Determination of Chinese hamster ovary cell-derived recombinant thyrotropin by reversed-phase liquid chromatography

Human bone morphogenetic protein-2 (hBMP-2) characterization by physical-chemical, immunological and biological assays

Commercially available preparations of methionyl-human BMP-2 and CHO-derived hBMP-2, which belongs to the transforming growth factor β (TGF-β) superfamily, were used for a complete characterization. This protein is an extremely efficient osteoinductor that plays an important role during bone regeneration and embryonic development. Characterization was carried out via SDS-PAGE and Western blotting, followed by reversed-phase HPLC, size-exclusion HPLC and MALDI-TOF-MS. The classical in vitro bioassay, based on the induction of alkaline phosphatase activity in C2C12 cells, confirmed that hBMP-2 biological activity is mostly related to the dimeric form, being ~ 4-fold higher for the CHO-derived glycosylated form when compared with the E. coli counterpart. The E. coli-derived met-hBMP-2 has shown, by MALDI-TOF-MS, a large presence of the bioactive dimer. A more complex molecular mass (MM) distribution was found for the CHO-derived product, whose exact MM has never been reported because of its variable glycosylation. A method based on RP-HPLC was set up, allowing a quantitative and qualitative hBMP-2 determination even directly on ongoing culture media. Considering that hBMP-2 is highly unstable, presenting moreover an extremely high aggregate value, we believe that these data pave the way to a necessary characterization of this important factor when synthesized by DNA recombinant techniques in different types of hosts.

Human thyroid-stimulating hormone synthesis in human embryonic kidney cells and related N-glycoprofiling analysis for carbohydrate composition determination

A strain of embryonic human kidney cells (HEK293) was transiently co-transfected with the expression vectors coding for the α- and β-subunits of human thyroid-stimulating hormone (hTSH), and, for the first time, a human cell-derived recombinant hTSH was synthesized and extensively characterized. The purification strategy involving two steps provided an overall yield of 55% and a purity level > 90%. The purified material (hTSH-HEK) was analyzed and compared to a CHO-derived recombinant preparation (hTSH-CHO) and to a pituitary-derived (hTSH-Pit) preparation. The three preparations showed an equivalent purity (> 95%) with a hTSH-HEK molecular mass 2.1% lower than that of hTSH-CHO and 2.7% higher than that of hTSH-Pit. Remarkable differences were found in the carbohydrate moiety, the lowest sialic acid content and highest fucose content being observed in hTSH-HEK. In vivo biological activity was confirmed for the three preparations, the hTSH-HEK bioactivity being 39 and 16% lower than those of hTSH-CHO and hTSH-Pit, respectively. The hTSH-HEK circulatory half-life (t _1/2) was also shorter than those of hTSH-CHO (1.5-fold) and hTSH-Pit (1.2-fold). According to these findings, HEK-293-derived hTSH can be considered to be useful for clinical applications, in view as well of its human origin and particular carbohydrate composition.

Determination of recombinant Interferon-α2 in E. coli periplasmic extracts by reversed-phase high-performance liquid chromatography

Reversed-phase high-performance liquid chromatography (RP-HPLC) has been used to analyze Interferon α-2 (IFN-α2) as a pure protein or as a pharmaceutical preparation: a method for analyzing periplasmic IFN-α2 directly in osmotic shock extract has, however, never been reported. This work describes an RP-HPLC methodology for the qualitative and quantitative analysis of human IFN-α2a and IFN-α2b directly in bacterial periplasmic extracts or in purified preparations. The analytical method has been set up and validated for accuracy, precision, linearity, sensitivity and specificity. A recovery test indicated an average bias of ∼1%, intra-day and inter-day quantitative determinations presented relative standard deviations always≤5%, while the working sensitivity was of ∼0.3μg of IFN-α2 (RSD=5%). The method proved to be suitable for detecting and quantifying also glycosylated and oxidized forms and N-methionylated IFN-α2 molecules, it was, however, not able to distinguish between IFN-α2a and IFN-α2b. This rapid methodology allows the application of RP-HPLC as a powerful tool to monitor the production yield and quality of IFN-α2 in osmotic shock fluids, right after, or even during the fermentation process.

