Collagen Scaffolds Incorporating Select Therapeutic Agents to Facilitate a Reparative Response in a Standardized Hemiresection Defect in the Rat Spinal Cord

A multifaceted therapeutic approach involving biomaterial scaffolds, neurotrophic factors, exogenous cells, and antagonists to axon growth inhibitors may ultimately prove necessary for the treatment of defects resulting from spinal cord injury (SCI). The objective of this study was to begin to lay the groundwork for such strategies by implanting type I collagen scaffolds alone and incorporating individually a soluble Nogo receptor, chondroitinase ABC (ChABC), and mesenchymal stem cells (MSCs) into a standardized 3-mm-long hemiresection defect in the rat spinal cord. Statistically significant improvement in hindlimb motor function between the first and fourth weeks post-SCI was recorded for the scaffold-alone group and for the ChABC and MSC groups, but not the control group. Four weeks post-SCI, the scaffolds appeared intact with open pores, which were infiltrated with host cells. Of note is that in some cases, a few growth-associated protein 43 (GAP-43)-positive axons were seen reaching the center of the scaffold in the scaffold-alone and ChABC groups, but not in control animals. Angiogenic cells were prevalent in the scaffolds; however, the number of both macrophages and angiogenic cells in the scaffolds was significantly less than in the control lesion at 4 weeks. The results lay the foundation for future dose–response studies and to further investigate a range of therapeutic agents to enhance the regenerative response in SCI.Gates Millennium Scholars Program (Fellowship

The Use of Extracorporeal Shock Wave-Stimulated Periosteal Cells for Orthotopic Bone Generation

The cambium cells of the periosteum, which are known osteoprogenitor cells, have limited suitability for clinical applications of tissue engineering in their native state due to their low cell number (2–5 cells thick). Extracorporeal shock waves (ESWs) have been shown to cause rapid periosteal cambium cell proliferation and subsequent periosteal osteogenesis. This work investigates a novel strategy for orthotopic bone generation: applying ESW therapy as a noninvasive, inexpensive, and rapid method for stimulating cambium cell proliferation, and combining these cells with a bioactive scaffold for bone growth. ESWs applied to the rabbit medial tibia resulted in a significant 2.7-fold increase in cambium cell number and a 4-fold increase in cambium cell thickness at 4 days post-ESW. ESW-stimulated, or nontreated control, periosteal cells were elevated in situ and overlaid on an anorganic bovine bone scaffold to interrogate their ability to form bone. At 2 weeks post-surgery, there was a significant increase in all key outcome variables for the ESW-stimulated group when compared with controls: a 4-fold increase in osseous tissue in the upper half of the scaffold underlying the periosteum; a 12-fold increase in osseous tissue overlying the scaffold; and a 2-fold increase in callus size. These results successfully demonstrated the efficacy of ESW-stimulated periosteum for orthotopic bone generation