Effect of Antioxidants and Apoptosis Inhibitors on Cryopreservation of Murine Germ Cells Enriched for Spermatogonial Stem Cells

Inhibition of reactive oxygen species generation by N-Acetyl Cysteine can mitigate male germ cell toxicity induced by bisphenol analogs

The estrogen-like effect of bisphenol A (BPA) disrupting the maintenance of functional male germ cells is associated with male sub-fertility. This study investigated toxicity of male germ cells induced by four bisphenol analogs: BPA, BPAF, BPF, and BPS. The investigation of bisphenol analogs' impact on male germ cells included assessing proliferation, apoptosis induction, and the capacity to generate reactive oxygen species (ROS) in GC-1 spermatogonia (spg) cells, specifically type B spermatogonia. Additionally, the therapeutic potential and protective effects of N-Acetyl Cysteine (NAC) and NF-κB inhibitor parthenolide was evaluated. In comparison to BPA, BPF and BPS, BPAF exhibited the most pronounced adverse effect in GC-1 spg cell proliferation. This effect was characterized by pronounced inhibition of phosphorylation of PI3K, AKT, and mTOR, along with increased release of cytochrome c and subsequent cleavages of caspase 3, caspase 7, and poly (ADP-ribose) polymerase. Both NAC and parthenolide were effective reducing cellular ROS induced by BPAF. However, only NAC demonstrated a substantial recovery in proliferation, accompanied by a significant reduction in cytochrome c release and cleaved PARP. These results suggest that NAC supplementation may play an effective therapeutic role in countering germ cell toxicity induced by environmental pollutants with robust oxidative stress-generating capacity.

N-Acetyl-L-cysteine attenuates titanium dioxide nanoparticle (TiO2 NP)-induced autophagy in male germ cells

Titanium dioxide nanoparticles (TiO2 NPs) are widely used in consumer products, raising concerns about their impact on human health. This study investigates the effects of TiO2 NPs on male germ cells while focusing on cell proliferation inhibition and underlying mechanisms. This was done by utilizing mouse GC-1 spermatogonia cells, an immortalized spermatogonia cell line. TiO2 NPs induced a concentration-dependent proliferation inhibition with increased reactive oxygen species (ROS) generation. Notably, TiO2 NPs induced autophagy and decreased ERK phosphorylation. Treatment with the ROS inhibitor N-Acetyl-l-cysteine (NAC) alleviated TiO2 NPs-induced autophagy, restored ERK phosphorylation, and promoted cell proliferation. These findings call attention to the reproductive risks posed by TiO2 NPs while also highlighting NAC as a possible protective agent against reproductive toxins.

Recovering Spermatogenesis By Protected Cryopreservation Using Metformin and Transplanting Spermatogonial Stem Cells Into Testis in an Azoospermia Mouse Model

Cryopreservation and transplantation of spermatogonial stem cells (SSCs) may serve as a new method to restore male fertility in patients undergoing chemotherapy or radiotherapy. However, SSCs may be damaged during cryopreservation due to the production of reactive oxygen species (ROS). Therefore, different antioxidants have been used as protective agents. Studies have shown that metformin (MET) has antioxidant activity. The aim of this study was to assess the antioxidant and antiapoptotic effects of MET in frozen-thawed SSCs. In addition, the effect of MET on the proliferation and differentiation of SSCs was evaluated. To this end, SSCs were isolated from mouse pups aged 3-6 days old, cultured, identified by flow cytometry (ID4, INTEGRIN β1+), and finally evaluated for survival and ROS rate. SSCs were transplanted after busulfan and cadmium treatment. Cryopreserved SSCs with and without MET were transplanted after 1 month of cryopreservation. Eight weeks after transplantation, the recipient testes were evaluated for the expression of apoptosis (BAX, BCL2), proliferation (PLZF), and differentiation (SCP3, TP1, TP2, PRM1) markers using immunohistochemistry, Western blot, and quantitative real-time polymerase chain reaction. The findings revealed that the survival rate of SSCs was higher in the 500 μm/mL MET group compared to the other groups (50 and 5000 μm/mL). MET significantly decreased the intracellular ROS production. Transplantation of SSCs increased the expression level of proliferation (PLZF) and differentiation (SCP3, TP1, TP2, PRM1) markers compared to azoospermia group, and their levels were significantly higher in the MET group compared to the cryopreservation group containing basic freezing medium (p < 0.05). MET increased the survival rate of SSCs, proliferation, and differentiation and decreased the ROS production and the apoptosis rate. Cryopreservation by MET seems to be effective in treating infertility.

New strategies for germ cell cryopreservation: Cryoinjury modulation

Cryopreservation is an option for the preservation of pre- or post-pubertal female or male fertility. This technique not only is beneficial for human clinical applications, but also plays a crucial role in the breeding of livestock and endangered species. Unfortunately, frozen germ cells, including oocytes, sperm, embryos, and spermatogonial stem cells, are subject to cryoinjury. As a result, various cryoprotective agents and freezing techniques have been developed to mitigate this damage. Despite extensive research aimed at reducing apoptotic cell death during freezing, a low survival rate and impaired cell function are still observed after freeze-thawing. In recent decades, several cell death pathways other than apoptosis have been identified. However, the relationship between these pathways and cryoinjury is not yet fully understood, although necroptosis and autophagy appear to be linked to cryoinjury. Therefore, gaining a deeper understanding of the molecular mechanisms of cryoinjury could aid in the development of new strategies to enhance the effectiveness of the freezing of reproductive tissues. In this review, we focus on the pathways through which cryoinjury leads to cell death and propose novel approaches to enhance freezing efficacy based on signaling molecules.

Oxidative stress-induced apoptosis and autophagy: Balancing the contrary forces in spermatogenesis

Spermatogenesis is a complex process in the testis and is a cornerstone of male infertility. The abundance of unsaturated fatty acid and high cell division rate make male germs cells prone to DNA deterioration. ROS-mediated oxidative stress triggers DNA damage, autophagy, and apoptosis in male germ cells, which are critical causative factors that lead to male infertility. The complex connection and molecular crosstalk between apoptosis and autophagy is seen at multifaceted levels that interconnect the signaling pathways of these two processes. Multilevel interaction between apoptosis and autophagy is a seamless state of survival and death in response to various stressors. Interaction between multiple genes and proteins such as the mTor signaling pathway, Atg12 proteins, and the death adapter proteins, such as Beclin 1, p53, and Bcl-2 family proteins, validates such a link between these two phenomena. Testicular cells being epigenetically different from somatic cells, undergo numerous significant epigenetic transitions, and ROS modulates the epigenetic framework of mature sperm. Epigenetic deregulation of apoptosis and autophagy under oxidative stress conditions can cause sperm cell damage. The current review recapitulates the current role of prevailing stressors that generate oxidative stress leading to the induction of apoptosis and autophagy in the male reproductive system. Considering the pathophysiological consequences of ROS-mediated apoptosis and autophagy, a combinatorial approach, including apoptosis inhibition and autophagy activation, a therapeutic strategy to treat male idiopathic infertility. Understanding the crosslink between apoptosis and autophagy under stress conditions in male germ cells may play an essential role in developing therapeutic strategies to treat infertility.

