Development of a cell sheet transportation technique for regenerative medicine

Early Clinical Outcomes of the First Commercialized Human Autologous Ex Vivo Cultivated Oral Mucosal Epithelial Cell Transplantation for Limbal Stem Cell Deficiency: Two Case Reports and Literature Review

The first product in the world for ex vivo cultivated oral mucosal epithelial cell transplantation (COMET) to treat limbal stem cell deficiency (LSCD), named Ocural^®, was launched in June 2021 in Japan. COMET was performed on two patients, including the first case in the post-marketing phase of Ocural^®. Pathological and immunohistochemical examinations were also carried out using specimens obtained before and after COMET and the spare cell sheet. In case 1, the ocular surface remained free from epithelial defects for approximately six months. In case 2, although defect of the cornea-like epithelia was observed after COMET for one month, it was resolved after the insertion of lacrimal punctal plugs. In case 1, adjuvant treatment was interrupted due to an accident during the second month after COMET, resulting in conjunctival ingrowth and corneal opacity. Eventually, a lamellar keratoplasty was required at six months after COMET. Immunohistochemistry revealed the presence of markers for stem cells (p63, p75), proliferation (Ki-67), and differentiation (Keratin-3, -4, and -13) in both the cornea-like tissue after COMET and a cultivated oral mucosal epithelial cell sheet. In conclusion, Ocural^® can be accomplished without major complications, and the stem cells derived from oral mucosa might be successfully engrafted.

Clinical Trial of Autologous Cultivated Limbal Epithelial Cell Sheet Transplantation for Patients with Limbal Stem Cell Deficiency

OBJECTIVE OR PURPOSE

To confirm the efficacy and safety of Good Manufacturing Practice (GMP)-compliant autologous cultivated limbal epithelial cell sheets in government-controlled clinical trials that adhered to Good Clinical Practice stipulations for patients with unilateral limbal stem cell deficiency (LSCD).

DESIGN

A prospective, multi-center, open-label, uncontrolled, single-arm clinical trial.

SUBJECTS, PARTICIPANTS OR CONTROLS

Ten consecutive eyes of 10 patients with unilateral LSCD were followed for two years after surgery. Preoperative LSCD stage was IIB in four eyes and III in six eyes.

METHODS

A limbal tissue biopsy was obtained from the healthy eye, after which limbal stem cells were dissociated and cultivated on temperature-responsive culture surfaces. All cell sheets were fabricated in a GMP-grade facility under established standard operating procedures. Cell sheets were evaluated using defined shipment criteria before transplantation, and only those that met the criteria were used. The cell sheet was transplanted onto each of the patients' diseased eye after removing the conjunctival scar tissue that covered the corneal surface. The severity of LSCD was determined according to a staging method agreed upon by global consensus, with eyes evaluated as being in stages IA-C representing successful corneal epithelial reconstruction. LSCD diagnosis and staging were determined by the trial's Eligibility Judgment Committee and Effect Assessment Committee using slit-lamp photographs including fluorescein staining. Both committees comprised two or three third-party cornea specialists, who were provided with information anonymously and randomly.

MAIN OUTCOME MEASURE

Corneal epithelial reconstruction rate was the primary endpoint.

RESULTS

Corneal epithelial reconstruction was successful in six of 10 eyes (60%) one year postoperatively and was significantly higher than the 15% clinically significant efficacy rate achieved by allogeneic limbal transplantation. The reconstruction rate was 70% of eyes two years postoperatively. Additionally, improvements in visual acuity were noted in 50% and 60% of eyes at one and two years, respectively. No clinically significant transplantation-related adverse events were observed.

CONCLUSION

The efficacy and safety of cultivated limbal epithelial cell sheet transplantation were thus confirmed, and the cell sheet, named Nepic, is now approved as a Cellular and Tissue-Based Product in Japan.

Institutional and infrastructure challenges for hospitals producing advanced therapies in the UK: the concept of 'point-of-care manufacturing readiness'

Aim: To propose the concept of point-of-care manufacturing readiness for analyzing the capacity that a country, a health system or an institution has developed to manufacture therapies in clinical settings (point-of-care manufacture). The focus is on advanced therapies (cell, gene and tissue engineering therapies) in the UK. Materials & methods: Literature review, analysis of quantitative data, and qualitative interviews with professionals and practitioners developing and administering advanced therapies. Results: Three components of point-of-care manufacturing readiness are analyzed staff and institutional procedures, infrastructure, and relations between hospitals and service providers. Conclusion: The technical and regulatory experience that has been gained through manufacturing advanced therapies at small scale in hospitals qualifies the UK for more complex and larger-scale production of therapies in the future.

