Cryopreservation of hMSCs seeded silk nanofibers based tissue engineered constructs

Specifics of Cryopreservation of Hydrogel Biopolymer Scaffolds with Encapsulated Mesenchymal Stem Cells

The demand for regenerative medicine products is growing rapidly in clinical practice. Unfortunately, their use has certain limitations. One of these, which significantly constrains the widespread distribution and commercialization of such materials, is their short life span. For products containing suspensions of cells, this issue can be solved by using cryopreservation. However, this approach is rarely used for multicomponent tissue-engineered products due to the complexity of selecting appropriate cryopreservation protocols and the lack of established criteria for assessing the quality of such products once defrosted. Our research is aimed at developing a cryopreservation protocol for an original hydrogel scaffold with encapsulated MSCs and developing a set of criteria for assessing the quality of their functional activity in vitro. The scaffolds were frozen using two alternative types of cryocontainers and stored at either -40 °C or -80 °C. After cryopreservation, the external state of the scaffolds was evaluated in addition to recording the cell viability, visible changes during subsequent cultivation, and any alterations in proliferative and secretory activity. These observations were compared to those of scaffolds cultivated without cryopreservation. It was shown that cryopreservation at -80 °C in an appropriate type of cryocontainer was optimal for the hydrogels/adipose-derived stem cells (ASCs) tested if it provided a smooth temperature decrease during freezing over a period of at least three hours until the target values of the cryopreservation temperature regimen were reached. It was shown that evaluating a set of indicators, including the viability, the morphology, and the proliferative and secretory activity of the cells, enables the characterization of the quality of a tissue-engineered construct after its withdrawal from cryopreservation, as well as indicating the effectiveness of the cryopreservation protocol.

Integrated construction of silkworm cocoon-inspired 3D scaffold for improving cell manufacture and cryopreservation

Although cellular therapy holds enormous promise in treating intractable diseases, its application potential has been significantly hampered due to the scarcity of reliable and consistent cell sources. Therefore, a high-efficiency strategy that improves cell production and storage is desperately needed. Herein, we develop a versatile 3D bioinspired scaffold (Cryosilk) for improving scalable cell manufacture and cryopreservation. A bottom-up fabrication technique integrating electrospinning, in situ surface functionalization and freeze-shaping was explored to construct Cryosilk with biomimetic features and functions of silkworm cocoons. Cryosilk is composed of a core-shell heterostructure with silk fibroin/poly alanine fiber core and silk sericin shell, generating a 3D cocoon-mimicking fibrous structure. Importantly, Cryosilk possesses improved thermal conductivity and ice crystal resistance capability, thus enabling to cryopreserve biological samples with minimal cryodamage. Furthermore, Cryosilk not only promotes cell adhesion and growth, but achieves rapid and uniform rewarming process, which provides high cryopreservation efficacy for immune cells and stem cells. Particularly, Cryosilk can maintain cell viability and biofunctions of stem cell-scaffold constructs after freeze-thawing, which can be directly implanted to promote wound healing. Thus, Cryosilk offers unprecedented efficacy in cell manufacture and cryopreservation, which provides sufficient and high-quality precious cells and tissue engineered scaffolds for cellular therapy.

Xenotransplantation of cryopreserved human clumps of mesenchymal stem cells/extracellular matrix complexes pretreated with IFN-γ induces rat calvarial bone regeneration

Introduction

Three-dimensional (3D) clumps of mesenchymal stem cells (MSCs)/extracellular matrix (ECM) complexes, composed with cells and self-produced intact ECM, can be grafted into defect areas without artificial scaffold to induce successful bone regeneration. Moreover, C-MSCs pretreated with IFN-γ (C-MSCsγ) increased the immunomodulatory enzyme indoleamine 2,3-dioxygenase (IDO) expression and thereby inhibited T cell activity. Xenotransplantation of human C-MSCsγ suppressed host T cell immune rejection and induced bone regeneration in mice. Besides, we have also reported that C-MSCs retain the 3D structure and bone regenerative property even after cryopreservation. To develop the "off-the-shelf" cell preparation for bone regenerative therapy that is promptly provided when needed, we investigated whether C-MSCsγ can retain the immunosuppressive and osteogenic properties after cryopreservation.

