Translating Spermatogonial Stem Cell Transplantation to the Clinic - Male Germline Stem Cells Developmental and Regenerative Potential - page 244

since SSC preservation and transplantation are not likely to be covered by patients'
healthcare insurance while the techniques are in the experimental stage. Efforts
should be made to minimize or eliminate the potential financial burdens to patients.

11.4.2 Testis Cell Isolation in the Clinic

Isolation of testicular cells from human patients intended for eventual
retransplantation back into the patient falls under the purview of the U.S. Food and
Drug Administration's Center for Biologics Evaluation and Research (CBER), by
the authority of the Public Health Service (PHS) Act §351(a). However, autologous
cryopreserved testicular tissues and cells isolated, prepared, and cryopreserved in
particular ways could be considered exempt from PHS Act §351 regulation and
would fall under PHS Act §361. In order to qualify for §361 exemption, testicular
cell “products” would have to meet all of the criteria in FDA regulations 21 CFR
1271.10(a), including: (1) the product is minimally manipulated, (2) the product is
intended for homologous use (i.e., spermatogenesis), (3) product “manufacture”
does not involve combination with another article, except for water, crystalloids, or
a sterilizing, preserving, or storage agent (not raising new clinical safety concerns
for the HCT/P), and (4) the product does not have a systemic effect and is not
dependent upon the metabolic activity of living cells for its primary function or, if
it has such an effect, it is intended for autologous use or allogeneic use in close
relatives or for reproductive use. Thus, human testicular cells intended for ultimate
retransplantation into a patient must be processed using reagents suitable for human
use and in Clinical Laboratory Improvement Amendment (CLIA)-certified facili-
ties by certified personnel.
Patient testicular cells for eventual autologous transplant must also be cryopre-
served for long-term storage. There is limited information about cryopreservation
of human testicular cells. Human testis cells cryopreserved for 3 months have been
shown to exhibit similar xenotransplant colonization potential to freshly isolated
cells, although viability and recovery of frozen-thawed cells is not known (Nagano
et al. 2002 ). Similar outcomes were observed for cryopreserved adult and juvenile
rhesus macaque testis cells, which exhibited similar phenotypic and functional
attributes to fresh testis cells (Hermann et al. 2007, 2009 ). Additional studies are
necessary to determine the best conditions for freezing human testicular cells to
maximize recovery of healthy SSCs for future therapeutic application.

11.4.3 Human SSC Culture

In vitro SSC amplification using culture is one potential method for maximizing the
therapeutic potential of SSCs recovered from a testicular biopsy. Robust protocols
for culturing mouse and rat SSCs have been reported over the past several years