Matrix budget twin

chondrocyte, alive: the cell keeps working while you watch. Every motion runs at a rate from a source, and the panel below drives it.

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Control panel

One chondrocyte and the matrix it keeps: move a slider and the territory, the budget and the readouts follow.

Matrix volume held per cell

102,171 um3

102,171 to 102,171 um3 across the sourced ranges. No sourced capacity for this quantity, so the bar places this cell between the smallest and the largest the sourced ranges allow.

One cubic millimetre of human articular cartilage holds a counted number of chondrocytes and a measured cell volume fraction. Divide the millimetre among the cells, take out the cell itself, and what is left is the matrix one chondrocyte is alone responsible for. No blood supply, no neighbour, no second cell in the lacuna. This is the quantity the cell must build and maintain, so it is the twin's budget.

source 1 source 2,

Inputs

Aggrecan secretion 1 on/off

0 to 1 on/off · bovine · radiolabel chase in alginate bead culture · Mok SS et al. 1994, J Biol Chem: Aggrecan synthesized by mature bovine chondrocytes suspended in alginate · source

Primary export of the chondrocyte. 0 silences the secretion carrier animation. Rate is the sourced transit half-time of 4 hours for aggrecan leaving the pericellular zone.

PCM aggrecan density 20 aggregates shown

5 to 40 aggregates shown · human articular cartilage · histological review of published EM and immunolabelling studies · Buckwalter JA, Mankin HJ 1998, Instructional Course Lectures: Articular cartilage: tissue design and chondrocyte-matrix interactions · source

Count range 5 to 40 is illustrative, spanning sparse (OA-like) to dense (healthy chondron); no abstract stated a count per unit volume of PCM aggrecan aggregates.

Collagen II fibril bundles 15 bundles shown

5 to 30 bundles shown · human articular cartilage · histological review of published EM and fibril-diameter studies · Buckwalter JA, Mankin HJ 1998, Instructional Course Lectures · source

Count range 5 to 30 is illustrative; fibril counts per volume were not in the abstracts swept.

Cell diameter 13 um

10 to 20 um · human · confocal microscopy with unbiased stereology · Hunziker EB, Quinn TM, Hauselmann HJ 2002, Osteoarthritis Cartilage; span from Buckwalter JA, Mankin HJ 1998, Instructional Course Lectures, https://pubmed.ncbi.nlm.nih.gov/9571449/ · source

mean cell diameter measured at 13 um; the 10 to 20 um slider span is the articular chondrocyte range given in the Buckwalter review

Readouts

Chondrocytes per mm3 (context constant)

9,626 cells/mm3

9,626 to 9,626 cells/mm3 exact

human, medial femoral condyle, donors aged 23 to 49 · confocal microscopy with unbiased stereology (Hunziker 2002); fixed at measured mean; slider removed because cell density is a tissue context property, not a property of the individual cell the twin shows · source 1

Exact given inputs.

Cell share of tissue volume (context constant)

1.65 percent

1.65 to 1.65 percent exact

human, medial femoral condyle · confocal microscopy with unbiased stereology (Hunziker 2002); fixed at measured mean · source 1

Exact given inputs.

Aggrecan half-life (context constant)

95 days

95 to 95 days exact

bovine, alginate bead culture · radiolabel chase (Mok 1994); interterritorial pool half-life; fixed because the engine cannot reroute a rate from a param slider · source 1

Exact given inputs.

Zone synthesis factor (context constant)

1 x

1 to 1 x exact

bovine articular cartilage · quantitative autoradiography (Wong 1996); fixed at superficial zone default; slider removed because rate scaling is not wired to a visual body · source 1

Exact given inputs.

Tissue territory per cell

103,885 um3

103,885 to 103,885 um3 propagated

human · one cubic millimetre is 1e9 cubic micrometres, divided by the counted cell density · source 1

Interval from evaluating at the ends of each input range; assumes the formula moves one way in each input.

Volume of the cell itself

1,150 um3

1,150 to 1,150 um3 exact

definition · sphere of the measured mean diameter; the chondrocyte is near spherical in the deep zone and flattened in the superficial zone, so this is the deep zone case · source 1

Exact given inputs.

Matrix held per unit of cell

88.8 fold

24.4 to 195 fold propagated

human · matrix volume per cell divided by the volume of the cell holding it · source 1

Interval from evaluating at the ends of each input range; assumes the formula moves one way in each input.

