MECANISMOS MOLECULARES QUE CONTROLAN EL DESARROLLO DE LA EXTREMIDAD DE LOS VERTEBRADOS

¿Cómo un grupo de células indiferenciadas pueden formar estructuras y tejidos altamente organizados y diferenciados?, ¿Cuál es la naturaleza de las señales que dictan estos eventos? ¿Cómo son los procesos del desarrollo que actúan para que las diferentes especies desarrollen estructuras similares pero adaptadas al medio en el que viven? Uno de los modelos que han permitido responder en parte a estas interrogantes es la extremidad embrionaria. A partir de los estudios en la extremidad embrionaria se han propuesto una serie de interesantes paradigmas que han cambiado la percepción de ver a los procesos del desarrollo como aislados y poco dinámicos. En esta revisión, destacamos aquellos estudios que han contribuido de manera amplia a entender la inducción de la formación de la extremidad y el establecimiento de los centros organizadores que controlan su morfogénesis, así como el patrón esquelético que incluye la diferenciación del cartílago y la muerte celular

Regulation of α5 and αV Integrin Expression by GDF-5 and BMP-7 in Chondrocyte Differentiation and Osteoarthritis.

The Integrin β1 family is the major receptors of the Extracellular matrix (ECM), and the synthesis and degradation balance of ECM is seriously disrupted during Osteoarthritis (OA). In this scenario, integrins modify their pattern expression and regulate chondrocyte differentiation in the articular cartilage. Members of the Transforming growth factor beta (Tgf-β) Superfamily, such as Growth differentiation factor 5 (Gdf-5) and Bone morphogenetic protein 7 (Bmp-7), play a key role in joint formation and could regulate the integrin expression during chondrocyte differentiation and osteoarthritis progression in an experimental OA rat model. Decrease of α5 integrin expression in articular cartilage was related with chondrocyte dedifferentiation during OA progression, while increase of α1, α2, and α3 integrin expression was related with fibrous areas in articular cartilage during OA. Hypertrophic chondrocytes expressed αV integrin and was increased in the articular cartilage of rats with OA. Integrin expression during chondrocyte differentiation was also analyzed in a micromass culture system of mouse embryo mesenchymal cells, micromass cultures was treated with Gdf-5 or Bmp-7 for 4 and 6 days, respectively. Gdf-5 induced the expression of the α5 sub-unit, while Bmp-7 induced the expression of the αV sub-unit. This suggests a switch in signaling for prehypertrophic chondrocyte differentiation towards hypertrophy, where Gdf-5 could maintain the articular chondrocyte phenotype and Bmp-7 would induce hypertrophy. Decrease of Ihh expression during late stages of OA in rat model suggest that the ossification in OA rat knees and endochondral ossification could be activated by Bmp-7 and αV integrin in absence of Ihh. Thus, chondrocyte phenotype in articular cartilage is similar to prehypetrophic chondrocyte in growth plate, and is preserved due to the presence of Indian hedgehog (Ihh), Gdf-5 and α5 integrin to maintain articular cartilage and prevent hypertrophy

Mechanisms of epithelial thickening due to IL-1 signalling blockade and TNF-α administration differ during wound repair and regeneration

IL-1 and TNF-α are always present during wound repair, but their pleiotropic and synergistic effects are incompletely understood. In this work, we evaluated the role of IL-1 in wound repair, and examined whether TNF-α administration impaired scarless wound repair. First, we characterised wound repair in outbred CD-1 mice according to age and sex in an ear punch wound model. Then, we examined the effects of Interleukin 1 receptor antagonist (IL-1ra) and TNF-α placement inside ear wounds by means of loaded Heparin beads in young and middle-aged male and female mice. Wounds in middle-aged females repaired with scarless characteristics, whereas those in young males showed fibrotic scarring. Rather than improving wound repair in young males, IL-1 signalling blockade increased epithelial thickness and IL-1β and TNF-α expression, and diminished epidermal apoptosis. TNF-α impaired wound repair in middle-aged females, which exhibited acanthosis and overexpression of IL-1, but no change in apoptosis. These findings suggest that this mechanism of epidermal thickening differs from that observed in IL1-ra–treated animals

Regulation of integrin expression by Growth differentiation factor (Gdf)-5 and Bone morphogenetic protein (Bmp)-7 during chondrogenesis.

