Application of the BioRobot EZ1 in a forensic laboratory

Applications of artificial intelligence in forensic sciences: Current potential benefits, limitations and perspectives

In recent years, new studies based on artificial intelligence (AI) have been conducted in the forensic field, posing new challenges and demonstrating the advantages and disadvantages of using AI methodologies to solve forensic well-known problems. Specifically, AI technology has tried to overcome the human subjective bias limitations of the traditional approach of the forensic sciences, which include sex prediction and age estimation from morphometric measurements in forensic anthropology or evaluating the third molar stage of development in forensic odontology. Likewise, AI has been studied as an assisting tool in forensic pathology for a quick and easy identification of the taxonomy of diatoms. The present systematic review follows the PRISMA 2020 statements and aims to explore an emerging topic that has been poorly analyzed in the forensic literature. Benefits, limitations, and forensic implications concerning AI are therefore highlighted, by providing an extensive critical review of its current applications on forensic sciences as well as its future directions. Results are divided into 5 subsections which included forensic anthropology, forensic odontology, forensic pathology, forensic genetics, and other forensic branches. The discussion offers a useful instrument to investigate the potential benefits of AI in the forensic fields as well as to point out the existing open questions and issues concerning its application on real-life scenarios. Procedural notes and technical aspects are also provided to the readers.

Validation of the Applied Biosystems RapidHIT ID instrument and ACE GlobalFiler Express sample cartridge

Rapid DNA platforms are fully automated systems capable of processing DNA from biological samples and interpreting the results in approximately 90 minutes with minimal human intervention. With a greater reliance on the system than on the analyst, validation data are especially needed to define the performance and limitations of commercially available Rapid DNA systems. Thus, validation studies of a Rapid DNA workflow consisting of the Applied Biosystems RapidHIT ID Instrument and RapidLINK software with a focus on the ACE GlobalFiler Express Sample Cartridge and reference buccal swabs were performed in accordance with Scientific Working Group on DNA Analysis Methods Validation Guidelines. These validation studies included assessments of sensitivity, contamination, concordance, reproducibility and repeatability, stability, inhibition, mixtures, sample reprocessing, precision, and first-pass success rate. Overall, the current Applied Biosystems RapidHIT ID Instrument with the ACE GlobalFiler Express sample cartridge was found to be a reliable tool for generation of STR profiles from reference-type buccal swabs.

Internal validation and improvement of mitochondrial genome sequencing using the Precision ID mtDNA Whole Genome Panel

With the recent advances in next-generation sequencing (NGS), mitochondrial whole-genome sequencing has begun to be applied to the field of the forensic biology as an alternative to the traditional Sanger-type sequencing (STS). However, experimental workflows, commercial solutions, and output data analysis must be strictly validated before being implemented into the forensic laboratory. In this study, we performed an internal validation for an NGS-based typing of the entire mitochondrial genome using the Precision ID mtDNA Whole Genome Panel (Thermo Fisher Scientific) on the Ion S5 sequencer (Thermo Fisher Scientific). Concordance, repeatability, reproducibility, sensitivity, and heteroplasmy detection analyses were assessed using the 2800 M and 9947A standard control DNA as well as typical casework specimens, and results were compared with conventional Sanger sequencing and another NGS sequencer in a different laboratory. We discuss the strengths and limitations of this approach, highlighting some issues regarding noise thresholds and heteroplasmy detection, and suggesting solutions to mitigate these effects and improve overall data interpretation. Results confirmed that the Precision ID Whole mtDNA Genome Panel is highly reproducible and sensitive, yielding useful full mitochondrial DNA sequences also from challenging DNA specimens, thus providing further support for its use in forensic practice.

Involvement of ILR4α and TLR4 in miscarriages

BACKGROUND

The purpose of this study was to analyze the involvement of signaling via Interleukin-4-Receptor α (IL4Rα) and Toll like receptor (TLR) 4 at the fetomaternal interface in the process of early pregnancy.

