The activity of TGF-beta1 is regulated primarily extracellularly where the secreted latent form must be modified to expose the active molecule. Here we show that thrombospondin-1 is responsible for a significant proportion of the activation of TGF-beta1 in vivo. Histological abnormalities in young TGF-beta1 null and thrombospondin-1 null mice were strikingly similar in nine organ systems. Lung and pancreas pathologies similar to those observed in TGF-beta1 null animals could be induced in wild-type pups by systemic treatment with a peptide that blocked the activation of TGF-beta1 by thrombospondin-1. Although these organs produced little active TGF-beta1 in thrombospondin null mice, when pups were treated with a peptide derived from thrombospondin-1 that could activate TGF-beta1, active cytokine was detected in situ, and the lung and pancreatic abnormalities reverted toward wild type.

Mice lacking TGF-β3 exhibit an incompletely penetrant failure of the palatal shelves to fuse leading to cleft palate. The defect appears to result from impaired adhesion of the apposing medial edge epithelia of the palatal shelves and subsequent elimination of the mid-line epithelial seam. No craniofacial abnormalities were observed. This result demonstrates that TGF-β3 affects palatal shelf fusion by an intrinsic, primary mechanism rather than by effects secondary to craniofacial defects.Members of the transforming growth factor-β (TGF-β) gene family have biological activities that control cell proliferation, migration and differentiation, regulation of extracellular matrix deposition and epithelial-mesenchymal transformation [1][2][3] . Mammals contain three highly conserved isoforms of TGF-β, termed TGF-β1, TGF-β2 and TGF-β3, which display distinctive, although at times overlapping, spatial and temporal expression patterns [4][5][6] . Previous studies suggested that TGF-β3 may play a crucial role during palatogenesis 7-9 , Meckel's cartilage formation 10 , cardiac morphogenesis 11 , mammary gland development 12 and wound healing 13 . Other tissues expressing TGF-β3 in significant levels are cartilage, bone, brain and lung [4][5][6]14 .In mammalian palatogenesis apposition of the palatal shelves, adhesion of the medial edge epithelia (MEE) and subsequent elimination of the epithelial seam lead to a seamless mesenchymal shelf separating the oral and nasal cavities 15 . In vitro organ culture studies indicate that TGF-β1 and TGF-β2 accelerate palatal shelf fusion 16,17 and that antisense oligodeoxynucleotides or neutralizing antibodies to TGF-β3, but not to TGF-β1 or TGF-β2, block the fusion process 9 . We have now created mice deficient in TGF-β3, and show that this factor has a role in palatal shelf fusion by means of an intrinsic, primary mechanism and not by effects secondary to craniofacial morphometrics. A comparison of this defect to the inflammatory disorder of TGF-β1-deficient mice [18][19][20][21] Mutation of TGF-β3 in ES cellsThe TGF-β3 gene was mutated in ES cells (Fig. 1a) by replacing exon 6, the first full exon encoding sequences of the active domain of the protein, with the neomycin-resistance gene from pMC1neo 22 . Diagnostic Southern blots of the clone I98 indicated that the locus was successfully targeted; the proper genomic regions flanking both sides of the target site remained intact (Fig. 1b). Probing with a neo-gene probe indicated that there was only one integration site (not shown). Consequently, only the TGF-β3 locus has been disrupted. RT-PCR analysis of whole 11.5- (Fig. 1c) and 15.5-day embryos (not shown) indicated no TGF-β3 expression in homozygous mutant embryos, and revealed no significant change in the expression of TGF-β1 or TGF-β2 in the absence of TGF-β3. Cleft palate in TGF-β3 null mutantsThe targeted ES cell clone I98 was used to produce chi-maeric mice, which were mated with CF-1, C57BL/6 or 129/Sv mice. Heterozygous offspring showed no apparent phenotype. Interc...

The critical cell signals that trigger cardiac hypertrophy and regulate the transition to heart failure are not known. To determine the role of G␣q-mediated signaling pathways in these events, transgenic mice were constructed that overexpressed wild-type G␣q in the heart using the ␣-myosin heavy chain promoter. Two-fold overexpression of G␣q showed no detectable effects, whereas 4-fold overexpression resulted in increased heart weight and myocyte size along with marked increases in atrial naturietic factor (Ϸ55-fold), ␤-myosin heavy chain (Ϸ8-fold), and ␣-skeletal actin (Ϸ8-fold) expression, and decreased (Ϸ3-fold) ␤-adrenergic receptor-stimulated adenylyl cyclase activity. All of these signals have been considered markers of hypertrophy or failure in other experimental systems or human heart failure. Echocardiography and in vivo cardiac hemodynamic studies indeed revealed impaired intrinsic contractility manifested as decreased fractional shortening (19 ؎ 2% vs. 41 ؎ 3%), dP͞dt max, a negative force-frequency response, an altered Starling relationship, and blunted contractile responses to the ␤-adrenergic agonist dobutamine. At higher levels of G␣q overexpression, frank cardiac decompensation occurred in 3 of 6 animals with development of biventricular failure, pulmonary congestion, and death. The element within the pathway that appeared to be critical for these events was activation of protein kinase C. Interestingly, mitogen-activated protein kinase, which is postulated by some to be important in the hypertrophy program, was not activated. The G␣q overexpressor exhibits a biochemical and physiologic phenotype resembling both the compensated and decompensated phases of human cardiac hypertrophy and suggests a common mechanism for their pathogenesis.

