Reversible cross-linking and CO treatment as an approach in red cell stabilization

Concise Review: Considering Optimal Temperature for Short-Term Storage of Epithelial Cells

Transplantation of novel tissue-engineered products using cultured epithelial cells is gaining significant interest. While such treatments can readily be provided at centralized medical centers, delivery to patients at geographically remote locations requires the establishment of suitable storage protocols. One important aspect of storage technology is temperature. This paper reviews storage temperature for above-freezing point storage of human epithelial cells for regenerative medicine purposes. The literature search uncovered publications on epidermal cells, retinal pigment epithelial cells, conjunctival epithelial cells, corneal/limbal epithelial cells, oral keratinocytes, and seminiferous epithelial cells. The following general patterns were noted: (1) Several studies across different cell types inclined toward 4 and 16°C being suitable short-term storage temperatures. Correspondingly, almost all studies investigating 37°C concluded that this storage temperature was suboptimal. (2) Cell death typically escalates rapidly following 7–10 days of storage. (3) The importance of the type of storage medium and its composition was highlighted by some of the studies; however, the relative importance of storage medium vs. storage temperature has not been investigated systematically. Although a direct comparison between the included investigations is not reasonable due to differences in cell types, storage media, and storage duration, this review provides an overview, summarizing the work carried out on each cell type during the past two decades.

Current Approaches of Preservation of Cells During (freeze-) Drying

The widespread application of therapeutic cells requires a successful stabilization of cells for the duration of transport and storage. Cryopreservation is currently considered the gold standard for the storage of active cells; however, (freeze-) drying cells could enable higher shelf life stability at ambient temperatures and facilitate easier transport and storage. During (freeze-) drying, freezing, (primary and secondary) drying and also the reconstitution step pose the risk of potential cell damage. To prevent these damaging processes, a wide range of protecting excipients has emerged, which can be classified, according to their chemical affiliation, into sugars, macromolecules, polyols, antioxidants and chelating agents. As many excipients cannot easily permeate the cell membrane, researchers have established various techniques to introduce especially trehalose intracellularly, prior to drying. This review aims to summarize the main damaging mechanisms during (freeze-) drying and to introduce the most common excipients with further details on their stabilizing properties and process approaches for the intracellular loading of excipients. Additionally, we would like to briefly explain recently discovered advantages of drying microorganisms, sperm, platelets, red blood cells, and eukaryotic cells, paying particular attention to the drying technique and residual moisture content.

Shape-Preserved Transformation of Biological Cells into Synthetic Hydrogel Microparticles

The synthesis of materials that can mimic the mechanical, and ultimately functional, properties of biological cells can broadly impact the development of biomimetic materials, as well as engineered tissues and therapeutics. Yet, it is challenging to synthesize, for example, microparticles that share both the anisotropic shapes and the elastic properties of living cells. Here, a cell-directed route to replicate cellular structures into synthetic hydrogels such as polyethylene glycol (PEG) is described. First, the internal and external surfaces of chemically fixed cells are replicated in a conformal layer of silica using a sol-gel process. The template is subsequently removed to render shape-preserved, mesoporous silica replicas. Infiltration and cross-linking of PEG precursors and dissolution of the silica result in a soft hydrogel replica of the cellular template as demonstrated using erythrocytes, HeLa, and neuronal cultured cells. The elastic modulus can be tuned over an order of magnitude (≈10-100 kPa) though with a high degree of variability. Furthermore, synthesis without removing the biotemplate results in stimuli-responsive particles that swell/deswell in response to environmental cues. Overall, this work provides a foundation to develop soft particles with nearly limitless architectural complexity derived from dynamic biological templates.

Effects of autologous, cross-linked erythrocytes on isolated hypoperfused rabbit heart dynamics

The present study was aimed at assessing the effects of either red blood cells (RBC) or RBC cross-linked with the bifunctional dimethyl suberimidate reagent (C-RBC) on contractile force (CFo), heart rate (HR) and coronary flow (CF) of the isolated rabbit heart hypoperfused with RBC suspensions under 30 mm Hg constant pressure. RBC or C-RBC caused a rapid and marked reduction of CF, CFo and HR. In RBC-treated hearts, however, reperfusion with Tyrode solution partially restored the initial myocardial parameters, while in C-RBC-treated hearts a rapid impairment of diastolic relaxation with a subsequent, steady and increasing heart contracture was observed. Histological analysis showed that in C-RBC-perfused hearts either capillaries or precapillary arterioles were occluded by C-RBC in spite of extensive washings with Tyrode solution. These findings indicate that C-RBC impair coronary circulation markedly and irreversibly.

Effects of work place carbon monoxide exposure on blood viscosity

Both blood viscosity and carbon monoxide (CO) has been associated with cardiovascular diseases (CVDs). In order to investigate the effects of chronic low-level CO exposure on the determinants of blood viscosity (hematocrit, plasma viscosity, erythrocyte deformability, and erythrocyte aggregation), 10 men exposed to CO at work for at least 6 months and 10 healthy controls were included in the study. Plasma viscosity was determined by a cone-plate viscometer, erythrocyte deformability and erythrocyte aggregation by laser-assisted optical rotational cell analyzer. Mean plasma viscosity of the group exposed to CO (1.4 +/- 0.1 mPa.sn) was significantly higher than that of the controls (1.2 +/- 0.06 mPa.sn) (p < .05). Plasma fibrinogen level of the CO group (275 +/- 11 mg/dL) was slightly higher than that of the controls (263 +/- 14 mg/dL). The rise in plasma viscosity by chronic low-level CO exposure may be the mechanism of CO-induced increase in the risk for CVDs.