PATIENTS AND METHODS

Placenta specimens of 46 patients in early pregnancy were analyzed (normal pregnancy (n = 15), spontaneous (n = 15) and habitual abortion (n = 16)). TLR4 and IL4Rα were analyzed by immunohistochemistry, immunofluorescence and real time PCR. Statistical analysis was carried out using SPSS 23 and Microsoft Excel.

RESULTS

IL4Rα could be detected in trophoblast cells of all groups. It was significantly downregulated in the syncytiotrophoblast of spontaneous and recurrent abortions (p = 0.001), and in decidual tissue of spontaneous abortions (p = 0.001). Expression of TLR4 was decreased in the intermediate villous trophoblast (IVT) and decidua of spontaneous abortions (p = 0.04 & 0.003, respectively). On mRNA level expression of IL4Rα and TLR4 was significantly decreased in the group of recurrent miscarriages (IL4Rα p = 0.002, TLR4 p = 0.004).

CONCLUSION

This study contributes new findings to the understanding of the complex molecular interplay at the fetomaternal interface in normal pregnancy and miscarriages. For the first time signaling via IL4Rα being involved at the very beginning of the generation of new life could demonstrated. Moreover, new evidence was provided regarding TLR4 playing a pivotal role in early pregnancy.

Multiple Reaction Monitoring Tandem Mass Spectrometry Approach for the Identification of Biological Fluids at Crime Scene Investigations

Knowledge of the nature of biofluids at a crime scene is just as important as DNA test to link the nature of the biofluid, the criminal act, and the dynamics of the crime. Identification of methods currently used for each biological fluid (blood, semen, saliva, urine) suffer from several limitations including instability of assayed biomolecules, and low selectivity and specificity; as an example of the latter issue, it is not possible to discriminate between alpha-amylase 1 (present in saliva) and alpha-amylase 2 (present in semen and vaginal secretion. In this context, the aim of the work has been to provide a predictive protein signature characteristic of each biofluid by the recognition of specific peptides unique for each protein in a single analysis. A panel of four protein biomarkers for blood, four for saliva, five for semen, and two for urine has been monitored has been monitored by using a single multiple reaction monitoring (MRM)-based method targeting concomitantly 46 different peptides. Then, The optimized method allows four biological matrices to be identified when present on their own or in 50:50 mixture with another biofluid. Finally, a valid strategy combining both DNA analysis and liquid chromatographic-tandem mass spectrometric multiple reaction monitoring (LC-MS-MRM) identification of biofluids on the same sample has been demonstrated to be particularly effective in forensic investigation of real trace evidence collected at a crime scene.

Isolation and genetic analysis of pure cells from forensic biological mixtures: The precision of a digital approach

Latest genotyping technologies allow to achieve a reliable genetic profile for the offender identification even from extremely minute biological evidence. The ultimate challenge occurs when genetic profiles need to be retrieved from a mixture, which is composed of biological material from two or more individuals. In this case, DNA profiling will often result in a complex genetic profile, which is then subject matter for statistical analysis. In principle, when more individuals contribute to a mixture with different biological fluids, their single genetic profiles can be obtained by separating the distinct cell types (e.g. epithelial cells, blood cells, sperm), prior to genotyping. Different approaches have been investigated for this purpose, such as fluorescent-activated cell sorting (FACS) or laser capture microdissection (LCM), but currently none of these methods can guarantee the complete separation of different type of cells present in a mixture. In other fields of application, such as oncology, DEPArray™ technology, an image-based, microfluidic digital sorter, has been widely proven to enable the separation of pure cells, with single-cell precision. This study investigates the applicability of DEPArray™ technology to forensic samples analysis, focusing on the resolution of the forensic mixture problem. For the first time, we report here the development of an application-specific DEPArray™ workflow enabling the detection and recovery of pure homogeneous cell pools from simulated blood/saliva and semen/saliva mixtures, providing full genetic match with genetic profiles of corresponding donors. In addition, we assess the performance of standard forensic methods for DNA quantitation and genotyping on low-count, DEPArray™-isolated cells, showing that pure, almost complete profiles can be obtained from as few as ten haploid cells. Finally, we explore the applicability in real casework samples, demonstrating that the described approach provides complete separation of cells with outstanding precision. In all examined cases, DEPArray™ technology proves to be a groundbreaking technology for the resolution of forensic biological mixtures, through the precise isolation of pure cells for an incontrovertible attribution of the obtained genetic profiles.

