regenerative medicine? quick easy question!?

. On January 19, 2001, the US Food and Drug Administration published a registration and listing final rule that requires human cells, tissue and cellular and tissue-based product establishments to register with the agency and list their human cells, tissues, and cellular and tissue-based products. The final rule, 21 CFR Part 1271, became effective on April 4, 2001 for human tissues intended for transplantation that are regulated under section 361 of the PHS Act and 21 CFR Part 1270 at www.fda.gov/CBER/tissue/tisreg.htm. This is a comprehensive plan for regulating human cells, tissues and cellular and tissue-based products that would include establishment registration and product listing, donor-suitability requirements, good tissue practice regulations and other requirements. Similar programs that deal with good practice have been instituted in most countries where stem cell based or tissue based treatments are being examined for clinical applications. Procedures to confirm that cell differentiation only occurs along desired lineages will also be a necessary component of these regulations. Compliance procedures will also eventually require evaluation of the karyotypic stability of the cells and assessment of the possibility of formation of genetic alterations due solely to the manipulation of cells in vitro. The same potential for self-renewal and plasticity that makes adult, fetal tissue derived or embryonic stem cells attractive cell sources for the eventual production of engineered tissues also raises concern about the possibility for tumorigenicity of the stem cell source. Regulatory frameworks may eventually decide to support implantation of differentiated tissues rather than growth factor primed cell-matrix constructs to reduce the risk of tumor formation. Even though human embryonic stem cells have been shown to generate cell types found in the lung, differentiation has not been consistently directed efficiently towards a single cell lineage. Although ESC are self renewing, the possibility of tumor formation exists41 which is an important consideration in the selection of clinically applicable cell sources. Endogenous lung stem cells pose less risk of becoming tumorogenic. The risk that growth factor-primed and activated adult or tissue specific stem cells have the capacity to give rise to cancer or can result in tumor formation is low. Reports identifying lung tissue specific tumorogenic lung cancer stem cell populations42 or transformed counterparts of lung-derived stem cells that have the potential to give rise to carcinomas8 have shown that the transforming events required to initiate tumorogenic properties in stem cells require more than the normal effects of growth factor activation and priming for the purposes of cell differentiation and induction of tissue formation. It is also important to note that there was no indication of tumor formation from implantation of in vitro amplified, growth factor primed SLPCs into severe combined immunodeficient mice by Cortiella et al.7