The Role of Promyelocytic Leukemia Zinc Finger (PLZF) and Glial-Derived Neurotrophic Factor Family Receptor Alpha 1 (GFRα1) in the Cryopreservation of Spermatogonia Stem Cells

The cryopreservation of spermatogonia stem cells (SSCs) has been widely used as an alternative treatment for infertility. However, cryopreservation itself induces cryoinjury due to oxidative and osmotic stress, leading to reduction in the survival rate and functionality of SSCs. Glial-derived neurotrophic factor family receptor alpha 1 (GFRα1) and promyelocytic leukemia zinc finger (PLZF) are expressed during the self-renewal and differentiation of SSCs, making them key tools for identifying the functionality of SSCs. To the best of our knowledge, the involvement of GFRα1 and PLZF in determining the functionality of SSCs after cryopreservation with therapeutic intervention is limited. Therefore, the purpose of this review is to determine the role of GFRα1 and PLZF as biomarkers for evaluating the functionality of SSCs in cryopreservation with therapeutic intervention. Therapeutic intervention, such as the use of antioxidants, and enhancement in cryopreservation protocols, such as cell encapsulation, cryoprotectant agents (CPA), and equilibrium of time and temperature increase the expression of GFRα1 and PLZF, resulting in maintaining the functionality of SSCs. In conclusion, GFRα1 and PLZF have the potential as biomarkers in cryopreservation with therapeutic intervention of SSCs to ensure the functionality of the stem cells.

Synthesis of Poly(2-(methylsulfinyl)ethyl methacrylate) via Oxidation of Poly(2-(methylthio)ethyl methacrylate): Evaluation of the Sulfoxide Side Chain on Cryopreservation

Conventional cryopreservation solutions rely on the addition of organic solvents such as DMSO or glycerol, but these do not give full recovery for all cell types, and innovative cryoprotectants may address damage pathways which these solvents do not protect against. Macromolecular cryoprotectants are emerging, but there is a need to understand their structure-property relationships and mechanisms of action. Here we synthesized and investigated the cryoprotective behavior of sulfoxide (i.e., "DMSO-like") side-chain polymers, which have been reported to be cryoprotective using poly(ethylene glycol)-based polymers. We also wanted to determine if the polarized sulfoxide bond (S⁺O^- character) introduces cryoprotective effects, as this has been seen for mixed-charge cryoprotective polyampholytes, whose mechanism of action is not yet understood. Poly(2-(methylsulfinyl)ethyl methacrylate) was synthesized by RAFT polymerization of 2-(methylthio)ethyl methacrylate and subsequent oxidation to sulfoxide. A corresponding N-oxide polymer was also prepared and characterized: (poly(2-(dimethylamineoxide)ethyl methacrylate). Ice recrystallization inhibition assays and differential scanning calorimetry analysis show that the sulfoxide side chains do not modulate the frozen components during cryopreservation. In cytotoxicity assays, it was found that long-term (24 h) exposure of the polymers was not tolerated by cells, but shorter (30 min) incubation times, which are relevant for cryopreservation, were tolerated. It was also observed that overoxidation to the sulfone significantly increased the cytotoxicity, and hence, these materials require a precision oxidation step to be deployed. In suspension cell cryopreservation investigations, the polysulfoxides did not increase cell recovery 24 h post-thaw. These results show that unlike hydrophilic backboned polysulfides, which can aid cryopreservation, the installation of the sulfoxide group onto a polymer does not necessarily bring cryoprotective properties, highlighting the challenges of developing and discovering macromolecular cryoprotectants.

Evaluation of Nrf2/ARE Signaling Pathway in the Presence of Pentoxifylline as a Cryoprotectant in Mouse Spermatogonial Stem Cells

The process of spermatogonial stem cell cryopreservation (SSCs) in young male cancer survivors is associated with increased reactive oxygen species (ROS), DNA fragmentation, apoptosis, decreased cell activity, and finally reduced fertility of SSCs. Therefore, it is necessary to add cryoprotectants to the freezing medium to minimize the injuries associated with cryopreservation. In addition, the Nrf2/ARE pathway is a main cellular pathway that regulates the antioxidant defense system. The purpose of this study was to evaluate the cryoprotective effect of pentoxifylline (PTX) on SSCs after freezing-thawing through the Nrf2/ARE pathway. SSCs extracted from neonatal mice testes were isolated and their purity was measured by flow cytometry with GDNF family receptor alpha-1 (GFRα1) and inhibitor of differentiation 4 (ID4). After culturing, the cells were frozen in different groups for 1 month. After freezing-thawing, cell viability, colonization rate, and intracellular ROS, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) were evaluated. Quantitative real-time polymerase chain reaction and western blotting were done to assess the expression levels of Nrf2, Keap-1, PI3K, and AKT genes and proteins. The survival and colonization rates of SSCs, SOD, and CAT levels, and Nrf2, PI3K, and AKT expression levels were significantly higher in the PTX group compared with the other cryopreservation groups. The Keap-1 expression level and the ROS and MDA production levels also decreased significantly in the PTX group (p-value <0.05). According to our findings, PTX can activate the antioxidant defense through the Nrf2/ARE signaling pathway; therefore, it could be a suitable cryoprotectant candidate for freezing and long-term storage of SSCs in the clinical setting.

Antioxidant Effect of Melatonin on Proliferation, Apoptosis, and Oxidative Stress Variables in Frozen-Thawed Neonatal Mice Spermatogonial Stem Cells

Cryopreservation of spermatogonial stem cells (SSCs) is an important method to restore and maintain fertility in preadolescent children suffering from cancer. For protection of SSCs from cryoinjury, various antioxidant agents have been used. The aim of this study was to assess the antiapoptotic and antioxidant effects of melatonin in frozen-thawed SSCs. SSCs were isolated from testes of neonatal mice (3-6 days old) and their purities were measured by flow cytometry with promyelocytic leukemia zinc finger protein. After culturing, the cells were frozen in two groups (1) control and (2) melatonin (100 μM) and stored for 1 month. Finally, the cell viability, colonization rate, expression of Bcl-2 and BAX gene, and intracellular reactive oxygen species (ROS) were evaluated after freezing-thawing. Melatonin increased the viability and colonization of SSCs and Bcl-2 gene expression. It also diminished BAX gene expression and intracellular ROS. The results of this study show that melatonin with antioxidant and antiapoptotic effects can be used as an additive for freezing and long-term storage of cells and infertility treatment in the clinic.

Melatonin in cryopreservation media improves transplantation efficiency of frozen-thawed spermatogonial stem cells into testes of azoospermic mice

Background

Cryostorage of spermatogonial stem cells (SSCs) is an appropriate procedure for long-term storage of SSCs for fertility preservation. However, it causes damage to cellular structures through overproduction of ROS and oxidative stress. In this study, we examined the protective effect of melatonin as a potent antioxidant in the basic freezing medium to establish an optimal cryopreservation method for SSCs.

Methods

SSCs were obtained from the testes of neonatal male mice aged 3–6 days. Then, 100 μM melatonin was added to the basic freezing medium containing DMSO for cryopreservation of SSCs. Viability, apoptosis-related markers (BAX and BCL2), and intracellular ROS generation level were measured in frozen–thawed SSCs before transplantation using the MTT assay, immunocytochemistry, and flow cytometry, respectively. In addition, Western blotting and immunofluorescence were used to evaluate the expression of proliferation (PLZF and GFRα1) and differentiation (Stra8 and SCP3) proteins in frozen–thawed SSCs after transplantation into recipient testes.

