Research Projects:

The Delaware Center for Musculoskeletal Research Projects Awards offer needed assistance to early-career investigators on the path to research independence.

Summary: Preclinical animal models are an increasingly powerful tool for studying biological systems, with exciting opportunities in fields including musculoskeletal and women’s health. While the use of these biological models is increasing, many questions remain in longitudinal, concurrent shifts across systems of the body. In this proposal, novel imaging and biomechanical approaches will be combined to assess the relevance of cyclical changes in the female hormonal environment on overall function and specifically on tendon structure and function. Within the rat model, the effects of ovariectomy will be assessed compared to an unaltered population. Specifically, non-invasive imaging and functional analyses will be used to track changes in in vivo tissue health and whole body performance, with further detailed analysis of the musculoskeletal tissues in the knee joint performed ex vivo using a suite of novel experimental approaches. Understanding the systemic effects associated with either regularly cycling hormones or altered hormonal environments resulting from ovariectomy has the potential to improve both our interpretation of prior studies in female preclinical models and will establish baseline knowledge of the relative fluctuations in hormonal and musculoskeletal health in female preclinical models. Along with the immediate information gained in this study, the outcomes of this work will better prepare the field for studies are times of significant hormonal changes in females such as puberty, pregnancy, and menopause. Given the relevance of these events to half of the population, the potential impacts of this work are wide-spread and highly great interest in the area of improving human health.

Summary: Tissue engineered muscles offer a means to replace the function of damaged or diseased skeletal muscle. To engineer new muscle, muscle progenitor cells (MPCs) are combined with biomaterial scaffolds, which provide a microenvironment for MPCs to fuse into contractile muscle fibers. However, these approaches have not yet demonstrated clinical benefit, as there are no U.S. FDA approved tissue engineered muscle therapies. A critical barrier to the translation of these therapies are hurdles in the manufacturing and expansion of patient-derived MPCs that are combined with biomaterials. MPCs are heterogeneous on a single-cell level in terms of their muscle-forming capacity. Furthermore, in vitro expansion of MPCs propagates these heterogeneities and leads to loss of cellular potency. This ultimately leads to heterogeneous and subpotent batches of MPCs that are utilized for engineered muscle. Thus, there is a critical need to develop improved manufacturing approaches to reduce the heterogeneity of MPCs and enhance their potency. We hypothesize that the levels of cell adhesion receptors on MPCs are indicative of their potency to differentiate into muscle fibers. This hypothesis will lead to novel approaches to sort heterogeneous MPC subpopulations and genetically modify the cells’ receptors to control muscle formation. We will focus on integrin and cadherin adhesion receptors, given their critical function for MPC fusion into muscle fibers. Furthermore, we have collected preliminary data showing that β1-integrin expression can identify MPC subpopulations of varying muscle forming potency. We will explore the following Aims: (Aim 1) We will utilize fluorescence activated cell sorting to sort subpopulations of MPCs by the magnitude of various integrins and cadherins that have been shown to be critical to MPC muscle forming capacity. We will then evaluate the ability of these subpopulations to form contractile muscle fibers in hydrogels in vitro. (Aim 2) We will utilize CRISPRa to upregulate β1-integrin expression in heterogeneous populations of MPCs. We will compare these CRISPR-modified cells to unmodified cells in their ability to form 1) muscle fibers in hydrogels in vitro and 2) engineered muscle in decellularized matrices that will be implanted into a murine model of volumetric muscle loss. Success of this project will lead to novel approaches to enhance the potency of manufactured MPCs for muscle tissue engineering and will enhance the clinical success of these therapies in treating muscle injuries and diseases.

