Stem Cell Cryopreservation

Results from recent animal experiments have also indicated another possible method of preserving testicular function during gonadotoxic therapy. In 1994, Brinster et al. (66) demonstrated that stem cells isolated from a donor mouse could be injected into the seminiferous tubules of a sterile recipient mouse and reinitiate spermatogenesis. More recently, the same group demonstrated that spermatogenesis can be achieved in previously sterile mice after cryopreservation and subsequent then injection of donor stem cells into the testis. Potentially, therefore, stem cells could be harvested from the human testis before the start of sterilizing therapy, freeze-stored, and reimplanted at a later date, with a subsequent spermatogenesis return.

A clinical trial testing this hypothesis is currently underway in adults: 16 men have had testicular tissue harvested shortly before commencing treatment with sterilizing chemotherapy for Hodgkin's disease or NHL. In each case, a 0.5-cm cube of testicular tissue has been subjected to enzymatic digestion to produce a single cell suspension that, after equilibration in cryoprotectant, has been stored in liquid nitrogen (67). Seven men have now successfully completed chemotherapy, and thawed testicular suspension has been reinjected into the donor testis. Semen analysis has demonstrated a spermatogenesis return in one man at the time of writing. However, this may simply represent spontaneous spermatogenesis recovery, as is seen in a small proportion of men after treatment, rather than repopulation from cryopreserved stem cells. The lack of greater success may relate to problems reinjecting the testicular suspension. The seminiferous tubules in adult men are too fibrous to allow direct injection, and, therefore, an indirect approach had to be used. This consisted of injecting into the rete testes and relying on retrograde flow to fill the tubules; this may not occur to a sufficient extent to allow repopulation and a return of spermatogenesis. Further studies are currently being undertaken using nondisaggregated testicular tissue, and the results are awaited with interest.

Table 2

Summary of Fertility in Adult Men After Treatment of Different Malignancies

Table 2

Summary of Fertility in Adult Men After Treatment of Different Malignancies

Diagnosis

Treatment

Fertility After Treatment

Hodgkin's disease

MVPP

Azoospermia in >90%

MOPP

Azoospermia in >90%

ChlVPP/EVA hybrid

Azoospermia in >90%

COPP

Azoospermia in >90%

ABVD

Temporary azoospermia with normal

sperm count in all at 18 mo

Non-Hodgkin's lymphoma

CHOP

Permanent azoospermia in approx 30%

VAPEC-B

Normospermia in >95%

VACOP-B

Normospermia in >95%

MACOP-B

Normospermia in >95%

VEEP

Normospermia in >95%

Bone marrow transplant

Cyclophosphamide alone

FSH raised in 40%

for several malignancies

Busulphan and

FSH raised in 80%

cyclophosphamide

CBV

FSH raised in >95%

High-dose melphalan

FSH raised in >95%

BEAM

Testicular cancer

Cisplatin-carboplatin-

Normospermia in 50% at 2 yr,

based therapy and 80% at 5 yr

MVPP, mustine, vinblastine, procarbazine, and prednisolone; MOPP, mustine, vincristine, procarbazine, and prednisolone; ChlVPP/EVA, chlorambucil, vinblastine, prednisolone, procarbazine, doxorubicin, vincristine, and etoposide; COPP, cyclophosphamide, vincristine, procarbazine, and prednisolone; ABVD, adriamycin, bleomycin, vinblastine, and dacarbazine; CHOP, cyclophosphamide, doxorubicin, vincristine, and prednisolone; VAPEC-B, vincristine, doxorubicin, prednisolone, etoposide, cyclophosphamide, and bleomycin; VACOP-B, vinblastine, doxorubicin, prednisolone, vincristine, cyclophosphamide, and bleomycin; MACOP-B, mustine in place of vinblastine; VEEP, vincristine, etoposide, epirubicin, and prednisolone; CBV, cyclophosphamide; BCNU, and etoposide; BEAM, BCNU, etoposide, Ara-C, and melphalan.

based therapy and 80% at 5 yr

MVPP, mustine, vinblastine, procarbazine, and prednisolone; MOPP, mustine, vincristine, procarbazine, and prednisolone; ChlVPP/EVA, chlorambucil, vinblastine, prednisolone, procarbazine, doxorubicin, vincristine, and etoposide; COPP, cyclophosphamide, vincristine, procarbazine, and prednisolone; ABVD, adriamycin, bleomycin, vinblastine, and dacarbazine; CHOP, cyclophosphamide, doxorubicin, vincristine, and prednisolone; VAPEC-B, vincristine, doxorubicin, prednisolone, etoposide, cyclophosphamide, and bleomycin; VACOP-B, vinblastine, doxorubicin, prednisolone, vincristine, cyclophosphamide, and bleomycin; MACOP-B, mustine in place of vinblastine; VEEP, vincristine, etoposide, epirubicin, and prednisolone; CBV, cyclophosphamide; BCNU, and etoposide; BEAM, BCNU, etoposide, Ara-C, and melphalan.

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