Stemness of spermatogonial stem cells encapsulated in alginate hydrogel during cryopreservation

Hydrogel encapsulation facilitates a low-concentration cryoprotectant for cryopreservation of mouse testicular tissue

Cryopreserved testicular tissue offers a promising method to restore fertility in male infertility patients. Current protocols rely on high concentrations of penetrating cryoprotectants (pCPAs), such as dimethyl sulfoxide (DMSO), which necessitating complex washing procedures and posing risks of toxicity. Hydrogel encapsulation presents a non-toxic alternative for cellular cryopreservation. This study investigates the effects of various types, concentrations, and thicknesses of hydrogel encapsulation on the cryopreservation of mouse testicular tissue. Testicular tissues loaded with varying concentrations of DMSO were encapsulated in alginate or gelatin-methacryloyl (GelMA) hydrogels. We evaluated hydrogels as potential CPAs to reduce pCPA concentrations and determine optimal combinations for cryopreservation. Post-cryopreservation, tissues were cultured using organ culture methods to assess spermatogenesis progression. Cryomicroscopy and differential scanning calorimetry (DSC) were used to examine ice crystal formation, melting enthalpy, and non-freezing water content in different hydrogels during cooling. Results indicate that 3 % alginate or 5 % GelMA hydrogel with thin encapsulation optimally preserves mouse testicular tissue. Using 20 % DMSO in 5 % GelMA thin encapsulation showed comparable apoptosis rates, improved morphology, higher mitochondrial activity, and enhanced antioxidant capacity compared to conventional 30 % DMSO without encapsulation. This suggests that hydrogel encapsulation reduces pCPA concentration by 10 %, thereby mitigating toxic damage. Hydrogel encapsulation can reduce basement membrane shrinkage of testicular tissue during cryopreservation. Moreover, frozen tissues remained viable with preserved germ cells after being cultured for one week on alginate methacryloyl (AlgMA) hydrogel using the gas-liquid interphase method. Cryomicroscopy and DSC studies confirmed the hydrogel's ability to inhibit ice crystal growth. In conclusion, this study introduces novel strategies for male fertility preservation and advances cryopreservation technology for clinical applications in assisted reproduction.

Controlled hydrogel-based encapsulation of macrophages determines cell survival and functionality upon cryopreservation

The development of novel cell-based therapies has increased the necessity to improve the long-term storage of cells. The current method of cryopreservation is far from optimal, causing ice-associated mechanical and osmotic damage to sensitive cells. Cell encapsulation is emerging as a new strategy to overcome those current limitations; however, few data are applicable to slow freezing, with conflicting results and multiple experimental conditions. The objective of this research work was to evaluate the impact of capsule size and encapsulation method on cell survival and functionality after a conventional freezing protocol. To this end, cells were encapsulated in alginate beads of different sizes, spanning the range of 200-2000 µm thanks to multiple extrusion techniques and conditions, and further cryopreserved using a slow cooling rate (-1°C/min) and 10 % DMSO as cryoprotectant. Our data show that there is a strong correlation between bead size and cell survival after a slow cooling cryopreservation process, with cell viabilities ranging from 7 to 70 % depending on the capsule size, with the smallest capsules (230 µm) achieving the highest level of survival. The obtained results indicate that the beads' diameter, rather than their morphology or the technique used, plays a significant role in the post-thawing cell survival and functionality. These results show that a fine control of cell encapsulation in alginate hydrogels is required when it comes to overcoming the current limitations of long-term preservation techniques by slow cooling.

The Effect of Chitosan/Alginate/Graphene Oxide Nanocomposites on Proliferation of Mouse Spermatogonial Stem Cells