Volume turned over per day

745 um3/day

745 to 745 um3/day propagated

human geometry with bovine turnover · an upper bound, not a measurement: the whole matrix volume decayed at the aggrecan half-life, where ln(2) is the natural logarithm of 2. Collagen II turns over far more slowly than aggrecan, so the true whole-matrix figure is lower. Species are mixed here, human for the geometry and bovine for the half-life · source 1 · source 2

Interval from evaluating at the ends of each input range; assumes the formula moves one way in each input.

Turnover in units of the cell

0.648 cell volumes/day

0.178 to 1.42 cell volumes/day propagated

human geometry with bovine turnover · the upper-bound daily volume expressed as multiples of the cell's own body; carries the same upper-bound caveat · source 1 · source 2

Interval from evaluating at the ends of each input range; assumes the formula moves one way in each input.

Demand at this zone factor

745 um3/day

745 to 745 um3/day propagated

bovine for both the zone factor and the half-life · the upper-bound daily volume scaled by the measured 10-fold synthetic difference between superficial and radial zone chondrocytes; a scaling, not a second measurement · source 1 · source 2

Interval from evaluating at the ends of each input range; assumes the formula moves one way in each input.

Withheld

Aggrecan mass held per cell

No sourced value for this yet: converting the matrix volume to an aggrecan mass needs a measured aggrecan concentration in human articular cartilage, and no abstract read in this pass stated one, so the volume is shown instead

Collagen II synthesis rate

No sourced value for this yet: no abstract read in this pass gave a collagen II synthesis or turnover rate per chondrocyte, and the aggrecan half-life cannot stand in for it because collagen II turns over far more slowly

Pericellular matrix thickness

No sourced value for this yet: the pericellular matrix reviews read in this pass describe the structure and its mechanics without stating a thickness in micrometres, so no slider is offered for it

Oxygen tension at the cell

No sourced value for this yet: the low oxygen tension of deep zone cartilage is described in the reviews without a measured partial pressure in any abstract read in this pass

Chondrocytes per mm3

Tissue-level context: the twin shows one cell; density is a readout in derived (territory_volume) but has no body on the stage to scale. Slider removed; value feeds the derived calculations as its default.

Cell share of tissue volume

Tissue-level context: fraction of matrix vs cell in bulk tissue; feeds matrix_to_cell_ratio and matrix_volume_at_aggrecan_rate in derived but no drawn body carries this number.

Aggrecan half-life

Rate context: the aggrecan_turnover_near and _far processes in life.json use hardcoded ln(2)/halflife values; the generic engine cannot reroute a rate from a param slider, so the slider is removed. The halflife is stated in the life.json source notes.

Zone synthesis factor

Rate context: zone_synthesis rate in life.json is a fixed sourced value; the generic engine cannot scale it from this param. Slider removed; the factor is noted in zone_adjusted_demand in derived.

Sources

Hunziker EB, Quinn TM, Hauselmann HJ. Quantitative structural organization of normal adult human articular cartilage. Osteoarthritis Cartilage 2002

human, medial femoral condyle · confocal microscopy with unbiased stereology

Mok SS et al. Aggrecan synthesized by mature bovine chondrocytes suspended in alginate. Identification of two distinct metabolic matrix pools. J Biol Chem 1994

bovine · radiolabel chase in alginate bead culture

Wong M, Wuethrich P, Eggli P, Hunziker E. Zone-specific cell biosynthetic activity in mature bovine articular cartilage. J Orthop Res 1996

young adult bovine · confocal microscopic stereology with quantitative autoradiography

Buckwalter JA, Mankin HJ. Articular cartilage: tissue design and chondrocyte-matrix interactions. Instructional Course Lectures 1998

human, review · review

Wilusz RE, Sanchez-Adams J, Guilak F. The structure and function of the pericellular matrix of articular cartilage. Matrix Biol 2014

review · review

Research use only. Every number here is geometry on published ranges, not a measurement of any individual.

Substances tested 11

All substances →

Interleukin-1 alpha and interleukin-1 beta catabolic cytokine

acts on IL-1 receptor on the chondrocyte

Stimulate matrix proteoglycan degradation and inhibit glycosaminoglycan synthesis in cartilage explants. The reference catabolic insult: most chondroprotective compounds in this table are tested against it.

dose: not stated in the abstract · bovine nasal cartilage explants; rabbit articular chondrocytes · cartilage organ culture and chondrocyte culture · Smith RJ, Chin JE, Sam LM, Justen JM 1991, Arthritis Rheum · source

Interleukin-1 receptor antagonist protein (IRAP) receptor antagonist, the protein anakinra is built on

acts on IL-1 receptor, blocking IL-1 alpha and IL-1 beta binding

Concentration-dependent suppression of IL-1 effects in cartilage organ culture. Inhibited binding of radiolabelled IL-1 alpha to rabbit articular chondrocytes and suppressed collagenase, gelatinase, stromelysin and prostanoid production by IL-1-activated chondrocytes.

