells (MSCs) play a crucial role in regulating normal skeletal homeostasis and, in case of injury, in bone healing and reestablishment of skeletal integrity. Recent scientific literature is focused on the development of bone regeneration models where MSCs are combined with biomimetic three-dimensional scaffolds able to direct MSC osteogenesis. In this work the osteogenic potential of human MSCs isolated from adipose tissue (hADSCs) has been evaluated in vitro in combination with collagen/Mg doped hydroxyapatite scaffolds. Results demonstrate the high osteogenic potential of hADSCs when cultured in specific differentiation induction medium, as revealed by the Alizarin Red S staining and gene expression profile analysis. In combination with collagen/hydroxyapatite scaffold, hADSCs differentiate into mature osteoblasts even in the absence of specific inducing factors; nevertheless, the supplement of the factors markedly accelerates the osteogenic process, as confirmed by the expression of specific markers of pre-osteoblast and mature osteoblast stages, such as osterix, osteopontin (also known as bone sialoprotein I), osteocalcin and specific markers of extracellular matrix maturation and mineralization stages, such as ALPL and osteonectin. Hence, the present work demonstrates that the scaffold per se is able to induce hADSCs differentiation, while the addition of osteo-inductive factors produces a significant acceleration of the osteogenic process. This observation makes the use of our model potentially interesting in the field of regenerative medicine for the treatment of bone defects.

Objective: Erdheim‐Chester disease (ECD) is a rare form of non–Langerhans' cell histiocytosis (LCH) of unknown etiology, characterized by diffuse histiocyte infiltration of bones and soft tissue. The purpose of this study was to assess cell proliferation and expression of cytokines, chemokines, and chemokine receptors that may potentially be important in histiocyte accumulation in ECD lesions.Methods: Biopsies were performed on 3 patients with ECD. The diagnosis of the disease was based on clinical signs including typical radiologic osteosclerosis, and on the detection of foamy CD68+,CD1a− non–Langerhans' cell histiocytes on histologic examination. The expression of the proliferation marker Ki‐67 as well as of selected chemokine/chemokine receptor pairs and cytokines was analyzed by immunohistochemistry.Results: In all samples, Ki‐67 was undetectable in CD68+ histiocytes. Conversely, these cells expressed the chemokines CCL2 (monocyte chemotactic protein 1), CCL4/macrophage inflammatory protein 1β (MIP‐1β), CCL5/RANTES, CCL20/MIP‐3α, and CCL19/MIP‐3β, and their counter‐receptors CCR1, CCR2, CCR3, CCR5, CCR6, and CCR7. Moreover, ECD histiocytes expressed interferon‐γ–inducible 10‐kd protein (CXCL10), which is specifically induced by interferon‐γ, and interleukin‐6 and RANKL, which are both implicated in bone remodeling. Finally, all cases showed a Th1‐type lymphocyte infiltrate.Conclusion: Our data indicate that, similar to LCH, ECD lesions are characterized by a complex cytokine and chemokine network, which may orchestrate histiocyte activation and accumulation through an autocrine loop and contribute to the pathogenesis of the disease.