Male survivors of childhood cancer have been known to be afflicted with azoospermia. To combat this, the isolation and purification of spermatogonial stem cells (SSCs) are crucial. Implementing scaffolds that emulate the extracellular matrix environment is vital for promoting the regeneration and proliferation of SSCs. This research aimed to evaluate the efficiency of nanocomposite scaffolds based on alginate, chitosan, and graphene oxide (GO) in facilitating SSCs proliferation. To analyze the cytotoxicity of the scaffolds, an MTT assay was conducted at 1, 3, and 7 days, and the sample containing 30 µg/mL of GO (ALGCS/GO30) exhibited the most favorable results, indicating its optimal performance. The identity of the cells was confirmed using flow cytometry with C-Kit and GFRα1 markers. The scaffolds were subjected to various analyses to characterize their properties. FTIR was employed to assess the chemical structure, XRD to examine crystallinity, and SEM to visualize the morphology of the scaffolds. To evaluate the proliferation of SSCs, qRT-PCR was used. The study's results demonstrated that the ALGCS/GO30 nanocomposite scaffold exhibited biocompatibility and facilitated the attachment and proliferation of SSCs. Notably, the scaffold displayed a significant increase in proliferation markers compared to the control group, indicating its ability to support SSC growth. The expression level of the PLZF protein was assessed using the Immunocytochemistry method. The observations confirmed the qRT-PCR results, which indicated that the nanocomposite scaffolds had higher levels of PLZF protein expression than scaffolds without GO. The biocompatible ALGCS/GO30 is a promising alternative for promoting SSC proliferation in in vitro applications.

Advances of three-dimensional (3D) culture systems for in vitro spermatogenesis

The loss of germ cells and spermatogenic failure in non-obstructive azoospermia are believed to be the main causes of male infertility. Laboratory studies have used in vitro testicular models and different 3-dimensional (3D) culture systems for preservation, proliferation and differentiation of spermatogonial stem cells (SSCs) in recent decades. The establishment of testis-like structures would facilitate the study of drug and toxicity screening, pathological mechanisms and in vitro differentiation of SSCs which resulted in possible treatment of male infertility. The different culture systems using cellular aggregation with self-assembling capability, the use of different natural and synthetic biomaterials and various methods for scaffold fabrication provided a suitable 3D niche for testicular cells development. Recently, 3D culture models have noticeably used in research for their architectural and functional similarities to native microenvironment. In this review article, we briefly investigated the recent 3D culture systems that provided a suitable platform for male fertility preservation through organ culture of testis fragments, proliferation and differentiation of SSCs.

Biomaterials for Testicular Bioengineering: How far have we come and where do we have to go?

Traditional therapeutic interventions aim to restore male fertile potential or preserve sperm viability in severe cases, such as semen cryopreservation, testicular tissue, germ cell transplantation and testicular graft. However, these techniques demonstrate several methodological, clinical, and biological limitations, that impact in their results. In this scenario, reproductive medicine has sought biotechnological alternatives applied for infertility treatment, or to improve gamete preservation and thus increase reproductive rates in vitro and in vivo. One of the main approaches employed is the biomimetic testicular tissue reconstruction, which uses tissue-engineering principles and methodologies. This strategy pursues to mimic the testicular microenvironment, simulating physiological conditions. Such approach allows male gametes maintenance in culture or produce viable grafts that can be transplanted and restore reproductive functions. In this context, the application of several biomaterials have been proposed to be used in artificial biological systems. From synthetic polymers to decellularized matrixes, each biomaterial has advantages and disadvantages regarding its application in cell culture and tissue reconstruction. Therefore, the present review aims to list the progress that has been made and the continued challenges facing testicular regenerative medicine and the preservation of male reproductive capacity, based on the development of tissue bioengineering approaches for testicular tissue microenvironment reconstruction.

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.

Solid surface vitrification of goat testicular cell suspension enriched for spermatogonial stem cells