Cytotoxic and genotoxic effects of 131 I and 60 Co in follicular thyroid cancer cell (WRO) with and without recombinant human thyroid-stimulating hormone treatment

Normally, differentiated thyroid cancer (DTC) tends to be biologically indolent, highly curable and has an excellent prognosis. However, the treatment may fail when the cancer has lost radioiodine avidity. The present study was carried out in order to evaluate the cytotoxic and genotoxic effects of ¹³¹ I and ⁶⁰ Co and radioiodine uptake in WRO cells, derived from DTC, harboring the BRAF^V600E mutation. WRO cells showed a relatively slow cell cycle of 96.3 h with an unstable karyotype containing various double minutes. The genotoxicity assay (micronucleus test) showed a relative high radioresistance to ¹³¹ I (0.07-3.70 MBq/mL), independent of treatment with recombinant human thyroid-stimulating hormone (rhTSH). For the cytotoxicity assay, WRO cells were also relatively resistant to ⁶⁰ Co (range: 0.2-8.3 Gy), but with a gradual decrease of viability as a function of time for higher doses (20 and 40 Gy, starting from the fifth to sixth day). For internal irradiation with ¹³¹ I, WRO cells showed a decline in viability at radioactive concentration higher than 1.85 MBq/mL; this was even more effective at 3.70 MBq/mL, but only when preceded by rhTSH, in coincidence with the highest level of ¹³¹ I uptake. These data show promising results, since the loss of the ability of thyroid cells to concentrate radioiodine is considered to be one of the main factors responsible for the failure of ¹³¹ I therapy in patients with DTC. The use of tumor-derived cell lines as a model for in vivo tumor requires, however, further investigations and deep evaluation of the corresponding in vivo effects. Environ. Mol. Mutagen. 58:451-461, 2017. © 2017 Wiley Periodicals, Inc.

Enhancement of human thyrotropin synthesis by sodium butyrate addition to serum-free CHO cell culture

The influence of sodium butyrate (NaBu) on the synthesis of recombinant human thyrotropin (r-hTSH) by CHO cells was investigated for the first time. A volumetric productivity of ~10 μg hTSH/mL was repeatedly obtained, with a 3.3-fold increase over a control culture carried out in the absence of NaBu. Since NaBu can induce CHO cell apoptosis and cell growth arrest, the increase in specific productivity was even higher, i.e., ca. 5-fold. Analysis of the N-glycan composition of r-hTSH obtained with the addition of NaBu to the culture medium showed an approximately 12 % increase in the amount of sialic acid, as well as in total carbohydrate, partly due to the increase in the site occupancy from 2.77 to 2.93 glycans per mole of hTSH. The two hormone preparations were characterized by N-glycan structural analysis, which showed that NaBu increased the bi-antennary structures by ca. 13 % while decreasing the tri-antennary structures by approximately the same amount. The in vivo biological activity and pharmacokinetic behavior (clearance) were found to be similar for the two hormone preparations.

Laboratory production of human prolactin from CHO cells adapted to serum-free suspension culture

Human prolactin (hPRL) is a polypeptide with 199 amino acids and a molecular mass of 23 kDa. Previously, a eukaryotic hPRL expression vector was used to transfect Chinese hamster ovary (CHO) cells: this work describes a fast and practical laboratory adaptation of these transfected cells, in ~40 days, to grow in suspension in serum-free medium. High cell densities of up to 4.0 × 10(6) cell/ml were obtained from spinner flask cultures and a stable and continuous production process was developed for at least 30 days. Two harvesting strategies were set up, 50 or 100 % of the total conditioned medium being collected daily and replaced by fresh culture medium. The volumetric productivity was 5-7 μg hPRL/ml, as determined directly in the collected medium via reversed-phase HPLC (RP-HPLC). A two-step process based on a cationic exchanger followed by size exclusion chromatography was applied to obtain purified hPRL from conditioned medium. Two hPRL isoforms, non-glycosylated and glycosylated, could also be separated by high-performance size-exclusion chromatography (HPSEC) and, when analyzed by RP-HPLC, HPSEC, Western blotting, and bioassay, were found to be comparable to the World Health Organization International Reference Reagent of hPRL. These results are useful for the practical scale-up to the pilot and industrial scale of a bioprocess based on CHO cell culture.

