Enhanced expression of transforming growth factor-beta isoforms in the neural tube of embryos derived from diabetic mice exposed to cyclophosphamide

The orphan GPCR, Gpr161, regulates the retinoic acid and canonical Wnt pathways during neurulation

The vacuolated lens (vl) mouse mutation arose on the C3H/HeSnJ background and results in lethality, neural tube defects (NTDs) and cataracts. The vl phenotypes are due to a deletion/frameshift mutation in the orphan GPCR, Gpr161. A recent study using a null allele demonstrated that Gpr161 functions in primary cilia and represses the Shh pathway. We show the hypomorphic Gpr161(vl) allele does not severely affect the Shh pathway. To identify additional pathways regulated by Gpr161 during neurulation, we took advantage of naturally occurring genetic variation in the mouse. Previously Gpr161(vl-C3H) was crossed to different inbred backgrounds including MOLF/EiJ and the Gpr161(vl) mutant phenotypes were rescued. Five modifiers were mapped (Modvl: Modifier of vl) including Modvl5(MOLF). In this study we demonstrate the Modvl5(MOLF) congenic rescues the Gpr161(vl)-associated lethality and NTDs but not cataracts. Bioinformatics determined the transcription factor, Cdx1, is the only annotated gene within the Modvl5 95% CI co-expressed with Gpr161 during neurulation and not expressed in the eye. Using Cdx1 as an entry point, we identified the retinoid acid (RA) and canonical Wnt pathways as downstream targets of Gpr161. QRT-PCR, ISH and IHC determined that expression of RA and Wnt genes are down-regulated in Gpr161(vl/vl) but rescued by the Modvl5(MOLF) congenic during neurulation. Intraperitoneal RA injection restores expression of canonical Wnt markers and rescues Gpr161(vl/vl) NTDs. These results establish the RA and canonical Wnt as pathways downstream of Gpr161 during neurulation, and suggest that Modvl5(MOLF) bypasses the Gpr161(vl) mutation by restoring the activity of these pathways.

Gene Expression by Fibroblasts Seeded on Small Intestinal Submucosa and Subjected to Cyclic Stretching

Extracellular matrix scaffolds derived from porcine small intestinal submucosa (SIS-ECM) have been shown to promote the formation of site-specific tissue in a number of preclinical animal studies. However, this constructive remodeling process requires that the scaffold be subjected to a site-specific mechanical environment. The specific quantitative effects of mechanical loading on the gene expression patterns of fibroblasts seeded on SIS-ECM are unknown and yet very important in the tissue remodeling process. The objective of the present study was to evaluate the expression of collagen type I (Col I), collagen type III (Col III), smooth muscle actin (SMA), tenascin-C (TN-C), matrix metalloprotease-2 (MMP-2), matrix metalloprotease-9 (MMP-9), transforming growth factor-beta1 (TGF-beta1), and transforming growth factor-beta3 (TGF-beta3) by fibroblasts subjected to various magnitudes (0%, 5%, 10%, and 15%) and frequencies (0.1 Hz, 0.3 Hz, and 0.5 Hz) of stretch. A new cyclic-stretching tissue culture (CSTC) system was developed. This system consists of eight independently controlled culture chambers that can be operated in a sterile incubator. Each chamber includes a load cell so that the load in each scaffold can be monitored. It was found that different stretching regimens led to complex and distinctive patterns of gene expression by fibroblasts seeded onto SIS-ECM. In general, the fibroblasts increased expression of Col I up to 5-fold and decreased that of Col III with increased frequency of stretch. In addition, the fibroblasts exhibited a contractile phenotype with increased expression of SMA, TN-C, and TGF-beta1. These findings support the concept that the mechanical environment of a remodeling ECM scaffold may have substantial effects on the behavior of cells within the scaffold and contribute to the site-specific tissue remodeling that has been observed in in vivo studies.