The science behind GRP
How GRP was discovered, what is known about it, and every publication you can check.
Understanding GRP biology
Gla-Rich Protein (GRP) is a small vitamin K-dependent protein involved in the regulation of pathological calcification and inflammation. Its exceptionally high density of γ-carboxyglutamic acid (Gla) residues enables GRP to bind calcium and calcium phosphate mineral with high affinity, a property that underlies at least some of its biological functions.
Gla-rich protein (GRP) is an unusually Gla-rich vitamin K-dependent protein containing a high density of potential γ-carboxylation sites distributed throughout its sequence. The extent and distribution of γ-carboxylation in native GRP remain largely undefined and are likely influenced by vitamin K availability and other biological factors, giving rise to multiple molecular forms with potentially distinct functional properties. Consequently, the overall carboxylation status of full-length GRP cannot currently be resolved using a single antibody. Antibodies directed against individual carboxylation-sensitive epitopes therefore provide a valuable approach for investigating epitope-specific GRP carboxylation in biological samples.
GRP is measured across different biological matrices as total GRP (tGRP), regardless of γ-carboxylation status. To support mechanistic studies we supply a polyclonal antibody against total GRP (C-terminal GRP), used in Western blot, immunolocalization, immunofluorescence, flow cytometry and immunogold electron microscopy, together with carboxylation-state specific monoclonal antibodies against a γ-carboxylated epitope (cGRP) and an uncarboxylated epitope (ucGRP) of human GRP. The monoclonal antibodies support comparative tissue localization studies using matched cGRP and ucGRP monoclonal antibodies, by immunolocalization and immunofluorescence.
Conditions addressed
GRP is increasingly recognized as a biomarker and regulator of pathological calcification, chronic inflammation, and tissue remodeling across multiple disease areas.
Cardiovascular
Vascular calcification, atherosclerosis, valve disease
Nephrology
CKD-MBD, cardiovascular risk, calciphylaxis, dialysis complications
Osteoarthritis
Cartilage calcification, joint inflammation
Dermatology
Skin calcification, connective tissue disorders
Oncology
Breast cancer, skin cancer, tumor-associated microcalcifications
Our VKDP expertise
- • 24 years of VKDP research
- • Published clinical research collaborations
- • Expanding service portfolio
Research collaborations
- • CCMAR, University of Algarve
- • Hospital collaborations (Nephrology, Cardiology)
- • European research consortia
- • International academic partnerships
Publications library
Explore our 20 publications establishing the science behind GRP and its clinical applications.
Biochemia Medica • 2026 • 36(2):344-353
Factors associated with Gla-rich protein serum concentrations in healthy adults
Marreiros C et al.
Determined serum total GRP concentrations in 254 healthy adults with the GenoGla sandwich ELISA, providing baseline data for future clinical studies.
Biomaterials Advances • 2026 • 184:214833
Bioengineered baculovirus-derived extracellular vesicles loaded with of γ-carboxylated Gla-rich protein: Dual modulation of inflammation and vascular calcification
Viegas C et al.
Developed a baculovirus-based platform to produce extracellular vesicles loaded with γ-carboxylated GRP, demonstrating dual anti-inflammatory and anti-calcific activity.
Journal of Clinical Medicine • 2024 • 13(23):7429
Gla-Rich Protein Is Associated with Vascular Calcification, Inflammation, and Mineral Markers in Peritoneal Dialysis Patients
Marreiros C et al.
Demonstrated the clinical relevance of circulating GRP in peritoneal dialysis patients through its association with vascular calcification, inflammation and mineral metabolism markers.
International Journal of Molecular Sciences • 2024 • 25(22):12406
Gla Rich Protein (GRP) Mediates Vascular Smooth Muscle Cell (VSMC) Osteogenic Differentiation, Extracellular Vesicle (EV) Calcification Propensity, and Immunomodulatory Properties
Viegas CSB et al.
Demonstrated that GRP regulates osteogenic differentiation of vascular smooth muscle cells, extracellular vesicle calcification and immune responses involved in vascular calcification.
Diagnostics • 2022 • 12(2):496
Gla-Rich Protein, Magnesium and Phosphate Associate with Mitral and Aortic Valves Calcification in Diabetic Patients with Moderate CKD
Silva AP et al.
Demonstrated associations between GRP, magnesium, phosphate and mitral and aortic valve calcification in diabetic patients with moderate CKD.
International Journal of Molecular Sciences • 2022 • 23(24):16114
Targeting a Silent Disease: Vascular Calcification in Chronic Kidney Disease
Marreiros C et al.
Reviewed current challenges in the early detection of vascular calcification in chronic kidney disease, covering underlying mechanisms, diagnostic approaches and the role of GRP.
International Journal of Molecular Sciences • 2022 • 23(9):4813
Nanoencapsulation of Gla-Rich Protein (GRP) as a Novel Approach to Target Inflammation
Viegas CSB et al.
