Changes in biological activity of placenta extracts depend on its storage temperature

BACKGROUND: Cryopreservation is a critical method for the long-term storage of biological tissues, including human placental extracts (HPEs). Preserving the biological activity of these tissues during storage is essential for medical applications, particularly for their anti-inflammatory and anti-aggregation properties. The impact of storage temperature on the biological efficacy of HPEs remains a crucial area of study. OBJECTIVE: To investigate the effect of different cryopreservation temperatures on the preservation of biological activities in human placental extracts and their fractions, with a particular focus on their effects on erythrocyte thermal hemolysis and ADP-induced platelet aggregation. MATERIALS AND METHODS: Human placentas were collected after normal pregnancies from healthy parturients and cryopreserved at −20°C, −80°C, and −196°C for up to six months. Placental extracts and fractions were analyzed for their impact on erythrocyte thermal stability and platelet aggregation using spectrophotometric methods. Calorimetric studies were conducted to assess the phase state of placenta tissues at low temperatures. RESULTS: Extracts from placentas stored at −20°C for six months lost their ability to reduce erythrocyte hemolysis and platelet aggregation. Storage at −80°C and −196°C preserved these activities for at least six months. Calorimetric analysis revealed the presence of unfrozen water in placenta tissues at −20°C, contributing to the degradation of biological activity. CONCLUSION: Cryopreservation at −80°C or lower effectively preserves the biological activity of placental extracts for extended periods, making these temperatures ideal for long-term storage in medical applications.