Results

The data showed that adding melatonin to the cryopreservation medium markedly increased the viability and reduced intracellular ROS generation and apoptosis (by decreasing BAX and increasing BCL2) in the frozen–thawed SSCs (p < 0.05). The expression levels of proliferation (PLZF and GFRα1) and differentiation (Stra8 and SCP3) proteins and resumption of spermatogenesis from frozen–thawed SSCs followed the same pattern after transplantation.

Conclusions

The results of this study revealed that adding melatonin as an antioxidant to the cryopreservation medium containing DMSO could be a promising strategy for cryopreservation of SSCs to maintain fertility in prepubertal male children who suffer from cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03029-1.

Chemical approaches to cryopreservation

Cryopreservation of cells and biologics underpins all biomedical research from routine sample storage to emerging cell-based therapies, as well as ensuring cell banks provide authenticated, stable and consistent cell products. This field began with the discovery and wide adoption of glycerol and dimethyl sulfoxide as cryoprotectants over 60 years ago, but these tools do not work for all cells and are not ideal for all workflows. In this Review, we highlight and critically review the approaches to discover, and apply, new chemical tools for cryopreservation. We summarize the key (and complex) damage pathways during cellular cryopreservation and how each can be addressed. Bio-inspired approaches, such as those based on extremophiles, are also discussed. We describe both small-molecule-based and macromolecular-based strategies, including ice binders, ice nucleators, ice nucleation inhibitors and emerging materials whose exact mechanism has yet to be understood. Finally, looking towards the future of the field, the application of bottom-up molecular modelling, library-based discovery approaches and materials science tools, which are set to transform cryopreservation strategies, are also included.

Co-supplementation of freezing media with trehalose and vitamin C on cell viability and apoptotic gene expression in ovine spermatogonial stem cells

The purpose of this research was to investigate the trehalose and vitamin C (Vit C) co-supplementation of freezing media to create a successful cryopreservation protocol for conservation of ovine spermatogonial stem cells (SSCs). SSCs were cryopreserved and cultured with an essential freezing medium containing 200 mM trehalose, 40 µg/mL Vit C, and a combination of both for 3 weeks. Cell viability, colony number and diameter and mRNA levels of Bax, and Bcl-2 genes were evaluated before and after cryopreservation with quantitative real-time PCR. The results showed that cells cryopreserved in freezing medium containing 200 mM of trehalose plus 40 µg/mL Vit C had considerably greater cell viability than the control group (P<0.0001). Up to the 3rd week of cell culture, supplementation of freezing medium with 200 mM trehalose resulted in significantly lower colonies diameters than in the control group. No significant differences were observed during the 1st to 2nd weeks in colony diameter and number of colonies between cells cryopreserved in the freezing medium containing either Vit C or trehalose compared with the control groups. Following thawing, the mRNA level of Bax in the Vit C + trehalose group was drastically lower than in those treated with trehalose or Vit C only (P<0.0001). High expression of Bcl-2 in the 40 µg/mL Vit C group was recorded in the thawed cells compared to the control group (P<0.0001). These findings indicate that the concomitant use of antioxidants and sugar in the freezing medium can improve the quality and viabi­lity of SSCs after freezing via different mechanisms. Further studies are needed to clarify apoptosis and cell biomarkers in SSCs during freezing and thawing.

Current scenario and challenges ahead in application of spermatogonial stem cell technology in livestock

PURPOSE

Spermatogonial stem cells (SSCs) are the source for the mature male gamete. SSC technology in humans is mainly focusing on preserving fertility in cancer patients. Whereas in livestock, it is used for mining the factors associated with male fertility. The review discusses the present status of SSC biology, methodologies developed for in vitro culture, and challenges ahead in establishing SSC technology for the propagation of superior germplasm with special reference to livestock.

METHOD

Published literatures from PubMed and Google Scholar on topics of SSCs isolation, purification, characterization, short and long-term culture of SSCs, stemness maintenance, epigenetic modifications of SSCs, growth factors, and SSC cryopreservation and transplantation were used for the study.

RESULT

The fine-tuning of SSC isolation and culture conditions with special reference to feeder cells, growth factors, and additives need to be refined for livestock. An insight into the molecular mechanisms involved in maintaining stemness and proliferation of SSCs could facilitate the dissemination of superior germplasm through transplantation and transgenesis. The epigenetic influence on the composition and expression of the biomolecules during in vitro differentiation of cultured cells is essential for sustaining fertility. The development of surrogate males through gene-editing will be historic achievement for the foothold of the SSCs technology.

CONCLUSION

Detailed studies on the species-specific factors regulating the stemness and differentiation of the SSCs are required for the development of a long-term culture system and in vitro spermatogenesis in livestock. Epigenetic changes in the SSCs during in vitro culture have to be elucidated for the successful application of SSCs for improving the productivity of the animals.

Autophagy modulation alleviates cryoinjury in murine spermatogonial stem cell cryopreservation

BACKGROUND

Cryopreservation can expand the usefulness of spermatogonial stem cells (SSCs) in various fields. However, previous investigations that have attempted to modulate cryoinjury-induced mechanisms to increase cryoprotective efficiency have mainly focused on apoptosis and necrosis.

OBJECTIVES

This study aimed to establish an effective molecular-based cryoprotectant for SSC cryopreservation via autophagy modulation.

MATERIALS AND METHODS

To determine the efficacy of autophagy modulation, we assessed the recovery rate and relative proliferation rate and performed western blotting for the determination of autophagy flux, immunocytochemistry and real-time quantitative polymerase chain reaction (RT-qPCR) for SSC characterization, and spermatogonial transplantation for in vivo SSC functional activity.

RESULTS

The results showed that a basal level of autophagy caused a higher relative proliferation rate (pifithrin-μ 0.01 μM, 184.2 ± 11.2%; 3-methyladenine 0.01 μM, 175.3 ± 10.3%; pifithrin-μ 0.01 μM + 3-methyladenine 0.01 μM, P3, 224.6 ± 22.3%) than the DMSO control (100 ± 6.2%). All treatment groups exhibited normal characteristics, suggesting that these modulators could be used as effective cryoprotectants without changing the properties of the undifferentiated germ cells. According to the results of the in vivo spermatogonial transplantation assay, the colonies per total number of cultured SSCs was significantly higher in the pifithrin-μ 0.01 μM (1596.7 ± 172.5 colonies), 3-methyladenine 0.01 μM (1522.1 ± 179.2 colonies), and P3 (1727.5 ± 196.5 colonies) treatment groups than in the DMSO control (842.8 ± 110.08 colonies), which was comparable to that of the fresh control (1882.1 ± 132.1 colonies).

DISCUSSION

A basal level of autophagy is more essential for resilience in frozen SSCs after thawing, rather than the excessive activation or inhibition of autophagy.

CONCLUSION

A basal level of autophagy plays a critical role in the pro-survival response of frozen SSCs after thawing; herein, a new approach by which SSC cryoprotective efficiency can be improved was identified.