Methods

Confluent human MSCs that had formed on the cellular sheet were scratched using a micropipette tip and then torn off. The sheet was rolled to make a round clump of cells. The round cell clumps were incubated with a growth medium for 3 days, and then C-MSCs were obtained. To generate C-MSCsγ, after 2 days' culture, C-MSCs were stimulated with 50 ng/ml of IFN-γ. Both C-MSCs and C-MSCsγ were cryopreserved for 2 days and then thawed to obtain Cryo-C-MSCs and Cryo-C-MSCsγ, respectively. The biological properties of those cell clumps were assessed in vitro. In addition, to test whether human Cryo-C-MSCsγ attenuates immune rejection to induce bone regeneration, a xenograft study using a rat calvarial defect was performed.

Results

Both IFN-γ pretreatment and cryopreservation process did not affect the 3D structure and cell viability in all human cell clumps. Interestingly, Cryo-C-MSCsγ showed significantly increased IDO mRNA expression equivalent to C-MSCsγ. More importantly, xenotransplantation of human C-MSCsγ and Cryo-C-MSCsγ induced rat calvarial bone regeneration by suppressing rat T cells infiltration and the grafted human cells reduction in the grafted area. Finally, there were no human donor cells in the newly formed bone, implying that the bone reconstruction by C-MSCsγ and Cryo-C-MSCsγ can be due to indirect host osteogenesis.

Conclusion

These findings implied that Cryo-C-MSCsγ can be a promising bone regenerative allograft therapy that can be certainly and promptly supplied on demand.

Alginate functionalized biomimetic 3D scaffold improves cell culture and cryopreservation for cellular therapy

The clinical translation of cellular therapy is hampered by the scarcity of reliable and consistent cell sources. In this study, we developed an exquisite scaffold featuring the hierarchical structure and biofunctions of silkworm cocoons (CryoSiCo), for boosting cell manufacture and cryopreservation. CryoSiCo was constructed by a creative bottom-up fabrication technique integrating electrospinning, in situ surface functionalization and freeze-shaping, generating a 3D cocoon-mimicking fibrous scaffold composed of graphene oxide-incorporated polylactic acid/gelatin inner fiber core and alginate outer fiber shell. CryoSiCo provided rapid and uniform rewarming for cryopreserved cells, and maximally maintained cell viability and proliferation capability, allowing for effective cryopreservation. Importantly, CryoSiCo could cryopreserve stem cell-scaffold constructs with high cell survival and functions, which can be directly implanted to restore tissue defects. Thus, CryoSiCo represents an appealing biomimetic strategy for storing precious cells and tissue engineered constructs, showing a broad application for fundamental research and applied medicine.

Cryopreservation of Tissue-Engineered Scaffold-Based Constructs: from Concept to Reality

Creation of scaffold-based tissue-engineered constructs (SB TECs) is costly and requires coordinated qualified efforts. Cryopreservation enables longer shelf-life for SB TECs while enormously enhancing their availability as medical products. Regenerative treatment with cryopreserved SB TECs prepared in advance (possibly prêt-à-porter) can be started straight away on demand. Animal studies and clinical trials indicate similar levels of safety for cryopreserved and freshly prepared SB TECs. Although cryopreservation of such constructs is more difficult than that of cell suspensions or tissues, years of research have proved the principal possibility of using ready-to-transplant SB TECs after prolonged cryostorage. Cryopreservation efficiency depends not only on the sheer viability of adherent cells on scaffolds after thawing, but largely on the retention of proliferative and functional properties by the cells, as well as physical and mechanical properties by the scaffolds. Cryopreservation protocols require careful optimization, as their efficiency depends on multiple parameters including cryosensitivity of cells, chemistry and architecture of scaffolds, conditions of cell culture before freezing, cryoprotectant formulations, etc. In this review we discuss recent achievements in SB TEC cryopreservation as a major boost for the field of tissue engineering and biobanking.

