Successful cryopreservation of mouse oocytes by using low concentrations of trehalose and dimethylsulfoxide

Preservation protocols for human adipose tissue-derived adult stem cells

The development of simple but effective storage protocols for adult stem cells will greatly enhance their use and utility in tissue-engineering applications. There are three primary storage techniques, freezing (cryopreservation), drying (anhydrobiosis), and freeze drying (lyophilization), each with its own advantages and disadvantages. Cryopreservation has shown the most promise but is a fairly complex process, necessitating the use of chemicals called cryoprotective agents (CPAs), freezing equipment, and obviously, storage in liquid nitrogen. Preservation by desiccation is an alternative that attempts to reproduce a naturally occurring preservative technique, namely, the phenomenon of anhydrobiosis and requires the use of high (and possibly, toxic) concentration of CPAs as well as disaccharides (sugars). Lyophilization works by first cryopreserving (freezing) the material and then desiccating (drying) it by the process of sublimation or the conversion of ice (solid) to water vapor (gas phase). The purpose of this chapter is to present a general overview of these storage techniques and the optimal protocols/results obtained in our laboratory for long-term storage of adult stem cells using freezing storage and drying storage.

Efficient derivation of embryonic stem cells from nuclear transfer and parthenogenetic embryos derived from cryopreserved oocytes

Deriving histocompatible embryonic stem (ES) cells by somatic cell nuclear transfer (SCNT) and parthenogenetic activation (PA) requires fresh oocytes, which prevents their applications in humans. Here, we evaluated the efficiency of deriving ES cells from mature metaphase II (MII) and immature metaphase I (MI) vitrified oocytes, by PA or SCNT, in a mouse model. We successfully generated ES cell lines from PA (MII and MI) and SCNT (MII and MI) blastocysts. These cell lines expressed genes and antigens characteristic of pluripotent ES cells and produced full-term pups upon tetraploid embryo complementation. This study established an animal model for efficient generation of patient-specific ES cell lines using cryopreserved oocytes. This is a major step forward in the application of therapeutic cloning and parthenogenetic technology in human regenerative medicine and will serve as an important alternative to the iPS cell technology in countries/regions where these technologies are permitted.

Cryopreservation of mammalian oocytes by using sugars: Intra- and extracellular raffinose with small amounts of dimethylsulfoxide yields high cryosurvival, fertilization, and development rates

Accumulation of intra- and extracellular sugars such as trehalose, glucose, and raffinose is central to survival strategies of a variety of organisms coping with extreme conditions including freezing and almost complete drying. The objective of the present study was to investigate the potential application of intra- and extracellular raffinose in combination with low concentrations of dimethylsulfoxide (Me(2)SO) to mammalian oocyte cryopreservation. To this end, the fertilization and embryonic development of cryopreserved metaphase II (M II) mouse oocytes were studied in comparison to unfrozen controls. For cryopreservation, M II oocytes were microinjected with 0.1M raffinose, and then cooled to -196 degrees C in the presence of either 0.3M raffinose and 0.5M Me(2)SO (cryopreservation group 1) or 0.3M raffinose and 1.0M Me(2)SO (cryopreservation group 2). The control groups included untreated oocytes (untreated control) and oocytes microinjected with raffinose, but not frozen (injection control). The post-thaw survival rates were 83.9% and 80.6% for the cryopreservation group 1 and 2, respectively. The fertilization and blastocyst rates in the cryopreservation group 1 (90.0% and 77.8%, respectively) and 2 (94.6% and 72.5%, respectively) were also high and similar to the ones of the injection controls (97.8% and 78.5%, respectively) and untreated controls (98.8% and 83.6%, respectively). These results are consistent with the findings of our earlier studies and support the use of sugars as intra- and extracellular cryoprotectants. Furthermore, the results of the present study indicate that the presence of intra- and extracellular sugars alleviates high concentrations of conventional penetrating cryoprotectants, and thus minimizes their toxicity.

Determination of the quaternary phase diagram of the water-ethylene glycol-sucrose-NaCl system and a comparison between two theoretical methods for synthetic phase diagrams

Characterization of the thermodynamic properties of multi-solute aqueous solutions is of critical importance for biological and biochemical research. For example, the phase diagrams of aqueous systems, containing salts, saccharides, and plasma membrane permeating solutes, are indispensible in the field of cryobiology and pharmacology. However, only a few ternary phase diagrams are currently available for these systems. In this study, an auto-sampler differential scanning calorimeter (DSC) was used to determine the quaternary phase diagram of the water-ethylene glycol-sucrose-NaCl system. To improve the accuracy of melting point measurement, a "mass-redemption" method was also applied for the DSC technique. Base on the analyses of these experimental data, a comparison was made between the two practical approaches to generate phase diagrams of multi-solute solutions from those of single-solute solutions: the summation of cubic polynomial melting point equations versus the use of osmotic virial equations with cross coefficients. The calculated values of the model standard deviations suggested that both methods are satisfactory for characterizing this quaternary system.

Retrieval of rhesus monkey (Macaca mulatta) oocytes by ultrasound-guided needle aspiration: problems and solutions

Oocytes of nonhuman primates such as rhesus monkeys are excellent models for diverse studies on developmental biology, epigenetics, human reproduction, and assisted reproductive technologies, as well as on transgenics. Such studies require numerous oocytes that can be retrieved after controlled ovarian stimulation. Currently, most primate centers use laparoscopic aspiration or laparotomy followed by aspiration to collect rhesus oocytes, although the ultrasound-guided needle aspiration is more advantageous due to reduced infection risk, less injury, and a shorter recovery period. Yet, some initial difficulties associated with the ultrasound-guided needle aspiration limit its broader application. The objective of the present study was to address these obstacles. By presenting practical solutions to the initial difficulties, results from our study show that it is possible to collect a mean number of 38 +/- 10 rhesus oocytes per hormonally stimulated female. These results compare favorably to the average number of rhesus oocytes collected using the laparoscopic approach and suggest that when initial obstacles are overcome, the ultrasound-guided oocyte retrieval represents a good alternative to more invasive approaches.

Application of intra- and extracellular sugars and dimethylsulfoxide to human oocyte cryopreservation

PURPOSE

Oocyte cryopreservation may avoid many complications of human embryo freezing and provide future fertility for women undergoing cancer therapy. The objective of this study was to explore the application of intra- and extracellular sugars in combination with small amounts of dimethylsulfoxide (DMSO) to human oocyte cryopreservation as an alternative approach.

METHODS

Discarded human oocytes that were obtained from IVF patients under informed consent and IRB approval, were cryopreserved by slow cooling to -196 degrees C after being randomly distributed into three groups: (i) DMSO control without intra- and extracellular sugar; (ii) extracellular sugar (raffinose) + DMSO; and (iii) intra- and extracellular sugar (trehalose and raffinose, respectively) + DMSO. Subsequently, all cryopreserved oocytes were thawed rapidly, and their survival was assessed by morphological criteria after 24 h of culture.

RESULTS

A total of 71 oocytes were evaluated in three groups with survival rates of 88.5% (23/26), 68.2% (15/22), and 52.2% (12/23) for intra- and extracellular sugar+DMSO, extracellular sugar+DMSO, and DMSO control groups, respectively.

CONCLUSION

These results support the use of intra- and extracellular sugars as an alternative approach for cryopreservation of human oocytes.