Cryoprotective Effect of Pentoxifylline on Spermatogonial Stem Cell During Transplantation into Azoospermic Torsion Mouse Model

Preserving the spermatogonial stem cells (SSCs) in long periods of time during the treatment of male infertility using stem cell banking systems and transplantation is an important issue. Therefore, this study was conducted to develop an optimal cryopreservation protocol for SSCs using 10 mM pentoxifylline (PTX) as an antioxidant in basal freezing medium. Testicular torsion-a mouse model for long-term infertility-was used to transplant fresh SSCs (n = 6), fresh SSCs treated with PTX (n = 6), cryopreserved SSCs with basal freezing medium (n = 6), and cryopreserved SSCs treated with PTX (n = 6). Eight weeks after germ cell transplantation, samples were assessed for proliferation, through evaluation of Ddx4 and Id4 markers, and differentiation via evaluation of C-Kit and Sycp3, Tnp1, Tnp2, and Prm1 markers. According to morphological and flow cytometry results, SSCs are able to form colonies and express Gfra1, Id4, α6-integrin, and β1-integrin markers. We found positive influence from PTX on proliferative and differentiative markers in SSCs transplanted to azoospermic mice. In the recipient testis, donor SSCs formed spermatogenic colonies and sperm. Respecting these data, adding pentoxifylline is a practical way to precisely cryopreserve germ cells enriched for SSCs in cryopreservation, and this procedure could become an efficient method to restore fertility in a clinical setup. However, more studies are needed to ensure its safety in the long term.

Influence of adding zeolite loaded with different charges to semen extender on sperm quality in rabbits after cryopreservation

The aim of the present study was to investigate the effect of supplementing rabbit semen extender with zeolite loaded with different charges (Z⁺ or Z^-, Z^±) on sperm cryopreservation. Semen was collected from six healthy, fertile New Zealand rabbit bucks using an artificial vagina. The collected ejaculates were pooled and diluted with a tris-yolk fructose (TYF) extender supplemented with Z^± (+16, +12, +8, -16, -12, and -8) at a concentration of 1% for a final sperm concentration of 25 × 10⁶ sperm cells/mL. The diluted semen samples were then cryopreserved in 0.25 mL straws and stored in liquid nitrogen for 1 month. To evaluate sperm quality, we examined sperm progressive motility, vitality, morphological abnormalities, and plasma membrane integrity. In addition, apoptotic rates were determined using flow cytometry and by examining sperm ultrastructure under a transmission electron microscope (TEM). Moreover, total antioxidant capacity and markers of lipid peroxidation were measured in the extender after thawing. Addition of Z^± had a positive effect on progressive motility, vitality, and membrane integrity after an equilibration period and post-thawing as compared with the controls (P < 0.05). Z^± supplementation, particularly with a strong negative charge, also decreased the percentages of apoptotic and necrotic sperm cells compared to controls (P < 0.05), as shown both by flow cytometry and TEM. This was not associated with any marked effects on the oxidative biomarkers in the extender. In conclusion, addition of Z^± to semen extender improved post-thawing sperm quality by improving sperm characteristics, decreasing apoptosis, and minimizing sperm damage during cryopreservation.

Trehalose can effectively protect sheep epididymis epithelial cells from oxidative stress

Trehalose, a naturally nontoxic disaccharide that does not exist in mammals, stabilizes cell membrane integrity under oxidative stress conditions, the mechanism of which is still unclear. Here, we analyzed the effects of trehalose on sheep epididymis epithelial cell (EEC) proliferation and its possible mechanisms. To study the effect of trehalose on EECs, EECs were isolated from testes of 12-month-old sheep; cell counting kit-8 (CCK-8) was used to measure the growth of the cells. Cell proliferation was evaluated by assaying cell cycle and apoptosis, and RT-PCR was utilized to identify the epididymal molecular markers glutathione peroxidase 5 (GPX5) and androgen receptor (AR). Next, reactive oxygen species (ROS) content was evaluated by a dichloro-dihydro-fluorescein diacetate (DCFH-DA) probe. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities were evaluated by enzyme chemistry methods, and GPX5 expression was evaluated by qRT-PCR and enzyme-linked immunosorbent assay (ELISA). The results showed that 100 mM trehalose significantly improved the proliferation potential of EECs, in which the cells could be serially passaged 14 times with continued normal GPX5 and AR marker gene expression in vitro. The trehalose can increase significantly a proportion of EECs in S phase (P<0.01) and decrease significantly the apoptotic rate of EECs (P<0.01) compared to the control. Moreover, the trehalose decreased ROS significantly (P<0.01) and increased CAT (P<0.01) and GSH-Px (P<0.05) activities significantly in EECs. GPX5 mRNA and protein expression were also significantly upregulated in trehalose-treated EECs (P<0.05 and P<0.01 respectively). Our study suggested that exogenous trehalose exhibited antioxidant activity through increasing the activities of CAT, GSH-Px, and the expression level of GPX5 and could be employed to maintain vitality of sheep EECs during long-term in vitro culture.

Photobiomodulation as an antioxidant substitute in post-thawing trauma of human stem cells from the apical papilla

Cryopreservation, the most common method of preserving stem cells, requires post-processing because it produces trauma to the cells. Post-thawing trauma typically induces cell death, elevates reactive oxygen species (ROS) concentration, and lowers mitochondrial membrane potential (MMP). Although this trauma has been solved using antioxidants, we attempted to use photobiomodulation (PBM) instead of chemical treatment. We used a 950-nm near-infrared LED to create a PBM device and chose a pulsed-wave mode of 30 Hz and a 30% duty cycle. Near-infrared radiation (NIR) at 950 nm was effective in reducing cell death caused by hydrogen peroxide induced-oxidative stress. Cryodamage also leads to apoptosis of cells, which can be avoided by irradiation at 950 nm NIR. Irradiation as post-processing for cryopreservation had an antioxidant effect that reduced both cellular and mitochondrial ROS. It also increased mitochondrial mass and activated mitochondrial activity, resulting in increased MMP, ATP generation, and increased cytochrome c oxidase activity. In addition, NIR increased alkaline phosphatase (ALP) activity, a biomarker of differentiation. As a result, we identified that 950 nm NIR PBM solves cryodamage in human stem cells from the apical papilla, indicating its potential as an alternative to antioxidants for treatment of post-thawing trauma, and further estimated its mechanism.

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.

Antioxidant or Apoptosis Inhibitor Supplementation in Culture Media Improves Post-Thaw Recovery of Murine Spermatogonial Stem Cells

We postulated that supplementation of antioxidant or apoptosis inhibitor in post-thaw culture media of spermatogonial stem cells (SSCs) alleviates reactive oxygen species (ROS) generation and apoptosis. Our aim was to develop an effective culture media for improving post-thaw recovery of SSCs. To determine the efficacy of supplementation with hypotaurine (HTU), α-tocopherol (α-TCP), and Z-DEVD-FMK (ZDF), we assessed the relative proliferation rate and SSC functional activity and performed a ROS generation assay, apoptosis assay, and western blotting for determination of the Bax/Bcl-xL ratio, as well as immunocytochemistry and real-time quantitative polymerase chain reaction (RT-qPCR) for SSC characterization. The relative proliferation rates with HTU 400 μM (133.7 ± 3.2%), α-TCP 400 μM (158.9 ± 3.6%), and ZDF 200 μM (133.1 ± 7.6%) supplementation were higher than that in the DMSO control (100 ± 3.6%). ROS generation was reduced with α-TCP 400 μM (0.8-fold) supplementation in comparison with the control (1.0-fold). Early apoptosis and Bax/Bcl-xL were lower with α-TCP 400 μM (2.4 ± 0.4% and 0.5-fold) and ZDF 200 μM (1.8 ± 0.4% and 0.3-fold) supplementation in comparison with the control (5.3 ± 1.4% and 1.0-fold) with normal characterization and functional activity. Supplementation of post-thaw culture media with α-TCP 400 μM and ZDF 200 μM improved post-thaw recovery of frozen SSCs via protection from ROS generation and apoptosis after cryo-thawing.