Droplet-based vitrification of adherent human induced pluripotent stem cells on alginate microcarrier influenced by adhesion time and matrix elasticity

The gold standard in cryopreservation is still conventional slow freezing of single cells or small aggregates in suspension, although major cell loss and limitation to non-specialised cell types in stem cell technology are known drawbacks. The requirement for rapidly available therapeutic and diagnostic cell types is increasing constantly. In the case of human induced pluripotent stem cells (hiPSCs) or their derivates, more sophisticated cryopreservation protocols are needed to address this demand. These should allow a preservation in their physiological, adherent state, an efficient re-cultivation and upscaling upon thawing towards high-throughput applications in cell therapies or disease modelling in drug discovery. Here, we present a novel vitrification-based method for adherent hiPSCs, designed for automated handling by microfluidic approaches and with ready-to-use potential e.g. in suspension-based bioreactors after thawing. Modifiable alginate microcarriers serve as a growth surface for adherent hiPSCs that were cultured in a suspension-based bioreactor and subsequently cryopreserved via droplet-based vitrification in comparison to conventional slow freezing. Soft (0.35%) versus stiff (0.65%) alginate microcarriers in concert with adhesion time variation have been examined. Findings revealed specific optimal conditions leading to an adhesion time and growth surface (matrix) elasticity dependent hypothesis on cryo-induced damaging regimes for adherent cell types. Deviations from the found optimum parameters give rise to membrane ruptures assessed via SEM and major cell loss after adherent vitrification. Applying the optimal conditions, droplet-based vitrification was superior to conventional slow freezing. A decreased microcarrier stiffness was found to outperform stiffer material regarding cell recovery, whereas the stemness characteristics of rewarmed hiPSCs were preserved.

Construction of transplantable artificial vascular tissue based on adipose tissue-derived mesenchymal stromal cells by a cell coating and cryopreservation technique

Prevascularized artificial three-dimensional (3D) tissues are effective biomaterials for regenerative medicine. We have previously established a scaffold-free 3D artificial vascular tissue from normal human dermal fibroblasts (NHDFs) and umbilical vein-derived endothelial cells (HUVECs) by layer-by-layer cell coating technique. In this study, we constructed an artificial vascular tissue constructed by human adipose tissue-derived stromal cells (hASCs) and HUVECs (ASCVT) by a modified technique with cryopreservation. ASCVT showed a higher thickness with more dense vascular networks than the 3D tissue based on NHDFs. Correspondingly, 3D-cultured ASCs showed higher expression of several angiogenesis-related factors, including vascular endothelial growth factor-A and hepatic growth factor, compared to that of NHDFs. Moreover, perivascular cells in ASCVT were detected by pericyte markers, suggesting the differentiation of hASCs into pericyte-like cells. Subcutaneous transplantation of ASCVTs to nude mice resulted in an engraftment with anastomosis of host's vascular structures at 2 weeks after operation. In the engrafted tissue, the vascular network was surrounded by mural-like structure-forming hASCs, in which some parts developed to form vein-like structures at 4 weeks, suggesting the generation of functional vessel networks. These results demonstrated that cryopreserved human cells, including hASCs, could be used directly to construct the artificial transplantable tissue for regenerative medicine.

Adherent cell thawing by infrared radiation

Cryopreservation of adherent cells is crucial for commercial cell therapy technology, including effective distribution and storage. Fast thawing has been shown to increase cell recovery in vitrified samples. Previously, radiofrequency (RF) has been investigated as a heating source on large samples, either with or without magnetic particles. Also, laser heating with the aid of dye or nanoparticles has been utilized on sub-millimeter samples successfully. For slow freezing cryopreservation methods, the influence of rate of thawing on viability is less clear. Cryopreservation of surface adhered cells result in many cases in detachment from the surface. We illustrate how intense infrared radiation from a focused halogen illuminator accelerates thawing. We show that two epithelial cell lines, retinal pigment epithelium cells and heterogeneous human epithelial colorectal adenocarcinoma cells, can be effectively cryopreserved and recovered using a combination of slow freezing and fast thawing under infrared illumination. We were able to successfully thaw samples, of 2-4 mm thick, including the media, on the order of a second, providing a heating rate of thousands of Kelvin per minute. Under optimal conditions, we observed higher post-thawing cell viability rates and higher cell adhesion with infrared thawing than with water bath thawing. We suggest that bulk warming with infrared radiation has an advantage over surface warming of surface-attached cells, as it alleviates cell stress during the process of thawing. These findings will pave the way for novel approaches to treating substrate-adhered cells and 3D scaffolds with cells and organoids. This technology may serve as a crucial component in lab-on-chip systems for medical testing and therapeutic use.

