The leech: a novel invertebrate model for studying muscle regeneration and diseases.

We focused our studies on the leech, Hirudo medicinalis. This invertebrate has a relative anatomical simplicity and is a reliable model for studying a variety of basic events, such as tissue repair, which has a striking similarity with vertebrate responses. Hirudo is also a good invertebrate model to test the actions of drugs and gene products, since the responses evoked by the different stimuli are clear and easily detectable due to their small size and anatomical simplicity. Here we review the use of this invertebrate model to investigate muscle regeneration and the role of hematopoietic stem cells in this process. Our recent data, summarized in this review, demonstrate that the injection of an appropriate combination of the matrigel biopolymer supplemented with Vascular Endothelial Growth factor (VEGF) in the leech Hirudo medicinalis is a remarkably effective tool for isolating a specific population of hematopoietic/endothelial precursor cells, which in turn can differentiate in muscle cells. Thus leeches can be considered as a new emerging model for studying endothelial and hematopoietic precursors cells involved in muscle post-natal growth and regeneration processes.

In vivo isolation and characterization of stem cells with diverse phenotypes using growth factor impregnated biomatrices.

BACKGROUND: The stimulation to differentiate into specific cell types for somatic stem cells is largely due to a series of internal and external signals coming from the microenvironment that surrounds the stem cell. Even though intensive research has been made, the basic mechanisms of plasticity and/or the molecules regulating stem cells proliferation and differentiation are not completely determined. Potential answers concerning the problems could be derived from the studies of stem cells in culture. METHODOLOGY/PRINCIPLE FINDINGS: We combine a new procedure (using the matrigel biopolymer supplemented with a selected cytokine/growth factor) with classic techniques such as light, confocal and electron microscopy, immunohistochemistry and cell culture, to perform an analysis on stem cells involved in the leech (Hirudo medicinalis) repair tissues. The leech has a relative anatomical simplicity and is a reliable model for studying a variety of basic events, such as tissue repair, which has a striking similarity with vertebrate responses. Our data demonstrate that the injection of an appropriate combination of the matrigel biopolymer supplemented with a selected cytokine/growth factor in the leech Hirudo medicinalis is a remarkably effective tool for isolating a specific cell population in vivo. A comparative analysis of biopolymer in vivo sorted stem cells indicates that VEGF recruited cells of a hematopoietic/endothelial phenotype whereas MCP-1/CCL2 isolated cells that were of an early myeloid lineage. CONCLUSION: Our paper describes, for the first time, a method allowing not only the isolation of a specific cell population in relation to the cytokine utilized but also the possibility to culture a precise cell type whose isolation is otherwise quite difficult. This approach could be broadly applied to isolate stem cells of diverse origins based on the recruitment stimuli employed.