Exposure to DMSO during infancy alters neurochemistry, social interactions, and brain morphology in long-evans rats

INTRODUCTION

Dimethyl sulfoxide (DMSO) is a widely used solvent to dissolve hydrophobic substances for clinical uses and experimental in vivo purposes. While usually regarded safe, our prior studies suggest changes to behavior following DMSO exposure. We therefore evaluated the effects of a five-day, short-term exposure to DMSO on postnatal infant rats (P6-10).

METHODS

DMSO was intraperitoneally injected for five days at 0.2, 2.0, and 4.0 ml/kg body mass. One cohort of animals was sacrificed 24 hr after DMSO exposure to analyze the neurometabolic changes in four brain regions (cortex, hippocampus, basal ganglia, and cerebellum) by hydrophilic interaction liquid chromatography. A second cohort of animals was used to analyze chronic alterations to behavior and pathological changes to glia and neuronal cells later in life (P21-P40).

RESULTS

164 metabolites, including key regulatory molecules (retinoic acid, orotic acid, adrenic acid, and hypotaurine), were found significantly altered by DMSO exposure in at least one of the brain regions at P11 (p < .05). Behavioral tests showed significant hypoactive behavior and decreased social habits to the 2.0 and 4.0 ml DMSO/kg groups (p < .01). Significant increases in number of microglia and astrocytes at P40 were observed in the 4.0 ml DMSO/kg group (at p < .015.) CONCLUSIONS: Despite short-term exposure at low, putatively nontoxic concentrations, DMSO led to changes in behavior and social preferences, chronic alterations in glial cells, and changes in essential regulatory brain metabolites. The chronic neurological effects of DMSO exposure reported here raise concerns about its neurotoxicity and consequent safety in human medical applications and clinical trials.

Inhibition of Caspase-8 Activity Improves Freezing Efficiency of Male Germline Stem Cells in Mice

Cryopreservation of male germline stem cells (GSCs) is an essential technique for their long-term preservation and utilization in various fields. However, the specific apoptosis pathways involved in cryoinjury during freezing remain unclear. Therefore, our study sought to identify the pathways involved in cryoinjury-induced apoptosis and thereby to improve freezing efficiency during GSC cryopreservation through the creation of a specific molecular-based cryoprotectant. The activities of caspase-8, caspase-9, caspase-3, and caspase-7 were assessed by Western blot analyses to determine the role of specific apoptosis pathways in GSC cryoinjury. Specifically, the role of a specific caspase was identified by recovery rate, relative proliferation rate, Annexin V/propidium iodide co-staining, and caspase activity using its inhibitor and activator. Moreover, the safety of the cryoprotectant was assessed by immunofluorescence and quantitative real-time polymerase chain reaction (qRT-PCR). Furthermore, the efficacy of the molecular-based cryoprotectant was assessed using frozen cells in the presence of dimethyl sulfoxide (DMSO) (control), trehalose, a caspase-8 inhibitor Z-IETD-FMK [ZIF], or a mixture of the aforementioned compounds, after which the changes in Src signaling were measured. Our results demonstrated that caspase-8 plays a major role in cryoinjury-induced apoptosis and therefore its inhibition improves freezing efficiency. Specifically, a significantly higher relative proliferation rate was observed in the Z-IETD-FMK 0.01 μM-treated cells than in the DMSO control (100% ± 6.2% vs. 189.8% ± 9.5%), with decreases in both early apoptosis (16.6% ± 2.2% vs. 7.5% ± 1.0%) and caspase-8 activity (1.0-fold vs. 0.4-fold). The relative proliferation rate was significantly higher in the cryoprotectant mixture (246.0% ± 12.2%) than other individual treatment groups (trehalose 200 mM, 189.8% ± 9.5%; Z-IETD-FMK 0.01 μM, 189.7% ± 2.2%) with no significant differences in Src signaling. Therefore, our findings provide novel insights into the development of freezing protocols to enhance GSC freezing efficiency, thereby facilitating the wider adoption of GSCs in the livestock industry and/or clinical trials.

Effect of miR-30a-5p on Apoptosis, Colonization, and Oxidative Stress Variables in Frozen-Thawed Neonatal Mice Spermatogonial Stem Cells

Cryopreservation of spermatogonial stem cells (SSCs) is a useful method for fertility preservation in preadolescent children suffering from cancer. However, SSCs may become damaged during cryopreservation due to the generation of reactive oxygen species (ROS). For this reason, various antioxidant agents have been used to protect SSCs from cryopreservation-induced damages. Recently, it has been reported that miR-30a-5p has antiapoptotic and antioxidant activity. The aim of this study was to assess the antiapoptotic and antioxidant effects of miR-30a-5p mimics in frozen-thawed SSCs. To this end, SSCs were isolated from male BALB/C mice (3-6 days old) and cultivated for 14 days. After the detection of optimum concentration, a miR-30a-5p mimic or miR-30a-5p inhibitor with Lipofectamine was transfected into SSCs and, finally, the cell groups were frozen for 1 week. After thawing, different properties, including cell viability (using MTT), colonization of SSCs (number and diameter of colonies), ROS generation (using DCFH-DA assay), levels of malondialdehyde (MDA) and superoxide dismutase (SOD), and gene expression of Bcl-2 and BAXBax (using quantitative real-time PCR), were investigated. The transfection of SSCs with miR-30a-5p mimics before the freezing-thawing process significantly increased the viability, number, and diameter of SSCs colonies. Also, the miR-30a-5p mimic decreased the levels of ROS production and MDA, but it increased the SOD levels. Moreover, the miR-30a-5p mimic decreased BAX and increased Bcl-2 expression in frozen-thawed SSCs. The transfection of SSCs with the miR-30a-5p mimic can increase cell viability and antioxidant defense, and it can decrease apoptosis during the freezing-thawing process. If SSC is able to produce spermatozoa after the transfection of miR-30a-5p and the freezing-thawing process, it can be suggested as a promising strategy for the cryopreservation of SSCs in prepubertal boys suffering from cancer.

Cryopreserved skin epithelial cell sheet combined with acellular amniotic membrane as an off-the-shelf scaffold for urethral regeneration

BACKGROUND

Autologous tissue transplantation for urethral repair is often limited and causes donor site complications. Here, a cryopreserved rabbit skin epithelial cell sheet (SEC) combined with an acellular amniotic membrane (AM) was used to repair rabbit urethral defects.

METHODS

Abdominal skin was collected from 4-week-old New Zealand rabbits, and primary epithelial cells were extracted and cultured to form a cell sheet. Fresh SEC-AMs were constructed and cryopreserved. A cryopreservation system including optimized medium, two-pump perfusion, a programmed freezer and liquid nitrogen storage was established. Cell viability, mechanical strength, electron microscopy, and histological staining were performed in vitro after 1 month. Next, the sheets were transplanted subcutaneously for 2 weeks, and the graft was used to repair the rabbit urethral defect. Urinary function was measured and samples were collected for histological staining after 1 month.

