Loading Human Mesenchymal Stem Cells with Trehalose by Fluid-Phase Endocytosis

The encapsulation and intracellular delivery of trehalose using a thermally responsive nanocapsule

The thermally responsive wall permeability of an empty core-shell structured Pluronic nanocapsule (together with its temperature dependent size and surface charge) was successfully utilized for encapsulation, intracellular delivery, and controlled release of trehalose, a highly hydrophilic small (M(W) = 342 D) molecule (a disaccharide of glucose) that is exceptional for long-term stabilization of biologicals (particularly at ambient temperatures). It was found that trehalose can be physically encapsulated in the nanocapsule using a soaking-freeze-drying-heating procedure. The nanocapsule is capable of physically withholding trehalose with negligible release in hours for cellular uptake at 37 degrees C when its wall permeability is low. A quick release of the encapsulated sugar can be achieved by thermally cycling the nanocapsule between 37 and 22 degrees C (or lower). A significant amount of trehalose (up to 0.3 M) can be delivered into NIH 3T3 fibroblasts by incubating the cells with the trehalose-encapsulated nanocapsules at 37 degrees C for 40 min. Moreover, cytotoxicity of the nanocapsule for the purpose of intracellular delivery of trehalose was found to be negligible. Altogether, the thermally responsive nanocapsule is effective for intracellular delivery of trehalose, which is critical for the long-term stabilization of mammalian cells at ambient temperatures and the eventual success of modern cell-based medicine.

Trehalose As a “Chemical Chaperone”

Trehalose is a disaccharide of glucose that is found at high concentrations in a wide variety of organisms that naturally survive drying in nature. Many years ago we reported that this molecule has the remarkable ability to stabilize membranes and proteins in the dry state. A mechanism for the stabilization rapidly emerged, and it was sufficiently attractive that a myth grew up about trehalose as a universal protectant and chemical chaperone. Many of the claims in this regard can be explained by what is now known about the physical properties of this interesting sugar. It is emerging that these properties may make it unusually useful in stabilizing intact cells in the dry state.

Effects of trehalose co-incubation on in vitro matured prepubertal ovine oocyte vitrification

Our aim was to evaluate if loading prepubertal ovine oocyte with trehalose would impact on their further developmental potential in vitro and if it would improve their survival to vitrification procedures. COCs matured in vitro with (TRH) or without (CTR) 100mM trehalose were tested for developmental potential after in vitro fertilization and culture. Trehalose uptake was measured by the antrone spectrophotometric assay. No differences were recorded between the two experimental groups in fertilization rates (91.1 CTR vs 92.5% TRH), cleavage rates calculated on fertilized oocytes (96.1 CTR vs 95.4% TRH), first cleavage kinetic (56.1 CTR vs 51% TRH), and blastocyst rates (14.3 CTR vs 13.0% TRH). Anthrone assay revealed that in TRH group trehalose concentration/oocyte was 2.6microM. MII oocytes were then vitrified using cryoloops in TCM 199 containing 20% FCS, sucrose 0.5M, 16.5% Me(2)SO, 16.5% EG and plunged in LN(2). After warming, oocytes from TRH and CTR groups were tested for membrane integrity using the propidium iodide (PI)/Hoechst differential staining, and for developmental ability after in vitro fertilization. Trehalose in maturation medium affected membrane resistance (P<0.01) to vitrification/warming but not fertilization and cleavage rates. The differential staining showed a lower number of PI positive cells in TRH group compared to CTR one (14.3 vs 24.7%, respectively). Fertilization rates and cleavage rates did not differ between the two groups (55.3 and 41% for TRH and 47.7 and 41.7% for CTR, respectively). In conclusion trehalose in maturation medium stabilizes cell membranes during vitrification/warming of prepubertal ovine oocytes but does not affect fertilization and cleavage rates after warming.