This study reports solid surface vitrification (SSV) of goat testicular cell suspensions (TCS) enriched for spermatogonial stem cells (SSCs). The TCS was isolated from pre-pubertal goat testis by enzymatic digestion, enriched for SSCs by filtration and differential plating, and were vitrified-warmed by SSV. The study showed that SSV could successfully vitrify goat TCS although the percentage of live cells in the vitrified-warmed group was lower (74.8 ± 4.1%) than in non-vitrified control (80.6 ± 6.27%). The vitrified-warmed TCS formed putative SSC colonies upon their in vitro culture, but the colony size of vitrified-warmed cells (24.3 ± 1.8 μm) was smaller than those of non-vitrified warmed cells (58.4 ± 2.5 μm). Mitochondrial activity (0.40 vs. 0.38 A U.), population doubling time (33.45 ± 1.25 h vs. 31.86 ± 1.90 h), and the cell proliferation rate (0.72 ± 0.10 vs. 0.75 ± 0.11 per day) of total cells (including putative SSCs and other somatic cells) did not differ (p > 0.05) between control and SSV vitrified-warmed groups. However, during in vitro culture for 96 h, vitrified-warmed cells showed significantly lower (0.75 vs. 1.33 A U.; p < 0.05) mitochondrial activity than non-vitrified controls. The DCFDA assay showed that ROS activity was significantly (p < 0.05) higher in vitrified-warmed cells (52.8 ± 4.1 A U) than non-vitrified control cells (32.8 ± 2.1 AU). In conclusion, our results suggest that SSC-enriched goat TCS could be successfully cryopreserved by SSV. However, ROS-induced damages to cell cytoplasmic components reduce their cellular proliferation and require further improvement in the protocol. To the best of our knowledge, this study is the first report on the SSV of SSC-enriched goat TCS.

Use of alginate hydrogel to improve long-term 3D culture of spermatogonial stem cells: stemness gene expression and structural features

The quality and quantity of a spermatogonial stem-cell (SSC) culture can be measured in less time using a 3D culture in a scaffold. The present study investigated stemness gene expression and the morphological and structural characterization of SSCs encapsulated in alginate. SSCs were harvested from BALB/c neonatal mice testes through two-step mechanical and enzymatic digestion. The spermatogonial populations were separated using magnetic-activated cell sorting (MACS) using an anti-Thy1 antibody and c-Kit. The SSCs then were encapsulated in alginate hydrogel. After 2 months of SSC culturing, the alginate microbeads were extracted and stained to evaluate their histological properties. Real-time polymerase chain reaction (PCR) was performed to determine the stemness gene expression. Scanning electron microscopy (SEM) was performed to evaluate the SSC morphology, density and scaffold structure. The results showed that encapsulated SSCs had decreased expression of Oct4, Sox2 and Nanos2 genes, but the expression of Nanog, Bcl6b and Plzf genes was not significantly altered. Histological examination showed that SSCs with pale nuclei and numerous nucleolus formed colonies. SEM evaluation revealed that the alginate scaffold structure preserved the SSC morphology and density for more than 60 days. Cultivation of SSCs on alginate hydrogel can affect Oct4, Sox2 and Nanos2 expression.

Evaluation of co-cultured spermatogonial stem cells encapsulated in alginate hydrogel with Sertoli cells and their transplantation into azoospermic mice

An in vitro spermatogonial stem cell (SSC) culture can serve as an effective technique to study spermatogenesis and treatment for male infertility. In this research, we compared the effect of a three-dimensional alginate hydrogel with Sertoli cells in a 3D culture and co-cultured Sertoli cells. After harvest of SSCs from neonatal mice testes, the SSCs were divided into two groups: SSCs on a 3D alginate hydrogel with Sertoli cells and a co-culture of SSCs with Sertoli cells for 1 month. The samples were evaluated by quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays and bromodeoxyuridine (BrdU) tracing, haematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) staining after transplantation into an azoospermic testis mouse. The 3D group showed rapid cell proliferation and numerous colonies compared with the co-culture group. Molecular assessment showed significantly increased integrin alpha-6, integrin beta-1, Nanog, Plzf, Thy-1, Oct4 and Bcl2 expression levels in the 3D group and decreased expression levels of P53, Fas, and Bax. BrdU tracing, and H&E and PAS staining results indicated that the hydrogel alginate improved spermatogenesis after transplantation in vivo. This finding suggested that cultivation of SSCs on alginate hydrogel with Sertoli cells in a 3D culture can lead to efficient proliferation and maintenance of SSC stemness and enhance the efficiency of SSC transplantation.