Summary: Temporomandibular joint disorder (TMJD) is a heterogeneous disease which is characterized by severe pain that negatively affects masticatory function. In the United States, TMJDs affect over 10 million individuals predominantly in middle-aged adults (20-40 years-of-age) with a higher prevalence in women than in men (NIDCR). Treatment outcomes for TMJDs are highly variable which may be attributed to the gap in knowledge of the underlying pathogenic mechanisms. Hence, a better understanding of the major contributors and causative mechanisms in TMJD may significantly improve outcome following therapeutic and/or surgical intervention. Whereas the contribution of disc degeneration in TMJD is well established, the functional consequence of impaired tendon and tendon-bone insertion in TMJD is poorly understood. Recent studies have shown that defects in tendon and tendon-bone insertion development as well as dysregulated cell signaling that negatively affect these tissues can cause deformities in TMJ (Roberts et al., 2019). Jaw movement creates biomechanical forces that are generated by the pterygoid and masseter muscles which are transmitted across tendon and tendon-bone insertion and connect to the mandibular condyle. Our preliminary studies have shown that impaired telopeptide lysyl hydroxylation and cross-linking due to Fkbp10-deficiency induces heterotopic ossification (HO) in TMJ and substantially increases mandibular condyle length and width in postnatal mice. In addition, we found that Fkbp10 deletion induces aberrant aSMA-expressing cells in the tendon and tendon-bone insertion concomitant with an increase in ectopic bone formation in the medial condyle of TMJ. Preliminary data also showed enhanced pSmad1/5 expression in the tendon and tendon-bone insertion in TMJ, indicating dysregulated BMP signaling. Based on these preliminary data, we will test the hypothesis that alterations in telopeptide lysyl hydroxylation in tendons of TMJ causes HO and functional defects due to abnormal differentiation of aSMA-expressing progenitor cells that is dependent on aberrant BMP signaling. Specifically, we will (Aim 1) determine the functional consequence of impaired procollagen I telopeptide lysyl hydroxylation and cross-linking in TMJ homeostasis, (Aim 2) determine if Fkbp10 deletion triggers tissue injury and alters aSMA-expressing progenitor cell populations, and (Aim 3) determine if pharmacological inhibition of aberrant BMP signaling can prevent HO in TMJ of Fkbp10-deficient mice. The proposed studies will provide the foundational basis and additional preliminary data to develop a competitive investigator-initiated R01 or equivalent NIH research proposal.​

Pilots 2025-26:

Summary: Anterior cruciate ligament (ACL) injuries and subsequent reconstruction surgery (ACLR) have an incidence rate of approximately 200,000 a year in the United States. One of the most used graft types especially among young athletes is the bone-patellar tendon-bone (BTPB) autograft, but the post operative healing of this graft site is not well understood. Objectives of this proposed project are to investigate the changes in patellar tendon morphology (B-mode ultrasound imaging, MRI) and mechanical properties (shear wave elastography and shear wave tensiometry) of the patellar tendon throughout the first six months of healing after BPTB graft harvest.​

Summary: Since 2013, over 27 mutations of PLS3 gene have been identified in patients with either reduced or defective fimbrin, resulting in X-linked early onset osteoporosis with severe low bone mineral density and multiple fractures in men and milder symptoms in women carriers. The PLS3-encoded fimbrin is an actin-binding/bundling protein and highly expressed in osteocyte dendrites. Although defects of osteocytes and osteocyte mechanotransduction were suspected, the pathologies underlying the early onset osteoporosis associated with PLS3 mutations have not been elucidated. The Co-PIs (Fowler and Wang) have complementary expertise on cytoskeleton and osteocyte mechanobiology. Their team made an intriguing discovery: the osteocytic dendrites of male Pls3 knockout (KO) mice appeared normal at 2 months of age, but nearly completely lost F-actin staining at 6 months. Furthermore, these mutant mice showed severe osteoporosis and impaired skeletal response to mechanical stimulation, in contrast to the age-matched wild type mice with robust bone formation under the same magnitude of loading. These preliminary data lead us to investigate the roles of the F-actin cytoskeleton in early onset osteoporosis caused by Pls3 mutations. Our ultimate goal is to submit an NIH R01 proposal and provide definitive pathological mechanisms for Pls3 mutations.