Long-term and short-term preservation strategies for tissue engineering and regenerative medicine products: state of the art and emerging trends

There is an ever-growing need of human tissues and organs for transplantation. However, the availability of such tissues and organs is insufficient by a large margin, which is a huge medical and societal problem. Tissue engineering and regenerative medicine (TERM) represent potential solutions to this issue and have therefore been attracting increased interest from researchers and clinicians alike. But the successful large-scale clinical deployment of TERM products critically depends on the development of efficient preservation methodologies. The existing preservation approaches such as slow freezing, vitrification, dry state preservation, and hypothermic and normothermic storage all have issues that somehow limit the biomedical applications of TERM products. In this review, the principles and application of these approaches will be summarized, highlighting their advantages and limitations in the context of TERM products preservation.

Manufacture and Quality Control of Human Umbilical Cord-Derived Mesenchymal Stem Cell Sheets for Clinical Use

Human umbilical cord-derived mesenchymal stem cell (UC−MSC) sheets have attracted much attention in cell therapy. However, the culture media and coating matrix used for the preparation of UC−MSC sheets have not been safe enough to comply with current clinical drug standards. Moreover, the UC−MSC sheet preservation systems developed before did not comply with Good Manufacturing Practice (GMP) regulations. In this study, the culture medium and coating matrix were developed for UC−MSC sheet production to comply with clinical drug standards. Additionally, the GMP-compliant preservation solution and method for the UC−MSC sheet were developed. Then, quality standards of the UC−MSC sheet were formulated according to national and international regulations for drugs. Finally, the production process of UC−MSC sheets on a large scale was standardized, and three batches of trial production were conducted and tested to meet the established quality standards. This research provides the possibility for clinical trials of UC−MSC sheet products in the development stage of new drugs and lays the foundation for industrial large-scale production after the new drug is launched.

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

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

Temporary Storage of the Human Nasal Tissue and Cell Sheet for Wound Repair

Temporary storage of nasal tissues and nasal cell sheets, which entails transportation between hospitals and cell culture facilities, is an important issue in regenerative medicine. Herein, we investigated the preservation of chilled and frozen nasal tissues and expiry dates of ready-to-use nasal cell sheets. Although the cell number in preserved tissues was lower than that in fresh tissue, nasal cell sheets could be fabricated from tissues that had been refrigerated for 5 days and frozen-thawed over 5 days. Moreover, the nasal mucosal cell sheets were preserved in a non-hazardous buffer. The cell number, viability, and structure were not maintained in saline containing E-cadherin for 2 days; however, these were maintained in Hank's balanced salt solution for 2 days, but not for 5 days. To assess the proliferation capacity of cells in the stored cell sheets, we performed cell sheet grafting assays in vitro. Cell sheets stored in Hank's balanced salt solution for 2 days adhered to collagen gel and expanded normally. Our results show that nasal tissues can be stored temporarily in refrigerators or deep freezers, and Hank's balanced salt solution can be used for preservation of ready-to-use cell sheets for a few days.

Response of human oral mucosal epithelial cells to different storage temperatures: A structural and transcriptional study

PURPOSE

Seeking to improve the access to regenerative medicine, this study investigated the structural and transcriptional effects of storage temperature on human oral mucosal epithelial cells (OMECs).

METHODS

Cells were stored at four different temperatures (4°C, 12°C, 24°C and 37°C) for two weeks. Then, the morphology, cell viability and differential gene expression were examined using light and scanning electron microscopy, trypan blue exclusion test and TaqMan gene expression array cards, respectively.

RESULTS

Cells stored at 4°C had the most similar morphology to non-stored controls with the highest viability rate (58%), whereas the 37°C group was most dissimilar with no living cells. The genes involved in stress-induced growth arrest (GADD45B) and cell proliferation inhibition (TGFB2) were upregulated at 12°C and 24°C. Upregulation was also observed in multifunctional genes responsible for morphology, growth, adhesion and motility such as EFEMP1 (12°C) and EPHA4 (4°C-24°C). Among genes used as differentiation markers, PPARA and TP53 (along with its associated gene CDKN1A) were downregulated in all temperature conditions, whereas KRT1 and KRT10 were either unchanged (4°C) or downregulated (24°C and 12°C; and 24°C, respectively), except for upregulation at 12°C for KRT1.

