Jz. Yang et al., TREATMENT WITH 5-AMINOLEVULINIC ACID AND PHOTOACTIVATING LIGHT CAUSESDESTRUCTION OF PREIMPLANTATION MOUSE EMBRYOS, Fertility and sterility, 63(5), 1995, pp. 1088-1093
Objective: To evaluate the direct effect of photodynamic treatment wit
h 5-aminolevulinic acid (ALA) on preimplantation mouse embryos in an i
n vitro setting.Design: Preimplantation mouse embryos were incubated w
ith or without ALA for 5 hours and followed immediately by light expos
ure for 0, 5, or 15 minutes. Comparison of the viability and blastocys
t formation was made among different treatment groups. Setting: A conv
entional laboratory setting with embryo culture facilities. Interventi
ons: Female CD1 mice were superovulated with pregnant mare serum gonad
otropin and hCG before mating. Four- and eight-cell embryos and compac
ted morulae were flushed from the oviducts and incubated with 0, 0.1,
0.5, 1.0, or 5.0 mM ALA for 5 hours. Embryos subsequently were exposed
to photoactivating light for 0, 5, or 15 minutes. Main Outcome Measur
es: Microscopic assessment of embryo quality at 12 hours and determina
tion of the percentage of embryos progressing to the blastocyst stage
at 36 or 60 hours. Results: Incubation of embryos with 0.1, 0.5, 1.0,
5.0 mM ALA without light resulted in 87.3% +/- 1.6%, 84.9% +/- 3.4%, 8
1.4% +/- 1.8%, and 82.8% +/- 4.7% of the embryos developing to blastoc
ysts, respectively. In the absence of ALA, light exposure for 0, 5, or
15 minutes resulted in 93.8% +/- 2.3%, 92.3% +/- 2.2%, and 85.9% +/-
1.7% blastocyst formation. Combining treatment of ALA at the same conc
entrations with light resulted in 33.3% +/- 2.1%, 0.7% +/- 0.9%, 0%, 0
% (5-minute light), 13.3% +/- 1.0%, 0%, 1.6% +/- 1.3%, 0% (15-minute l
ight) blastocyst formation, respectively. When gross morphology was us
ed to assess embryo viability at 12 hours, similar results were observ
ed. Measurement of the fluorescent spectrum of embryos incubated with
ALA indicated that protoporphyrin IX had been formed. Conclusion: Phot
odynamic ablation of mouse embryos was achieved with ALA under in vitr
o conditions. These results indicate that preimplantation mouse embryo
s are capable of converting ALA to the photosensitizer, protoporphyrin
IX, and are susceptible to subsequent photoablation. A photodynamic e
ffect on the embryo may be important to the successful application of
this technique to the treatment of human ectopic pregnancy.