Subtopic Deep Dive
Osteopontin in Immune Regulation
Research Guide
What is Osteopontin in Immune Regulation?
Osteopontin (OPN) acts as a matricellular protein with cytokine-like functions in regulating T-cell polarization, macrophage activation, and inflammatory responses in autoimmune diseases.
OPN is highly expressed in chronic inflammatory conditions and localizes around immune cells (Scatena et al., 2007, 636 citations). Knockout studies show OPN modulates osteoclast formation and immune cell function without altering bone development (Rittling et al., 1998, 429 citations). Over 500 papers explore its roles in inflammation and immunity, linking bone matrix proteins to adaptive responses.
Why It Matters
OPN bridges extracellular matrix biology to immune regulation, influencing macrophage polarization in atherosclerosis (Giachelli et al., 1993, 642 citations) and inflammatory diseases (Lund et al., 2009, 508 citations). In autoimmune contexts, OPN promotes Th1/Th17 responses, offering targets for MS and rheumatoid arthritis therapies. Hayman (2008, 360 citations) highlights TRAP-OPN interactions in osteoclast-immune cell crosstalk, impacting bone loss in inflammation.
Key Research Challenges
RGD-Dependent vs Independent Signaling
OPN signals via integrins (αvβ3) and CD44 receptors, but distinguishing RGD-independent immune effects remains unclear (Scatena et al., 2007). Post-translational modifications like phosphorylation alter T-cell binding. Giachelli et al. (1993) note challenges in isolating vascular inflammation roles.
Translating Knockout Phenotypes
OPN-null mice show normal bone but altered in vitro osteoclastogenesis (Rittling et al., 1998), complicating in vivo immune interpretations. Compensatory mechanisms mask inflammation defects. Lund et al. (2009) identify context-specific functions in glomerulonephritis.
Quantifying OPN Isoforms in Disease
Thrombin-cleaved OPN fragments drive distinct immune responses, but isoform-specific assays lack standardization (Scatena et al., 2007). Measuring full-length vs cleaved forms in MS or atherosclerosis hinders biomarkers. Hayman (2008) links TRAP expression to osteoclast-immune overlap.
Essential Papers
Osteopontin is elevated during neointima formation in rat arteries and is a novel component of human atherosclerotic plaques.
Cecilia M. Giachelli, Na-Young Bae, M Almeida et al. · 1993 · Journal of Clinical Investigation · 642 citations
In an earlier report, we used differential cloning to identify genes that might be critical in controlling arterial neointima formation (Giachelli, C., N. Bae, D. Lombardi, M. Majesky, and S. Schwa...
Osteopontin
Marta Scatena, Lucy Liaw, Cecilia M. Giachelli · 2007 · Arteriosclerosis Thrombosis and Vascular Biology · 636 citations
Osteopontin (OPN) is a multifunctional molecule highly expressed in chronic inflammatory and autoimmune diseases, and it is specifically localized in and around inflammatory cells. OPN is a secrete...
The role of osteopontin in inflammatory processes
Susan Amanda Lund, Cecilia M. Giachelli, Marta Scatena · 2009 · Journal of Cell Communication and Signaling · 508 citations
Osteopontin (OPN) is a matricellular protein that mediates diverse biological functions. OPN is involved in normal physiological processes and is implicated in the pathogenesis of a variety of dise...
Mice Lacking Osteopontin Show Normal Development and Bone Structure but Display Altered Osteoclast Formation In Vitro
Susan R. Rittling, Hiroko Matsumoto, Marc D. McKee et al. · 1998 · Journal of Bone and Mineral Research · 429 citations
Abstract We have used homologous recombination in embryonic stem cells to generate mice with a targeted disruption of the osteopontin (Opn, or Spp1, for secreted phosphoprotein 1) gene. Mice homozy...
Tartrate-resistant acid phosphatase (TRAP) and the osteoclast/immune cell dichotomy
Alison R. Hayman · 2008 · Autoimmunity · 360 citations
Tartrate-resistant acid phosphatase (TRAP), once considered to be just a histochemical marker of osteoclasts is now recognised to be a molecule of widespread occurrence with functions in both the s...
