Biomedical Engineering Reference
In-Depth Information
stem cell donors, the donor's blood, and for umbilical cord blood donors, the mother's blood,
would be required to be tested for HIV, cytomegalovirus, HTLV, syphilis and hepatitis
infection....physical examination of perspective donors would include screening for high
risk for HIV, hepatitis, CJD and tuberculosis”. 8 The same paragraph also states that “..the
agency intends to recommend, but not require, that testing be performed when stem cells
will be used in the person from whom they were obtained. In such a case the agency would
recommend only thed following tests: HBsAg, anti-HCV, anti-HIV-1, anti-HIV-2, HIV-1-Ag
and HTLV-I/II. The agency also would recommend that the history and physical examina-
tion of the donor include screening for high risk HIV and hepatitis. The agency would
require that record-keeping and labeling reveal which of the recommended tests were per-
formed and their results, as well as which of the recommended tests were not performed”.
Nonetheless, for tissue engineering purposes, autologous cell preparations can also be ob-
tained from donors resulting positive to some of the exclusion criteria. As for the circumstances
justifying the use and storage of such cells or tissues, the agency requires “ (1) that the cells be
labeled as “biohazard”, (2) that autologous products also be labeled as “autologous use only”;
(3) written advanced informed consent of the recipient be documented; (4) there be docu-
mented concurrence of the recipient's physician before the cells could be released from the cell
bank.” 8
Aging
Primary human cell divide for a limited number of cycles, undergoing a senescence degen-
erative phase thereafter. A senescent cell may also have lost the biological properties of the
young differentiated phenotype that physiologically constitutes the tissue of origin. Senescent
cells can be useless for tissue engineering purposes. It is therefore necessary to record number of
doublings of any cell population used for tissue engineering purpose, starting with the biopsy
and including procedural steps before and after the cryopreservation passage, if performed.
The number of the in vitro doubling must not hinder the proliferation capacity of the ex-
panded cells.
Chromosomal Alterations
Prolonged culturing of mammalian cells increases the risk of quali-quantitative chromo-
somal alterations in the cell genome. Standard karyotyping techniques should be applied to
evaluate the stability of the expanded cell population karyotype.
Differentiated Phenotype Loss
During the in vitro culturing cell may loose, partially or totally, the expression of specific
markers of their differentiated state. By converse they may acquire the expression of new mark-
ers that are not typical of their physiological phenotype. Both of these events may compromise
the cells future reinsertion in the tissue of origin. Such an eventuality must be verified by means
of immunohystochemical analysis, possibly targeting specific gene products of the tissue under
investigation (for example keratins for the epithelia). The possible existence of a contaminant
cell population harvested at the time of the biopsy—able to propagate and progressively substi-
tute the cell population of interest—must also be exploited. Immunocytochemistry and PCR
techniques are the suggested approach to tag and check this eventuality. 18
Neoplastic Phenotype
The neoplastic transformation is a rare phenomenon in mammalian and human cells. None-
theless the exposure to several ancillary products (cytokines, hormones, growth factors, viral
vectors) may alter the cell predisposition and increase the risk of neoplastic occurrences. Ab-
sence of risk must be assessed before the use of the cell/composite product in humans either by
in vitro culturing techniques or by transplantation in immunodeficient animals. Assays should
be planned for the process quality assessment if not feasible for each different human autolo-
gous culture.
 
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