New insights into hydroxyectoine synthesis and its transcriptional regulation in the broad-salt growing halophilic bacterium Chromohalobacter salexigens

Elucidating the mechanisms controlling the synthesis of hydroxyectoine is important to design novel genetic engineering strategies for optimizing the production of this biotechnologically relevant compatible solute. The genome of the halophilic bacterium Chromohalobacter salexigens carries two ectoine hydroxylase genes, namely ectD and ectE, whose encoded proteins share the characteristic consensus motif of ectoine hydroxylases but showed only a 51.9% identity between them. In this work, we have shown that ectE encodes a secondary functional ectoine hydroxylase and that the hydroxyectoine synthesis mediated by this enzyme contributes to C.␣salexigens thermoprotection. The evolutionary pattern of EctD and EctE and related proteins suggests that they may have arisen from duplication of an ancestral gene preceding the directional divergence that gave origin to the orders Oceanospirillales and Alteromonadales. Osmoregulated expression of ectD at exponential phase, as well as the thermoregulated expression of ectD at the stationary phase, seemed to be dependent on the general stress factor RpoS. In contrast, expression of ectE was always RpoS-dependent regardless of the growth phase and osmotic or heat stress conditions tested. The data presented here suggest that the AraC-GlxA-like EctZ transcriptional regulator, whose encoding gene lies upstream of ectD, plays a dual function under exponential growth as both a transcriptional activator of osmoregulated ectD expression and a repressor of ectE transcription, privileging the synthesis of the main ectoine hydroxylase EctD. Inactivation of ectZ resulted in a higher amount of the total ectoines pool at the expenses of a higher accumulation of ectoine, with maintenance of the hydroxyectoine levels. In addition to the transcriptional control, our results suggest a strong post-transcriptional regulation of hydroxyectoine synthesis. Data on the accumulation of ectoine and hydroxyectoine in rpoS and ectZ strains pave the way for using these genetic backgrounds for metabolic engineering for hydroxyectoine production.

Human Amniotic Membrane: A review on tissue engineering, application, and storage

Human amniotic membrane (hAM) has been employed as scaffolding material in a wide range of tissue engineering applications, especially as a skin dressing and as a graft for corneal treatment, due to the structure of the extracellular matrix and excellent biological properties that enhance both wound healing and tissue regeneration. This review highlights recent work and current knowledge on the application of native hAM, and/or production of hAM-based tissue-engineered products to create scaffolds mimicking the structure of the native membrane to enhance the hAM performance. Moreover, an overview is presented on the available (cryo) preservation techniques for storage of native hAM and tissue-engineered products that are necessary to maintain biological functions such as angiogenesis, anti-inflammation, antifibrotic and antibacterial activity.

Growth and albumin secretion of mouse fetal liver cells cryopreserved within porous polymer scaffolds as a viable cell source for bioartificial livers

To clinically apply bioartificial livers (BALs), an effective liver cell cryopreservation method is required for a stable cell supply. In this study, we performed tissue-engineered construct (TEC) cryopreservation of fetal liver cells (FLCs) in which FLCs cultured within a porous polymer scaffold were cryopreserved. Growth and albumin secretion in TEC-cryopreserved FLCs after thawing were compared to freshly isolated FLCs (control experiments). The effect of preculture duration prior to cryopreservation (0-3 weeks) on these functions was also examined. In the three-dimensional cultures, the TEC-cryopreserved FLCs with preculturing showed constant growth, and this growth was comparable to controls. On the contrary, the TEC-cryopreserved FLCs without preculturing did not proliferate after thawing. Albumin secretion of TEC-cryopreserved FLCs with preculturing rapidly increased up to day 12 and high secretory activity comparable to controls was maintained thereafter in FLCs with 1- or 2-week preculturing, suggesting this as an appropriate preculture duration. Compared to conventionally cryopreserved FLCs, growth and albumin secretion in the TEC-cryopreserved FLCs were significantly higher, indicating their usefulness as a potent cell source for BALs.

Dimethyl sulfoxide: a central player since the dawn of cryobiology, is efficacy balanced by toxicity?

Dimethyl sulfoxide (DMSO) is the cryoprotectant of choice for most animal cell systems since the early history of cryopreservation. It has been used for decades in many thousands of cell transplants. These treatments would not have taken place without suitable sources of DMSO that enabled stable and safe storage of bone marrow and blood cells until needed for transfusion. Nevertheless, its effects on cell biology and apparent toxicity in patients have been an ongoing topic of debate, driving the search for less cytotoxic cryoprotectants. This review seeks to place the toxicity of DMSO in context of its effectiveness. It will also consider means of reducing its toxic effects, the alternatives to its use and their readiness for active use in clinical settings.