Efficient isolation of the subunits of recombinant and pituitary glycoprotein hormones

Complete dissociation into subunits was attained by incubating Chinese hamster ovary (CHO)-derived or native human thyrotropin, follitropin and lutropin overnight at 37 degrees C in acetic acid. The alpha-and beta-subunits of the pituitary glycoprotein hormones were rapidly and quantitatively isolated by reversed-phase high-performance liquid chromatography (RP-HPLC). A dissociation efficiency of > 98% was obtained on the basis of mass determinations of the heterodimers and subunits carried out via mass spectrometry. CHO-derived or native subunits were isolated on a C4 column (80-90% total recovery) and characterized comparatively for purity, hydrophobicity, molecular mass and charge distribution by HPLC, mass spectrometry, sodium dodecylsulfate-polyacrylamide gel electrophoresis and isoelectric focusing. Thyrotropin was used as a model for showing that, after subunit reassociation, the in vivo bioactivity of the hormone was completely restored. The method described is mild, practical, flexible, and can be adapted to dissociate microgram amounts of native or recombinant glycoprotein hormones, allowing characterization of each subunit.

Evaluation of the cytogenetic effects of (131)I preceded by recombinant human thyrotropin (rhTSH) in peripheral lymphocytes of Wistar rats

The present study was carried out to investigate the cytogenetic effects of therapeutic exposure to radioiodine preceded by rhTSH in an animal model. Three groups of Wistar rats (n = 6) were used: one group was treated only with (131)I (11.1 MBq/animal); the other two groups received rhTSH (1.2 mug/rat of either Thyrogen or rhTSH-IPEN, respectively) 24 h before administration of radioiodine. The percentage of lymphocytes with chromosome aberrations and the average number of aberrations and of dicentrics per cell were determined on blood samples collected 24 h, 7 and 30 days after administration of (131)I. The data show that the treatment with radioiodine alone or associated with rhTSH resulted in a greater quantity of chromosome alterations in relation to basal values after 24 h, with a gradual decline after 7 and 30 days of treatment. An increase in chromosome alterations was also seen after rhTSH treatment alone. Neither of the treatments, i.e., with (131)I alone or associated with hormone, resulted in an aneugenic effect or influenced the kinetics of cellular proliferation in rat blood lymphocytes. There was no significant difference between the cytogenetic effects of Thyrogen and rhTSH-IPEN treatment. These data suggest that the treatment with radioiodine, associated or not with rhTSH, affects to a limited extent a relatively small number of cells although the occurrence of late stochastic effects could not be discarded.

Secretion of mouse growth hormone by transduced primary human keratinocytes: prospects for an animal model of cutaneous gene therapy

BACKGROUND

Keratinocytes are a very attractive vehicle for ex vivo gene transfer and systemic delivery because proteins secreted by these cells may reach the circulation via a mechanism that mimics the natural process.

METHODS

An efficient retroviral vector (LXSN) encoding the mouse growth hormone gene (mGH) was used to transduce primary human keratinocytes. Organotypic raft cultures were prepared with these genetically modified keratinocytes and were grafted onto immunodeficient dwarf mice (lit/scid).

RESULTS

Transduced keratinocytes presented a high and stable in vitro secretion level of up to 11 microg mGH/10(6)cells/day. Conventional epidermal sheets made with these genetically modified keratinocytes, however, showed a drop in secretion rates of > 80% due to detachment of the epithelium from its substratum. Substitution of conventional grafting methodologies with organotypic raft cultures completely overcame this problem. The stable long-term grafting of such cultures onto lit/scid mice could be followed for more than 4 months, and a significant weight increase over the control group was observed in the first 40 days. Circulating mGH levels revealed a peak of 21 ng/ml just 1 h after grafting but, unfortunately, these levels rapidly fell to baseline values.

CONCLUSIONS

mGH-secreting primary human keratinocytes presented the highest in vitro expression and peak circulatory levels reported to date for a form of GH with this type of cells. Together with previous data showing that excised implants can recover a remarkable fraction of their original in vitro mGH secretion efficiency in culture, the factors that might still hamper the success of this promising model of cutaneous gene therapy are discussed.