Optimized Configuration of Fixed-Tip Robotic Liquid-Handling Stations for the Elimination of Biological Sample Cross-Contamination

Robotic liquid-handling stations (RLHSs) are the mainstay of high-throughput biomedical/forensic DNA sample processing facilities. These liquid-handling systems can be alternatively tooled with either disposable or fixed-tip pipetting heads. The use of disposable tips is often perceived as the best tip configuration to eliminate cross-contamination between biological samples processed on liquid-handling stations. However, this suppression can be effectively achieved on instruments equipped with fixed tips with optimally designed tip wash station (WS) configurations. Fixed-tip instruments offer many significant sample processing advantages with respect to precision, pipetting of liquids that may contain aggregates, and operational cost. This report discusses how cross-contamination suppression was achieved for the reliable processing of forensic casework samples on specially configured fixed-tip TECAN Genesis RSP/Freedom EVO RLHSs. A critical analysis of the major components involved in tip washing, as well as the specifications of a redesigned tip-washing routine that increases wash effectiveness and significantly reduces processing time and cost is also presented.

DNA Extraction: Organic and Solid-Phase

DNA extraction remains a critical step in DNA profiling of biological material recovered from scenes of crime. In the forensic community several methods have gained popularity, including Chelex(®), organic extraction, and solid-phase extraction. While some laboratories streamlined their processes and only use one method we have retained several methods and continue to use these for different sample types. In this chapter we present three methods that have been used for several years in our laboratory.

The expression of thyroid hormone receptors (THR) is regulated by the progesterone receptor system in first trimester placental tissue and in BeWo cells in vitro

BACKGROUND

Thyroid hormones are essential for the maintenance of pregnancy and a deficiency in maternal thyroid hormones has been associated with early pregnancy losses. The aim of this study was a systematic investigation of the influence of mifepristone (RU 486) on the expression of the thyroid hormone receptor (THR) isoforms THRα1, THRα2, THRβ1 and THRβ2 on protein and mRNA-level.

METHODS

Samples of placental tissue were obtained from patients with mifepristone induced termination of pregnancy (n=13) or mechanical induced termination of normal pregnancy (n=20), each from the 4th to 13th week of pregnancy. Expression of THRα1, THRα2, THRβ1 and THRβ2 was analysed on protein level by immunohistochemistry and on mRNA level by real time RT-PCR (TaqMan). The influence of progesterone on THR gene expression was analysed in the trophoblast tumour cell line BeWo by real time RT-PCR (TaqMan).

RESULTS

Nuclear expression of THRα1, THRα2 and THRβ1 is downregulated on protein level in mifepristone (RU 486) treated villous trophoblast tissue. In decidual tissue, we found a significant downregulation only for THRα1 in mifepristone treated tissue. On mRNA level, we also found a significantly reduced expression of THRA but no significant downregulation for THRB in placental tissue. The gene THRA encodes the isoform THRα and the gene THRB encodes the isoform THRβ. The majority of cells expressing the thyroid hormone receptors in the decidua are decidual stromal cells. In addition, in vitro experiments with trophoblast tumour cells showed that progesterone significantly induced THRA but not THRB expression.

CONCLUSIONS

Termination of pregnancy with mifepristone (RU 486) leads to a downregulation of THRα1, THRα2 and THRβ1 in villous trophoblasts and in addition to a decreased expression of THRA in placental tissue. Decreased expression of THRα1 induced by RU486 could also be found in the decidua. Therefore inhibition of the progesterone receptor may be responsible for this downregulation. This assumption is supported by the finding, that stimulation of the progesterone receptor by progesterone itself up-regulated THRA in trophoblast cells in vitro.

