Waste recombinant DNA: effectiveness of thermo-treatment to manage potential gene pollution

Comparison of two independent systematic reviews of trials of recombinant human bone morphogenetic protein-2 (rhBMP-2): the Yale Open Data Access Medtronic Project

BACKGROUND

It is uncertain whether the replication of systematic reviews, particularly those with the same objectives and resources, would employ similar methods and/or arrive at identical findings. We compared the results and conclusions of two concurrent systematic reviews undertaken by two independent research teams provided with the same objectives, resources, and individual participant-level data.

METHODS

Two centers in the USA and UK were each provided with participant-level data on 17 multi-site clinical trials of recombinant human bone morphogenetic protein-2 (rhBMP-2). The teams were blinded to each other's methods and findings until after publication. We conducted a retrospective structured comparison of the results of the two systematic reviews. The main outcome measures included (1) trial inclusion criteria; (2) statistical methods; (3) summary efficacy and risk estimates; and (4) conclusions.

RESULTS

The two research teams' meta-analyses inclusion criteria were broadly similar but differed slightly in trial inclusion and research methodology. They obtained similar results in summary estimates of most clinical outcomes and adverse events. Center A incorporated all trials into summary estimates of efficacy and harms, while Center B concentrated on analyses stratified by surgical approach. Center A found a statistically significant, but small, benefit whereas Center B reported no advantage. In the analysis of harms, neither showed an increased cancer risk at 48 months, although Center B reported a significant increase at 24 months. Conclusions reflected these differences in summary estimates of benefit balanced with small but potentially important risk of harm.

CONCLUSIONS

Two independent groups given the same research objectives, data, resources, funding, and time produced broad general agreement but differed in several areas. These differences, the importance of which is debatable, indicate the value of the availability of data to allow for more than a single approach and a single interpretation of the data.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42012002040 and CRD42012001907 .

Persistence and renaturation efficiency of thermally treated waste recombinant DNA in defined aquatic microcosms

To validate the possibility of horizontal gene transfer (HGT) from thermally denatured recombinant DNA discharged into the eco-system, a constructed plasmid was used to investigate the persistence and renaturation efficiency of thermally denatured recombinant DNA in defined aquatic microcosms. The results revealed that there was undecayed recombinant plasmid pMDLKJ material being discharged into the aquatic microcosms even after thermal treatment at either 100°C (using boiling water) or at 120°C (using an autoclave). The plasmid had a relatively long persistence time. At least 10(2) copies μL(-1) of a specific 245 bp fragment of the plasmid could be detected after 12 h and a specific 628 bp fragment could be detected up to 2 h. The thermally denatured recombinant DNA could efficiently renature and recover its functional double stranded structure in aquatic microcosms and the highest concentration of double-stranded DNA (dsDNA) occurred around 1 h after the thermally denatured DNA was added to the system. These results imply that when thermally treated recombinant DNAs are discharged into aquatic environments, they have enough time to renature and possibly transfer to other organisms. In addition, the recombinant DNA added to aquatic microcosms could be absorbed by the seston particles in water, such as mineral, organic and colloids particles with a maximum absorption value of about 5.18 ng L(-1). This absorbed DNA could persist longer in aquatic environments than free recombinant DNA, thus further favoring HGT.

Potential ecological risks of thermal-treated waste recombination DNA discharged into an aquatic environment

It has been shown that thermal-treatment at 100 ° C can denature deoxyribonucleic acid (DNA), yet this does not cause it to break down completely. To clarify the risk of gene pollution from thermal-treated recombinant DNA, the renaturation characteristics of thermal-denatured plasmid pET-28b and its persistence in aquatic environments were investigated. The results revealed that the double-stranded structure and transforming activity of the thermal-treated plasmid DNA could be recovered even if the thermal-treatment was conducted at 120 ° C. The presence of sodium chloride (NaCl) and ethylenediamine tetraacetic acid (EDTA) led to the increase of renaturation efficiency of the denatured DNA. When thermal-treated plasmid DNA was discharged into simulated aquatic environments with pH values from 5 to 9, it showed a longer persistence at pH 7 and 8 than that at 5, 6 and 9; however, the denatured plasmid DNA could persist for more than 33 min at any pH. Moreover, a higher ionic strength further protected the thermal-denatured plasmids from degradation in the simulated aquatic environment. These results indicated that when the thermal-treated DNA was discharged into an aquatic environment, it might not break down completely in a short period. Therefore, there is the potential for the discarded DNA to renature and transform, which might result in gene pollution.