Serum-free and xenobiotic-free preservation of cultured human limbal epithelial cells

Limbal epithelial stem cell sheets from young donors have better regenerative potential

To investigate the stemness of limbal epithelial stem cell sheets in relation to the donor’s age. Human limbal explants from cadaveric donors were set on human amniotic membrane scaffolds with the xeno-free medium. We evaluated limbal epithelial sheet size, expression of stem/progenitor cell markers, and colony formation efficiency from donors of different age groups (age ≤ 45, age 45–65, and age > 65). Expression of the proliferation marker Ki67, stem/progenitor cell markers p63α and ABCG2, cornea specific marker PANCK, and differentiation marker CK12 were evaluated. To determine the effect of donor age on the storage period of limbal explant sheets, the limbal explant outgrowth sheets were stored in 4 °C for 2 days and analyzed for JC-1, p63α, and PANCK with FACS on each day. From days 6 to 12, the outgrowth area of the limbal epithelial stem cell sheet was significantly larger in the age ≤ 45 groups (296 ± 54.7 mm², day 9) compared to the other two age groups [age 45–65 group (278 ± 62.6 mm²), age > 65 group (257 ± 44.0 mm²), day 9] (p < 0.01). In terms of stemness, outgrowth cells from aged donors (age > 65) showed lower expression of stem/progenitor cell markers p63α and ABCG2 and decreased CFE compared to the other two groups. There were significantly more p63α+ cells in outgrowth cells in the age ≤ 45 group (18.2 ± 3.6%) compared to the age > 65 group (14.1 ± 4.6%; p < 0.01). Limbal explant outgrowth sheet on the age ≤ 45 group (32.7 ± 7.5%) had higher percentages of cells resisting staining by JC-1 compared with sheets under the age > 65 groups (25.7 ± 7.1%, p < 0.01) (JC-1^low). Cells from the age ≤ 45 group showed a higher clonogenic capacity than those from the other two age groups (45 < Age ≤ 65 CFE ratio = 0.7 ± 0.16, p < 0.01; 65 < Age CFE ratio = 0.3 ± 0.06, p < 0.01, vs. Age ≤ 45). In the age > 65 group, positive cells of p63α on D0, 1, and 2 were significantly lower compared to those in the age ≤ 45 group on the storage period (p < 0.01, respectively). Our results imply that donors younger than 65 years of age are a better source of limbal epithelial stem cell sheet generation with high regeneration potential.

Interleukin-13 increases the stemness of limbal epithelial stem cells cultures

This study aimed to determine the effect of interleukin-13 (IL13) on the stemness, differentiation, proliferation, clonogenicity, and morphology of cultured limbal epithelial cells (LECs). Human limbal explants were used to culture LECs up to the second passage (P0-P2) with or without IL13 (IL13+ and IL13-, respectively). Cells were analyzed by qPCR (for the expression of ΔNp63α, BMI-1, keratin (K) 3, K7, K12, K14, K17, mucin 4, and MKI67) and immunofluorescence staining for p63α. The clonogenic ability was determined by colony-forming assay (CFA), and their metabolic activity was measured by WST-1 assay. The results of the CFA showed a significantly increased clonogenic ability in P1 and P2 cultures when LECs were cultured with IL13. In addition, the expression of putative stem cell markers (ΔNp63α, K14, and K17) was significantly higher in all IL13+ cultures compared to IL13-. Similarly, immunofluorescence analysis showed a significantly higher percentage of p63α positive cells in P2 cultures with IL13 than without it. LECs cultures without IL13 lost their cuboidal morphology with a high nucleocytoplasmic ratio after P1. The use of IL13 also led to significantly higher proliferation in P2, which can be reflected by a higher ability to reach confluence in P2 cultures. On the other hand, IL13 had no effect on corneal epithelial cell differentiation (K3 and K12 expression), and the expression of the conjunctival marker K7 significantly increased in all IL13+ cultures compared to the respective cell culture without IL13. This study showed that IL13 enhanced the stemness of LECs by increasing the clonogenicity and the expression of putative stem cell markers of LECs while maintaining their stem cell morphology. We established IL13 as a culture supplement for LESCs, which increases their stemness potential in culture, even after the second passage, and may lead to the greater success of LESCs transplantation in patients with LSCD.

