Morphological and Immunohistochemical Identification of Villous M Cells in the Small Intestine of Newborn Piglets / Identificación Morfológica e Inmunohistoquímica de los Epiteliocitos Microplegados de las Vellosidades en el Intestino Delgado de Lechones Recién Nacidos

Microfold (M) cells act as antigen-sampling sites for initiating antigen specific mucosal immune responses, but they may also provide a gateway for enteropathogen entry. In this study we demonstrated villous M cells by morphological and immunohistochemical methods to be present in the three regions of the small intestine from newborn piglets. Immunohistochemical analysis, using anti- cytokeratin 18 (CK18) primary antibodies, showed a gradually decreased density of M cells from the lower crypt epithelium to the upper villous epithelium. The proportion of villous M cells was greater in the ileum than in the duodenum or the mid-jejunum. Ultrastructural observation revealed that villous M cells were mainly columnar in shape in the duodenum and the mid-jejunum, and appeared as more pocket-like structure in the ileum. These villous M cells exhibited short and irregular microvilli, rich vesicles and reduced glycocalyx, but lacked the lymphocyte-containing basolateral invagination. Our results support evidence that M cells can develop in the small intestinal villous epithelium of newborn piglets, implying that villous M cells may begin developing in the pig's small intestine during fetal stages, which depends neither on the influence of the mucosal lymphoid tissue nor the antigen from the intestinal lumen stimulation. In addition, the variable morphology and heterogeneity distribution of villous M cells in the three regions of the small intestine may be indicative of its different functional properties. This information extent our understanding of the diversity of M cells and provides important basic knowledge for further research on the actual role of villous M cells in neonate.

Los epiteliocitos microplegados (células M) actúan como receptores de antígeno para iniciar la respuesta inmune específica de las mucosas, pero también pueden proporcionar una puerta de entrada para enteropatógenos. En este estudio, se demostró por métodos morfológicos e inmunohistoquímicos que los epiteliocitos microplegados de las vellosidades están presentes en las tres regiones del intestino delgado de lechones recién nacidos. Se utilizaron anticuerpos primarios de citoqueratina 18 (CK18) para el análisis inmunohistoquímico, el cual mostró una disminución gradual de la densidad de los epiteliocitos microplegados desde el epitelio de las criptas inferiores hasta el epitelio de las vellosidades superiores. La proporción de los epiteliocitos microplegados, fue mayor en el íleon que el duodeno o yeyuno medio. La observación ultraestructural reveló que los epiteliocitos microplegados fueron principalmente de forma columnar en el duodeno y el yeyuno medio. Además, mostraron microvellosidades cortas e irregulares, muchas vesículas y glucocáliz reducidos, pero carecían de invaginaciones basolaterales contenedoras de linfocitos. Nuestros resultados apoyan la evidencia de que los epiteliocitos microplegados pueden desarrollarse en el epitelio de las vellosidades intestinales de los lechones recién nacidos, lo que implica que estas células pueden comenzar a desarrollarse en el intestino delgado del cerdo durante las etapas fetales, y no dependen ni de la influencia del tejido linfoide de las mucosas ni del antígeno para la estimulación del lumen intestinal. Además, la morfología y heterogeneidad de distribución de los epiteliocitos microplegados en las tres regiones del intestino delgado pueden ser indicativas de sus diferentes propiedades funcionales. Esta información mejora nuestra comprensión de la diversidad de los epiteliocitos microplegados y proporciona conocimientos básicos importantes para la investigación sobre el papel de los epiteliocitos microplegados en las vellosidades del neonato.

Effect of proinflammatory cytokines on growth factor expression of type n alveolar epithelial cells from neonate piglet lungs / 中国小儿急救医学

Objective To establish a method of isolation, purification and identification of type Ⅱ alveolar epithelial cells (AEC- K ) from neonate piglet lungs of 1 ～ 3 days old and to investigate effects of proinflammatory cytokines on expression of growth factors (GFs). The yield, viability and purity of AEC- Ⅱ obtained using different enzyme digestion and purifying methods were compared. Methods After the first 24-hour culture of AEC- Ⅱ ,the media containing interleukin (IL)-1β,IL-6 and IGF-Ⅰ at different concentrations were used to culture AEC-Ⅱ for another 48 hours. And then the cells were counted and the expressions of insulin-like growth factor (IGF-Ⅰ ), platelet-derived growth factor ( PDGF), surfactant proteins (SP) -A and SP-B mRNA were determined by real time PCR. Results A significantly higher yield of AEC-Ⅱ was achieved by digesting the lung with 30 unit/ml elastase and 0.1 % trypsin at 37 t for 20 min, the yield was (5.33 ±0.54) × 106 after adjusted by the weight of lung and heart (P <0.01). The number of purified AEC-II obtained by immune adherence method was (38.0 ±28.0) × 106 perpiglet which was higher than by the method of percoll. The optimal phenotype maintenance time of AEC- Ⅱ was the first 24～96 hours in the primary culture. With increasing concentrations of IL-1 β and IL-6, there were decreased proliferation and expression of SP-A and IGF-Ⅰ mRNA in the cultured AEC- Ⅱ ,but SP-B mRNA expression was not affected. Both AEC-Ⅱ proliferation and expression of SP-A, SP-B mRNA decreased significantly after cultured with anti-IGF-Ⅰ. Conclusion In a new model of cultured AEC-Ⅱ from neonate piglets, IL-1β and IL-6 inhibited AEC- Ⅱ proliferation and SP-A mRNA expression through IGF-Ⅰ -dependent mechanisms.