Effect of 'in air' freezing on post-thaw recovery of Callithrix jacchus mesenchymal stromal cells and properties of 3D collagen-hydroxyapatite scaffolds

Through enabling an efficient supply of cells and tissues in the health sector on demand, cryopreservation is increasingly becoming one of the mainstream technologies in rapid translation and commercialization of regenerative medicine research. Cryopreservation of tissue-engineered constructs (TECs) is an emerging trend that requires the development of practically competitive biobanking technologies. In our previous studies, we demonstrated that conventional slow-freezing using dimethyl sulfoxide (Me₂SO) does not provide sufficient protection of mesenchymal stromal cells (MSCs) frozen in 3D collagen-hydroxyapatite scaffolds. After simple modifications to a cryopreservation protocol, we report on significantly improved cryopreservation of TECs. Porous 3D scaffolds were fabricated using freeze-drying of a mineralized collagen suspension and following chemical crosslinking. Amnion-derived MSCs from common marmoset monkey Callithrix jacchus were seeded onto scaffolds in static conditions. Cell-seeded scaffolds were subjected to 24 h pre-treatment with 100 mM sucrose and slow freezing in 10% Me₂SO/20% FBS alone or supplemented with 300 mM sucrose. Scaffolds were frozen 'in air' and thawed using a two-step procedure. Diverse analytical methods were used for the interpretation of cryopreservation outcome for both cell-seeded and cell-free scaffolds. In both groups, cells exhibited their typical shape and well-preserved cell-cell and cell-matrix contacts after thawing. Moreover, viability test 24 h post-thaw demonstrated that application of sucrose in the cryoprotective solution preserves a significantly greater portion of sucrose-pretreated cells (more than 80%) in comparison to Me₂SO alone (60%). No differences in overall protein structure and porosity of frozen scaffolds were revealed whereas their compressive stress was lower than in the control group. In conclusion, this approach holds promise for the cryopreservation of 'ready-to-use' TECs.

Fabrication and evaluation of non-mulberry silk fibroin fiber reinforced chitosan based porous composite scaffold for cartilage tissue engineering

Lack of potential regenerative medicine to reconstruct damaged cartilage tissue has accelerated investigation and development of potential biomaterial for cartilage tissue engineering. In this study, we fabricated micron-sized non-mulberry silk fibroin fiber (SFF) using N,N-Dimethylacetamide (DMA_C)/10% LiBr solution and further used to develop SFF reinforced chitosan(CH) based porous scaffold with desired pore size, porosity, swelling and structural stability. The developed scaffold was characterized for its various physico-chemical, mechanical and biological properties. The developed CH/SFF composite scaffold facilitates human mesenchymal stem cell (hMSCs) attachment, colonization and extracellular matrix deposition. Furthermore, hMSCs shows significantly higher sulfated glycosaminoglycan deposition over CH/SFF in comparison to pure chitosan scaffold (control). Immunocytochemistry studies have shown enhanced expression of collagen type II and aggrecan by hMSCs over composite scaffold than chitosan scaffold. Thus, non-mulberry silk fibroin fiber reinforced chitosan based scaffold might be suitable scaffold that can act as a potential artificial matrix for cartilage tissue engineering.

Advances in the slow freezing cryopreservation of microencapsulated cells

Over the past few decades, the use of cell microencapsulation technology has been promoted for a wide range of applications as sustained drug delivery systems or as cells containing biosystems for regenerative medicine. However, difficulty in their preservation and storage has limited their availability to healthcare centers. Because the preservation in cryogenic temperatures poses many biological and biophysical challenges and that the technology has not been well understood, the slow cooling cryopreservation, which is the most used technique worldwide, has not given full measure of its full potential application yet. This review will discuss the different steps that should be understood and taken into account to preserve microencapsulated cells by slow freezing in a successful and simple manner. Moreover, it will review the slow freezing preservation of alginate-based microencapsulated cells and discuss some recommendations that the research community may pursue to optimize the preservation of microencapsulated cells, enabling the therapy translate from bench to the clinic.