Practical aspects of genetic identification of hallucinogenic and other poisonous mushrooms for clinical and forensic purposes

Aim

To assess the usefulness of a DNA-based method for identifying mushroom species for application in forensic laboratory practice.

Methods

Two hundred twenty-one samples of clinical forensic material (dried mushrooms, food remains, stomach contents, feces, etc) were analyzed. ITS2 region of nuclear ribosomal DNA (nrDNA) was sequenced and the sequences were compared with reference sequences collected from the National Center for Biotechnology Information gene bank (GenBank). Sporological identification of mushrooms was also performed for 57 samples of clinical material.

Results

Of 221 samples, positive sequencing results were obtained for 152 (69%). The highest percentage of positive results was obtained for samples of dried mushrooms (96%) and food remains (91%). Comparison with GenBank sequences enabled identification of all samples at least at the genus level. Most samples (90%) were identified at the level of species or a group of closely related species. Sporological and molecular identification were consistent at the level of species or genus for 30% of analyzed samples.

Conclusion

Molecular analysis identified a larger number of species than sporological method. It proved to be suitable for analysis of evidential material (dried hallucinogenic mushrooms) in forensic genetic laboratories as well as to complement classical methods in the analysis of clinical material.

Expression of Thyroid Hormone Receptors in Villous Trophoblasts and Decidual Tissue at Protein and mRNA Levels Is Downregulated in Spontaneous and Recurrent Miscarriages

Thyroid hormones are essential for the maintenance of pregnancy, and a deficiency in maternal thyroid hormones has been associated with early pregnancy losses. The expression of THRα1, THRβ1 and THRα2 increases with gestational age. The aim of this study was the investigation of the protein and mRNA-levels of THR isoforms THRα1, THRα2, THRβ1 and THRβ2 in normal, spontaneous and recurrent miscarriages. The identification of THR-expressing cells in the decidua was done with double immunofluorescence. The nuclear expression of THRα1, THRα2, THRβ1 and THRβ2 is downregulated at protein level in spontaneous and recurrent miscarriages in villous trophoblast tissue. In decidual tissue, we found a significant downregulation only for THRα1 in spontaneous miscarriages. For recurrent miscarriages, THRα1 and THRβ1 were both significantly downregulated in decidual tissue. By applying HLA-G as a trophoblast marker, we found a significant co-expression only for THRβ2. The results of our study show that thyroid hormone receptors THRα1, THRα2, THRβ1 and THRβ2 are downregulated in spontaneous and recurrent miscarriages. The majority of cells expressing the thyroid hormone receptors in the decidua are decidual stromal cells.

Comparison of an automated nucleic acid extraction system with the column-based procedure

Here, we assessed the extraction efficiency of a deployable bench-top nucleic acid extractor EZ1 in comparison to the column-based approach with complex sample matrices. A total of 48 EDTA blood samples and 81 stool samples were extracted by EZ1 automated extraction and the column-based QIAamp DNA Mini Kit. Blood sample extractions were assessed by two real-time malaria PCRs, while stool samples were analyzed by six multiplex real-time PCR assays targeting bacterial, viral, and parasitic stool pathogens. Inhibition control PCR testing was performed as well. In total, 147 concordant and 13 discordant pathogen-specific PCR results were obtained. The latter comprised 11 positive results after column-based extraction only and two positive results after EZ1 extraction only. EZ1 extraction showed a higher frequency of inhibition. This phenomenon was, however, inconsistent for the different PCR schemes. In case of concordant PCR results, relevant differences of cycle threshold numbers for the compared extraction schemes were not observed. Switches from well-established column-based extraction to extraction with the automated EZ1 system do not lead to a relevantly reduced yield of target DNA when complex sample matrices are used. If sample inhibition is observed, column-based extraction from another sample aliquot may be considered.