Developed a chitosan-based nanoformulation to improve GRP bioavailability while preserving its anti-inflammatory activity, providing proof of concept for future therapeutic applications.
Journal of Clinical Medicine • 2020 • 9(3):635
Gla-Rich Protein (GRP) as an Early and Novel Marker of Vascular Calcification and Kidney Dysfunction in Diabetic Patients with CKD: A Pilot Cross-Sectional Study
Silva AP et al.
First clinical study of circulating GRP in diabetic CKD patients, highlighting low circulating GRP as a potential early marker of vascular calcification and kidney dysfunction.
Aging (Albany NY) • 2019 • 11(5):1323-1324
A dual role for GRP in cardiovascular disease
Viegas CSB, Simes DC
Outlined the emerging concept of GRP as a dual regulator of vascular calcification and inflammation in cardiovascular disease.
Aging (Albany NY) • 2019 • 11(12):4274-4299
The interplay between mineral metabolism, vascular calcification and inflammation in Chronic Kidney Disease (CKD): challenging old concepts with new facts
Viegas C et al.
Reviewed the interplay between mineral metabolism, vascular calcification and inflammation in chronic kidney disease, challenging traditional concepts and highlighting the emerging role of GRP.
Arteriosclerosis, Thrombosis, and Vascular Biology • 2018 • 38(3):575-587
Chronic Kidney Disease Circulating Calciprotein Particles and Extracellular Vesicles Promote Vascular Calcification
Viegas CSB et al.
Identified GRP as a component of circulating calciprotein particles and extracellular vesicles involved in vascular calcification in chronic kidney disease.
Scientific Reports • 2018 • 8:4961
Ucma/GRP inhibits phosphate-induced vascular smooth muscle cell calcification via SMAD-dependent BMP signalling
Willems BA et al.
Demonstrated that Ucma/GRP protects against phosphate-induced vascular smooth muscle cell calcification via SMAD-dependent BMP signalling.
Immunity and Inflammation in Health and Disease (Academic Press / Elsevier) • 2018 • pp. 189-201
Inflammation and Calcification in the Vascular Tree; Insights Into Atherosclerosis
Viegas CSB, Simes DC
Reviewed the interplay between inflammation and calcification in the vascular tree and its role in atherosclerosis, discussing the emerging role of GRP within this context.
PLOS ONE • 2017 • 12(5):e0177829
Gla-rich protein function as an anti-inflammatory agent in monocytes/macrophages: Implications for calcification-related chronic inflammatory diseases
Viegas CSB et al.
Demonstrated that GRP acts as an endogenous anti-inflammatory mediator in monocytes and macrophages by reducing inflammatory cytokines and signaling pathways independently of its γ-carboxylation status.
Cellular and Molecular Life Sciences • 2016 • 73(5):1051-1065
Gla-rich protein is involved in the cross-talk between calcification and inflammation in osteoarthritis
Cavaco S et al.
Demonstrated that GRP participates in the cross-talk between calcification and inflammation in osteoarthritis, linking the two processes in joint tissue.
Arteriosclerosis, Thrombosis, and Vascular Biology • 2015 • 35(2):399-408
Gla-Rich Protein Acts as a Calcification Inhibitor in the Human Cardiovascular System
Viegas CSB et al.
Demonstrated that GRP inhibits vascular and valvular calcification by preventing osteochondrogenic differentiation and modulating extracellular vesicle-mediated mineralization.
Molecular Nutrition and Food Research • 2014 • 58(8):1636-1646
Insights into the association of Gla-rich protein and osteoarthritis, novel splice variants and γ-carboxylation status
Rafael MS et al.
Characterized GRP in healthy and osteoarthritic cartilage, describing the differential accumulation of carboxylated and undercarboxylated forms, and identifying novel splice variants with distinct carboxylation potential.
BioMed Research International • 2014 • 2014:340216
Gla-Rich Protein Is a Potential New Vitamin K Target in Cancer: Evidences for a Direct GRP-Mineral Interaction
Viegas CSB et al.
Characterized GRP expression and splicing in healthy and cancer tissues, describing differential accumulation of carboxylated and undercarboxylated forms and demonstrating direct calcium mineral binding.
The American Journal of Pathology • 2009 • 175(6):2288-2298
Gla-Rich Protein Is a Novel Vitamin K-Dependent Protein Present in Serum That Accumulates at Sites of Pathological Calcifications
Viegas CSB et al.
Characterized GRP as a circulating vitamin K-dependent protein present in serum, showing its presence in soft tissues such as skin and vascular system and its accumulation at sites of pathological soft tissue calcification, associated with tissue mineralization processes.
Journal of Biological Chemistry • 2008 • 283(52):36655-36664
Gla-rich Protein (GRP), A New Vitamin K-dependent Protein Identified from Sturgeon Cartilage and Highly Conserved in Vertebrates
Viegas CSB et al.
Reported the discovery of GRP as a novel vitamin K-dependent protein with an unusually high Gla content, first found in sturgeon cartilage and conserved throughout vertebrate evolution.