Bio-fabrication of stem-cell-incorporated corneal epithelial and stromal equivalents from silk fibroin and gelatin-based biomaterial for canine corneal regeneration

Corneal grafts are the imperative clinical treatment for canine corneal blindness. To serve the growing demand, this study aimed to generate tissue-engineered canine cornea in part of the corneal epithelium and underlying stroma based on canine limbal epithelial stem cells (cLESCs) seeded silk fibroin/gelatin (SF/G) film and canine corneal stromal stem cells (cCSSCs) seeded SF/G scaffold, respectively. Both cell types were successfully isolated by collagenase I. SF/G corneal films and stromal scaffolds served as the prospective substrates for cLESCs and cCSSCs by promoting cell adhesion, cell viability, and cell proliferation. The results revealed the upregulation of tumor protein P63 (P63) and ATP-binding cassette super-family G member 2 (Abcg2) of cLESCs as well as Keratocan (Kera), Lumican (Lum), aldehyde dehydrogenase 3 family member A1 (Aldh3a1) and Aquaporin 1 (Aqp1) of differentiated keratocytes. Moreover, immunohistochemistry illustrated the positive staining of tumor protein P63 (P63), aldehyde dehydrogenase 3 family member A1 (Aldh3a1), lumican (Lum) and collagen I (Col-I), which are considerable for native cornea. This study manifested a feasible platform to construct tissue-engineered canine cornea for functional grafts and positively contributed to the body of knowledge related to canine corneal stem cells.

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.

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.

Transplantation of human corneal limbal epithelial cell sheet harvested on synthesized carboxymethyl cellulose and dopamine in a limbal stem cell deficiency

This study aimed to evaluate the efficacy and safety of transplantation with human corneal limbal epithelial (HCLE) cell sheets cultured on carboxymethyl cellulose (CMC)-dopamine (DA)-coated substrates and harvested via enzymatic digestion of CMC with cellulase in a rabbit animal model of limbal stem cell deficiency (LSCD). Synthesized CMC-DA was pretreated onto the surface of culture plates. Then, HCLE cells were cultured on precoated CMC-DA and HCLE cell sheets were harvested using cellulase-containing cell culture medium. HCLE cell sheets were evaluated using a live/dead assay, histological examination, and immunofluorescence staining. For in vivo assessment, HCLE cell sheets were transplanted in a rabbit model of LSCD for 2 weeks to determine the effectiveness of the repair. Primary culture of HCLE cells stained positively for p63, cytokeratin (CK)15, and CK12. HCLE cell sheets were generated with a well-preserved morphology and transparency ranging in size from 15 to 19 mm after cellulase-assisted cell sheet generation. HCLE cell sheets uniformly stained positively for human mitochondria, p63, CK15, CK12, CK3/2p, and zonula occludens (ZO)-1. HCLE cell sheet transplantation in a rabbit model of LSCD improved the corneal opacity and neovascularization scores. Transplanted HCLE cell sheets stained positively for p63 and CK12. Transplantation of HCLE cell sheets harvested on CMC-DA coating combined with cellulase is a safe and efficient procedure for corneal epithelial regeneration in a rabbit model of LSCD. This system could enable a promising strategy to regenerate corneal epithelium by transplantation in ocular surface disorders.

Expansion of Human Limbal Epithelial Stem/Progenitor Cells Using Different Human Sera: A Multivariate Statistical Analysis

Transplantation of human cultured limbal epithelial stem/progenitor cells (LESCs) has demonstrated to restore the integrity and functionality of the corneal surface in about 76% of patients with limbal stem cell deficiency. However, there are different protocols for the expansion of LESCs, and many of them use xenogeneic products, being a risk for the patients’ health. We compared the culture of limbal explants on the denuded amniotic membrane in the culture medium—supplemental hormone epithelial medium (SHEM)—supplemented with FBS or two differently produced human sera. Cell morphology, cell size, cell growth rate, and the expression level of differentiation and putative stem cell markers were examined. Several bioactive molecules were quantified in the human sera. In a novel approach, we performed a multivariate statistical analysis of data to investigate the culture factors, such as differently expressed molecules of human sera that specifically influence the cell phenotype. Our results showed that limbal cells cultured with human sera grew faster and contained similar amounts of small-sized cells, higher expression of the protein p63α, and lower of cytokeratin K12 than FBS cultures, thus, maintaining the stem/progenitor phenotype of LESCs. Furthermore, the multivariate analysis provided much data to better understand the obtaining of different cell phenotypes as a consequence of the use of different culture methodologies or different culture components.

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.

Effects of explant size on epithelial outgrowth, thickness, stratification, ultrastructure and phenotype of cultured limbal epithelial cells

Purpose

Transplantation of limbal stem cells is a promising therapy for limbal stem cell deficiency. Limbal cells can be harvested from either a healthy part of the patient’s eye or the eye of a donor. Small explants are less likely to inflict injury to the donor site. We investigated the effects of limbal explant size on multiple characteristics known to be important for transplant function.