Pre-PCR processing in bioterrorism preparedness: improved diagnostic capabilities for laboratory response networks

Diagnostic DNA analysis using polymerase chain reaction (PCR) has become a valuable tool for rapid detection of biothreat agents. However, analysis is often challenging because of the limited size, quality, and purity of the biological target. Pre-PCR processing is an integrated concept in which the issues of analytical limit of detection and simplicity for automation are addressed in all steps leading up to PCR amplification--that is, sampling, sample treatment, and the chemical composition of PCR. The sampling method should maximize target uptake and minimize uptake of extraneous substances that could impair the analysis--so-called PCR inhibitors. In sample treatment, there is a trade-off between yield and purity, as extensive purification leads to DNA loss. A cornerstone of pre-PCR processing is to apply DNA polymerase-buffer systems that are tolerant to specific sample impurities, thereby lowering the need for expensive purification steps and maximizing DNA recovery. Improved awareness among Laboratory Response Networks (LRNs) regarding pre-PCR processing is important, as ineffective sample processing leads to increased cost and possibly false-negative or ambiguous results, hindering the decision-making process in a bioterrorism crisis. This article covers the nature and mechanisms of PCR-inhibitory substances relevant for agroterrorism and bioterrorism preparedness, methods for quality control of PCR reactions, and applications of pre-PCR processing to optimize and simplify the analysis of various biothreat agents. Knowledge about pre-PCR processing will improve diagnostic capabilities of LRNs involved in the response to bioterrorism incidents.

Purification of crime scene DNA extracts using centrifugal filter devices

BACKGROUND

The success of forensic DNA analysis is limited by the size, quality and purity of biological evidence found at crime scenes. Sample impurities can inhibit PCR, resulting in partial or negative DNA profiles. Various DNA purification methods are applied to remove impurities, for example, employing centrifugal filter devices. However, irrespective of method, DNA purification leads to DNA loss. Here we evaluate the filter devices Amicon Ultra 30 K and Microsep 30 K with respect to recovery rate and general performance for various types of PCR-inhibitory crime scene samples.

METHODS

Recovery rates for DNA purification using Amicon Ultra 30 K and Microsep 30 K were gathered using quantitative PCR. Mock crime scene DNA extracts were analyzed using quantitative PCR and short tandem repeat (STR) profiling to test the general performance and inhibitor-removal properties of the two filter devices. Additionally, the outcome of long-term routine casework DNA analysis applying each of the devices was evaluated.

RESULTS

Applying Microsep 30 K, 14 to 32% of the input DNA was recovered, whereas Amicon Ultra 30 K retained 62 to 70% of the DNA. The improved purity following filter purification counteracted some of this DNA loss, leading to slightly increased electropherogram peak heights for blood on denim (Amicon Ultra 30 K and Microsep 30 K) and saliva on envelope (Amicon Ultra 30 K). Comparing Amicon Ultra 30 K and Microsep 30 K for purification of DNA extracts from mock crime scene samples, the former generated significantly higher peak heights for rape case samples (P-values <0.01) and for hairs (P-values <0.036). In long-term routine use of the two filter devices, DNA extracts purified with Amicon Ultra 30 K were considerably less PCR-inhibitory in Quantifiler Human qPCR analysis compared to Microsep 30 K.

CONCLUSIONS

Amicon Ultra 30 K performed better than Microsep 30 K due to higher DNA recovery and more efficient removal of PCR-inhibitory substances. The different performances of the filter devices are likely caused by the quality of the filters and plastic wares, for example, their DNA binding properties. DNA purification using centrifugal filter devices can be necessary for successful DNA profiling of impure crime scene samples and for consistency between different PCR-based analysis systems, such as quantification and STR analysis. In order to maximize the possibility to obtain complete STR DNA profiles and to create an efficient workflow, the level of DNA purification applied should be correlated to the inhibitor-tolerance of the STR analysis system used.