Osteopontin: Roles in Implantation and Placentation1
Greg A. Johnson, Robert C. Burghardt, Fuller W. Bazer et al. · 2003 · Biology of Reproduction · 331 citations
Osteopontin (OPN) is an acidic member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family of extracellular matrix proteins/cytokines that undergoes extensive posttranslation...
The genetic transformation of bone biology
Gérard Karsenty · 1999 · Genes & Development · 314 citations
The skeleton, like every organ, has specific developmental and functional characteristics that define its identity in biologic and pathologic terms. Skeleton is composed of multiple elements of var...
Reading Guide
Foundational Papers
Start with Giachelli et al. (1993, 642 citations) for OPN in inflammation discovery, then Scatena et al. (2007, 636 citations) for immune localization, and Rittling et al. (1998, 429 citations) for knockout phenotypes establishing immune-bone links.
Recent Advances
Si et al. (2020, 291 citations) summarizes OPN in bone diseases with immune angles; Anborgh et al. (2010, 195 citations) covers tumor microenvironment roles overlapping inflammation.
Core Methods
Homologous recombination for Opn knockouts (Rittling et al., 1998); differential cloning for expression (Giachelli et al., 1993); immunohistochemistry and functional adhesion assays (Scatena et al., 2007).
How PapersFlow Helps You Research Osteopontin in Immune Regulation
Discover & Search
Research Agent uses searchPapers and citationGraph to map OPN's immune roles from Giachelli et al. (1993), revealing 642 citing papers on inflammation; exaSearch finds recent autoimmune links, while findSimilarPapers expands from Scatena et al. (2007) to 600+ related studies.
Analyze & Verify
Analysis Agent applies readPaperContent to extract OPN knockout data from Rittling et al. (1998), then verifyResponse with CoVe checks claims against abstracts; runPythonAnalysis processes citation networks with pandas for immune-bone correlations, graded via GRADE for evidence strength in macrophage studies.
Synthesize & Write
Synthesis Agent detects gaps in RGD-independent signaling from Lund et al. (2009), flags contradictions in knockout phenotypes; Writing Agent uses latexEditText, latexSyncCitations for OPN review drafts, and latexCompile to generate publication-ready sections with exportMermaid diagrams of integrin pathways.
Use Cases
"Analyze OPN knockout effects on macrophage activation from Rittling 1998 data."
Analysis Agent → readPaperContent (Rittling et al., 1998) → runPythonAnalysis (pandas quantify osteoclast metrics) → GRADE-verified statistical summary of immune alterations.
"Draft LaTeX review on OPN in T-cell polarization citing Scatena 2007."
Synthesis Agent → gap detection (immune signaling gaps) → Writing Agent → latexEditText (structure review) → latexSyncCitations (add 636-cited paper) → latexCompile (PDF output with figure).
"Find GitHub repos analyzing OPN expression datasets from Hayman 2008."
Research Agent → paperExtractUrls (Hayman 2008 TRAP data) → paperFindGithubRepo (immune cell scripts) → githubRepoInspect → runPythonAnalysis (reproduce osteoclast plots).
Automated Workflows
Deep Research workflow scans 50+ OPN papers via searchPapers → citationGraph → structured report on immune regulation from Giachelli (1993) cluster. DeepScan applies 7-step CoVe analysis to Rittling (1998) knockout claims with runPythonAnalysis checkpoints. Theorizer generates hypotheses on OPN-TRAP immune links from Hayman (2008).
Frequently Asked Questions
What defines osteopontin in immune regulation?
OPN is a secreted phosphoprotein acting as a cytokine, promoting Th1/Th17 polarization and macrophage chemotaxis via CD44 and integrins (Scatena et al., 2007).
What methods study OPN immune functions?
Knockout mice reveal osteoclast-immune defects (Rittling et al., 1998); immunohistochemistry localizes OPN in plaques (Giachelli et al., 1993); functional assays test cleaved isoforms (Lund et al., 2009).
What are key papers on OPN inflammation?
Giachelli et al. (1993, 642 citations) links OPN to neointima; Scatena et al. (2007, 636 citations) details cytokine roles; Lund et al. (2009, 508 citations) reviews disease processes.
What open problems exist in OPN research?
Isoform-specific immune effects lack biomarkers; translating in vitro osteoclast changes to in vivo autoimmunity remains unresolved (Rittling et al., 1998; Hayman, 2008).
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Part of the Bone and Dental Protein Studies Research Guide