Venu Pandit

Osteoarthritis (OA) remains a challenging disease due to the increased rate of incidence in the older population and the lack of a disease-modifying drug. BMP signaling plays a crucial role in chondrogenic differentiation and in the stability of articular cartilage. However, because BMP-2 also induces chondrocyte hypertrophy, it is not a viable drug for OA treatment. In contrast, the Bmpr1a biomimetic peptide can repair articular cartilage without inducing chondrocyte hypertrophy in the OA mouse model and in chondrocytes derived from patients diagnosed with OA. Despite this benefit, the mechanism by which the peptide drives chondrogenesis remains elusive. To explore this, we use a phosphoproteomics approach to identify pathways differentially activated by CK2.1. Specifically, we identified differentially phosphorylated phosphosites by CK2.1. Based on these phosphosites that we identified, we propose a molecular mechanism by which CK2.1 activates chondrogenesis. Notably, we predict that the mitogen-activated protein kinase (MAPK) pathway is regulated by CK2.1 to induce proteoglycan synthesis in C3H10T1/2 cells.

Bone marrow-derived mesenchymal stem cells (BMSCs), owing to their osteoblastogenic differentiation potential, are crucial for maintaining bone homeostasis and remodeling. Nevertheless, in aging and age-related bone diseases like osteoporosis, BMSCs show significantly diminished osteogenic potential, with a concomitant increase in adipogenic differentiation. The aged BMSCs also become desensitized to BMP2 stimulation to a large extent and exhibit aberrations in BMP2 signaling. However, the molecular mechanisms facilitating this shift in lineage commitment and mediating the cellular dysfunctions remain elusive. This knowledge gap hinders the development of regenerative strategies for skeletal aging and osteoporosis. This study employed an integrative tandem mass tag (TMT)-based phosphoproteomic and total proteomic profiling on BMSCs isolated from young (6-month) and aged (15-month) C57BL/6 (B6) mice to elucidate global alterations in both protein activity and expression. The analysis identified more than 500 proteins that underwent significant alterations (BH-adjusted p-value < 0.05) either in phosphorylation or expression between young and aged BMSCs. Many lineage-specific markers also underwent changes in both phosphorylation and expression with aging. Additionally, key biological processes, including cellular metabolism, clathrin-mediated endocytosis, and nucleocytoplasmic transport mechanisms, were enriched for the deregulated proteins. Signaling proteins, ERK-1/2, had increased activating phosphorylation in the aged BMSCs, while transcription factors Lrrfip1, Ruvbl1, and Ruvbl2 also exhibited dysregulated activity and abundance in the aged BMSCs. The findings from the study adds significant mechanistic insights into how aging disrupts signal transduction, metabolism, and transcriptional program in BMSCs, contributing to age-associated loss of bone mass and reduced skeletal regenerative capabilities. Through the identification of key mediators of BMSC dysfunction seen in aging, this work offers a strong foundation in devising potential therapeutic strategies to restore diminished osteogenic potential and treat osteoporosis.

Osteoarthritis (OA) is a common and debilitating degenerative joint disease associated with aging and more common among women. OA is a disease that affects many parts of the joint, including cartilage, subchondral bone, and the synovium. Although the exact cause of OA is still under investigation, major factors include dysregulation of inflammatory cytokines and loss of function of mesenchymal stem cells (MSCs). Unfortunately, current treatments for OA are limited to symptomatic management, including nonsteroidal anti-inflammatory drugs (NSAIDs), intra-articular injections such as hyaluronic acid (or cortisol), physical therapy, and surgical intervention, none of which can affect disease progression or provide permanent solutions. Currently there is no FDA approved treatment that can address the molecular basis of OA, although some promising candidates include bone marrow-derived MSC injection, adipose-derived MSC injection, pulsed electromagnetic field (PEMF), TissueGene-C, and CK2.1.

