The field of pancreatic stellate cell (PSC) biology is very young, as the essential in-vitro tools to study these cells (ie, methods to isolate and culture PSC) were only developed as recently as in 1998. Nonetheless, there has been an exponential increase in research output in this field over the past decade, with numerous research groups around the world focusing their energies into elucidating the biology and function of these cells. It is now well established that PSC are responsible for producing the stromal reaction (fibrosis) of two major diseases of the pancreas—chronic pancreatitis and pancreatic cancer. Despite exponentially increasing data, the methods for studying PSC remain variable. Although within individual laboratories methods are consistent, different methodologies used by various research groups make it difficult to compare results and conclusions. This article is not a review article on the functions of PSC. Instead, members of the Pancreatic Star Alliance (http://www.pancreaticstaralliance.com) discuss here and consolidate current knowledge, to outline and delineate areas of consensus or otherwise (eg, with regard to methodological approaches) and, more importantly, to identify essential directions for future research

The tissue inhibitors of metalloproteinases (TIMPs) regulate matrix metalloproteinase activity required for cell migration/invasion associated with cancer progression and angiogenesis. TIMPs also modulate cell proliferation in vitro and angiogenesis in vivo independent of their matrix metalloproteinase inhibitory activity. Here, we show that TIMP-2 mediates G₁ growth arrest in human endothelial cells through de novo synthesis of the cyclin-dependent kinase inhibitor p27^Kip1. TIMP-2-mediated inhibition of Cdk4 and Cdk2 activity is associated with increased binding of p27^Kip1 to these complexes in vivo. Protein-tyrosine phosphatase inhibitors or expression of a dominant negative Shp-1 mutant ablates TIMP-2 induction of p27^Kip1. Finally, angiogenic responses to fibroblast growth factor-2 and vascular endothelial growth factor-A in “motheaten viable” Shp-1-deficient mice are resistant to TIMP-2 inhibition, demonstrating that Shp-1 is an important negative regulator of angiogenesis in vivo.

White matter lesions are closely associated with cognitive impairment and motor dysfunction in the aged. To explore the pathophysiology of these lesions, the authors examined the expression of matrix metalloproteinase-2 (MMP-2) and MMP-9 in the white matter in a rat model of chronic cerebral hypoperfusion. After bilateral clipping of the common carotid arteries, myelin staining revealed demyelinating changes in the optic tract and the corpus callosum on day 7. Zymographic analyses indicated an increase in the level of MMP-2, but not MMP-9, after the hypoperfusion. Immunohistochemical analyses revealed the presence (most abundantly on day 3) of MMP-2–expressing activated microglia in the optic tract and corpus callosum. In contrast, the capillary endothelial cells expressed MMP-2 later. IgM-immunoreactive glial cells were absent in the sham-operated animals, but were present in the hypoperfused animals by day 3, reflecting the disrupted blood–brain barrier. These findings suggest that the main sources of the elevated MMP-2 were the microglia and the endothelium, and that these cells may contribute to the remodeling of the white matter myelin and microvascular beds in chronic cerebral hypoperfusion.