Strategies for cryopreservation of testicular cells and tissues in cancer and genetic diseases

Cryopreservation of testicular cells and tissues is useful for the preservation and restoration of fertility in pre-pubertal males expecting gonadotoxic treatment for cancer and genetic diseases causing impaired spermatogenesis. A number of freezing and vitrification protocols have thus been tried and variable results have been reported in terms of cell viability spermatogenesis progression and the production of fertile spermatozoa. A few studies have also reported the production of live offspring from cryopreserved testicular stem cells and tissues in rodents but their replication in large animals and human have been lacking. Advancement in in vitro spermatogenesis system has improved the possibility of producing fertile spermatozoa from the cryopreserved testis and has reduced the dependency on transplantation. This review provides an update on various cryopreservation strategies for fertility preservation in males expecting gonadotoxic treatment. It also discusses various methods of assessing and ameliorating cryoinjuries. Newer developments on in vitro spermatogenesis and testicular tissue engineering for in vitro sperm production from cryopreserved SSCs and testicular tissue are also discussed.

Advanced bioengineering of male germ stem cells to preserve fertility

In modern life, several factors such as genetics, exposure to toxins, and aging have resulted in significant levels of male infertility, estimated to be approximately 18% worldwide. In response, substantial progress has been made to improve in vitro fertilization treatments (e.g. microsurgical testicular sperm extraction (m-TESE), intra-cytoplasmic sperm injection (ICSI), and round spermatid injection (ROSI)). Mimicking the structure of testicular natural extracellular matrices (ECM) outside of the body is one clear route toward complete in vitro spermatogenesis and male fertility preservation. Here, a new wave of technological innovations is underway applying regenerative medicine strategies to cell-tissue culture on natural or synthetic scaffolds supplemented with bioactive factors. The emergence of advanced bioengineered systems suggests new hope for male fertility preservation through development of functional male germ cells. To date, few studies aimed at in vitro spermatogenesis have resulted in relevant numbers of mature gametes. However, a substantial body of knowledge on conditions that are required to maintain and mature male germ cells in vitro is now in place. This review focuses on advanced bioengineering methods such as microfluidic systems, bio-fabricated scaffolds, and 3D organ culture applied to the germline for fertility preservation through in vitro spermatogenesis.

Composition and Mechanism of Three-Dimensional Hydrogel System in Regulating Stem Cell Fate

Three-dimensional (3D) hydrogel systems integrating different types of stem cells and scaffolding biomaterials have an important application in tissue engineering. The biomimetic hydrogels that pattern cell suspensions within 3D configurations of biomaterial networks allow for the transport of bioactive factors and mimic the stem cell niche in vivo, thereby supporting the proliferation and differentiation of stem cells. The composition of a 3D hydrogel system determines the physical and chemical characteristics that regulate stem cell function through a biological mechanism. Here, we discuss the natural and synthetic hydrogel compositions that have been employed in 3D scaffolding, focusing on their characteristics, fabrication, biocompatibility, and regulatory effects on stem cell proliferation and differentiation. We also discuss the regulatory mechanisms of cell-matrix interaction and cell-cell interaction in stem cell activities in various types of 3D hydrogel systems. Understanding hydrogel compositions and their cellular mechanisms can yield insights into how scaffolding biomaterials and stem cells interact and can lead to the development of novel hydrogel systems of stem cells in tissue engineering and stem cell-based regenerative medicine. Impact statement Three-dimensional hydrogel system of stem cell mimicking the stemcell niche holds significant promise in tissue engineering and regenerative medicine. Exactly how hydrogel composition regulates stem cell fate is not well understood. This review focuses on the composition of hydrogel, and how the hydrogel composition and its properties regulate the stem cell adhesion, growth, and differentiation. We propose that cell-matrix interaction and cell-cell interaction are important regulatory mechanisms in stem cell activities. Our review provides key insights into how the hydrogel composition regulates the stem cell fate, untangling the engineering of three-dimensional hydrogel systems for stem cells.