Bone Morphogenetic Protein-2 (BMP2) is a growth factor that maintains bone homeostasis through the BMP receptor type Ia (BMPRIa) and type II (BMPRII). BMP2 promotes osteogenesis by inducing the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts; however, it can also trigger BMSC differentiation into adipocytes. BMP2’s osteo-inductive ability has made it a potential treatment for osteoporosis, yet its dual role in BMSC differentiation complicates its efficacy. High BMP2 levels cause BMPRIa cleavage, but the downstream effects and the mechanisms governing BMP2-induced osteogenesis or adipogenesis are unresolved. Here, we identify Caspase-1 as a key mediator of BMPRIa cleavage and its downstream effects on adipogenesis. We used primary BMSCs from C57BL/6 mice, stimulated with varying BMP2 concentrations, to explore BMP2-induced BMPRIa cleavage and its impact on PPARγ—a key regulator of adipogenesis. Western blotting and immunostaining using antibodies against BMPRIa and PPARγ uncovered BMPRIa cleavage and revealed the nuclear translocation of the cleaved segment, colocalizing with PPARγ. Caspase-1 inhibition significantly reduced BMPRIa cleavage and PPARγ expression, highlighting its pivotal role in adipogenic differentiation. Understanding the molecular mechanisms of BMP2-induced adipogenesis and Caspase-1 inhibition could improve BMP2 therapeutic efficacy for osteoporosis by promoting osteogenesis over adipogenesis.

Osteoarthritis (OA) represents the most prevalent form of joint disease, leading to considerable pain and functional disability. While surgical interventions and pain relief modalities are available, there is an urgent necessity for effective therapeutic strategies to restore the damage. Our research investigates CK2.1, an innovative peptide that has exhibited significant promise in stimulating chondrogenesis, specifically within articular chondrocytes, for the treatment of OA. In our study, we employed micromass cultures derived from chondrocytes of human OA patients to evaluate the effectiveness of CK2.1. We demonstrated that CK2.1 significantly enhanced proteoglycan synthesis in chondrocytes isolated from OA patients. This observation highlights CK2.1’s targeted action and potential as a novel therapeutic strategy for treating osteoarthritis.

Bone Morphogenetic Protein-2 (BMP-2) is a growth factor that maintains bone homeostasis through BMP receptor type-I (BMPRIa) and type II (BMPRII). BMP-2 promotes osteogenesis by inducing bone marrow mesenchymal stem cell (BMSC) differentiation into osteoblasts, but it can also trigger BMSC differentiation into adipocytes. BMP-2's osteo-inductive ability has made it a potential treatment for osteoporosis, yet its dual role in BMSC differentiation complicates its efficacy. The mechanisms governing BMP-2-induced adipogenesis remain unclear. High BMP-2 levels cause BMPRIa cleavage, but the downstream effects and determinants of osteogenesis or adipogenesis activation are unresolved. Here, we identify Caspase-1 as a key mediator of BMPRIa cleavage and its downstream effects on adipogenesis. We used primary BMSCs from C57BL/6 mice, stimulated with varying BMP-2 concentrations, to explore BMP-2-induced BMPRIa cleavage and its impact on PPARγ – a key regulator of adipogenesis. Western blotting and immunostaining using antibodies against BMPRIa and PPARγ uncovered BMPRIa cleavage and revealed the nuclear translocation of the cleaved segment, colocalizing with PPARγ. Caspase-1 inhibition significantly reduced BMPRIa cleavage and PPARγ expression, highlighting its pivotal role in adipogenic differentiation. Understanding the molecular mechanisms of BMP-2-induced adipogenesis and Caspase-1 inhibition could improve BMP-2 therapeutic efficacy for osteoporosis by promoting osteogenesis over adipogenesis.

