Discipline: Chemistry and Chemical Sciences
Subcategory: Biochemistry (not Cell and Molecular Biology and Genetics)
Room: Exhibit Hall A
Dominique Joseph - University of Missouri- Columbia
Co-Author(s): Catherine Omosule, University of Missouri, Columbia MO Victoria Gremminger, University of Missouri, Columbia MO Youngjae Jeong (PhD), University of Missouri, Columbia MO Sandra Kleiner (PhD), University of Missouri, Columbia MO Charlotte Phillips (PhD), University of Missouri, Columbia MO
Osteogenesis imperfecta (OI), also known as brittle bone disease, is an incurable connective tissue disorder primarily caused by mutations in the type I collagen genes and phenotypically manifested in type I collagen-containing tissues, particularly bone. The Sillence classification system identifies four main types of OI ranging in severity, with type I being mild; type II, perinatal lethal; type III, severely deforming; and type IV, moderately deforming. Our laboratory uses the OI murine (oim) model to study OI, where homozygous oim mice (oim/oim) model severe human type III OI and exhibit increased susceptibility to fractures, skeletal deformities, and muscle weakness. Bone is mechanosensitive and responds to high mechanical loads by stimulating new bone formation and altering bone geometry to withstand increased forces. Myostatin, a member of the TGF-β superfamily, is a negative regulator of muscle growth. Congenic inhibition of myostatin in heterozygous +/oim mice previously exhibited increase in muscle mass with concomitant increase in bone geometry and biomechanical strength as compared to +/oim mice. Additionally, pharmacological inhibition of myostatin in oim/oim mice using the soluble activin receptor type IIB-mFc (sActRIIB-mFc) fusion protein resulted in increased hindlimb skeletal muscle weight with improved contractile function. The underlying molecular mechanism of sActRIIB-mFc remains unknown, and negative side effects in humans have been noted, likely due to the receptor’s ability to bind multiple targets in addition to myostatin. This project was therefore aimed to identify the main sActRIIB-mFc targets responsible for the receptor’s benefit to muscle and bone. Among sActRIIB-mFc targets, myostatin and activin-A are known to regulate bone and muscle growth. Thus, we treated male and female oim/oim and wildtype (WT) mice with isotype control-antibody (ICA), anti-myostatin (anti-M), or anti-activin-A (anti-A) specific antibodies, independently and in combination (anti-M, anti-A) for 11 weeks, starting at 5 weeks of age to investigate their roles in bone and muscle health. Male oim/oim and WT mice treated with either anti-M or a combination of anti-A and anti-M antibodies had increased body weights when compared to ICA treated counterparts. Female oim/oim and WT mice also had increased body weights with both anti-M and the anti-A and anti-M combination treatment; with body weights of oim/oim mice in the anti-A and anti-M combination treatment group reaching WT ICA weights. Consistent with previous studies, these increased body weights are likely a result of increased muscle mass. In order to determine the differential impact of myostatin and activin-A inhibition on muscle and bone in the oim model, further analysis of muscle function and bone microarchitecture and biomechanical testing are still required.
Funder Acknowledgement(s): NIH-IMSD
Faculty Advisor: Dr. Charlotte Phillips, PhillipsCL@missouri.edu
Role: I completed the majority of this project. This includes the responsibilities of: breeding, injecting, weighing, and grip-strengthening mice, and compiling data into graphs. Mouse breeding was done by graduate students, and mouse dissections and tissue harvest were performed by our entire lab.