Ocular Fluid As a Replacement for Serum in Cell Cryopreservation Media

The role of high cholesterol in SARS-CoV-2 infectivity

Coronavirus disease 2019 (COVID19) is a respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The virus binds to angiotensinogen converting enzyme 2 (ACE2) which mediates viral entry into mammalian cells. COVID19 is notably severe in elderly and those with underlying chronic conditions. The cause of selective severity is not well understood. Here we show cholesterol and the signaling lipid phosphatidyl-inositol 4,5 bisphosphate (PIP₂) regulate viral infectivity through the localization of ACE2's into nanoscopic (<200 nm) lipid clusters. Uptake of cholesterol into cell membranes (a condition common to chronic disease) causes ACE2 to move from PIP₂ lipids to endocytic ganglioside (GM1) lipids, where the virus is optimally located for viral entry. In mice, age, and high fat diet increase lung tissue cholesterol by up to 40%. And in smokers with chronic disease, cholesterol is elevated two-fold, a magnitude of change that dramatically increases infectivity of virus in cell culture. We conclude increasing the ACE2 location near endocytic lipids increases viral infectivity and may help explain the selective severity of COVID-19 in aged and diseased populations.

Hydroxychloroquine blocks SARS-CoV-2 entry into the endocytic pathway in mammalian cell culture

Hydroxychloroquine (HCQ), a drug used to treat lupus and malaria, was proposed as a treatment for SARS-coronavirus-2 (SARS-CoV-2) infection, albeit with controversy. In vitro, HCQ effectively inhibits viral entry, but its use in the clinic has been hampered by conflicting results. A better understanding of HCQ’s mechanism of actions in vitro is needed. Recently, anesthetics were shown to disrupt ordered clusters of monosialotetrahexosylganglioside1 (GM1) lipid. These same lipid clusters recruit the SARS-CoV-2 surface receptor angiotensin converting enzyme 2 (ACE2) to endocytic lipids, away from phosphatidylinositol 4,5 bisphosphate (PIP₂) clusters. Here we employed super-resolution imaging of cultured mammalian cells (VeroE6, A549, H1793, and HEK293T) to show HCQ directly perturbs clustering of ACE2 receptor with both endocytic lipids and PIP₂ clusters. In elevated (high) cholesterol, HCQ moves ACE2 nanoscopic distances away from endocytic lipids. In cells with resting (low) cholesterol, ACE2 primarily associates with PIP₂ clusters, and HCQ moves ACE2 away from PIP₂ clusters—erythromycin has a similar effect. We conclude HCQ inhibits viral entry through two distinct mechanisms in high and low tissue cholesterol and does so prior to inhibiting cathepsin-L. HCQ clinical trials and animal studies will need to account for tissue cholesterol levels when evaluating dosing and efficacy.

Super-resolution microscopy in cultured cells is employed to dissect the effect of hydroxychloroquine (HCQ) at the plasma membrane and HCQ directly perturbs clustering of the SARS-CoV-2 receptor ACE2 with endocytic lipids and PIP2 clusters.

Regulation of beta-amyloid production in neurons by astrocyte-derived cholesterol

Alzheimer's disease (AD) is characterized by the presence of amyloid β (Aβ) plaques, tau tangles, inflammation, and loss of cognitive function. Genetic variation in a cholesterol transport protein, apolipoprotein E (apoE), is the most common genetic risk factor for sporadic AD. In vitro evidence suggests that apoE links to Aβ production through nanoscale lipid compartments (lipid clusters), but its regulation in vivo is unclear. Here, we use superresolution imaging in the mouse brain to show that apoE utilizes astrocyte-derived cholesterol to specifically traffic neuronal amyloid precursor protein (APP) in and out of lipid clusters, where it interacts with β- and γ-secretases to generate Aβ-peptide. We find that the targeted deletion of astrocyte cholesterol synthesis robustly reduces amyloid and tau burden in a mouse model of AD. Treatment with cholesterol-free apoE or knockdown of cholesterol synthesis in astrocytes decreases cholesterol levels in cultured neurons and causes APP to traffic out of lipid clusters, where it interacts with α-secretase and gives rise to soluble APP-α (sAPP-α), a neuronal protective product of APP. Changes in cellular cholesterol have no effect on α-, β-, and γ-secretase trafficking, suggesting that the ratio of Aβ to sAPP-α is regulated by the trafficking of the substrate, not the enzymes. We conclude that cholesterol is kept low in neurons, which inhibits Aβ accumulation and enables the astrocyte regulation of Aβ accumulation by cholesterol signaling.