CONCLUSIONS

Cells stored at 12°C and 24°C were stressed, although the expression levels of some adhesion-, growth- and apoptosis-related genes were favourable. Collectively, this study suggests that 4°C is the optimal storage temperature for maintenance of structure, viability and function of OMECs after two weeks.

The Effects of Prolonged Storage on ARPE-19 Cells Stored at Three Different Storage Temperatures

This study aimed to investigate how prolonged storage of adult retinal pigment epithelial (ARPE-19) cell sheets affects cell metabolism, morphology, viability, and phenotype. ARPE-19 cell sheets were stored at three temperatures (4 °C, 16 °C, and 37 °C) for three weeks. Metabolic status and morphology of the cells were monitored by sampling medium and examining cells by phase-contrast microscopy, respectively, throughout the storage period. Cell viability was analyzed by flow cytometry, and phenotype was determined by epifluorescence microscopy after the storage. Lactate production and glucose consumption increased heavily, while pH dropped considerably, through storage at 37 °C compared to 4 °C and 16 °C. During storage, morphology started to deteriorate first at 4 °C, then at 37 °C, and was maintained the longest at 16 °C. Viability of the cells after three weeks of storage was best preserved at 16 °C, while cells stored at 4 °C and 37 °C had reduced viability. Dedifferentiation indicated by reduced expression of retinal pigment epithelium-specific protein 65 (RPE65), zonula occludens protein 1 (ZO-1), and occludin after three weeks of storage was noticed in all experimental groups compared to control. We conclude that storage temperature affects the metabolic status of ARPE-19 cells and that 16 °C reduces metabolic activity while protecting viability and morphology.

Human serum albumin as a clinically accepted cell carrier solution for skin regenerative application

The rules governing Medicinal Products in the European Union necessitates the production of cell-based therapy in good manufacturing practice facilities. The produced cells may need several hours in transportation to reach the application sites. In this study, we investigated four candidate solutions for transporting human keratinocytes. The solutions are (1) normal saline, (2) saline with 2.5% human serum albumin (Saline + HSA), (3) chemically defined, xeno-free keratinocyte media and (4) keratinocyte media with pituitary bovine extract (PBE-media). One million keratinocytes from three donors were suspended in each solution and kept at 4 °C for up to 24 h. Cells kept in Saline + HSA showed higher viability after 1, 3 and 24 h. Then, equal number of viable cells were seeded on collagenous matrix and cultured for 48 h. The adhesion and colonization were higher in the cells kept in PBE-media, while the keratinocyte surface marker, cytokeratin 14, was present in all studied groups. These results confirmed the suitability of Saline + HSA as a cell transportation solution for clinical use, which will be the choice for the planned clinical trial. Keratinocyte PBE-media can be an alternative for cells transported for research purpose, if the same media type is going to be used in the following experiments.

Optisol-GS Storage of Cultured Human Limbal Epithelial Cells at Ambient Temperature Is Superior to Hypothermic Storage

PURPOSE

To investigate the feasibility of using Optisol-GS as a convenient, xenogeneic-free alternative for storage of cultured human limbal epithelial cells (HLECS) for use in treatment of limbal stem cell deficiency (LSCD). In the present study, we compared storage of cultured HLEC using the conventional hypothermic Optisol-GS storage method at 4°C versus storage at 23°C (room temperature).

MATERIALS AND METHODS

HLECs were cultured for three weeks on amniotic membrane (AM), transferred to polypropylene containers and stored in Optisol-GS for 4 days at 23°C and 4°C. A calcein-acetoxymethyl ester/ethidium homodimer-1 assay was used to assess viability. Morphology and phenotype were analyzed by light microscopy and immunohistochemistry, respectively.

RESULTS

Expression of stem cell and proliferation markers p63, ∆Np63α, ABCG2, K19, K3, Cx43, Ki67, and PCNA was maintained at pre-storage control levels during storage at 23°C. ABCG2 and PCNA expression were both significantly altered during storage at 4°C. HLEC cell sheet viability also significantly declined following storage at 4°C. HLEC sheets stored at 4°C demonstrated extensive detachment of basal cells from the AM in sharp contrast to storage at 23°C, where attachment to the AM was maintained throughout the storage period.