dose: 0.2 to 200 ng/ml, concentration-dependent · bovine nasal cartilage explants; rabbit articular chondrocytes · organ culture, receptor binding, enzyme assays · Smith RJ, Chin JE, Sam LM, Justen JM 1991, Arthritis Rheum · source

Engineered cationic IL-1 receptor antagonist protein therapeutic, charge-modified

acts on IL-1 receptor; the cationic charge drives uptake into the anionic cartilage matrix

Outperforms anakinra at joint retention and at preventing IL-1-induced cartilage inflammation. The problem it solves is residence time: anakinra clears the joint faster than the inflammation resolves.

dose: not stated in the abstract · not stated in the abstract · joint retention and cartilage inflammation assays · Boyer TL et al. 2026, Osteoarthritis Cartilage · source

Lorecivivint (SM04690) small-molecule intranuclear kinase inhibitor, Wnt pathway

acts on CDC-like kinase 2 (CLK2) and dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A)

Inhibits CLK2-mediated phosphorylation of SR splicing factors and DYRK1A-mediated phosphorylation of SIRT1 and FOXO1, modulating Wnt without touching beta-catenin. CLK2 inhibition induces early chondrogenesis; DYRK1A inhibition enhances mature chondrocyte function and carries the anti-inflammatory effect through NF-kB and STAT3. In the rat MIA model a single intra-articular injection increased joint cartilage, decreased pain and improved weight-bearing.

dose: single intra-articular injection, dose not stated in the abstract · human mesenchymal stem cells, chondrocytes and synovial fibroblasts in vitro; rat monosodium iodoacetate OA model · kinase assays, western blot, siRNA knockdown, qPCR, in vivo OA model · Deshmukh V et al. 2019, Osteoarthritis Cartilage · source

Sprifermin (recombinant human FGF-18) growth factor, disease-modifying OA drug candidate

acts on FGF receptor signalling in the chondrocyte

Promotes chondrocyte proliferation and extracellular matrix synthesis, increases cartilage thickness in a dose-dependent manner, and inhibits proteolytic enzyme activity. Reviewed as an effective DMOAD acting by both anti-catabolic and excitoanabolic routes.

dose: dose-dependent thickness increase reported; the doses are not stated in the abstract · review across models · review · Song Z et al. 2021, Front Cell Dev Biol · source

Sprifermin in explant storage medium growth factor, tissue preservation use

acts on FGF receptor signalling during cold storage of osteochondral allograft tissue

Tested for whether adding sprifermin during storage preserves the depth-dependent mechanical inhomogeneity of articular cartilage, the property fresh allografts lose at 4 degrees C.

dose: not stated in the abstract · articular cartilage explants, species not stated in the abstract · explant storage and depth-dependent mechanical testing · Meloni GR et al. 2019, Eur Cell Mater · source

Dexamethasone glucocorticoid

acts on glucocorticoid receptor

Two-sided. In injured cartilage and post-traumatic OA models it rescues matrix loss and chondrocyte viability. In healthy cartilage and isolated chondrocytes many studies report significant increases in apoptosis instead. Whether it protects or kills depends on dose, duration of exposure and the model used.

dose: dose and duration decide the direction of effect; values not stated in the abstract · review of animal studies and cartilage explant models · review · Black R, Grodzinsky AJ 2019, Eur Cell Mater · source

Eugenol plant phenylpropanoid

acts on ALK1/ALK5 ratio and downstream Smad signalling

Attenuated IL-1beta-induced falls in ACAN, COL2A1 and SOX9 and reduced IL-1beta-induced MMP13, ADAMTS5, COL10A1, RUNX2 and IL-6. Lowered the ALK1/ALK5 protein ratio, reduced Smad1/5/9 phosphorylation and increased Smad2/3 phosphorylation. The authors state docking and mutagenesis did not demonstrate direct eugenol-ALK1 binding.

dose: two concentrations tested; the values are not stated in the abstract · primary human chondrocytes; juvenile and aged mouse cartilage; mouse ACLT cohort · RT-qPCR, western blot, immunofluorescence, RNA sequencing, siRNA knockdown · Wang Y et al. 2026, Front Pharmacol · source

Every row rests on a PubMed abstract read in full by Chondro on 2026-09-12. A dose the abstract does not state is written as such, never guessed. Most of what has been tested on this cell was tested on it in osteoarthritis, so the table leans that way. Research reference, not medical advice.

