Jones Laboratory

Home Projects Lab Staff Publications Links

 

Research Summary

Our research focuses on the role of homeobox gene transcription factors and their targets in lung development and disease, including pulmonary arterial hypertension and breast cancer metastasis to the lung vasculature. In particular, we are concentrating on the following areas:

 

Homeobox genes & fetal lung vascular development

The origins of the pulmonary vasculature remain obscure. Recent work in our laboratory, however, has shown that the paired-related homeobox gene, Prx1, is required for lung vascularization. Initial studies using fetal mouse lung tissue revealed that Prx1 localizes to differentiating endothelial cells (ECs) within the distal fetal lung mesenchyme, as well as within ECs forming vascular networks later in development. To begin to determine whether Prx1 promotes EC differentiation, rat and mouse fetal lung mesodermal cells were stably transfected with full-length Prx1 cDNA, resulting in their morphological transformation to an EC-like phenotype. In addition, Prx1-transformed cells acquired the ability to form vascular networks on Matrigel. Thus, Prx1 might function by promoting both pulmonary EC differentiation within the fetal lung mesoderm (i.e. vasculogenesis), as well as their subsequent incorporation into vascular networks (i.e. angiogenesis). To understand how Prx1 participates in this latter process, we focused on tenascin-C (TN-C), an extracellular matrix (ECM) protein induced by Prx1. Importantly, a TN-C-rich ECM surrounds Prx1-positive pulmonary vascular networks both in vivo and in tissue culture. Furthermore, we showed that TN-C is required for Prx1-dependent vascular network formation on Matrigel. Finally, to determine whether these results were relevant in vivo, we examined newborn Prx1-wild type (+/+) and -null (-/-) mice, and showed that Prx1 is critical for expression of TN-C expression and lung vascularization in vivo. Collectively, these studies provide a molecular framework for current work aimed at understanding how Prx1 controls vasculogenesis and angiogenesis in the developing lung.

 

Regulation & functions of tenascin-C in pulmonary arterial hypertension

What is pulmonary arterial hypertension? Pulmonary arterial hypertension (PAH) is defined by the presence of abnormally elevated pressures in the pulmonary vasculature either at rest or with exertion. This can be the result of primary pulmonary vascular abnormalities, as in idiopathic (“primary”) pulmonary arterial hypertension (IPAH), and pulmonary hypertension associated with collagen vascular diseases (e.g. systemic sclerosis), HIV infection, liver dysfunction and anorectic agent use. In addition, PAH can be secondary to left heart failure, thromboembolism and chronic hypoxemic lung disorders (e.g. emphysema). Associated with elevated pulmonary vascular pressures in PAH are derangements in cardiovascular function and gas exchange which resultant hypoxemia and limitations in cardiac output. Together, these abnormalities cause dyspnea and exercise limitations. Eventually, the increased afterload results in right-sided cardiac dysfunction, failure and eventual patient death. Previously, the median survival of patients with PAH was reported as 2.8 years from diagnosis. More recently, advances in medical therapies have resulted in both reduced morbidity and mortality. Nevertheless, IPAH is likely to be an under-diagnosed disease for which no cure exists.

 

Recently, familial, sporadic and secondary forms of PAH have been linked to mutations in BMP type II receptors (BMPRII), yet the molecular targets of this pathway remain elusive. Nevertheless, we have shown that Prx1 and TN-C are co-induced within hypertensive vascular lesions in patients with familial PAH (FPAH). To understand how Prx1 and TN-C are regulated, pulmonary artery smooth muscle cells (SMCs) isolated from normal and FPAH subjects were evaluated to show that expression of these molecules was greater in FPAH SMCs. Next, we demonstrated that Prx1 and TN-C gene promoter activities were also significantly higher in FPAH versus normal SMCs, and that Prx1 overexpression in normal SMCs activates TN-C transcription. To delineate how BMPRII controls TN-C, the Smad-1/5/8 (i.e. R-Smad) signaling pathway was studied. Phosphorylation and nuclear localization of Smad-1/5/8 was suppressed in TN-C-producing FPAH SMCs, whereas blocking Smad-1/5/8 activity in normal SMCs induced TN-C. Since ERK1/2-MAPKs antagonize R-Smad-dependent signaling, and because ERK1/2 promotes TN-C transcription, we determined whether ERK1/2 controls TN-C via suppression of Smad-1/5/8. ERK1/2 activity was greater in FPAH SMCs, and pharmacologic inhibition of these effectors in FPAH SMCs activated Smad-1/5/8 whilst suppressing TN-C. Collectively, these studies reveal the existence of a novel signaling network relevant to PAH underscored by BMPRII mutations. These studies will lead to the identification of novel targets for intervention and treatment, which include both transcriptional and extracellular mediators of the PAH phenotype.