CONCLUSIONS

The present study demonstrates the feasibility of short-term storage of cultured HLECs in Optisol-GS, which offers a convenient standardized xenogeneic-free storage method. Storage temperature highly affected the results. Maintenance of cell viability, morphology and undifferentiated proliferative phenotype of cultured HLEC sheets favored storage at 23°C.

Analysis of human nasal mucosal cell sheets fabricated using transported tissue and blood specimens

Previously, we succeeded in transplanting autologous nasal mucosal cell sheets in the middle ears of 5 patients, who underwent cholesteatoma resection, which prevents recurrence of cholesteatoma in clinical settings. Current good manufacturing practice (GMP) standards for human cell cultivation requires the establishment of cell processing centers (CPC) which act as germ-free facilities. However, due to practical difficulties involved in establishing and maintaining such facilities at each individual hospital, a functional transport system is felt to be needed for the continuation of effective regenerative therapy. In the current study, nasal mucosal tissue and autologous blood obtained from 3 human volunteers were transported for over 3 h. Disinfected nasal tissues were cultured using keratinocyte culture medium, which included autologous serum prepared from blood. After 24 d, cultured nasal mucosal cells were transported for over 3 h and subsequently assessed for cell number, viability and purity. Moreover, CK4, CK8, and CK18 were analyzed the suitability of these nasal mucosal cell sheets for middle ear regenerative therapy.

Overall, we confirmed that nasal mucosal cell sheets can be fabricated using transported nasal mucosal tissue and blood. This study would be contribute to establish a new regenerative therapy for clinical application, accompanied with transportation between companies and hospitals.

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Transportation of nasal mucosal tissue and blood.

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Characterizing of nasal mucosal cell sheet by immunohistology.

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Transportation of nasal mucosal cell sheet as pre-clinical study.

A simple and static preservation system for shipping retinal pigment epithelium cell sheets

The ability to move cells and tissues from bench to bedside is an essential aspect of regenerative medicine. In this study, we propose a simple and static shipping system to deliver tissue-engineered cell sheets. Notably, this system is electronic-device-free and simplified to minimize the number of packing and opening steps involved. Shipping conditions were optimized, and application and verification of the system were performed using human iPS cell-derived or fetal retinal pigment epithelium (RPE) cell sheets. The temperature of the compartments within the insulated container was stable at various conditions, and filling up the cell vessel with medium effectively prevented turbulence-induced mechanical damage to the RPE cell sheets. Furthermore, no abnormal changes were observed in RPE morphology, transepithelial electrical resistance, or mRNA expression after transit by train and car. Taken together, our simple shipping system has the potential to minimize the costs and human error associated with bench to bedside tissue transfer. This specially designed regenerative tissue shipping system, validated for use in this field, can be used without any special training. This study provides a procedure for easily sharing engineered tissues with the goal of promoting collaboration between laboratories and hospitals and enhancing patient care.

High Throughput Screening of Additives Using Factorial Design to Promote Survival of Stored Cultured Epithelial Sheets

There is a need to optimize storage conditions to preserve cell characteristics during transport of cultured cell sheets from specialized culture units to distant hospitals. In this study, we aimed to explore a method to identify additives that diminish the decrease in the viability of stored undifferentiated epidermal cells using multifactorial design and an automated screening procedure. The cultured cells were stored for 7–11 days at 12°C in media supplemented with various additives. Effects were evaluated by calcein staining of live cells as well as morphology. Twenty-six additives were tested using (1) a two-level factorial design in which 10 additives were added or omitted in 64 different combinations and (2) a mixture design with 5 additives at 5 different concentrations in a total of 64 different mixtures. Automated microscopy and cell counting with Fiji enabled efficient processing of data. Significant regression models were identified by Design-Expert software. A calculated maximum increase of live cells to 37 ± 6% was achieved upon storage of cell sheets for 11 days in the presence of 6% glycerol. The beneficial effect of glycerol was shown for epidermal cell sheets from three different donors in two different storage media and with two different factorial designs. We have thus developed a high throughput screening system enabling robust assessment of live cells and identified glycerol as a beneficial additive that has a positive effect on epidermal cell sheet upon storage at 12°C. We believe this method could be of use in other cell culture optimization strategies where a large number of conditions are compared for their effect on cell viability or other quantifiable dependent variables.