Methods

Human limbal epithelial cells were expanded from large versus small explants (3 versus 1 mm of the corneal circumference) for 3 weeks and characterized by light microscopy, immunohistochemistry, and transmission electron microscopy. Epithelial thickness, stratification, outgrowth, ultrastructure and phenotype were assessed.

Results

Epithelial thickness and stratification were similar between the groups. Outgrowth size correlated positively with explant size (r = 0.37; P = 0.01), whereas fold growth correlated negatively with explant size (r = –0.55; P < 0.0001). Percentage of cells expressing the limbal epithelial cell marker K19 was higher in cells derived from large explants (99.1±1.2%) compared to cells derived from small explants (93.2±13.6%, P = 0.024). The percentage of cells expressing ABCG2, integrin β1, p63, and p63α that are markers suggestive of an immature phenotype; Keratin 3, Connexin 43, and E-Cadherin that are markers of differentiation; and Ki67 and PCNA that indicate cell proliferation were equal in both groups. Desmosome and hemidesmosome densities were equal between the groups.

Conclusion

For donor- and culture conditions used in the present study, large explants are preferable to small in terms of outgrowth area. As regards limbal epithelial cell thickness, stratification, mechanical strength, and the attainment of a predominantly immature phenotype, both large and small explants are sufficient.

Critical Functionality Effects from Storage Temperature on Human Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium Cell Suspensions

Human induced pluripotent stem cell (hiPSC)-derived retinal pigment epithelium (hiPSC-RPE) cells suspension have the potential for regenerative treatment. However, practical regenerative applications with hiPSC-RPE cells require the development of simple and cost-effective non-freezing preservation methods. We investigated the effect of non-freezing temperatures on suspended hiPSC-RPE cells in various conditions and analysed mechanisms of cell death, anoikis, Rho GTPases, hypoxia, microtubule destruction, and cell metabolism. Cells stored at 37 °C had the lowest viability due to hypoxia from high cell metabolism and cell deposits, and cells preserved at 4 °C were damaged via microtubule fragility. Cell suspensions at 16 °C were optimal with drastically reduced apoptosis and negligible necrosis. Moreover, surviving cells proliferated and secreted key proteins normally, compared to cells without preservation. hiPSC-RPE cell suspensions were optimally preserved at 16 °C. Temperatures above or below the optimal temperature decreased cell viability significantly yet differentially by mechanisms of cell death, cellular metabolism, microtubule destruction, and oxygen tension, all relevant to cell conditions. Surviving cells are expected to function as grafts where high cell death is often reported. This study provides new insight into various non-freezing temperature effects on hiPSC-RPE cells that are highly relevant to clinical applications and may improve cooperation between laboratories and hospitals.

Conjugation of carboxymethyl cellulose and dopamine for cell sheet harvesting

This manuscript focuses on the cell sheet preparation methodology with the conjugation of carboxymethylcellulose (CMC) and dopamine (DA).

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.

Comparative study of substrate free and amniotic membrane scaffolds for cultivation of limbal epithelial sheet

Transplantation of cultivated limbal epithelial transplantation has been proven to restore the corneal surface in limbal stem cell deficiency (LSCD). Here we comparatively investigated the optimized conditions and the efficiency of limbal epithelial sheet growth in three media conditions as well as with substrate free (transwell), human amniotic membrane (HAM) sutured onto transwell inserts (HAMTW), and HAM slide scaffold (HAMS). Outcomes evaluated were outgrowth sheet size from limbal explants, expression of stem/progenitor cell markers p63α, ABCG2 and CK15, and colony formation efficiency (CFE). Additionally, limbal epithelial sheets on HAMS were transplanted into corneas of LSCD rabbit models. Limbal epithelial sheets with 5% human AB serum showed the greatest increase in ABCG2 efflux activity (JC1^low), p63α expression, and CFE compared in both conditions without HAM and with HAM, respectively. The outgrowth sheet size, cell yield, and Ki67 expression were increased in limbal epithelial sheets on HAMS compared to transwell and HAMTW. ABCG2 efflux activity, p63α and CK15 expressions, and CFE were also increased in limbal epithelial sheets on HAMS as well. In corneas of transplanted rabbit LSCD models, p63α expressions were noted in the basal layers and CK12 expressions were observed in superficial layers. Cultivation of limbal epithelial sheet on HAMS with xeno-free medium enhances the growth and stemness of limbal epithelial sheets.

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.

