Engineering bone grafts with enhanced bone marrow and native scaffolds.

The translation of tissue engineering approaches to the clinic has been hampered by the inability to find suitable multipotent cell sources requiring minimal in vitro expansion. Enhanced bone marrow (eBM), which is obtained by reaming long bone medullary canals and isolating the solid marrow putty, has large quantities of stem cells and demonstrates significant potential to regenerate bone tissues. eBM, however, cannot impart immediate load-bearing mechanical integrity or maintain the gross anatomical structure to guide bone healing. Yet, its putty-like consistency creates a challenge for obtaining the uniform seeding necessary to effectively combine it with porous scaffolds. In this study, we examined the potential for combining eBM with mechanically strong, osteoinductive trabecular bone scaffolds for bone regeneration by creating channels into scaffolds for seeding the eBM. eBM was extracted from the femurs of adult Yorkshire pigs using a Synthes reamer-irrigator-aspirator device, analyzed histologically, and digested to extract cells and characterize their differentiation potential. To evaluate bone tissue formation, eBM was seeded into the channels in collagen-coated or noncoated scaffolds, cultured in osteogenic conditions for 4 weeks, harvested and assessed for tissue distribution and bone formation. Our data demonstrates that eBM is a heterogenous tissue containing multipotent cell populations. Furthermore, coating scaffolds with a collagen hydrogel significantly enhanced cellular migration, promoted uniform tissue development and increased bone mineral deposition. These findings suggest the potential for generating customized autologous bone grafts for treating critical-sized bone defects by combining a readily available eBM cell source with decellularized trabecular bone scaffolds.

F2 screening for resistance to pyramided Bacillus thuringiensis maize in Louisiana and Mississippi populations of Diatraea saccharalis (Lepidoptera: Crambidae).

BACKGROUND: In the mid-southern region of the United States, sugarcane borer, Diatraea saccharalis (F.), is a major target pest of transgenic maize expressing Bacillus thuringiensis (Bt) proteins. Novel transgenic maize technologies containing two or more pyramided Bt genes for controlling lepidopteran pests have recently become commercially available. Insect resistance management (IRM) is an important issue in the sustainable use of Bt crop technologies. The objective of this study was to determine the frequency of resistance alleles in field populations of D. saccharalis to the new pyramided Bt maize technologies. RESULTS: A total of 382 F(2) family lines derived from 735 feral larvae/pupae of D. saccharalis collected from six locations in Louisiana and Mississippi during 2008 and 2009 were screened for resistance to three new Bt maize technologies: MON 89034, Genuity™ VT Triple Pro™ and SmartStax™. None of the 382 F(2) isoline families survived on the Bt maize leaf tissue for ≥ 12 days in the F(2) screen. The joint frequency for two- or three-gene resistance models with 95% probability in these populations was estimated to be < 0.0063 to MON 89034 and < 0.003 to VT Triple Pro™ and SmartStax™. CONCLUSION: These results suggest that the resistance allele frequency in D. saccharalis to the three pyramided Bt maize technologies is low in the mid-southern region of the United States, which should meet the rare resistance assumption of the currently used IRM strategy for Bt maize.