Trehalose, a novel mTOR-independent autophagy enhancer, accelerates the clearance of mutant huntingtin and alpha-synuclein

Trehalose, a disaccharide present in many non-mammalian species, protects cells against various environmental stresses. Whereas some of the protective effects may be explained by its chemical chaperone properties, its actions are largely unknown. Here we report a novel function of trehalose as an mTOR-independent autophagy activator. Trehalose-induced autophagy enhanced the clearance of autophagy substrates like mutant huntingtin and the A30P and A53T mutants of alpha-synuclein, associated with Huntington disease (HD) and Parkinson disease (PD), respectively. Furthermore, trehalose and mTOR inhibition by rapamycin together exerted an additive effect on the clearance of these aggregate-prone proteins because of increased autophagic activity. By inducing autophagy, we showed that trehalose also protects cells against subsequent pro-apoptotic insults via the mitochondrial pathway. The dual protective properties of trehalose (as an inducer of autophagy and chemical chaperone) and the combinatorial strategy with rapamycin may be relevant to the treatment of HD and related diseases, where the mutant proteins are autophagy substrates.

3-O-methyl-D-glucose improves desiccation tolerance of keratinocytes

Transplantation of autologous skin grafts and tissue engineered skin replacements for the treatment of burns, trauma, and ulcerative wounds has been shown to restore a protective barrier to infection and fluid loss, reduce heat loss, provide mechanical strength, diminish pain, and dampen the hypermetabolic stress response to thermal injury. Patencies of these grafts depend mainly on the high viability and sustained function of the enmeshed keratinocytes. With growing demand in tissue replacement therapies, development of successful and economical preservation techniques for skin grafts and replacements becomes essential. In this regard, if attained, desiccated state storage offers an economical solution to availability, storage, and transportation problems. Recent studies indicate that carbohydrates are very efficient in stabilizing mammalian cells against various types of stresses, including those associated with cryopreservation and desiccation. In this study we introduce the use of 3-O-methyl-D-glucose (3-OMG), a nonmetabolizable glucose derivative, as a new means of providing protection for keratinocytes undergoing desiccation. We show that with decreasing water contents, viability of the cells decreases; however, at the same water content the immediate post-rehydration viability and long-term survival of the cells exposed to 3-OMG are much higher than those of controls.

Dry storage of sperm: applications in primates and domestic animals

Cryopreservation of spermatozoa, oocytes and embryos, as well as somatic cells or cell lines for cloning from cells, are all options for the long-term storage of unique genotypes and endangered species. Spermatozoal cryopreservation and storage currently require liquid nitrogen or ultralow refrigeration-based methods for long- or short-term storage, which requires routine maintenance and extensive space requirements. The preservation of stem cells also has strict requirements for long-term storage to maintain genetic integrity. Dessicated (lyopreserved) sperm and stem cells will provide an unprecedented type of long-term storage without the need for expensive and burdensome cryogenic conditions. Experiments were conducted to determine an effective intracellular concentration of the lyoprotectant trehalose. High-pressure liquid chromatography studies revealed that trehalose can be incorporated into mature sperm cells as well as spermatogonial stem cells from rhesus monkeys. In addition, using fourier transform infrared spectroscopy, we determined that thermotropic phase transitions for fresh ejaculates from rhesus monkey and stallion sperm occurred at 10-15, 33-37 and 55-59 degrees C. Preliminary studies in our laboratory have indicated that spermatogonial stem cells can be dried to <3 g g(-1) water and maintain viability following rehydration. Studies in our laboratory have provided preliminary results suggesting that the desiccated storage of sperm and spermatogonial stem cells may be a viable alternative to conventional cryopreservation.