The behavior of the human erythrocyte as an imperfect osmometer: A hypothesis

The human erythrocyte does not behave as a perfect osmometer that is its volume does not change as predicted with the change of the tonicity of the medium, as if there was a fraction of the cell water not participating in the osmotic exchange. A mechanism of control of the erythrocyte shape has been previously proposed in which Band 3 (AE1), the protein anion exchanger of Cl(-) and HCO(3)(-), plays a central role. Specifically, decrease and increase of the ratio of its outward-facing conformation and inward-facing conformation (Band 3(o)/Band 3(i)) contract and relax the membrane skeleton, thus favoring echinocytosis and stomatocytosis, respectively. The equilibrium Band 3(o)/Band 3(i) ratio is determined by the Donnan equilibrium ratio of anions and protons, increasing with it (r=Cl(i)(-)/Cl(o)(-)=HCO 3(i)(-)/HCO 3(o)(-)=H(o)(+)/H(i)(+)). The Donnan ratio is influenced by the erythrocyte transport and metabolic activities. The volume change of the human erythrocyte alters the skeleton conformation as it is accompanied by a change of the membrane curvature. Thus, the mechanism could be a hypothesis for explaining the behavior of the human erythrocyte as an imperfect osmometer since the Donnan ratio controls the Band 3(o)/Band 3(i) ratio which controls the volume by a control of the degree of contraction or relaxation of the skeleton. Predictions made by the hypothesis on the Ponder's coefficient R' values in the presence of sucrose or Band 3 substrates slowly transported as well as on the participation of Band 3 in the osmotic hemolysis appear to be corroborated by previous observations. If the hypothesis was valid, it would follow that there is a pressure gradient across the erythrocyte membrane. The equilibrium volume is antagonistically determined by the Donnan ratio per se and Band 3. Band 3, rather than the ratio of surface-to-volume, primarily controls the osmotic hemolysis.

Phospholipid vesicles increase the survival of freeze-dried human red blood cells

In a previous report [Z. Török, G. Satpathy, M. Banerjee, R. Bali, E. Little, R. Novaes, H. Van Ly, D. Dwyre, A. Kheirolomoom, F. Tablin, J.H. Crowe, N.M. Tsvetkova, Preservation of trehalose loaded red blood cells by lyophilization, Cell Preservation Technol. 3 (2005) 96-111.], we presented a method for preserving human red blood cells (RBCs) by loading them with trehalose and then freeze-drying. We have now improved that method, based on the discovery that addition of phospholipid vesicles to the lyophilization buffer substantially reduces hemolysis of freeze-dried RBCs after rehydration. The surviving cells synthesize 2,3-DPG, have low levels of methemoglobin, and have preserved morphology. Among the lipid species we studied, unsaturated PCs were found to be most effective in suppressing hemoglobin leakage. RBC-vesicle interactions depend on vesicle size and structure; unilamellar liposomes with average diameter of less than 300 nm were more effective in reducing the hemolysis than multilamellar vesicles. Trehalose loaded RBCs demonstrated high survival and low levels of methemoglobin during 10 weeks of storage at 4 degrees C in the dry state when lyophilized in the presence of liposomes.

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.

Effects of blood product storage protectants on blood coagulation1 1The opinions expressed herein are the private views of the authors and are not to be construed as official or reflecting the views of the Department of the Army or the Department of Defense

The ever-increasing demand for blood products challenges scientists to develop new and more effective techniques for their preservation. The progress of these novel preservation technologies uses a wide variety of cryoprotectant, lyoprotectant, and other preservatives, which will need to be explored and assessed for their biological effects during blood product formulation. The leading factor in protectant selection is for their ability to provide superior preservation for a particular blood product. We believe that such protectants used in blood product development should also be evaluated for their ability to preserve normal hemostasic mechanisms. In this review, high-molecular-weight cryoprotectants, lyoprotectants, polyols, amino acids, antioxidants, and surfactants, used because of their protective properties, were evaluated for their possible role in relation to their effect on normal hemostatic mechanisms.

From anhydrobiosis to freeze-drying of eukaryotic cells

Using what has been learned from nature, it has become possible to stabilize biological structures, including intact cells, in the dry state. Stabilization of cells or tissues in the dried state is of considerable practical significance, as is described in this review. The need for stabilization of cells in the dried state is particularly urgent in bloodbanks, where proper storage of blood cells (platelets and erythrocytes) is still a major problem. Human blood platelets are stored in blood banks for 5 days, after which they are discarded according to Federal regulation. This short lifetime has led to a chronic shortage of platelets. We report here that platelets can be preserved by freeze-drying them with trehalose, a sugar found at high concentrations in organisms that naturally survive drying. We suggest that this finding will obviate the storage problem with platelets and that the principles established here may be extended to more complex eukaryotic cells.