Overcoming inhibition in real-time diagnostic PCR

PCR is an important and powerful tool in several fields, including clinical diagnostics, food analysis, and forensic analysis. In theory, PCR enables the detection of one single cell or DNA molecule. However, the presence of PCR inhibitors in the sample affects the amplification efficiency of PCR, thus lowering the detection limit, as well as the precision of sequence-specific nucleic acid quantification in real-time PCR. In order to overcome the problems caused by PCR inhibitors, all the steps leading up to DNA amplification must be optimized for the sample type in question. Sampling and sample treatment are key steps, but most of the methods currently in use were developed for conventional diagnostic methods and not for PCR. Therefore, there is a need for fast, simple, and robust sample preparation methods that take advantage of the accuracy of PCR. In addition, the thermostable DNA polymerases and buffer systems used in PCR are affected differently by inhibitors. During recent years, real-time PCR has developed considerably and is now widely used as a diagnostic tool. This technique has greatly improved the degree of automation and reduced the analysis time, but has also introduced a new set of PCR inhibitors, namely those affecting the fluorescence signal. The purpose of this chapter is to view the complexity of PCR inhibition from different angles, presenting both molecular explanations and practical ways of dealing with the problem. Although diagnostic PCR brings together scientists from different diagnostic fields, end-users have not fully exploited the potential of learning from each other. Here, we have collected knowledge from archeological analysis, clinical diagnostics, environmental analysis, food analysis, and forensic analysis. The concept of integrating sampling, sample treatment, and the chemistry of PCR, i.e., pre-PCR processing, will be addressed as a general approach to overcoming real-time PCR inhibition and producing samples optimal for PCR analysis.

Hair Analysis for Determination of Isoniazid Concentrations and Acetylator Phenotype during Antituberculous Treatment

Background. Analysis of isoniazid (INH) uptake has been based on measurement of plasma concentrations providing a short-term and potentially biased view. Objectives. To establish hair analysis as a tool to measure long-term uptake of INH and to assess whether acetylator phenotype in hair reflects N-acetyltransferase-2 (NAT2) genotype. Design and Methods. INH and acetyl-INH concentrations in hair were determined in patients on INH treatment for M. tuberculosis infection using high pressure liquid chromatography/mass spectrometry. Acetyl-INH/INH ratios were correlated with NAT-2 genotype. Results. Hair concentrations of INH, determined in 40 patients, were not dependent on ethnic group or body mass index and were significantly higher in male compared to female patients (median (range) 2.37 ng/mg (0.76–4.9) versus 1.11 ng/mg (0.02–7.20) (P = 0.02). Acetyl-INH/INH ratios were a median of 15.2% (14.5 to 31.7) in homozygous rapid acetylator NAT-2 genotype and 37.3% (1.73 to 51.2) in the heterozygous rapid acetylator NAT-2 genotype and both significantly higher than in the slow acetylator NAT-2 genotype with 5.8% (0.53 to 14.4) (P < 0.05). Conclusions. Results of hair analysis for INH showed lower concentrations in females. Acetyl-INH/INH ratios were significantly lower in patients with slow acetylator versus rapid acetylator genotypes.

Automated Extraction of DNA from Blood and PCR Setup using a Tecan Freedom EVO Liquid Handler for Forensic Genetic STR Typing of Reference Samples

We have implemented and validated automated protocols for DNA extraction and PCR setup using a Tecan Freedom EVO liquid handler mounted with the Te-MagS magnetic separation device (Tecan, Mannedorf, Switzerland). The protocols were validated for accredited forensic genetic work according to ISO 17025 using the Qiagen MagAttract DNA Mini M48 kit (Qiagen GmbH, Hilden, Germany) from fresh whole blood and blood from deceased individuals. The workflow was simplified by returning the DNA extracts to the original tubes minimizing the risk of misplacing samples. The tubes that originally contained the samples were washed with MilliQ water before the return of the DNA extracts. The PCR was setup in 96-well microtiter plates. The methods were validated for the kits: AmpFSTR Identifier, SGM Plus and Yfiler (Applied Biosystems, Foster City, CA), GenePrint FFFL and PowerPlex Y (Promega, Madison, Wl). The automated protocols allowed for extraction and addition of PCR master mix of 96 samples within 3.5 h. In conclusion, we demonstrated that (1) DNA extraction with magnetic beads and (2) PCR setup for accredited, forensic genetic short tandem repeat typing can be implemented on a simple automated liquid handler leading to the reduction of manual work, and increased quality and throughput.

