Browsing by Author "Gregory, Carl"

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Advanced Methods for Mimicking the Osteogenic Niche to Heal Bone
Molecular And Cellular Medicine; TAMHSC; https://hdl.handle.net/20.500.14641/638; DHHS-NIH-National Institute of Arthritis and Musculoskeletal and Skin Diseases
DESCRIPTION (provided by applicant): Of the 13 million yearly fractures that occur in the United States, about 10% fail to repair and in extreme cases this can result in immobility or amputation. While autologous bone grafts are the most effective method to heal complex defects, the available graft material is limited, and the procedure involves additional surgery known to cause chronic donor-site pain in many patients. Human mesenchymal stem cells (hMSCs) have been intensely investigated for their ability to promote bone healing, but results have been variable and disappointing. This is partly due to variability in cell preparations that occurs through donor variation or through inconsistent culture methodologies. Our work has also indicated that hMSCs are not retained at the site of injury for sufficient time to achieve engraftment and promote repair. In an attempt to solve these problems, we recently demonstrated that acceleration of canonical Wnt signaling with the small molecule PPAR¿ inhibitor GW9662 produces osteogenically enhanced hMSCs (OEhMSCs). Further, these OEhMSCs produce extracellular matrix (hMatrix) that dramatically increases OEhMSC retention and bone repair in calvarial and femoral defects. Our central hypothesis for this proposal is that an injectable microsphere vehicle co-administering GW9662, hMatrix and hMSCs will promote osteo- repair through a mechanism that involves extended hMSC retention, trophic factor secretion and paracrine activation of the host stroma. Our hypothesis will be tested via three Specific Aims. Aim 1: Optimize the delivery of OEhMSCs, hMatrix and GW9662 via collagen/poly (lactide-co-glycolide) capsules in vitro. Aim 2: Evaluate bone repair in immune-compromised murine models of calvarial and femoral trauma. Aim 3: Delineate the mechanisms by which the hMatrix components collagen types VI and XII and their cognate integrins increase OEhMSC retention and expression of osteoinductive and angiogenic paracrine factors. These studies will lay the groundwork for translating this novel hMSC-based method for osteo-repair to the clinic. Successful completion of this project could lead to a revolutionary new method for bone repair that could effectively dismiss the need for autologus bone graft in regenerative orthopedics. Our multi-disciplinary team of stem cell biologists, biochemists, bioengineers, orthopedic clinicians and commercialization experts are highly equipped to achieve the goals of the project.
Nanoengineered bone repair scaffolds generated from stem cells and their secreted products for improved spinal fusion
Molecular And Cellular Medicine; TAMU; https://hdl.handle.net/20.500.14641/638; DHHS-NIH-National Institute of Arthritis and Musculoskeletal and Skin Diseases
Degenerative disc disease is an epidemic, ultimately resulting in untenable pain and immobility. In advanced cases, spinal fusion is performed where vertebrae are surgically fixed with a mechanical device and an osteogenic material (bone substitute) is bridged between them in an attempt to induce fusion. Of the 600,000 yearly procedures performed in the US, the most common is posterolateral lumbar arthrodesis but the failure rate can reach 25-40% with standard commercial bone substitutes. The reason for failure rests in part with limited biocompatibility of synthetic bone substitutes, inconsistencies with processed cadaveric bone substitutes and in some cases, health complications caused by supraphysiologic doses of bone morphogenic protein. Autologous bone grafts are much more effective, but the approach is associated with donor site morbidity and the volume of available graft is limited. Compromising strategies that employ bone substitutes and bone marrow aspirate (BMA) are becoming common, but efficacy continues to be limited by the bone substitute. The fact that spine related disability is a growing global problem and standard of care interventions have an unacceptable failure rate clearly demonstrates the need for implants that safely and effectively promote bone fusion. The successes and failures of past spinal fusion strategies indicate that a bone substitute that mimics autograft will meet this need. Therefore, the goal of this proposal is to develop a 3D printed biomimetic bone graft substitute (the scaffold) by an innovative combination of stem cell biology, matrix biology, and biomedical engineering. The scaffold will consist of a tough, porous and flexible nanoengineered hydrogel consisting of gelatin methacrylate (gel-MA) coated with extracellular matrix (ECM) purified from osteogenically enhanced human mesenchymal stem cells derived from induced pluripotent stem cells (OEihMSCs). By mimicking the composition of bone matrix, OEihMSC-derived ECM is highly osteogenic. The gel-MA will be further enhanced by addition of novel silicate nanoparticles that impart stiffness and further stimulate osteogenesis. The scaffold will be designed to drive fusion with efficacy equivalent to autograft, but it will be manufactured from a standardized and sustainable source of materials. To achieve this goal, we will: optimize methodology for the generation of various forms of scaffold with a range of gel-MA, nanosilicate and ECM formulations with variations in macroporosity and stiffness (Aim1), optimize attachment, distribution, viability and osteogenesis of cells on the scaffold using in vitro 3D cell culture assays based on rotating wall bioreactor technology (Aim2) and finally, test the optimized scaffold with human BMA in a rodent posterolateral fusion model, incorporating imaging and biomechanical testing approaches (Aim 3). The rationale for this approach is that it has the capacity to satisfy a need for safe and effective autologous bone repair scaffolds for a rapidly growing population. With the current disposition of the FDA favoring autologous and minimally manipulated cytotherapeutic preparations, this strategy is well suited to clinical translation.