 

PENN/CMREF Center for Pulmonary Arterial Hypertension Research
(Director, Peter L Jones, Ph.D.)

The Cardiovascular Medical Research and Education Fund (CMREF: www.ipahresearch.org) is a non-profit fund operated solely for charitable, scientific and educational purposes. The CMREF mission is to aid in uncovering the etiology and pathogenesis of idiopathic pulmonary arterial hypertension (IPAH), in pursuit of the ultimate goal of its treatment and cure. In 2006, the CMREF awarded a 5 year center grant to aid in establishing a Penn/CMREF Cell Core, directed by Dr. Peter Lloyd Jones. In collaboration with numerous Investigators, including Dr. Darren Taichman at The Hospital of the University of Pennsylvania, the Penn CMREF IPAH Center for Pulmonary Arterial Hypertension Research will: (1) Acquire control and IPAH tissues and fluid; (2) Isolate control and IPAH lung vascular, circulating cells and fluids; (3) Phenotype control and IPAH lung vascular, circulating cells and fluids; (4) Test, Preserve & Bank Cells; (5) Immortalize control & IPAH cells; (6) Distribute cells and fluids to the CMREF/IPAH network; (7) Define an IPAH plasma proteome and IPAH cell signalome; (8) Prepare material for network partners & interact with other Investigators; (9) Generate, coordinate and manage data. It is anticipated that the Penn/CMREF Center will help to rapidly expand knowledge in IPAH research, diagnoses and treatment.

 

Cellular & molecular basis of lung branching morphogenesis

Recent studies by our group and our collaborator, Dr. Sarah A Gebb, Ph.D., (University of Colorado Health Sciences Center) have demonstrated that the low oxygen environment of the fetus plays a critical role in lung branching morphogenesis. In lung explant culture, fetal oxygen tension acts to maintain appropriate spatial expression of markers of epithelial (i.e. surfactant protein C and sonic hedgehog) and endothelial (i.e flk-1 and PECAM) differentiation. The factors mediating this response, however, remain elusive. The extracellular matrix (ECM) plays an important role in development, providing a scaffold for tissue organization and a cell-matrix interface that transduces cellular signals, dictates cell shape and function, and modulates cellular responses to a broad range of extrinsic and intrinsic factors. Several ECM proteins are known to promote lung branching morphogenesis, including the ECM protein tenascin-C (TN-C). Little is known, however, about the mechanisms governing TN-C expression, deposition and turnover in the developing lung. In addition, it is not clear how TN-C works to promote lung branching morphogenesis. Our initial studies demonstrate that, when compared to normoxia (i.e. 21% O 2) fetal oxygen tension (i.e. 3% O 2) promotes lung branching morphogenesis by locally inhibiting the activity of matrix metalloproteinases (MMPs) at potential branch points. In turn, such local MMP inhibition leads to the accumulation of mesenchymal TN-C, which subsequently supports branching morphogenesis of the adjacent epithelium. Current studies aim to define how TN-C, MMPs and hypoxia interact to control the activity of receptor tyrosine kinases that are known to play a pivotal role in fetal lung branching morphogenesis.

 

Mechanisms of breast cancer cell homing to the lung vasculature

Endothelial cells (ECs) from the macrovascular (e.g. pulmonary artery) and microvascular (e.g. pulmonary capillary) beds are phenotypically and functionally distinct. Consistent with this, recent studies showed that metastatic breast cells interact with macrovascular, rather than microvascular lung ECs (Muschel). Since the extracellular matrix (ECM) protein tenascin-C (TN-C) is preferentially expressed by lung macrovascular ECs following injury, and TN-C expression is predictive of breast metastasis to the lung, we hypothesize that extracellular TN-C produced by lung macrovascular ECs, in response to breast metastases, acts as a homing signal for tumor cells to the lung. Using human tissue, animal models and organotypic cultures, we are defining new pathways that may be responsible for lung TN-C: breast cancer interactions. It is hope that targeting these pathways will lead to new clues regarding the pathobiology and treatment of breast cancer.

Home Projects Lab Staff Publications Links

Laboratory Address

The Institute For Medicine & Engineering

1010 Vagelos Research Laboratories,

The University of Pennsylvania,

3340 Smith Walk Philadelphia,

PA 19104-6383

Telephone: (215) 898 0048

Fax: (215) 573 6815

E-mail: jonespl@mail.med.upenn.edu