Extracting evidence from forensic DNA analyses: future molecular biology directions

Molecular biology tools have enhanced the capability of the forensic scientist to characterize biological evidence to the point where it is feasible to analyze minute samples and achieve high levels of individualization. Even with the forensic DNA field's maturity, there still are a number of areas where improvements can be made. These include: enabling the typing of samples of limited quantity and quality; using genetic information and novel markers to provide investigative leads; enhancing automation with robotics, different chemistries, and better software tools; employing alternate platforms for typing DNA samples; developing integrated microfluidic/microfabrication devices to process DNA samples with higher throughput, faster turnaround times, lower risk of contamination, reduced labor, and less consumption of evidentiary samples; and exploiting high-throughput sequencing, particularly for attribution in microbial forensics cases. Knowledge gaps and new directions have been identified where molecular biology will likely guide the field of forensics. This review aims to provide a roadmap to guide those interested in contributing to the further development of forensic genetics.

Optimization of DNA Extraction from Low-Yield and Degraded Samples Using the BioRobot�EZ1 and BioRobot�M48

Robotic extraction of DNA from dilutions of blood and semen using either the BioRobots EZ1 or BioRobots M48 consistently produced lower recoveries than standard organic extractions of the same samples. In an effort to increase the efficiency of robotically extracted DNA, glycogen and carrier RNA were added following cell lysis. The addition of glycogen, postlysis, resulted in no improvement in DNA recovery with the BioRobot EZ1. However, when carrier RNA was added to the cell lysate of limited and degraded samples extracted on the EZ1 or the M48, DNA recoveries dramatically increased four- to 20-fold. DNA yields obtained by robotic extraction in the presence of carrier RNA were as high, or higher, as those obtained by organic extraction lacking carrier RNA, while experiments that utilized carrier RNA in both types of extractions showed increased sensitivity for both methods. Furthermore, carrier RNA substantially increased the recovery of fragmented DNA with the EZ1.

Topical calcineurin inhibitors decrease the production of UVB-induced thymine dimers from hairless mouse epidermis

BACKGROUND

An increased incidence of ultraviolet-light-related skin tumours is a well-known problem in patients undergoing posttransplantation immunosuppression with systemic calcineurin inhibitors such as cyclosporine A or tacrolimus. UV-related carcinogenesis as a consequence of long-term treatment of sun-exposed sites with topical calcineurin inhibitors is therefore of theoretical concern.

RESULTS

In this study, we show that tacrolimus acts as a UVB filter when incorporated into liposome membranes. In hairless mice pretreated with 1% pimecrolimus cream, 0.1% tacrolimus ointment or vehicle, the amount of epidermal thymine dimers, measured 1 h after 1 J/cm2 of UVB irradiation, was decreased by 89, 84 and 47%, respectively, as compared to untreated mice. Forty-eight hours after UVB irradiation, 97, 89 and 93% of epidermal thymine dimer levels were removed in pimecrolimus-, tacrolimus- or vehicle-treated mice, respectively. In contrast, 69% of thymine dimers, originally present in much higher amounts than in treated mice, were removed from untreated controls. UVB-induced apoptosis was less pronounced in treated mice.

CONCLUSION

Taken together, these results suggest that topical calcineurin inhibitors prevent DNA photodamage due to a filter effect of both vehicle and active components, whereas they do not affect the clearance of DNA photoproducts.