During aging, disruptions in various signaling pathways become more common. Some older patients will exhibit irregular bone morphogenetic protein (BMP) signaling, which can lead to osteoporosis (OP)—a debilitating bone disease resulting from an imbalance between osteoblasts and osteoclasts. In 2002, the Food and Drug Administration (FDA) approved recombinant human BMP-2 (rhBMP-2) for use in spinal fusion surgeries as it is required for bone formation. However, complications with rhBMP-2 arose and primary osteoblasts from OP patients often fail to respond to BMP-2. Although patient samples are available for study, previous medical histories can impact results. Consequently, the C57BL/6 mouse line serves as a valuable model for studying OP and aging. We find that BMP receptor type Ia (BMPRIa) is upregulated in the bone marrow stromal cells (BMSCs) of 15-month-old mice, consistent with prior data. Furthermore, conjugating BMP-2 with Quantum Dots (QDot^®s) allows effective binding to BMPRIa, creating a fluorescent tag for BMP-2. Furthermore, after treating BMSCs with methyl-β-cyclodextrin (MβCD), a disruptor of cellular endocytosis, BMP signaling is restored in 15-month-old mice, as shown by von Kossa assays. MβCD has the potential to restore BMPRIa function, and the BMP signaling pathway offers a promising avenue for future OP therapies.

Protein kinase CK2 (CK2) influences one-fifth of the cellular phosphoproteome. It regulates almost all cellular pathways and is thus a critical switch between biological processes within a cell. Inhibition of CK2 reverses oncogene addiction of tumor and alters tumor microenvironment. The success of this strategy and its clinical translation opens new opportunities. Targeting CK2 in musculoskeletal disorders is promising. Clinical manifestations of these disorders include dysfunctional inflammation, dysregulated cell differentiation, and senescence. Processes regulated by CK2 include all of these. Its emerging role in senescence also indicates its function’s centrality in cellular metabolism. This review summarizes considerations for targeting CK2 in musculoskeletal disorders. We have discussed the implications of CK2-regulated processes in musculoskeletal disorders.

As humans age, aberrancies in several signaling pathways occur. In the aging population, some patients display abnormal bone morphogenetic protein (BMP) signaling. This can lead to osteoporosis (OP), a debilitating bone disorder caused by an imbalance between osteoblasts and osteoclasts. In 2002, the Food and Drug Administration (FDA) approved usage of recombinant human BMP-2 (rhBMP-2) during spinal fusion surgery as it is crucial for bone formation. However, complications have been reported with rhBMP-2 and primary osteoblasts isolated from OP patients are unresponsive to BMP-2. While patient samples are available, previous medical history may alter results. Therefore, C57BL/6 mice, an aging model that displays aberrant BMP-signaling, can be utilized to investigate OP and aging. We show that BMP receptor type Ia (BMPRIa) is upregulated in the bone marrow stromal cells (BMSCs) of 15-month mice similar to previous data. We show that a conjugation between BMP-2 and Quantum Dots (QDot®s) effectively binds to BMPRIa and can investigate BMP-2 activity. After incubating BMSCs with methyl-β-cyclodextrin (MβCD), BMP-signaling is restored in 15-month mice as shown by western blotting and the von Kossa assay. MβCD may be used to rescue BMPRIa and the BMP-signaling pathway can be utilized by future therapeutics to treat OP.

Casein Kinase ІІ (CK2) is one of the most versatile kinases. Its involvement in almost all cellular pathways makes it the Master Regulator of biochemical processes in a cell. This kinase is essential in regulating inflammation, cell differentiation, and cell cycle regulation. Often simultaneously. Its emerging role in senescence also indicates its function's centrality in cellular metabolism. The strategy to target this kinase to treat musculoskeletal disorders seems effective. These disorders often include a component of inflammation, dysregulated cell differentiation, and aging. This review focuses on CK2 target discovery and the diversity of its substrate interactions. We then transition toward the implication of CK2 in musculoskeletal disorders. Through a summary of current strategies for CK2 targeting with a new approach, we discuss the potential aspects that could be addressed in future drug research.