The emerging importance of lymphatics in health and disease: an NIH workshop report.

The lymphatic system (LS) is composed of lymphoid organs and a network of vessels that transport interstitial fluid, antigens, lipids, cholesterol, immune cells, and other materials in the body. Abnormal development or malfunction of the LS has been shown to play a key role in the pathophysiology of many disease states. Thus, improved understanding of the anatomical and molecular characteristics of the LS may provide approaches for disease prevention or treatment. Recent advances harnessing single-cell technologies, clinical imaging, discovery of biomarkers, and computational tools have led to the development of strategies to study the LS. This Review summarizes the outcomes of the NIH workshop entitled "Yet to be Charted: Lymphatic System in Health and Disease," held in September 2022, with emphasis on major areas for advancement. International experts showcased the current state of knowledge regarding the LS and highlighted remaining challenges and opportunities to advance the field.

A synthetic peptide from transforming growth factor beta type III receptor inhibits liver fibrogenesis in rats with carbon tetrachloride liver injury.

Transforming growth factor beta1 (TGF-beta1) is a pleiotropic cytokine, which displays potent profibrogenic effects and is highly expressed in fibrotic livers. For this reason, development of TGF-B1 inhibitors might be of great importance to control liver fibrogenesis as well as other undesired side effects due to this cytokine. Potential peptide inhibitors of TGF-beta1 (derived from TGF-beta1 and from its type III receptor) were tested in vitro and in vivo using different assays. Peptides P11 and P12, derived from TGF-beta1, and P54 and P144, derived from its type III receptor, prevented TGF-beta1-dependent inhibition of MV1Lu proliferation in vitro and markedly reduced binding of TGF-beta1 to its receptors. P144 blocked TGF-beta1-dependent stimulation of a reporter gene under the control of human alpha2(I) collagen promoter. Intraperitoneal administration of P144 also showed potent antifibrogenic activity in vivo in the liver of rats receiving CCl4. These rats also showed a significant decrease in the number of activated hepatic stellate cells as compared with those treated with saline only. These results suggest that short synthetic peptides derived from TGF-beta1 type III receptor may be of value in reducing liver fibrosis in chronic liver injury.

Reciprocal modulation of matrix metalloproteinase-13 and type I collagen genes in rat hepatic stellate cells.

Collagen degradation by matrix metalloproteinases is the limiting step in reversing liver fibrosis. Although collagen production in cirrhotic livers is increased, the expression and/or activity of matrix metalloproteinases could be normal, increased in early fibrosis, or decreased during advanced liver cirrhosis. Hepatic stellate cells are the main producers of collagens and matrix metalloproteinases in the liver. Therefore, we sought to investigate whether they simultaneously produce alpha1(I) collagen and matrix metalloproteinase-13 mRNAs. In this communication we show that expression of matrix metalloproteinase-13 mRNA is reciprocally modulated by tumor necrosis factor-alpha and transforming growth factor-beta1. When hepatic stellate cells are co-cultured with hepatocytes, matrix metalloproteinase-13 mRNA is up-regulated and alpha1(I) collagen is down-regulated. Injuring hepatocytes with galactosamine further increased matrix metalloproteinase-13 mRNA production. Confocal microscopy and differential centrifugation of co-cultured cells revealed that matrix metalloproteinase-13 is localized mainly within hepatic stellate cells. Studies performed with various hepatic stellate cell lines revealed that they are heterogeneous regarding expression of matrix metalloproteinase-13. Those with myofibroblastic phenotypes produce more type I collagen whereas those resembling freshly isolated hepatic stellate cells express matrix metalloproteinase-13. Overall, these findings strongly support the notion that alpha1(I) collagen and matrix metalloproteinase-13 mRNAs are reciprocally modulated.

Trichostatin A, a histone deacetylase inhibitor, suppresses collagen synthesis and prevents TGF-beta(1)-induced fibrogenesis in skin fibroblasts.

Excessive production of collagens by alpha-smooth muscle actin (alpha-SMA)-positive myofibroblasts leads to fibrotic skin diseases, such as hypertrophic scarring. This process is characterized by an imbalance between extracellular matrix (ECM) synthesis and degradation, while transforming growth factor beta (TGF-beta(1)), known to be a key mediator of fibrogenesis, is up-regulated. In this study we have investigated the possible antifibrogenic effect of Trichostatin A (TSA), a histone deacetylase inhibitor, on rat skin fibroblasts in culture. mRNA steady-state levels and de novo protein synthesis of procollagen types I and III and alpha-SMA were inhibited when skin fibroblasts were treated with 100 nM TSA with or without TGF-beta(1). While the transcription rate of the procollagen alpha1(I) gene was increased following TSA or TGF-beta(1) treatment, TSA abrogated the stimulatory effect of TGF-beta(1) on procollagen alpha1(I) transcription when both compounds were added simultaneously. The reduction of procollagen alpha1(I) and alpha1(III) mRNA steady-state levels by TSA did not require de novo protein synthesis, while the effect of TSA on alpha-SMA mRNA steady-state levels was cycloheximide-sensitive. Interestingly, TSA affected TGF-beta(1) and its downstream mediators, i.e., the Smad family proteins. TSA strongly induced in a biphasic way the expression of 5'TG3' interacting factor (TGIF), a known endogenous corepressor molecule of the TGF-beta(1) signaling pathway. Addition of exogenous TGF-beta(1) did not interfere with the effect of TSA on the TGIF mRNA level. Our study shows that inhibition of histone deacetylases by TSA reduces expression of fibrosis-related genes in skin fibroblasts and this coincides by alterations in the TGF-beta(1) signaling pathway.