Cryopreserved clumps of mesenchymal stem cell/extracellular matrix complexes retain osteogenic capacity and induce bone regeneration

BACKGROUND

Three-dimensional (3D) cultured clumps of mesenchymal stem cell (MSC)/extracellular matrix (ECM) complexes (C-MSCs) consist of cells and self-produced ECM. C-MSCs can regulate cellular functions in vitro and can be grafted into a defect site without an artificial scaffold to induce bone regeneration. Long-term cryopreservation of C-MSCs, which can enable them to serve as a ready-to-use cell preparation, may be helpful in developing beneficial cell therapy for bone regeneration. Therefore, the aim of this study was to investigate the effect of cryopreservation on C-MSCs.

METHODS

MSCs isolated from rat femurs were cultured in growth medium supplemented with ascorbic acid. To obtain C-MSCs, confluent cells that had formed on the cellular sheet were scratched using a micropipette tip and were then torn off. The sheet was rolled to make a round clumps of cells. The C-MSCs were cryopreserved in cryomedium including 10% dimethyl sulfoxide.

RESULTS

Cryopreserved C-MSCs retained their 3D structure and did not exhibit a decrease in cell viability. In addition, stem cell marker expression levels and the osteogenic differentiation properties of C-MSCs were not reduced by cryopreservation. However, C-MSCs pretreated with collagenase before cryopreservation showed a lower level of type I collagen and could not retain their 3D structure, and their rates of cell death increased during cryopreservation. Both C-MSC and cryopreserved C-MSC transplantation into rat calvarial defects induced successful bone regeneration.

CONCLUSION

These data indicate that cryopreservation does not reduce the biological properties of C-MSCs because of its abundant type I collagen. More specifically, cryopreserved C-MSCs could be applicable for novel bone regenerative therapies.

Cryopreservation of Human Mesenchymal Stem Cells in an Allogeneic Bioscaffold based on Platelet Rich Plasma and Synovial Fluid

Transplantation of mesenchymal stem cells (MSCs) has emerged as an alternative strategy to treat knee osteoarthritis. In this context, MSCs derived from synovial fluid could provide higher chondrogenic and cartilage regeneration, presenting synovial fluid as an appropriate MSCs source. An allogeneic and biomimetic bioscaffold composed of Platelet Rich Plasma and synovial fluid that preserve and mimics the natural environment of MSCs isolated from knee has also been developed. We have optimized the cryopreservation of knee-isolated MSCs embedded within the aforementioned biomimetic scaffold, in order to create a reserve of young autologous embedded knee MSCs for future clinical applications. We have tested several cryoprotectant solutions combining dimethyl sulfoxide (DMSO), sucrose and human serum and quantifying the viability and functionality of the embedded MSCs after thawing. MSCs embedded in bioscaffolds cryopreserved with DMSO 10% or the combination of DMSO 10% and Sucrose 0,2 M displayed the best cell viabilities maintaining the multilineage differentiation potential of MSCs after thawing. In conclusion, embedded young MSCs within allogeneic biomimetic bioscaffold can be cryopreserved with the cryoprotectant solutions described in this work, allowing their future clinical use in patients with cartilage defects.

Enhanced cryopreservation of MSCs in microfluidic bioreactor by regulated shear flow

Cell-matrix systems can be stored for longer period of time by means of cryopreservation. Cell-matrix and cell-cell interaction has been found to be critical in a number of basic biological processes. Tissue structure maintenance, cell secretary activity, cellular migration, and cell-cell communication all exist because of the presence of cell interactions. This complex and co-ordinated interaction between cellular constituents, extracellular matrix and adjacent cells has been identified as a significant contributor in the overall co-ordination of tissue. The prime objective of this investigation is to evaluate the effects of shear-stress and cell-substrate interaction in successful recovery of adherent human mesenchymal-stem-cells (hMSCs). A customized microfluidic bioreactor has been used for the purpose. We have measured the changes in focal-point-adhesion (FPAs) by changing induced shear stress inside the bioreactor. The findings indicate that with increase in shear stress, FPAs increases between substrate and MSCs. Further, experimental results show that increased FPAs (4e-3 μbar) enhances the cellular survivability of adherent MSCs. Probably, for the first time involvement of focal point interaction in the outcome of cryopreservation of MSCs has been clarified, and it proved a potentially new approach for modification of cryopreservation protocol by up-regulating focal point of cells to improve its clinical application.