RESULTS

We confirmed that cryopreservation damage of SECs was reduced by composition with acellular AMs in terms of high cell activity. The SEC mechanical strength was also enhanced by AMs, which was convenient for the operation. In in vivo experiments, we transplanted sheets into the groin area for two weeks and found that cryopreservation reduced inflammatory cell infiltration and significantly improved vascular density. In the urethral repair experiment, the near-normal passive urine flow rate, smooth mucosa of the gross specimen, intact epithelialization and abundant neovascularization were confirmed in the cryopreserved-SEC-AM group compared with the other groups.

CONCLUSIONS

Cryopreserved SEC-AMs demonstrated similar outcomes of rabbit urethral defect repair as fresh SEC-AMs, showing good clinical application prospects.

Mitochondrial Dysfunction and Oxidative Stress Caused by Cryopreservation in Reproductive Cells

Mitochondria, fundamental organelles in cell metabolism, and ATP synthesis are responsible for generating reactive oxygen species (ROS), calcium homeostasis, and cell death. Mitochondria produce most ROS, and when levels exceed the antioxidant defenses, oxidative stress (OS) is generated. These changes may eventually impair the electron transport chain, resulting in decreased ATP synthesis, increased ROS production, altered mitochondrial membrane permeability, and disruption of calcium homeostasis. Mitochondria play a key role in the gamete competence to facilitate normal embryo development. However, iatrogenic factors in assisted reproductive technologies (ART) may affect their functional competence, leading to an abnormal reproductive outcome. Cryopreservation, a fundamental technology in ART, may compromise mitochondrial function leading to elevated intracellular OS that decreases sperm and oocytes' competence and the dynamics of fertilization and embryo development. This article aims to review the role played by mitochondria and ROS in sperm and oocyte function and the close, biunivocal relationships between mitochondrial damage and ROS generation during cryopreservation of gametes and gonadal tissues in different species. Based on current literature, we propose tentative hypothesis of mechanisms involved in cryopreservation-associated mitochondrial dysfunction in gametes, and discuss the role played by antioxidants and other agents to retain the competence of cryopreserved reproductive cells and tissues.

Biobanked human foreskin epithelial cell sheets reduce inflammation and promote wound healing in a nude mouse model

BACKGROUND

Human epithelial cell sheets (ECSs) are used to clinically treat epithelial conditions such as burns, corneal blindness, middle ear cholesteatoma and vitiligo. As a widely used material in clinic, there is little information on the biobanking of ECSs and its repair effect after storage.

RESULTS

Two methods for biobanking foreskin ECSs were compared in a short term (7 days): 4-degree storage and programmed cryopreservation. Cell sheet integrity, viability, apoptosis, immunogenicity, mechanical properties and function were evaluated. In vivo, ECSs were directly transplanted to skin defect models and histological examination was performed at 1 week postoperatively. We successfully extracted human foreskin-derived primary epithelial cells and fabricated them into ECSs. Compared with 4-degree storage, programmed cryopreservation preserved the ECS structural integrity, enhanced the mechanical properties, decreased HLA-I expression, and increased cell viability and survival. An increased proportion of melanocytes with proliferative capacity remained in the cryopreserved sheets, and the undifferentiated epithelial cells were comparable to those of the fresh sheets. In vivo, cryopreserved ECSs could reduce inflammatory cell infiltration and promote connective tissue remodeling, epithelial cell proliferation and vascular regeneration.

CONCLUSIONS

Programmed cryopreservation of ECSs was superior and more feasible than 4-degree storage and the cryopreserved ECSs achieved satisfying skin wound healing in vivo. We anticipate that the off-the-shelf ECSs could be quickly used, such as, to repair human epithelial defect in future.

Current and Future Perspectives for the Cryopreservation of Cord Blood Stem Cells

Hematopoietic stem cell (HSC) transplantation is a well-established procedure for the treatment of many blood related malignancies and disorders. Before transplantation, HSC are collected and cryopreserved until use. The method of cryopreservation should preserve both the number and function of HSC and downstream progenitors responsible for long- and short-term engraftment, respectively. This is especially critical for cord blood grafts, since the cell number associated with this stem cell source is often limiting. Loss of function in cryopreserved cells occurs following cryoinjuries due to osmotic shock, dehydration, solution effects and mechanical damage from ice recrystallization during freezing and thawing. However, cryoinjuries can be reduced by 2 mitigation strategies; the use of cryoprotectants (CPAs) and use of control rate cooling. Currently, slow cooling is the most common method used for the cryopreservation of HSC graft. Moreover, dimethyl-sulfoxide (DMSO) and dextran are popular intracellular and extracellular CPAs used for HSC grafts, respectively. Yet, DMSO is toxic to cells and can cause significant side effects in stem cells' recipients. However, new CPAs and strategies are emerging that may soon replace DMSO. The aim of this review is to summarise key concepts in cryobiology and recent advances in the field of HSC cryobiology. Other important issues that need to be considered are also discussed such as transient warming events and thawing of HSC grafts.

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.

Effect of serum replacement on murine spermatogonial stem cell cryopreservation

Cryopreservation of spermatogonial stem cells (SSCs) is a necessity to preserve the genetic information of valuable livestock herds and to produce transgenic animals. However, serum, a key component that allows efficient cryopreservation, has many limitations attributed to its undefined composition, inter-batch variations, and contamination potential. Therefore, we aimed to establish a method for serum-free cryopreservation of SSCs. To evaluate the cryopreservation efficiency of serum replacements, we assessed the recovery rate, relative proliferation potential, proliferation capacity, and apoptosis capacity. SSCs were characterized, and their functional activity was determined through immunofluorescence, RT-qPCR, and spermatogonial transplantation. The efficiency of each serum replacement was compared to that of the negative control (10% DMSO in DPBS) and positive control (10% DMSO and 40% FBS in DPBS). Our results indicated that cryopreservation with 5% human serum albumin (rHSA) exhibited a higher relative proliferation potential (274.0 ± 13.4%) than with DMSO control (100 ± 8.6%), with no significant difference from the 40% FBS (190.0 ± 20.1%). Moreover, early apoptosis also significantly decreased to a greater extent with 5% rHSA (5.1 ± 0.7%) than with DMSO control (12.9 ± 0.8%) and was at a level comparable to the 40% FBS (4.9 ± 0.8%). In addition, the SSCs cryopreserved with 5% rHSA exhibited normal self-renewal and differentiation abilities. In conclusion, 5% rHSA is a potential serum replacement for SSC cryopreservation, with properties comparable to that of serum. These results would contribute to the application of SSCs in improving livestock and in future clinical trials for human infertility treatment.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

Effective cryopreservation protocol for preservation of male primate (Macaca fascicularis) prepubertal fertility

RESEARCH QUESTION

Can specimen types (cells versus tissues) and additive cryoprotectant agents contribute to efficient cryopreservation of primate spermatogonial stem cells (SSC)?

DESIGN

Testicular tissues or cells from four prepubertal monkeys were used in this study. The freezing efficacy of testicular tissue was compared with cell suspensions using conventional freezing media (1.4 mol/l dimethyl sulfoxide [DMSO]) and the efficacy of cryoprotectant additives (1.4 mol/l DMSO combined with trehalose 200 mmol/l, hypotaurine 14 mmol/l, necrostatin-1 50 µmol/l or melatonin 100 µmol/l) was evaluated in testicular tissue freezing.

