**2. The tissue banks and the "viability" of it's therapeutically products**

The TB are technical establishments whose main institutional objectives are collection, preservation, storage, release and distribution of biological tissues for therapeutic use in transplantation medicine. These objectives is met according to scientific criteria from agreed international protocols (Spanish Association of Tissue Banks: AEBT, International Atomic Energy Agency, IAEA, European Association of Tissue Banks: EATB; American Association of Tissue Banks: AATB) and according to the legal frameworks of the different countries and

<sup>\*</sup> Mc. Saldias1, G. Sanchez1, P. Martucci1, Mc. Acosta1, I. Alvarez1, R. Faccio2, L. Suescun2,

M. Romero2 and A. Mombru2

*<sup>1</sup> Instituto Nacional de Donación y Trasplante (INDT), Ministerio de Salud Pública - Fac. de Medicina, Uruguay* 

*<sup>2</sup> Laboratorio de Cristalografía, Estado Sólido y Materiales (DETEMA) Fac. de Química, Uruguay*

X Ray Diffraction: An Approach to Structural

(Orgel, 2011; Sottile, 2007; Sweeney, 2008).

matrix one.

Quality of Biological Preserved Tissues in Tissue Banks 443

molecular groups, organized into super families, are shown with a dynamic distribution, and functional modulated behavior, with variations between different tissues. This bio plasticity is observed even within the same tissue type, as homeostatic biochemical, and bio mechanical requirements, including interactions with various molecules: growth factors, cytokines, enzymes and other inducers synthesis products as well as lytic and degradative

The surface receptors of the cell membrane, in close contact with this complex and dynamic molecular ECM set, interact through the cytoskeleton to the genome, which modulates the different stages of ontogeny, growth and postnatal development sequences as well as molecular structural and functional physiology and patho physiology biological requirements of tissues. (Abraham, 2007; Bowers, 2010; Worthley, 2010). Related to the own collagen structure there are ligands and functional domains that take contact with other ECM molecules (fibronectin, proteoglicans, and collagen - collagen interactions) and with the neighbor cells microenvironment (cell integrin receptors). Several poly peptid sequences, (eg.: GFPGER: glycine - phenylalanine - hyroxyproline - glycine - glutamic acid - arginine) and ligands domains (eg.: Matrix Metalloproteinase Interaction Domain or MMP ID; Colagen V Cross-link site or Col V X-link), have been identified and play an important role in regulation of migration, proliferation, adhesion and apoptosis in biology cell tissues.

It is obvious therefore that the extra cellular medium, forms a molecular complex of plastic, in both dynamic up regulator as down regulator in constant cross talk with cell pole whose points of contact and mutual information imply the presence of binding sites at ECM structure related to cell surface receptors. Fibril collagen constitutes approximately 25% of tissues for all species of mammals and is the main component of the total molecules that make up the ECM. (Kielty, & Grant, 2002). To date, they have been described up to 29 different types of collagens with the corresponding genetic determinants. "Structural" Collagens in the ECM are called fibrils (Fibril Collagen) consisting of types I, II and III, V and XI. Type I constitute 90% of body collagen and mainly, perform mechanical resistance functions. In addition it provides three - dimensional modeling formation of tissues. An important bio molecular feature of our study is it hierarchical and sequenced shaping showing collagen. Taking collagen I model, pro collagen, amino acid primary structure have a intracellular synthesis (endoplasmic reticulum), with repeated tripeptides, design whose residues are Gly-Pro- Hyp or Gly-X- Hyp which Pro and Hyp are near to 17% and 33% respectively. Therefore 50% of the average 1000 residues of the total composition of the molecule, pro collagen, are other amino acids. Its length of 300 nm and width of 1.5 nm, is organized in a left-handed secondary structure of three amino acids per turn, with Gly residues central and peripheral Pro and Hyp out of the spiral. Three assembly helical pro collagen monomers (2 α1 and 1 α2) in right-handed configuration, determine the tropo collagen structure in the extra cellular space. In this space the molecule is arranged in staggered bundles with a gap of 67 nm by inter molecular bonds tropo collagen units, which gives to the collagen fibril new product design, a repetitive sequence which observed in the ME identified a characteristic D - banding. The final design shows collagen fibers arranged, spatially distributed in regular packages along the lines of force of the biomechanical characteristics of each tissue. This last aspect brings an added dimension of ordering design

given by the spatial distribution of fiber bundles, and their inter reciprocal space.

their ethical rules. On the other hand, tissue banking activities are carried out following strict bio-security criteria by the selection of suitable donors, permanent quality control and continuous management of physical plant, equipment, supplies procurement procedures, and end products, which must comply criteria for "viability" therapeutic apply.

According to (Pegg 2006) this concept of "viability," applies whenever a graft of tissue obtained as final product, meets the leading natural-biological function for which it was preserved, and that is pathologically affected in the recipient. This explains why there are different procedures and methods of conservation in TB, according to the type of tissues and its expected restored function.

In some cases, we must preserve, as the main function, a biological synthesis, which requires mandatory of vitality in cellular functions (eg, parathyroid glands, or ovarian tissue). In other cases, the objective is to preserve static and mechanical functions as a segmental allograft bone support, or biodynamic behavior, as in cases of preservation of blood vessels. This implies that "viability" is not necessarily synonymous with "cell vitality" and therefore the requirement is to preserve elements of the Extra Cellular Matrix (ECM).

Hence, the importance of assessing possible changes on the components of the ECM that TB procedures may be generate on processing and stocking biological tissues.