Alternative to FBS in animal cell culture - An overview and future perspective

Fetal bovine serum (FBS) is a widely used growth supplement in the in vitro culturing of animal and human cells, tissues and organs, notably due to the occurrence of abundant micro- and macronutrients, along with growth factors. Over the years, increasing demand, high price, batch-to-batch variability in quality and composition, increasing ethical concerns lead to the search for an alternative to FBS. Several approaches have been suggested and employed in the past, but none is implemented as widely as FBS, and each supplement has its own disadvantages. In this review, we described the importance of FBS in cell culture, discussed the issues associated with FBS use and presented the efforts made in the recent past to reduce or replace FBS. The potential of four different alternative sources to FBS, namely, bovine ocular fluid, sericin protein, human platelet lysate and earthworm heat inactivated coelomic fluid was evaluated. In the end, we present the conceptual perspective using the Human Platelet Lysate (HPL) and earthworm Heat Inactivated Coelomic Fluid (HI-CF) combination to alternate FBS and its context in scientific and economic impacts.

Vitrification of Dog Skin Tissue as a Source of Mesenchymal Stem Cells

The purpose of this study was to develop an efficient vitrification system for cryopreservation of dog skin tissues as a source of stable autologous stem cells. In this study, we performed vitrification using four different cryoprotectants, namely, ethylene glycol (EG), dimethyl-sulfoxide (Me2SO), EG plus Me2SO, and EG plus Me2SO plus sucrose, and analyzed the behaviors of cells established from warmed tissues. Tissues vitrified with 15% EG, 15% Me2SO, and 0.5 M sucrose had a normal histological appearance and the highest cell viability after cell isolation, and thus, this cocktail of cryoprotectants was used in subsequent experiments. We evaluated proliferation and apoptosis of cells derived from fresh and vitrified tissues. These cells had a normal spindle-like morphology after homogenization through subculture. Dog dermal skin stem cells (dDSSCs) derived from fresh and vitrified tissues had similar proliferation capacities, and similar percentages of these cells were positive for mesenchymal stem cell markers at passage 3. The percentage of apoptotic cell did not differ between dDSSCs derived from fresh and vitrified tissues. Real-time PCR analysis revealed that dDSSCs at passage 3 derived from fresh and vitrified tissues had similar expression levels of pluripotency (OCT4, SOX2, and NANOG), proapoptotic (BAX), and antiapoptotic (BCL2 and BIRC5) genes. Both types of dDSSCs successfully differentiated into the mesenchymal lineage (adipocytes and osteocytes) under specific conditions, and their differentiation potentials did not significantly differ. Furthermore, the mitochondrial membrane potential of dDSSCs derived from vitrified tissues was comparable with that of dDSSCs derived from fresh tissues. We conclude that vitrification of dog skin tissues using cocktail solution in combination of 15% EG, 15% Me2SO, and 0.5 M sucrose allows efficient banking of these tissues for regenerative stem cell therapy and conservation of genetic resources.

Effect of a Freezing Medium Containing Melatonin on Markers of Pre-meiotic and Post-meiotic Spermatogonial Stem Cells (SSCs) After Transplantation in an Azoospermia Mouse Model Due to Testicular Torsion

Spermatogonial stem cells (SSCs) are essential to the initiation of spermatogenesis. Cryopreservation, long-term maintenance, and auto-transplantation of SSCs could be a new treatment for infertility. The aim of this study was to add melatonin to the basic freezing medium and to evaluate its effect on the efficiency of the thawed SSCs after transplantation into the testicles of azoospermic mice. SSCs were isolated from newborn NMRI mice, and the cells were enriched to assess morphological features. The thawed SSCs were evaluated for survival, apoptosis, and ROS level before transplantation, and the proliferation (MVH and ID4) and differentiation (c-Kit, SCP3, TP1, TP2, and Prm1) markers of SSCs were examined using immunofluorescence, western blot, and quantitative real-time polymerase chain reaction (PCR) after transplantation. It was found that the survival rate of SSCs after thawing was significantly higher in the melatonin group compared with the cryopreservation group containing basic freezing medium, and the rate of apoptosis and level of ROS production also decreased significantly in the cryopreservation group with melatonin (p < 0.05). The expression of proliferation and differentiation markers after transplantation was significantly higher in the cryopreservation group with melatonin compared to the cryopreservation group (p < 0.05). The results suggest that adding melatonin to the basic freezing medium can effectively protect the SSCs by increasing the viability and reducing the ROS production and apoptosis and improve the transplantation efficiency of SSCs after cryopreservation, which will provide a significant suggestion for fertility protection in the clinic.

