Craniosynostosis and the role of stem/progenitor cells in premature suture fusion and accelerated bone formation
Craniosynostosis, the premature fusion of one or more cranial sutures, is a relatively common malformation occurring in one in 2,000 live human births and represents a clinical condition where bone formation is accelerated. Restriction of normal brain growth caused by prematurely fused sutures can lead to significant complications, and affected children face complex surgical remodeling of the skull to prevent functional and anatomical deficits. Furthermore, recent evidence suggests current surgical therapies are not entirely effective, thereby necessitating additional surgeries. Suture fusion, including that in nonsyndromic craniosynostosis (NSC), is controlled by a complex interaction between many different types of cells, tissue types, and growth factors. Enhanced bone formation during suture fusion may be related to increased local concentrations of tissue-produced bone-inducing factors (proteins) stemming from deficiencies in the local extracellular matrix (ECM) to appropriately bind and sequester these factors. New treatment strategies designed to control local concentrations of these factors employ the localized application of inhibitors of bone formation, yet this approach lacks long term effectiveness due to difficulties in delivering sufficient concentrations. Coupled with current surgical approaches, this strategy will likely only delay recurrence of suture fusion. Moreover, this approach does not take into consideration the impact of the extracellular matrix (ECM) and its contributions to protein signaling. Therefore, this proposal seeks to generate a carefully engineered, highly tunable ECM capable of binding locally produced bone-inducing proteins while providing a viable graft alternative to native bone tissue. To fulfill this goal, we will complete the following tasks: 1) Characterize the natural ECM produced by mesenchymal stem cells (MSCs) from patients diagnosed with NSC in each fused human suture and, upon comparing it to ECM produced by healthy human subjects, determine targets for engineering this matrix; 2) Modify the composition of ECM produced by MSCs from NSC patients to mimic the ECM composition produced by MSCs of healthy human patients; 3) Determine the response of bone-forming cells from patients affected by NSC to bone-inducing proteins when seeded on engineered graft biomaterials coated with modified ECMs; and 4) Determine the capacity of engineered biomaterials to modulate bone formation in a developing suture using an in vivo bone defect model. Successful completion of these proposed aims will yield several important outcomes that may lead to more effective strategies to reverse the damaging effects of premature fusion, provide new approaches to treat conditions where accelerated bone formation would be advantageous, and greatly facilitate the PI’s long-term goal of developing effective strategies for controlling stem cell fate with instructive biomaterials for tissue repair.
Congenital bone abnormalities, bone loss, and defects resulting from trauma pose a significant health problem that impacts individuals across the lifespan. Conventional therapies for bone-related abnormalities commonly require the grafting of bone segments into the defect (more than 500,000 procedures annually), yet a lack of sufficient material often precludes such therapies. Moreover, greater than 10% of all bone defects are nonhealing, with an even higher prevalence of nonunions in the elderly. Given that at least 20% of California’s population will be over the age of 65 by 2025, it is imperative that new approaches to bone repair are developed. This proposal has two primary goals. First, we seek to develop a novel approach for modulating bone repair using mesenchymal stem cells (MSCs) derived from patients diagnosed with nonsymptomatic craniosynostosis (NCS), a condition resulting in accelerated cranial suture fusion, by modulating the cell-produced local microenvironment. Second, we propose to exploit knowledge gained from the basic studies using these cells, tissues, and engineered biomaterials to control the rate of bone formation in vivo. Successfully achieving these primary goals will benefit the State of California and its citizens in several ways. Our findings may provide a novel means to treat children diagnosed with NSC by developing a novel bone graft. Clinical utilization of this system could markedly lower the recurrence of suture fusion, reduce the need for repeated surgical procedures, and conceivably improve the quality of life for these patients. These approaches could also have value in other health conditions where accelerated bone formation is warranted including osteogenesis imperfecta and osteoporosis. Also, the versatile technology developed here will have applications to other tissue engineering approaches that could benefit the biotechnology companies of California investing in regenerative medicine. Finally, we anticipate that the proposed studies will not only broaden the PI’s current research approaches to tissue repair by enhancing his development as an independent stem cell researcher, but will also directly benefit young scientists and researchers in training among the respective collaborating laboratories. Exposure of students to novel stem cell-related research may provide the greatest benefit to California by inspiring future leaders in science to pursue their research efforts within the state or develop products and therapies at California-based biotechnology companies.