RESULTS

The survival rate (46.0 ± 4.8% versus 33.7 ± 6.0%; P = 0.0286) and number of recovered cells (5.0 ± 1.5 × 10⁶ cells/g versus 0.7 ± 0.8 × 10⁶ cells/g; P = 0.0286) were significantly higher in frozen tissues than in frozen cell suspensions. After tissue freezing, a higher number of recovered PGP9.5⁺ cells were observed with 200 mmol/l trehalose treatment than in DMSO controls (2.4 ± 0.6 × 10⁶ cells/g versus 1.1 ± 0.3 × 10⁶ cells/g; P = 0.0164). Normal establishment of donor-derived colony was observed in SSC after tissue freezing with 200 mmol/l trehalose.

CONCLUSIONS

Testicular tissue freezing is more effective than single cell suspension freezing for higher recovery of undifferentiated spermatogonia. Moreover, it was verified that slow freezing using 200 mmol/l trehalose, 1.4 mol/l DMSO and 10% KnockOut™ Serum Replacement in Dulbecco's phosphate-buffered saline is an effective cryopreservation protocol for primate testicular tissue.

Necrostatin-1 improves the cryopreservation efficiency of murine spermatogonial stem cells via suppression of necroptosis and apoptosis

Cryopreservation of spermatogonial stem cells (SSCs) is important to preserve the lineages of valuable livestock and produce transgenic animals. Although interest in molecular-based cryopreservation methods have been increasing to improve their efficiency, the issue of necroptosis has not yet been considered. Therefore, the purpose of this study was to understand the role of necroptosis using necrostatin-1 (Nec-1), necroptosis inhibitor, in SSC cryopreservation, and to investigate the potential application of Nec-1 as a cryoprotectant. To determine the cryopreservation efficiency of Nec-1, we assessed recovery rate, proliferation potential, cellular membrane damage, RIP1 protein expression, apoptosis, and its mechanism. Stable characterization and functional activity of SSCs was determined via immunofluorescence, RT-qPCR, and in vivo transplantation of SSCs. Our results showed a higher proliferation potential in 50 μM Nec-1 (146.5 ± 16.8%) than in DMSO controls (100.0 ± 3.4%). Furthermore, the cryoprotective effects of Nec-1 were verified by a decrease in RIP1 expression (3.1 ± 0.2-fold vs. 1.3 ± 0.3-fold) and in early apoptosis (4.3 ± 0.8% vs. 2.6 ± 0.1%) compared to DMSO controls. Normal functional activity was observed in the SSCs after cryopreservation with 50 μM Nec-1. In conclusion, necroptosis could be a cause of cryoinjury, and their inhibitor may serve as potential effective cryoprotectant. This study will contribute to establish a molecular-based cryopreservation method, and thereby expanding the use of SSCs into the domestic livestock industry as well as for clinical applications.

Knockout serum replacement is an efficient serum substitute for cryopreservation of human spermatozoa

The freeze-thaw procedure causes irreversible structural and functional changes in human spermatozoa. In order to decrease the detrimental effects of cryopreservation and improve the quality of post-thawed spermatozoa, the constituents of the freezing solution attracted considerable attention. In this study, for the first time, we evaluated the efficacy of knockout serum replacement (KSR) as a substitute for human serum albumin (HSA) for cryopreservation of human spermatozoa. Twenty semen samples were collected from normozoospermic men and divided them into five equal groups. One of the aliquots was diluted with glycerol-based medium as a control group (CON). The other four aliquots were diluted with the sucrose solution containing 5% HSA (H5), 10% HSA (H10), 5% KSR (K5), and 10% KSR (K10). The diluted samples were frozen and preserved in liquid nitrogen. Post thawed sperm parameters including motion characteristics, viability, membrane integrity, mitochondrial activity, acrosome integrity and DNA intactness in all of the sucrose-based groups were comparable with glycerol-based medium. The replacement of HSA by 10% KSR in the freezing medium resulted in significantly higher post-thawed viability, acrosome integrity and DNA intactness compared with other sucrose-based groups. In conclusion, the addition of 10% KSR to the sucrose-based freezing solution improves the quality of post-thawed human spermatozoa and may have potential to develop chemically defined freezing medium.

Trehalose protects testicular tissue of dairy goat upon cryopreservation

The aim of this study was to investigate whether the addition of trehalose to cryomedia reduces cellular damage and improves gene expression in cryopreserved dairy goat testicular tissues. Testicular tissues were cryopreserved in cryomedia without or with trehalose at a concentration of 5%, 10%, 15%, 20% or 25%. Cryopreserved testicular tissues were analysed for TUNEL-positive cell number, expression of BAX, BCL-2, CREM, BOULE and HSP70-2. Isolated Leydig cells from cryopreserved tissue were cultured, and spent medium was evaluated for testosterone level. The results showed that though the TUNEL-positive cell number increased in cryopreserved testicular tissues, the presence of trehalose reduced apoptotic cell number significantly. Quantitative real-time polymerase chain reaction results showed that although the expression of BAX was upregulated following cryopreservation, the presence of trehalose downregulates it in cryopreserved testicular tissues. Expression of BCL-2, CREM, BOULE and HSP70-2 was downregulated following cryopreservation but the presence of trehalose significantly upregulated their expression in cryopreserved testicular tissues. Leydig cells isolated from testicular tissues cryopreserved with trehalose produced higher testosterone than the one without it (control). These results suggest that trehalose has a protective role in cryopreservation of dairy goat testicular tissue, and the most suitable trehalose concentration for cryopreservation is 15%.

The roles of reactive oxygen species and antioxidants in cryopreservation

Cryopreservation has facilitated advancement of biological research by allowing the storage of cells over prolonged periods of time. While cryopreservation at extremely low temperatures would render cells metabolically inactive, cells suffer insults during the freezing and thawing process. Among such insults, the generation of supra-physiological levels of reactive oxygen species (ROS) could impair cellular functions and survival. Antioxidants are potential additives that were reported to partially or completely reverse freeze-thaw stress-associated impairments. This review aims to discuss the potential sources of cryopreservation-induced ROS and the effectiveness of antioxidant administration when used individually or in combination.

Influence of Different Combinations of Permeable and Nonpermeable Cryoprotectants on the Freezing Capacity of Equine Sperm

This study was aimed to evaluate the effect of permeable cryoprotectants in combination with trehalose or sucrose on the freezing capacity of stallion sperm. For this purpose, the ejaculates (n = 24) were collected from four healthy mature Turkmen stallions. The ejaculates were pooled and diluted with one of the extenders containing a combination of 5% of permeating (dimethylacetamide [DMA]; dimethylformamide [DMF] or glycerol) and 50 mM of nonpermeating cryoprotectant agents (CPAs) (sucrose or trehalose) to a final concentration of 200 × 10⁶ spermatozoa/mL. The extended samples were cryopreserved and thawed using a standard protocol. The samples were evaluated for motion kinetics, morphological abnormalities, plasma membrane functionality (PMF), viability, and lipid peroxidation. The results showed that the sperm cryopreserved in extender containing DMA produced higher (P ≤ .05) total motility, straightness, straight line velocity, curvilinear velocity, and lower (P ≤ .05) lipid peroxidation (malondialdehyde [MDA] concentration) compared with DMF and glycerol groups. Overall, both DMA and DMF have shown higher (P ≤ .05) sperm motion kinetics, viability, PMF, and lower (P ≤ .05) morphological abnormalities and MDA concentration compared with the glycerol. However, except morphological abnormalities, all of the other parameters did not differ between trehalose and sucrose. Likewise, there was no interaction between permeating and nonpermeating CPAs (P ≥ .05) except in terms of sperm abnormalities (P ≤ .05). In conclusion, the use of DMA or DMF as alternative CPAs of glycerol could be more effective for successful cryopreservation of stallion sperm. The nonsignificant interaction between permeating and nonpermeating CPAs for most of the post-thaw sperm parameters negates possible synergism among these compounds.