Off the shelf cellular therapeutics: Factors to consider during cryopreservation and storage of human cells for clinical use

The field of cellular therapeutics has immense potential, affording an exciting array of applications in unmet medical needs. One of several key issues is an emphasis on getting these therapies from bench to bedside without compromising safety and efficacy. The successful commercialization of cellular therapeutics will require many to extend the shelf-life of these therapies beyond shipping "fresh" at ambient or chilled temperatures for "just in time" infusion. Cryopreservation is an attractive option and offers potential advantages, such as storing and retaining patient samples in case of a relapse, banking large quantities of allogeneic cells for broader distribution and use and retaining testing samples for leukocyte antigen typing and matching. However, cryopreservation is only useful if cells can be reanimated to physiological life with negligible loss of viability and functionality. Also critical is the logistics of storing, processing and transporting cells in clinically appropriate packaging systems and storage devices consistent with quality and regulatory standards. Rationalized approaches to develop commercial-scale cell therapies require an efficient cryopreservation system that provides the ability to inventory standardized products with maximized shelf life for later on-demand distribution and use, as well as a method that is scientifically sound and optimized for the cell of interest. The objective of this review is to bridge this gap between the basic science of cryobiology and its application in this context by identifying several key aspects of cryopreservation science in a format that may be easily integrated into mainstream cell therapy manufacture.

Selaginella bryopteris Aqueous Extract Improves Stability and Function of Cryopreserved Human Mesenchymal Stem Cells

The effective long-term cryopreservation of human mesenchymal stem cells (MSCs) is an essential prerequisite step and represents a critical approach for their sustained supply in basic research, regenerative medicine, and tissue engineering applications. Therefore, attempts have been made in the present investigation to formulate a freezing solution consisting of a combination of Selaginella bryopteris water-soluble extract with and without dimethyl sulfoxide (Me₂SO) for the efficient long-term storage of human umbilical cord blood- (hUCB-) derived MSCs. The cryopreservation experiment using the formulated freezing solution was further performed with hUCB MSCs in a controlled rate freezer. A significant increase in postthaw cell viability and cell attachment of MSCs was achieved with freezing medium containing Selaginella bryopteris water extract along with 10% Me₂SO as compared to the freezing medium containing Me₂SO (10% v/v) alone. Furthermore, the decreasing apoptotic events and reactive oxygen species production along with increasing expression of heat shock proteins also confirmed the beneficial effect of Selaginella bryopteris water extract. The beneficial effect of Selaginella bryopteris water extract was validated by its ability to render postpreservation high cell viability. In conclusion, the formulated freezing solution has been demonstrated to be effective for the standardization of cryopreservation protocol for hMSCs.

Replacement of serum with ocular fluid for cryopreservation of immature testes

Cryopreservation of immature testis is a feasible approach for germplasm preservation of male animals. Combinations of dimethyl sulfoxide (DMSO) and foetal bovine serum (FBS) are used for testis cryopreservation. However, an alternative to FBS is needed, because FBS is expensive. Buffalo ocular fluid (BuOF), a slaughter house by-product, could be an economical option. The objective of the present study was to assess whether BuOF can replace FBS for cryopreservation of immature mouse (Mus musculus), rat (Rattus norvegicus), and buffalo (Bubalus bubalis) testes. Results showed that rodent and buffalo testes frozen in DMSO (10% for rodents and 20% for buffalo) with 20% FBS or BuOF had similar numbers of viable and DNA-damaged cells (P > 0.05). The expression of cell proliferation- (PCNA) and apoptosis-specific proteins (Annexin V and BAX/BCL2 ratio) were also comparable in mouse and buffalo testes frozen in DMSO with FBS or BuOF (P > 0.05). Interestingly, rat testis frozen in DMSO with BuOF had lower expression of Annexin V protein than testis frozen in DMSO with FBS (P < 0.05). The percentage of meiotic germ cells (pachytene-stage spermatocytes) in xenografts from testis frozen either in DMSO with BuOF or FBS did not significantly differ in rats or buffalo (P > 0.05). These findings provide evidence that BuOF has potential to replace FBS for cryopreservation of immature rodent and buffalo testis. Further investigation is needed to explore whether BuOF can replace FBS for testis cryopreservation of other species.

Open encapsulation-vitrification for cryopreservation of algae

Vitrification offers a cost-effective solution for the preservation and management of genetic resources with, low-cost international movement of selected genetic materials and for long-term maintenance of stable stocks of a wide variety of microorganisms. However, its success is limited by the wide range of algal species. Here, we report a simple open encapsulation-vitrification protocol of cryopreservation. Results showed that ∼58% and ∼27% of Oocystis sp. survived vitrification-warming after the open and closed system of vitrification respectively when compared to non-cryopreserved controls. The improved success in an open system of vitrification was also observed in Anabaena sp. Furthermore, with the addition of 2-mercaptoethanol or glutathione the post-warming viability of vitrified algae in both open and closed system of vitrification was significantly improved (p < 0.05). The present case study aimed to develop a vitrification-based cryopreservation protocol and confirms an improvement in survival percentage over conventional encapsulation-vitrification method.