Trehalose uptake through P2X7 purinergic channels provides dehydration protection

The tetra-anionic form of ATP (ATP4-) is known to induce monovalent and divalent ion fluxes in cells that express purinergic P2X7 receptors and with sustained application of ATP it has been shown that dyes as large as 831 Da can permeate the cell membrane. The current study explores the kinetics of loading alpha,alpha-trehalose (342 Da) into ATP stimulated J774.A1 cells, which are known to express the purinergic P2X7 receptor. Cells that were incubated at 37 degrees C in a 50 mM phosphate buffer (pH 7.0) containing 225 mM trehalose and 5 mM ATP, were shown to load trehalose linearly over time. Concentrations of approximately 50 mM were reached within 90 min of incubation. Cells incubated in the same solution at 4 degrees C loaded minimally, consistent with the inactivity of the receptor at low temperatures. However, extended incubation at 37 degrees C (>60 min) resulted in zero next-day survival, with adverse effects appearing even with incubation periods as short as 30 min. By using a two-step protocol with a short time period at 37 degrees C to allow pore formation, followed by an extended loading period on ice, cells could be loaded with up to 50 mM trehalose while maintaining good next day recovery (49 +/- 12% by Trypan blue exclusion, 56 +/- 20% by alamarBlue assay). Cells porated by this method and allowed an overnight recovery period exhibited improved dehydration tolerance suggesting a role for ATP poration in the anhydrous preservation of cells.

Trehalose reduces aggregate formation and delays pathology in a transgenic mouse model of oculopharyngeal muscular dystrophy

Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant disease that presents in the fifth or sixth decade with dysphagia, ptosis and proximal limb weakness. OPMD is caused by the abnormal expansion of a polyalanine tract within the coding region of polyA binding protein nuclear 1 (PABPN1). The resultant mutant PABPN1 forms aggregates within the nuclei of skeletal muscle fibres. We have previously described a transgenic mouse model of OPMD that recapitulates the human disease and develops progressive muscle weakness accompanied by the formation of aggregates in skeletal muscle nuclei. The chemical chaperone trehalose has been used effectively to alleviate symptoms in a mouse model of Huntington's disease and is thought to elicit its effect by binding and stabilizing partially folded polyglutamine proteins and inhibiting the formation of aggregates. Here, we show that trehalose reduces aggregate formation and toxicity of mutant PABPN1 in cell models. Furthermore, oral administration of trehalose attenuated muscle weakness, reduced aggregate formation and decreased the number of TUNEL-labelled nuclei in skeletal muscle in an OPMD transgenic mouse model. Thus, anti-aggregation therapy may prove effective in the treatment of human OPMD.

Improved preservation of human red blood cells by lyophilization

The lyophilization of human red blood cells has important implications for blood transfusion in clinical medicine. In this study, sugars, human serum albumin, polyvinylpyrrolidone, and dimethyl sulfoxide were used as protective reagents for the lyophilization of red blood cells. Freezing temperature, shelf temperature, and the rehydration conditions were optimized. The results showed that extracellular disaccharides, especially trehalose, did not increase the recovery of hemoglobin. However, when the concentration of human serum albumin was higher than 25%, it had a considerable protective effect on the recovery of lyophilized red blood cells; the cellular hemoglobin recovery was over 70%, which was significantly higher than that in the group without human serum albumin (P<0.01). As the concentration of polyvinylpyrrolidone was increased, the extent of vitrification also increased. But when the concentration of polyvinylpyrrolidone was over 40%, the resulting concentration of free hemoglobin was over 1g/L, which was significantly higher than that with 40% (P<0.01). When lyophilization was carried out after freezing at different temperatures, the recovery of cells and hemoglobin was 70-80% and there were no significant differences among the five groups. When the shelf temperature was higher than -30 degrees C, the samples were partly collapsed, but when the shelf temperature was lower than -30 degrees C, the recovery of cells in the -40 and -45 degrees C groups was significantly higher than in the -30 and -35 degrees C groups (P<0.05). The recovery of cells and hemoglobin after lyophilization and rehydration in solutions containing low concentrations of polymers was over 80%, which is significantly higher than the other groups (P<0.01). In addition, when the temperature was higher than 25 degrees C, the concentration of free hemoglobin was significantly lower than it was at 4 degrees C (P<0.01). In conclusion, our study showed the lyophilization of red blood cells is feasible. Disaccharides have no protective effect on lyophilized cells when they are only extracellular and extensive vitrification may be not beneficial. Although the recovery of cells after lyophilization and rehydration by our method was over 70%, the ultrastructure of the cells may be compromised and some hemolysis does still exist. Further research is required.