Practical reversed-phase high-performance liquid chromatography method for laboratory-scale purification of recombinant human thyrotropin

A small, semi-preparative C(4) RP-HPLC column was used to set up the conclusive laboratory-scale purification of Chinese hamster ovary-derived human thyrotropin (hTSH), after a preliminary concentration-purification of an extremely dilute and poorly ( approximately 0.6 microg hTSH/mL; mass fraction=0.35%) conditioned medium on a cation exchanger. Several fractions of this eluate were repeatedly injected on the semi-preparative column, obtaining, in a single run (<1h chromatographic time), a concentrated pool ( approximately 1.2 mg/mL) of highly purified hTSH that could be further concentrated to >3 mg/mL and then efficiently lyophilized. The overall recovery in the rapid RP-HPLC purification step, including concentration and lyophilization, was of the order of 80%. The final product, when tested via a precise, single-dose in vivo bioassay, confirmed that it did not suffer any loss of bioactivity. This same methodology can be easily adapted to the small-scale purification of other recombinant products, even when obtained from genetically modified organisms at extremely low concentrations and mass fractions.

Analysis of intact human follicle-stimulating hormone preparations by reversed-phase high-performance liquid chromatography

A reversed-phase high-performance liquid chromatography (RP-HPLC) method for the qualitative and quantitative analysis of intact human follicle-stimulating hormone (hFSH) was established and validated for accuracy, precision and sensitivity. Human FSH is a dimeric glycoprotein hormone widely used as a diagnostic analyte and as a therapeutic product in reproductive medicine. The technique developed preserves the protein integrity, allowing the analysis of the intact heterodimeric form rather than just of its subunits, as is the case for the majority of the conditions currently employed. This methodology has also been employed for comparing the relative hydrophobicity of pituitary, urinary and two Chinese hamster ovary (CHO)-derived hFSH preparations, as well as of two other related glycoprotein hormones of the anterior pituitary: human thyroid-stimulating hormone (hTSH) and human luteinizing hormone (hLH). The least hydrophobic of the three glycohormones analyzed was hFSH, followed by hTSH and hLH. A significant difference (p<0.005) was observed in t(R) between the pituitary and recombinant hFSH preparations, reflecting structural differences in their carbohydrate moieties. Two main isoforms were detected in urinary hFSH, including a form which was significantly different (p<0.005) from the pituitary and recombinant preparations. The linearity of the dose-response curve (r=0.9965, n=15) for this RP-HPLC methodology, as well as an inter-assay precision of less than 4% for the quantification of different hFSH preparations and a sensitivity of the order of 40 ng, were demonstrated. The chromatographic behaviour and relative hydrophobicity of the individual subunits of the pituitary and recombinant preparations were also analyzed. Furthermore, the molecular mass of individual hFSH subunits and of the heterodimer were simultaneously determined by matrix-assisted laser desorption ionization time-of-flight mass spectral analysis (MALDI-TOF-MS). The present methodology represents, in our opinion, an essential tool for the characterization and quality control of this hormone, that is not yet described in the main pharmacopoeias.

Two-step chromatographic purification of recombinant human thyrotrophin and its immunological, biological, physico-chemical and mass spectral characterization

A purification strategy for rapidly obtaining recombinant human thyrotropin (rhTSH) was designed based on size exclusion and reversed-phase high-performance liquid chromatographic (HPLC) analysis, carried out on hTSH-secreting CHO cell conditioned medium. These analyses permitted the identification of the main contaminants to be eliminated. Considering that hTSH is highly hydrophobic and elutes only with the addition of organic solvents, hydrophobic interaction chromatography was adopted as the first purification step; this resulted in the elimination of, among others, the major contaminant. A second purification step, based on size exclusion chromatography, was then utilized, being effective in the elimination of other previously identified contaminating proteins. Useful purity, as high as 99% at the chemical reagent level, and recoveries (37%) were obtained by adopting this two step strategy, which also provided adequate material for physico-chemical, immunological and biological characterization. This included matrix-assisted laser desorption ionization time-of-flight mass spectral analysis (MALDI-TOF-MS), Western blotting analysis, in vivo biological assay, size-exclusion HPLC (HPSEC) and reversed-phase HPLC (RP-HPLC) analysis, which confirmed the integrity and bioactivity of our rhTSH in comparison with the only two reference preparations available at the milligram level of native (hTSH-NIDDK) and recombinant (Thyrogen) hTSH. Thyrogen and rhTSH-IPEN, when compared to pit-hTSH-NIDDK, presented more than twice as much biological activity and about 7% increased molecular mass by MALDI-TOF-MS analysis, an accurate heterodimer mass determination providing the Mr values of 29,611, 29,839 and 27,829, respectively. The increased molecular mass of the two recombinant preparations was also confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and HPSEC analysis. Comparing the two recombinant preparations, minor though interesting physico-chemical and biological differences were also observed.