Public datasets 12

GSE114007 RNA-seq, 38 samples Homo sapiens

Identification of transcription factors responsible for dysregulated networks in human osteoarthritis cartilage by global gene expression analysis

Fisch KM et al. 2018, Osteoarthritis Cartilage · paper · public at NCBI GEO; cited in 48 abstracts of the sweep, the most reused chondrocyte dataset found · accession resolved 2026-09-12 via eutils esummary

GSE57218 expression microarray, 73 samples Homo sapiens

Gene expression profiles from joint-matched macroscopically intact and OA affected cartilage of patients undergoing joint replacement surgery

Ramos YF et al. 2014, PLoS One · paper · public at NCBI GEO; joint-matched intact against affected cartilage from the same patient, which controls for donor · accession resolved 2026-09-12 via eutils esummary

GSE55235 expression microarray, 30 samples Homo sapiens

Identification of rheumatoid arthritis and osteoarthritis patients by transcriptome-based rule set generation

Woetzel D et al. 2014, Arthritis Res Ther · paper · public at NCBI GEO; cited in 35 abstracts of the sweep · accession resolved 2026-09-12 via eutils esummary

GSE55457 expression microarray, 33 samples Homo sapiens

Identification of rheumatoid arthritis and osteoarthritis patients by transcriptome-based rule set generation

Woetzel D et al. 2014, Arthritis Res Ther · paper · public at NCBI GEO; companion series to GSE55235 from the same study · accession resolved 2026-09-12 via eutils esummary

GSE51588 expression microarray, 50 samples Homo sapiens

Genome-wide Expression Profiles of Subchondral Bone in Osteoarthritis

Chou CH et al. 2013, Arthritis Res Ther · paper · public at NCBI GEO; subchondral bone rather than cartilage, the tissue on the other side of the tidemark · accession resolved 2026-09-12 via eutils esummary

GSE82107 expression microarray, 17 samples Homo sapiens

Synovial biopsies of osteoarthritis patients

Broeren MG et al. 2016, PLoS One · paper · public at NCBI GEO; synovium, not cartilage, and included because the sweep shows it paired with cartilage sets · accession resolved 2026-09-12 via eutils esummary

GSE169077 expression microarray, 11 samples Homo sapiens

Dysregulated gene expression in human osteoarthritis cartilage

no linked publication listed in GEO at the date resolved · public at NCBI GEO; cited in 25 abstracts of the sweep despite carrying no linked paper · accession resolved 2026-09-12 via eutils esummary

GSE117999 expression microarray, 24 samples Homo sapiens

Transcriptome comparison of cartilage from patients with and without osteoarthritis

no linked publication listed in GEO at the date resolved · public at NCBI GEO · accession resolved 2026-09-12 via eutils esummary

GSE324993 single-cell RNA-seq Homo sapiens

Single-cell RNA sequencing of chondrocytes from osteoarthritis (OA) patients and healthy controls

no linked publication listed in GEO at the date resolved · public at NCBI GEO; single-cell resolution, which the older bulk sets above do not give · accession resolved 2026-09-12 via eutils esummary

GSE308009 single-cell RNA-seq Mus musculus

Inhibition of the Gerozyme 15-Prostaglandin Dehydrogenase Promotes Articular Cartilage Regeneration in Osteoarthritis due to Injury or Aging [scRNA-Seq]

Singla M et al. 2026, Science · paper · public at NCBI GEO · accession resolved 2026-09-12 via eutils esummary

GSE232109 RNA-seq, high throughput sequencing Homo sapiens

Recapitulation of endochondral ossification by human pluripotent stem cell-derived SOX9+ sclerotomal progenitors

Xiong J et al. 2025, Nat Commun · paper · public at NCBI GEO · accession resolved 2026-09-12 via eutils esummary

GSE296290 single-cell multiome Bos taurus

Leveraging single cell multiomic analyses to identify gene regulatory networks that drive human articular cartilage cell fate

Jachim SK et al. 2026, Osteoarthritis Cartilage · paper · public at NCBI GEO; GEO lists the organism as Bos taurus while the series title says human, so read the series page before reuse · accession resolved 2026-09-12 via eutils esummary

Public datasets on the chondrocyte and articular cartilage. The first eight rows are the accessions cited most often across the 78,753 abstracts of the 2026-09-12 sweep, so they are the datasets this field actually reuses; the mention count is given for each. Every accession was resolved through NCBI eutils esummary on the date in its row and the title is the one GEO returns, not a paraphrase. Where GEO lists no linked paper the row says so rather than guessing one.