A small stress protein acts synergistically with trehalose to confer desiccation tolerance on mammalian cells

The ability to desiccate mammalian cells while maintaining a high degree of viability would be very important in many areas of biological science, including tissue engineering, cell transplantation, and biosensor technologies. Certain proteins and sugars found in animals capable of surviving desiccation might aid this process. We report here that human embryonic kidney (293H) cells transfected with the gene for the stress protein p26 from Artemia and loaded with trehalose showed a sharp increase in survival during air-drying. Further, we find vacuum-drying greatly improved the ability of the cells to survive, and that the physical shape and structure of the cellular sample had a large influence on recovery following rehydration. Cells suspended in a rounded droplet survived desiccation markedly better than those spread as a thin film. Finally, we used alamarBlue to monitor cellular metabolism and Hema 3 to assess colony formation after vacuum-drying. AlamarBlue fluorescence indicated that the transfected 293H cells expressing p26 (E11'L) grew much better than the control 293H cells. In fact, immediate survival and colony formation in E11'L cells increased as much as 34-fold compared with control cells when the samples were dried to a water content of 0.2 g H2O/g dry weight, as measured by gravimetric analysis. These results indicate that p26 improves cell survival following drying and rehydration, and suggest that dry storage of mammalian cells is a likely possibility in the future.

Dehydration damage of domain-exhibiting supported bilayers: an AFM study on the protective effects of disaccharides and other stabilizing substances

Atomic force microscopy (AFM) has been applied to characterize hydrated sphingomyelin/dioleoylphosphatidylcholine/cholesterol supported bilayers, after dehydration either in the absence or in the presence of several stabilizing substances. Such a study provides information about the effect of extreme environmental conditions on biological membranes and, in particular, on lipidic microdomains. Dehydration stress, indeed, is thought to cause both macroscopical damage and alterations of microdomains in biomembranes, leading to deleterious effects. These phenomena can be avoided if disaccharides are added during dehydration. In this work, we apply AFM imaging to directly visualize damage caused to supported lipid bilayers by water removal. We compare the efficiency of sucrose, trehalose, dextran, dimethyl sulfoxide, and glucose in preserving the structural integrity of domain-exhibiting model membranes. Finally, in addition to confirming previous findings, our results provide further insight into damage and alteration of microdomains in membranes as a consequence of stressful drying conditions.

Loading red blood cells with trehalose: a step towards biostabilization

A method for freeze-drying red blood cells (RBCs) while maintaining a high degree of viability has important implications in blood transfusion and clinical medicine. The disaccharide trehalose, found in animals capable of surviving dehydration can aid in this process. As a first step toward RBC preservation, we present a method for loading RBCs with trehalose. The method is based on the thermal properties of the RBC plasma membranes and provides efficient uptake of the sugar at 37 degrees C in a time span of 7 h. The data show that RBCs can be loaded with trehalose from the extracellular medium through a combination of osmotic imbalance and the phospholipid phase transition, resulting in intracellular trehalose concentrations of about 40 mM. During the loading period, the levels of ATP and 2,3-DPG are maintained close to the levels of fresh RBCs. Increasing the membrane fluidity through the use of a benzyl alcohol results in a higher concentration of intracellular trehalose, suggesting the importance of the membrane physical state for the uptake of the sugar. Osmotic fragility data show that trehalose exerts osmotic protection on RBCs. Flow cytometry data demonstrate that incubation of RBCs in a hypertonic trehalose solution results in a fraction of cells with different complexity and that it can be removed by washing and resuspending the RBCs in an iso-osmotic medium. The data provide an important first step in long-term preservation of RBCs.