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. 2023 Apr-Jun;24(2):69–84. doi: 10.18502/jri.v24i2.12491

Table 4.

Summary of the selected animal studies on cryoprotective effect of L-carnitine on freeze–thaw induced sperm damages

Authors Patients Treatment Freezing and thawing method Freezing media Results
Namik et al. (2000) 35 infertile men

  • -Acetyl-L-carnitine (2.5, 5, 10, and 20 mM).

  • - Progesterone (1 and 10 mM)

  • - Freezing: refrigerating the cryovials at 18°C for 30 min, cooling in nitrogen vapor and then plunging into liquid nitrogen at −196°C

  • - Thawing: placing cryovials in a 42°C water bath for 3 min

 TEST-yolk buffer containing glycerol (Irvine Scientific, US)

  • - No significant differences between control and progesterone and/or acetyl-L-carnitine samples for cryosurvival rate, motility, or membrane integrity
Zhang et al. (2000)

  • - Asthenozoospermic (AS) cases: 37.

  • - Normozoospermic (NS) cases: 33

 L-carnitine (LC) (1.0 g/l)

  • - Freezing: fast freezing

  • -Thawing: transferring the cryovials to a water bath of 37°C for 15 min

 Quinn’s Advantage Sperm Freezing Medium, (SAGE BioPharma, US)

  • - LC induced a significant improvement in post-thaw sperm fast forward motility, forward motility, total motility, and viability in both AS and NS samples.

  • -LC showed better protective effects towards AS for DNA fragmentation index and vitality in comparison to NS
Banihani et al. (2013) 22 infertile men L-carnitine (LC) 0.5 mg/ml

  • - Freezing: placing sample in the freezer at 20°C for 8 min, in the liquid nitrogen vapors at −80°C for 2 hr, and then in liquid nitrogen (−196°C)

  • -Thawing: incubation at 37°C for 20 min

 TEST-yolk buffer (Irvine Scientific, US)

  • - LC significantly improved sperm motility and vitality compared with the control.

  • - No statistical difference in the levels of DNA oxidation between samples (with LC) and controls (without LC)
Aliabadi et al. (2017) 30 healthy men

  • -L-carnitine dose: 1 ml medium containing 7 mg LC.

  • - Pentoxifylline (PT) dose: 1 ml medium containing 1 mg of PT

  • - Freezing: fast freezing

  • - Thawing: at 37°C for 10 min

 (Life Global, US)

  • - LC elevated the percentage of non-capacitated spermatozoa and percentages of acrosome intact spermatozoa compared with control and PT-treated sample.

  • - LC reduced the percentages of acrosome-reacted spermatozoa compared with the control and PT-treated samples.

  • - LC did not improve motility.

  • - LC protected the plasma membrane and acrosome integrity
Ghorbani et al. (2021) 20 healthy men

  • - L-carnitine (LC)-N-acetylcysteine (NAC).

  • - 6 groups: LC (1 and 10 mM), NAC (5 and 10 mM), and cryopreserved and fresh control groups

  • - Freezing: micro-droplet technique

  • - Thawing: placing samples in 5 ml of HTF (37°C) with 1% HSA, incubation at 37°C and in 5% CO2 for 5 min

 Solution containing 0.5 mol/L of sucrose and 5% human serum albumin (HSA, Sigma-Aldrich, US)

  • - No significant difference in total motility in the LC and NAC groups.

  • - Significantly higher progressive motility and motility in groups of LC and NAC.

  • - Significant increase in mitochondrial membrane potential (MMP) and plasma membrane integrity (PMI) in LC and NAC groups.

  • - Significant decrease in DNA damage and intracellular ROS in LC and NAC groups
Chavoshi Nezhad et al. (2021) 30 oligospermic men men

  • - L-carnitine dose :100 μM.

  • - Coenzyme Q10 (CoQ10) dose: 100 μM.

  • - Groups: 1) control before freezing, 2) LC, 3) CoQ10, 4) combination of L-C + CoQ10, 5) control freezing, 6) experimental freezing with L-C, 7) experimental freezing with CoQ10, and 8) experimental freezing with the combination of LC + CoQ10

  • - Freezing: fast freezing.

  • - Thawing: placing under running water for 1 to 2 min to reach normal temperature

 Human Sperm Preservation Medium (HSPM)

  • - LC significantly reduced the number of ROS in the pre and post freezing groups.

  • - Significant improvement was seen in the sperm motility of class B in the pre freezing groups with LC.

  • - After freezing, DNA fragmentation increased, but the addition of LC or CoQ10 decreased DNA fragmentation compared to the freezing control group.

  • - Addition of LC or CoQ10 to the sperm of the control group increased the number of sperms with normal protamine but this difference was not significant