Carboxymethyl cellulose enables silk fibroin nanofibrous scaffold with enhanced biomimetic potential for bone tissue engineering application

Novel silk fibroin (SF) and carboxymethyl cellulose (CMC) composite nanofibrous scaffold (SFC) were developed to investigate their ability to nucleate bioactive nanosized calcium phosphate (Ca/P) by biomineralization for bone tissue engineering application. The composite nanofibrous scaffold was prepared by free liquid surface electrospinning method. The developed composite nanofibrous scaffold was observed to control the size of Ca/P particle (≤100nm) as well as uniform nucleation of Ca/P over the surface. The obtained nanofibrous scaffolds were fully characterized for their functional, structural and mechanical property. The XRD and EDX analysis depicted the development of apatite like crystals over SFC scaffolds of nanospherical in morphology and distributed uniformly throughout the surface of scaffold. Additionally, hydrophilicity as a measure of contact angle and water uptake capacity is higher than pure SF scaffold representing the superior cell supporting property of the SF/CMC scaffold. The effect of biomimetic Ca/P on osteogenic differentiation of umbilical cord blood derived human mesenchymal stem cells (hMSCs) studied in early and late stage of differentiation shows the improved osteoblastic differentiation capability as compared to pure silk fibroin. The obtained result confirms the positive correlation of alkaline phosphatase activity, alizarin staining and expression of runt-related transcription factor 2, osteocalcin and type1 collagen representing the biomimetic property of the scaffolds. Thus, the developed composite has been demonstrated to be a potential scaffold for bone tissue engineering application.

Fabrication of poly(vinyl alcohol)-Carrageenan scaffolds for cryopreservation: Effect of composition on cell viability

The present investigation reports the fabrication of three dimensional (3D), interconnected, highly porous, biodegradable scaffolds using freeze-gelation technique. The hydrogels prepared with different ratios (5:5, 6:4, 7:3, 8:2 and 9:1) of poly(vinyl alcohol) (PVA) and Carrageenan (Car) was lyophilized to obtain their respective scaffolds. The PVA-Car scaffolds were further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The prepared scaffolds were found to be biodegradable and highly compatible with hemoglobin. Further, normal keratinocyte (HaCaT) and osteosarcoma (Saos-2) cells seeded on PVA-Car scaffolds were cryopreserved for 15days and their viability was checked at regular interval of 3days (0, 3, 6, 9, 12, 15 days) through MTT assay and fluorescence microscopy. Overall, the collective results indicate the scaffold constructs with 7:3 and 8:2 PVA-Car ratios possess ideal characteristics for tissue engineering applications and for long term cryopreservation of cells.

Mesenchymal stromal cells derived from various tissues: Biological, clinical and cryopreservation aspects

Originally isolated from bone marrow, mesenchymal stromal cells (MSCs) have since been obtained from various fetal and post-natal tissues and are the focus of an increasing number of clinical trials. Because of their tremendous potential for cellular therapy, regenerative medicine and tissue engineering, it is desirable to cryopreserve and bank MSCs to increase their access and availability. A remarkable amount of research and resources have been expended towards optimizing the protocols, freezing media composition, cooling devices and storage containers, as well as developing good manufacturing practices in order to ensure that MSCs retain their therapeutic characteristics following cryopreservation and that they are safe for clinical use. Here, we first present an overview of the identification of MSCs, their tissue sources and the properties that render them suitable as a cellular therapeutic. Next, we discuss the responses of cells during freezing and focus on the traditional and novel approaches used to cryopreserve MSCs. We conclude that viable MSCs from diverse tissues can be recovered after cryopreservation using a variety of freezing protocols, cryoprotectants, storage periods and temperatures. However, alterations in certain functions of MSCs following cryopreservation warrant future investigations on the recovery of cells post-thaw followed by expansion of functional cells in order to achieve their full therapeutic potential.

Effect of Hydroxyapatite Nanoparticles on Biotransport Phenomena in Freezing HeLa Cells

The effect of nanoparticles on subzero biotransport phenomena of living cells is very rare in the literature, although the information is of great importance for the application of nanotechnology in the field of cryobiology. In this study, subzero water transport phenomena in freezing HeLa cells in 1 × phosphate buffered saline (PBS) containing 0%, 0.05%, and 0.1% (w/w) hydroxyapatite (HA) nanoparticles with and without pre-incubation at 37 °C was quantitatively investigated. The results reveal that the presence of HA nanoparticles slightly facilitates the subzero water transport of HeLa cells.