Lack of immunogenicity of xenogeneic DNA from porcine biomaterials.

Background: Clinically useful biomaterials are derived from xenogeneic extracellular matrices, but extensive processes often used to remove all residual DNA are detrimental to their proper biological function. We hypothesized that deliberate and repeated injection of DNA extracted from clinically implantable, xenogeneic extracellular matrices might elicit an immune response in a well-established murine model that could ultimately lead to altered extracellular matrix remodeling. Methods: DNA was purified from unprocessed porcine extracellular matrices and processed extracellular matrices before sterilization (aseptic) and after sterilization. Groups of 10 mice were injected with these 3 purified DNAs and 3 controls: (1) DNA from E. coli; (2) DNA from unprocessed porcine extracellular matrices combined with interleukin-12 and methylated bovine serum albumin and emulsified in incomplete Freund's adjuvant; and (3) buffered saline. Immunizations occurred every 2 weeks for a total of 3 injections. Local cytokines and systemic anti-DNA antibodies were quantified 3 and 7 days after final injection. Results: The DNA extracted from unprocessed, aseptic, or sterilized porcine extracellular matrices failed to elicit a rejection response, and only with significant, proinflammatory adjuvant activation could such a response be seen. Without the adjuvants, biomaterial-derived DNA resulted in a mild accommodation cytokine response locally and no systemic anti-DNA antibody expression even at doses approximately 100-fold larger than would be clinically likely via extracellular matrix implantation. Conclusion: The immunological safety of porcine extracellular matrix biomaterials appears not to be related to DNA residues present. Such biomaterials need not be extensively processed, likely leading to detrimental changes in their bioactivity, solely in an effort to remove the mammalian DNA.

Are biologic grafts effective for hernia repair?: a systematic review of the literature.

Biologic grafts for hernia repair are a relatively new development in the world of surgery. A thorough search of the Medline database for uses of various biologic grafts in hernia shows that the evidence behind their application is plentiful in some areas (ventral, inguinal) and nearly absent in others (parastomal). The assumption that these materials are only suited for contaminated or potentially contaminated surgical fields is not borne out in the literature, with more than 4 times the experience being reported in clean fields and the average success rates being higher (93% vs 87%). Outcomes prove to be highly dependent on material source, processing methods and implant scenarios with failure rates ranging from zero to more than 30%. Small intestinal submucosa (SIS) grafts have an aggregate failure rate of 6.7% at 19 months whereas acellular human dermis (AHD) grafts have a failure rate of 13.6% at 12 months. Chemically cross-linked grafts have much less published data than the non-cross-linked materials. In particular, the search found 33 articles for SIS, 32 for AHD, and 13 for cross-linked porcine dermis. Furthermore, the cumulative level of evidence for each graft material was fairly low (2.6 to 2.9), and only 1 material (SIS) had level 1 evidence reported in any hernia type (inguinal and hiatal). Together, biologic grafts have published evidence showing success rates better than 90% overall and more than 2000 years of cumulative implant time. Improvements in materials, techniques, and patient selection are likely to improve these numbers as this field of surgery matures.

TILLING to detect induced mutations in soybean.

BACKGROUND: Soybean (Glycine max L. Merr.) is an important nitrogen-fixing crop that provides much of the world's protein and oil. However, the available tools for investigation of soybean gene function are limited. Nevertheless, chemical mutagenesis can be applied to soybean followed by screening for mutations in a target of interest using a strategy known as Targeting Induced Local Lesions IN Genomes (TILLING). We have applied TILLING to four mutagenized soybean populations, three of which were treated with ethyl methanesulfonate (EMS) and one with N-nitroso-N-methylurea (NMU). RESULTS: We screened seven targets in each population and discovered a total of 116 induced mutations. The NMU-treated population and one EMS mutagenized population had similar mutation density (approximately 1/140 kb), while another EMS population had a mutation density of approximately 1/250 kb. The remaining population had a mutation density of approximately 1/550 kb. Because of soybean's polyploid history, PCR amplification of multiple targets could impede mutation discovery. Indeed, one set of primers tested in this study amplified more than a single target and produced low quality data. To address this problem, we removed an extraneous target by pretreating genomic DNA with a restriction enzyme. Digestion of the template eliminated amplification of the extraneous target and allowed the identification of four additional mutant alleles compared to untreated template. CONCLUSION: The development of four independent populations with considerable mutation density, together with an additional method for screening closely related targets, indicates that soybean is a suitable organism for high-throughput mutation discovery even with its extensively duplicated genome.