Hydrogel Cryopreservation System: An Effective Method for Cell Storage

At present, living cells are widely used in cell transplantation and tissue engineering. Many efforts have been made aiming towards the use of a large number of living cells with high activity and integrated functionality. Currently, cryopreservation has become well-established and is effective for the long-term storage of cells. However, it is still a major challenge to inhibit cell damage, such as from solution injury, ice injury, recrystallization and osmotic injury during the thawing process, and the cytotoxicity of cryoprotectants. Hence, this review focused on different novel gel cryopreservation systems. Natural polymer hydrogel cryopreservation, the synthetic polymer hydrogel cryopreservation system and the supramolecular hydrogel cryopreservation system were presented, respectively. Due to the unique three-dimensional network structure of the hydrogel, these hydrogel cryopreservation systems have the advantages of excellent biocompatibility for natural polymer hydrogel cryopreservation systems, designability for synthetic polymer hydrogel cryopreservation systems, and versatility for supramolecular hydrogel cryopreservation systems. To some extent, the different hydrogel cryopreservation methods can confine ice crystal growth and decrease the change rates of osmotic shock in cell encapsulation systems. It is notable that the cryopreservation of complex cells and tissues is demanded in future clinical research and therapy, and depends on the linkage of different methods.

In vitro antiapoptotic effects of the calligonum extract on spermatogonial stem cells

BACKGROUND

Spermatogonial stem cells are the foundation of spermatogenesis and male fertility. So, their maintenance and culture are very important.

OBJECTIVE

In this study, we assessed protective effects of the Calligonum on in vitro viability and apoptotic and antiapoptotic genes expression of spermatogonial stem cells.

MATERIALS AND METHODS

After 24 hr of culture, the spermatogonial stem cells were treated with 30 μM dose of H₂O₂ and then 10 μg/ml the Calligonum extract was added for 3 wks. Viability was assessed by Trypan blue, apoptosis using PI-Annexin and finally Bax, Bcl-2 and P53 genes expression by Real-Time Polymerase chain reaction.

RESULTS

After 3 wk of treatment, viability in the Calligonum extract+H₂O₂ group was significantly higher than H₂O₂ group alone (p=0.001). In the Calligonum extract+H₂O₂ group, apoptosis, as well as expression of apoptotic genes (Bax and P53), was significantly lower than the group treated with H₂O₂ alone.

CONCLUSION

The results of this study showed that 30 μM H₂O₂ increased apoptosis but decreased viability in spermatogonial stem cells. Calligonum has antioxidant properties that can reduce apoptosis, Bax and P53 expression and increase the viability and Bcl-2 expression.

What is the best protocol to cryopreserve immature mouse testicular cell suspensions?

RESEARCH QUESTION

From a clinical perspective, which parameters grant optimal cryopreservation of mouse testicular cell suspensions?

DESIGN

We studied the effect of different cryopreservation rates, the addition of sugars, different vessels and the addition of an apoptotic inhibitor on the efficiency of testicular cell suspension cryopreservation. After thawing and warming, testicular cell suspensions were transplanted to recipient mice for further functional assay. After selecting the optimal cryopreservation procedure, a second experiment compared the transplantation efficiency between the selected freezing protocol and fresh testicular cell suspensions.

RESULTS

Multiple- and single-step freezing did not differ significantly in terms of recovered viable cells (RVC) (33 ± 28% and 38 ± 25%). The addition of sucrose did not result in a higher RVC (33 ± 20%). Cells frozen in vials recovered better than those frozen in straws (52 ± 20% versus 33 ± 20%; P = 0.0049). The inclusion of an apoptosis inhibitor (z-VAD[Oe]-FMK) significantly increased the RVC after thawing (61 ± 18% versus 50 ± 17%; P = 0.0480). When comparing the optimal cryopreservation procedure with fresh testicular cell suspensions, a lower RVC (63 ± 11% versus 92 ± 4%; P < 0.0001) and number of donor-derived spermatogonial stem cell colonies per testis (34.04 ± 2.34 versus 16.78 ± 7.76; P = 0.0051) were observed.

CONCLUSION

Upon freeze-thawing or vitrification-warming, and assessment of donor-derived spermatogenesis after transplantation, Dulbecco's modified Eagle's medium supplemented with 1.5M dimethyl-sulphoxide, 10% fetal calf serum and 60 µM of Z-VAD-(OMe)-FMK in vials at a freezing rate of -1°C/min was optimal.

Redox Homeostasis Plays Important Roles in the Maintenance of the Drosophila Testis Germline Stem Cells

Oxidative stress influences stem cell behavior by promoting the differentiation, proliferation, or apoptosis of stem cells. Thus, characterizing the effects of reactive oxygen species (ROS) on stem cell behavior provides insights into the significance of redox homeostasis in stem cell-associated diseases and efficient stem cell expansion for cellular therapies. We utilized the Drosophila testis as an in vivo model to examine the effects of ROS on germline stem cell (GSC) maintenance. High levels of ROS induced by alteration in Keap1/Nrf2 activity decreased GSC number by promoting precocious GSC differentiation. Notably, high ROS enhanced the transcription of the EGFR ligand spitz and the expression of phospho-Erk1/2, suggesting that high ROS-mediated GSC differentiation is through EGFR signaling. By contrast, testes with low ROS caused by Keap1 inhibition or antioxidant treatment showed an overgrowth of GSC-like cells. These findings suggest that redox homeostasis regulated by Keap1/Nrf2 signaling plays important roles in GSC maintenance.

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Germline stem cell homeostasis in the Drosophila testis is susceptible to ROS levels

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Oxidative stress decreases germline stem cell number by promoting differentiation

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EGFR signaling is involved in precocious GSC differentiation caused by high ROS levels

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Low levels of ROS can promote a growth of germline stem cells

Cryopreservation and its clinical applications

Cryopreservation is a process that preserves organelles, cells, tissues, or any other biological constructs by cooling the samples to very low temperatures. The responses of living cells to ice formation are of theoretical interest and practical relevance. Stem cells and other viable tissues, which have great potential for use in basic research as well as for many medical applications, cannot be stored with simple cooling or freezing for a long time because ice crystal formation, osmotic shock, and membrane damage during freezing and thawing will cause cell death. The successful cryopreservation of cells and tissues has been gradually increasing in recent years, with the use of cryoprotective agents and temperature control equipment. Continuous understanding of the physical and chemical properties that occur in the freezing and thawing cycle will be necessary for the successful cryopreservation of cells or tissues and their clinical applications. In this review, we briefly address representative cryopreservation processes, such as slow freezing and vitrification, and the available cryoprotective agents. In addition, some adverse effects of cryopreservation are mentioned.