A comparison of the effects of fetal bovine serum and newborn calf serum on cell growth and maintenance of cryopreserved mouse spermatogonial stem cells

Serum is a common supplement that is widely used to protect various cells and tissues from cryopreservation because it provides the necessary active components for cell growth and maintenance. In this study, we compared the effects of newborn calf serum (NCS) and fetal bovine serum (FBS) on the cryopreservation of mouse spermatogonial stem cells (SSCs). The isolated SSCs were cryopreserved in two groups: freezing medium that contained 10% DMSO (dimethyl sulfoxide) and 10% FBS in DMEM (Dulbecco's Modified Eagle's Medium) (group 1) and freezing medium that contained 10% DMSO and 10% NCS in DMEM (group 2). Real-time PCR was performed for stemness gene expression. The SSCs' viability was performed by trypan blue. We observed that the SSCs had increased viability in the NCS-freeze/thaw group (87.82%) compared to the FBS-freeze/thaw group (79.83%), but this increase was not statistically significant (P < 0.105). Promyelocytic leukemia zinc finger (Plzf) and Lin28 gene expression levels in the NCS-frozen/thawed SSCs were not significantly different compared to the FBS-frozen/thawed SSCs; however, Nanog gene expression increased considerably, and Dazl gene expression decreased significantly. The results in this study demonstrated that the presence of NCS in a solution of cryopreserved SSCs increased their viability after freeze/thawing and might promote the proliferation of cultivated SSCs in vitro by increasing the relative expression of Nanog.

Encapsulation of Satureja khuzistanica extract in alginate hydrogel accelerate wound healing in adult male rats

BACKGROUND

Finding the best dressing for a specific wound had continued from the past to present. The aim of this study was to evaluate the effect of encapsulated extract of Satureja khuzistanica in hydrogel alginate at wound healing.

METHODS

Thirty-two male Wistar rats with a puncture wound in the back of the neck skin were divided randomly into four groups including a control group, Satureja khuzistanica-treated group, hydrogel alginate-treated group, and Satureja khuzistanica encapsulated in hydrogel alginate-treated group. Rats were treated for 22 days. The skin samples were taken on 3rd, 7th, 14th, and 22nd days after treatment for light microscopy. Results were analyzed in accordance with Kruskal-Wallis and Friedman test (for histopathology analysis) by using SPSS v.22 software.

RESULTS

Macroscopically evaluations and measurement of wound size showed increased wound healing process in the treated groups. The complete improvement was created on the 14th day. The wound site was not observed on the 22nd day. But the wound site was observed on the 22nd day in the control group. Also, comparison of the percentage of wound healing between the treated and control groups on 3rd, 7th, 14th, and 22nd days showed a significant difference (p < 0.05). Comparison of the H&E stained sections in the studied groups showed that treated groups were effective on wound healing in comparison with the control group.

CONCLUSIONS

Encapsulated extract of Satureja khuzistanica in hydrogel alginate may accelerate wound improvement and increase the rate of wound healing without scar formation.

Encapsulation of rat cardiomyoblasts with alginate-gelatin microspheres preserves stemness feature in vitro

INTRODUCTION

The emergence of numerous tissue engineering and regenerative medicine techniques cell encapsulation paves a way to heal and restore the function of various injured tissues mainly cardiovascular system. Here, we aimed to investigate the role of alginate-gelatin encapsulation on the dynamic of rat cardiomyoblasts in vitro.

MATERIALS AND METHODS

Rat cardiomyoblasts cell line H9C2 were enclosed by using alginate-gelatin microspheres and incubated for 7 days. MTT method was used to examine cell viability. The level of genes associated with cardiomyoblasts maturation MYL7, NPPA, NKX2-5, and GATA4 real-time PCR. ELISA was used to measure the protein levels of Bcl-2 and Bax factor post-encapsulation. The level of SOD, GPx, and TAC was detected by biochemical analyses. Western blotting was performed to measure the content of AMP-activated protein kinase.

RESULTS

We found that encapsulation was able to increase the viability of rat cardiomyocytes after 7 days. The decreased level of Bcl-2 (p < 0.001) coincided with non-significant differences in the level of Bax (p > 0.05). The transcription level of all genes MYL7, NPPA, NKX2-5, and GATA4 were found to down-regulate compared to the control non-treated cells (p < 0.05). No significant differences were found regarding the level of SOD, GPx, and TAC compared to the control (p>0.05). According to western blotting, revealed a reduced level of AMPK following 7-day incubation of rat cardiomyoblasts (p < 0.05).

CONCLUSION

Data confirmed that the encapsulation of rat cardiomyoblasts with alginate-gelatin microspheres maintained the cells multipotentiality.