<p>Mouse micromass cultures without treatment (A–E), Gdf-5 treatment (F–J), and Bmp-7 treatment (K–O). Immunohistochemical stain for β1 (A, F, K), α1 (B, G, L), α5 (C, H, M), and αV (D, I, N) integrins, IgG control for Immunohostochemestry (E, J, O). Statistical analysis for integrin immunohistochemistry data (P), percentage of positive area for integrin β1, integrin α1, integrin α5, integrin αV and IgG control stains in micromasses with different treatments (control, GDF-5, and BMP-7); mean values are shown with Standard deviations (SD) (<i>n</i> = three independent experiments). One-way Analysis of variance (ANOVA). ***<i>P</i> ˂0.0001, <i>**p</i> ˂0.001, <i>*p</i> ˂0.05. Micromass cultures with Gdf-5 treatment induce α5 integrin expression and Bmp-7 treatment induces αV integrin expression.</p

Gdf-5 is associated with healthy articular cartilage and Bmp-7 is associated with OA.

<p>Immunofluorescence for Gdf-5 (A, B) and <i>in situ</i> hybridization for <i>Bmp-7</i> (C, D) in healthy rat articular cartilage (A, C) and at day 10 of OA (B, D) showed Gdf-5 expression in prehypertrophic chondrocytes in healthy articular cartilage. <i>Bmp-7</i> is associated with OA from day 10 post-surgery.</p

Regulation of Extracellular matrix (ECM) composition by Bone morphogenetic protein (BMP) family growth factors during chondrogenesis.

<p>Mouse micromass cultures without treatment (A–E), Gdf-5 treatment (F–J), and Bmp-7 treatment (K–O); Alcian blue stain (A–K) showed cartilage nodules, Immunohistochemical stain for type 1 collagen (A, F, K), type II collagen (C, H, M), aggrecan (D, I, N), and fibronectin (E, J, O). Statistical analysis for histochemical and immunohistochemical data, (P) = percentage of positive area for Alcian blue, type I collagen, type II collagen, aggrecan, and fibronectin stains in micromasses with different treatments; mean values are shown with Standard deviations (SD) (<i>n</i> = three independent experiments), One-way Analysis of variance (ANOVA). <i>***P</i> ˂0.0001; <i>**p</i> ˂0.001; <i>*p</i> ˂0.05). Gdf-5 mainly induces aggrecan expression, type II collagen, and fibronectin; aggrecan is an articular cartilage marker; in contrast, Bmp-7 induce type I collagen, an extracellular component of hypertrophic cartilage and bone.</p

Integrin α5 is expressed in healthy articular cartilage surface, and integrin α V on osteoarthritic articular cartilage recapitulates chondrocyte differentiation, as in the in cartilage growth plate.

<p>Immunohistochemical stain for β1 (A–D), α5 (E–H), αV (J–M) integrins; in healthy articular cartilage (A, E, J); during Osteoarthritis (OA) at day 5 (B, F, K), day 10 (C, G, L), and at day 20 (D, H, M), and in the growth plate cartilage, α5 integrin (I) and αV integrin (N). Fibronectin is localizes in the pericellular area of chondrocytes (R-U).</p

Regulation between α5 integrin and Ihh signaling.

<p><i>In situ</i> hybridization for Indian hedgehog (<i>Ihh</i>) gene (A–D), in healthy articular cartilage (A), during OA at day 5 (B), at day 10 (C), and at day 20 (D) showed decrease of <i>Ihh</i> gene expression in Osteoarthritis (OA). Immunofluorescence in mouse micromass cultures (E–H), without treatment (E, G) showed expression for Ihh (E) and integrin α5 (F); treatment micromasses with blocking antibodies (G, H) for integrin α5 inhibited Ihh expression (F), and treatment with blocking antibodies for Ihh inhibits integrin α5 expression (H).</p

Trends in Gliosis in Obesity, and the Role of Antioxidants as a Therapeutic Alternative

Obesity remains a global health problem. Chronic low-grade inflammation in this pathology has been related to comorbidities such as cognitive alterations that, in the long term, can lead to neurodegenerative diseases. Neuroinflammation or gliosis in patients with obesity and type 2 diabetes mellitus has been related to the effect of adipokines, high lipid levels and glucose, which increase the production of free radicals. Cerebral gliosis can be a risk factor for developing neurodegenerative diseases, and antioxidants could be an alternative for the prevention and treatment of neural comorbidities in obese patients. Aim: Identify the immunological and oxidative stress mechanisms that produce gliosis in patients with obesity and propose antioxidants as an alternative to reducing neuroinflammation. Method: Advanced searches were performed in scientific databases: PubMed, ProQuest, EBSCO, and the Science Citation index for research on the physiopathology of gliosis in obese patients and for the possible role of antioxidants in its management. Conclusion: Patients with obesity can develop neuroinflammation, conditioned by various adipokines, excess lipids and glucose, which results in an increase in free radicals that must be neutralized with antioxidants to reduce gliosis and the risk of long-term neurodegeneration