No abstract

Collagen gels were seeded with rabbit bone marrow-derived mesenchymal stem cells (MSCs) and contracted onto sutures at initial cell densities of I , 4, and 8 million cellslml. These MSC-collagen composites were then implanted into full thickness, full length, central defects created in the patellar tendons of the animals providing the cells. These autologous repairs were compared to natural repair of identical defects on the contralateral side. Biomechanical, histological, and morphometric analyses were performed on both repair tissue types at 6, 12, and 26 weeks after surgery. Repair tissues containing the MSC-collagen composites showed significantly higher maximum stresses and moduli than natural repair tissues at 12 and 26 weeks postsurgery. However, no significant differences were observed in any dimensional or mechanical properties of the repair tissues across seeding densities at each evaluation time. By 26 weeks, the repairs grafted with MSC-collagen composites were one-fourth of the maximum stress of the normal central portion of the patellar tendon with bone ends. The modulus and maximum stress of the repair tissues grafted with MSCLcollagen composites increased at significantly faster rates than did natural repairs over time. Unexpectedly, 28% of the MSC ~ collagen grafted tendons formed bone in the regenerating repair site. Except for increased repair tissue volume, no significant differences in cellular organization or histological appearance were observed between the natural repairs and MSC-collagen grafted repairs. Overall, these results show that surgically implanting tissue engineered MSC-collagen composites significantly improves the biomechanical properties of tendon repair tissues, although greater MSC concentrations produced no additional significant histological or biomechanical improvement.

Mesenchymal stem cells (MSCs) were isolated from bone marrow of 18 adult New Zealand White rabbits. These cells were culture expanded, suspended in type I collagen gel, and implanted into a surgically induced defect in the donor s right patellar tendon. A cell-free collagen gel was implanted into an identical control defect in the left patellar tendon. Repair tissues were evaluated biomechanically (n = 13) and histomorphometrically (n = 5) at 4 weeks after surgery. Compared to their matched controls, the MSC-mediated repair tissue demonstrated significant increases of 26% (p < 0.001), 18% (p < 0. 01), and 33% (p < 0.02) in maximum stress, modulus, and strain energy density, respectively. Qualitatively, there appeared to be minor improvements in the histological appearance of some of the MSC- mediated repairs, including increased number of tenocytes and larger and more mature-looking collagen fiber bundles. Morphometrically, however, there were no significant left-right differences in nuclear aspect ratio (shape) or nuclear alignment (orientation). Therefore, delivering a large number of mesenchymal stem cells to a wound site can significantly improve its biomechanical properties by only 4 weeks but produce no visible improvement in its microstructure.

Several diverse genetically engineered mouse models of pancreatic exocrine neoplasia have been developed. These mouse models have a spectrum of pathologic changes; however, until now, there has been no uniform nomenclature to characterize these changes. An international workshop, sponsored by The National Cancer Institute and the University of Pennsylvania, was held from December 1 to 3, 2004 with the goal of establishing an internationally accepted uniform nomenclature for the pathology of genetically engineered mouse models of pancreatic exocrine neoplasia. The pancreatic pathology in 12 existing mouse models of pancreatic neoplasia was reviewed at this workshop, and a standardized nomenclature with definitions and associated images was developed. It is our intention that this nomenclature will standardize the reporting of genetically engineered mouse models of pancreatic exocrine neoplasia, that it will facilitate comparisons between genetically engineered mouse models and human pancreatic disease, and that it will be broad enough to accommodate newly emerging mouse models of pancreatic neoplasia. (Cancer Res 2006; 66(1): 95-106)

Vascular tone control is essential in blood pressure regulation, shock, ischemia-reperfusion, inflammation, vessel injury/repair, wound healing, temperature regulation, digestion, exercise physiology, and metabolism. Here we show that a well-known growth factor, FGF2, long thought to be involved in many developmental and homeostatic processes, including growth of the tissue layers of vessel walls, functions in vascular tone control. Fgf2 knockout mice are morphologically normal and display decreased vascular smooth muscle contractility, low blood pressure and thrombocytosis. Following intra-arterial mechanical injury, FGF2-deficient vessels undergo a normal hyperplastic response. These results force us to reconsider the function of FGF2 in vascular development and homeostasis in terms of vascular tone control.