Effect of Transportation on Cultured Limbal Epithelial Sheets for Worldwide Treatment of Limbal Stem Cell Deficiency

Limbal stem cell deficiency can be treated with transplantation of cultured human limbal epithelial cells (LEC). It can be advantageous to produce LEC in centralized labs and thereafter ship them to eye clinics. The present study used transport simulations of LEC to determine if vigorous shaking during transport altered the viability, morphology and phenotype during a 4 day-long storage of LEC with a previously described serum-free storage method. Inserts with LEC cultured on amniotic membranes were sutured to caps inside air-tight containers with generous amounts of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES)-buffered minimal essential medium (MEM). The containers were distributed among the following testing conditions: 6 hours with full containers, 36 hours with full containers, 36 hours with container three quarters full of medium, and 36 hours with container full of medium containing a shear-protecting agent (Pluronic-F68). Compared to stored, but non-transported controls, no statistically significant changes in viability and immunohistochemical staining were observed. The epithelial sheets remained intact. However, an air-liquid interface in the containers reduced the number of desmosomes and hemi-desmosomes compared to the controls. In conclusion, cultured LEC sheets appear to endure vigorous shaking for at least 36 hours if the container is full.

Optimization of Storage Temperature for Retention of Undifferentiated Cell Character of Cultured Human Epidermal Cell Sheets

Cultured epidermal cell sheets (CES) containing undifferentiated cells are useful for treating skin burns and have potential for regenerative treatment of other types of epithelial injuries. The undifferentiated phenotype is therefore important for success in both applications. This study aimed to optimize a method for one-week storage of CES for their widespread distribution and use in regenerative medicine. The effect of storage temperatures 4 °C, 8 °C, 12 °C, 16 °C, and 24 °C on CES was evaluated. Analyses included assessment of viability, mitochondrial reactive oxygen species (ROS), membrane damage, mitochondrial DNA (mtDNA) integrity, morphology, phenotype and cytokine secretion into storage buffer. Lowest cell viability was seen at 4 °C. Compared to non-stored cells, ABCG2 expression increased between temperatures 8–16 °C. At 24 °C, reduced ABCG2 expression coincided with increased mitochondrial ROS, as well as increased differentiation, cell death and mtDNA damage. P63, C/EBPδ, CK10 and involucrin fluorescence combined with morphology observations supported retention of undifferentiated cell phenotype at 12 °C, transition to differentiation at 16 °C, and increased differentiation at 24 °C. Several cytokines relevant to healing were upregulated during storage. Importantly, cells stored at 12 °C showed similar viability and undifferentiated phenotype as the non-stored control suggesting that this temperature may be ideal for storage of CES.

Corneal regenerative medicine

Recently, regenerative medicine has become a highlighted field because it has great potential to induce a paradigm shift of supportive conventional therapy into definitive treatment. The cornea is the avascular, transparent, dome-shaped outermost layer of the eyeball, and it consists of three layers: epithelium, stroma, and endothelium. Conventional corneal transplantation, known as keratoplasty, has two main problems, a donor shortage and immunological rejection. Therefore, regenerative medicine has been applied to overcome these challenges. Regenerative medicine involving the corneal epithelium has been clinically applied, along with an understanding of corneal epithelial stem cell biology, earlier than that of the corneal stroma or endothelium. Thus, the effectiveness and safety of cultivated corneal or oral mucosal epithelial cell sheet transplantation have been reported by many researchers. Clinical studies on regenerative medicine for corneal stroma or endothelium have begun after basic and nonclinical study. Translational research has been performed to make corneal regenerative medicine a universal therapy. This article reviews corneal regenerative medicine.

Regenerative medicine for the cornea

Regenerative medicine for the cornea provides a novel treatment strategy for patients with corneal diseases instead of conventional keratoplasty. Limbal transplantation has been performed in patients with a limbal stem cell deficiency. This procedure requires long-term immunosuppression that involves high risks of serious eye and systemic complications, including infection, glaucoma, and liver dysfunction. To solve these problems, ocular surface reconstruction using cultured limbal or oral mucosal epithelial stem cells has been successfully applied to patients. However, cell sheets must be fabricated in a cell processing center (CPC) under good manufacturing practice conditions for clinical use, and the expenses of maintaining a CPC are too high for all hospitals to cover. Therefore, several hospitals should share one CPC to standardize and spread the application of regenerative therapy using tissue-engineered oral mucosal epithelial cell sheets. Consequently, we developed a cell transportation technique for clinical trial to bridge hospitals. This paper reviews the current status of regenerative medicine for the cornea.