Characterization and comparison of human limbal explant cultures grown under defined and xeno-free conditions

Human limbal epithelial cells (LECs) intended for treatment of limbal stem cell deficiency are commonly cultivated on a 3T3 feeder layer with complex culture medium supplemented with fetal bovine serum (FBS). However, FBS is a xenogeneic component containing poorly characterised constituents and exhibits quantitative and qualitative lot-to-lot variations. Human limbal explants were plated on untreated or fibrin coated plastic plates and cultured in two non-xenogeneic media (supplemented with either human serum or platelet lysate only). Our aim was to find out whether the characteristics of harvested LEC cultures are comparable to those of LEC cultivated in the gold standard - FBS-supplemented complex medium. The growth kinetics, cell proliferation, differentiation, stemness maintenance, apoptosis and contamination by other cell types were evaluated and compared among these conditions. In all of them LECs were successfully cultivated. Stemness was preserved in both xeno-free media. However, cells cultured with human serum on the fibrin-coated plates had the highest growth rate and cell proliferation and very low fibroblast-like cell contamination. These data suggest that xeno-free cell culture conditions can replace the traditional FBS-supplemented medium and thereby provide a safer protocol for ex vivo cultured limbal stem cell transplants.

Concise Review: Altered Versus Unaltered Amniotic Membrane as a Substrate for Limbal Epithelial Cells

Limbal stem cell deficiency (LSCD) can result from a variety of corneal disorders, including chemical and thermal burns, infections, and autoimmune diseases. The symptoms of LSCD may include irritation, epiphora, blepharospasms, photophobia, pain, and decreased vision. There are a number of treatment options, ranging from nonsurgical treatments for mild LSCD to various forms of surgery that involve different cell types cultured on various substrates. Ex vivo expansion of limbal epithelial cells (LEC) involves the culture of LEC harvested either from the patient, a living relative, or a cadaver on a substrate in the laboratory. Following the transfer of the cultured cell sheet onto the cornea of patients suffering from LSCD, a successful outcome can be expected in approximately three out of four patients. The phenotype of the cultured cells has proven to be a key predictor of success. The choice of culture substrate is known to affect the phenotype. Several studies have shown that amniotic membrane (AM) can be used as a substrate for expansion of LEC for subsequent transplantation in the treatment of LSCD. There is currently a debate over whether AM should be denuded (i.e., de-epithelialized) prior to LEC culture, or whether this substrate should remain intact. In addition, crosslinking of the AM has been used to increase the thermal and mechanical stability, optical transparency, and resistance to collagenase digestion of AM. In the present review, we discuss the rationale for using altered versus unaltered AM as a culture substrate for LEC. Stem Cells Translational Medicine 2018;7:415-427.

Corneal lenticule storage before reimplantation

Purpose

To explore the optimal lenticule storage conditions that maintain lenticule integrity and clarity.

Methods

A total of 99 lenticules obtained from myopic patients undergoing small incision lenticule extraction (SMILE) were divided into four combinations for short-term storage conditions: PBS, Dulbecco's Modified Eagle's Medium (DMEM), Optisol GS, or anhydrous glycerol. Two thirds of the lenticules were further stored for 4 weeks under eight different conditions. Clarity evaluation with transmittance measurements, cell-death assays with terminal deoxynucleotidyl transferase-mediated nick end labeling assay (TUNEL), collagen fibril spacing and necrotic response assessed with transmission electron microscopy (TEM), and immunohistochemistry analysis for human leukocyte antigens (HLAs) and CD45 for immunogenicity, and matrix metalloproteinase (MMP)-2 for keratocyte response, were undertaken at baseline, 48 h (short term), and 4 weeks (long term).

Results

The TUNEL and immunogenicity results were comparable among the groups. The mean percentage of TUNEL-positive cells across all groups was 24.3% ± 11.8% and 62.9% ± 20.7% at the 48 h and 4 week time points, respectively. HLA-ABC+, HLA-DR+, and CD45+ cells were extremely rare, and MMP-2 expression ranged from non-detectable to minimal, under all conditions at all time points. Transmittance at 4 weeks was significantly different among groups with the greatest maintenance of clarity seen in the lenticules stored initially in DMEM at 4 °C for 48 h followed by cryopreservation in serum-free medium or glycerol at 4 °C followed by storage at room temperature. At TEM analysis at 4 weeks, the lenticules cryopreserved in liquid nitrogen, regardless of storage solutions, had significantly narrower inter-fibrillar distance than controls, while glycerol-preserved lenticules, at either room temperature or -80 °C, maintained the inter-fibrillar distance.

Conclusions

Clarity, structural integrity, and low immunogenicity under various conditions, at 4 °C or room temperature for short-term storage, offer encouragement for lenticule storage. It can be undertaken without access to s specialized and potentially expensive laboratory setup at least within the first 48 h before transportation to larger facilities for long-term storage.