Novel lipid-protein-sugar particles (LPSPs) are potentially biocompatible because they are composed of naturally occurring ingredients and their expected tissue dwell times are relatively short. In this research, we used histological sections to study tissue reaction to LPSPs (4.4-microm median diameter) when used for sciatic nerve block in the rat. As a reference, we compared LPSPs to 60-microm median diameter poly(lactic-co-glycolic) acid (PLGA) microspheres (110,000 MW PLGA, glycolic/lactic ratio 65:35). Four days after injection, both particle types produced acute inflammation within the confines of the injectate, inflammation in adjacent tissues, and myotoxicity. Bupivacaine-free particles did not display myotoxicity, and inflammation in adjacent tissues was reduced. At 2 weeks, inflammation from LPSPs had almost disappeared, whereas PLGA microspheres had a foreign-body giant cell reaction until at least 8 weeks after injection. In contrast, 3.6-microm median diameter, 20,000-MW PLGA microspheres produced a primarily histiocytic reaction 2 weeks after injection. In summary, the LPSPs and PLGA microspheres studied herein have excellent biocompatibility, but tissue reaction to the former is of much shorter duration. Myotoxicity and inflammation of surrounding tissue is largely attributed to bupivacaine. Foreign-body giant cells may be attributed to particle size rather than a specific reaction to PLGA.

These results provide the first definitive evidence that normal human cells exhibit an intrinsic sex-specific response to E2 and suggest that sexual dimorphism may be an important variable in assessing the pathways that modulate cell behavior.

Demineralized bone matrix (DBM) has been touted as an excellent grafting material; however, there are no Level I studies that use DBM alone in humans to back up this claim. DBM functions best in a healthy tissue bed but should be expected to have little impact in an anoxic or avascular tissue bed, a situation often encountered in traumatic orthopaedic pathologies. Moreover, there is some evidence of differential potencies of DBM preparations based on donor variability and the manufacturing process. DBM efficacy may also be related to its formulation and the various carriers used. The fact that DBM is an allogeneic material opens up the potential for disease transmission. In addition, DBM activity may be altered by the hormonal status or nicotine use of a patient. In summary, although DBM has proven effective for bone induction in lower form animals, the translation to human clinical use for fracture healing, and the burden of proof, remains.

ADSCs can be readily cultured, encapsulated, and injected in alginate microspheres. Stem cells suspended in alginate microspheres survive in vivo and are seen to replicate in vitro.