chondrocyte digital twin

Matrix budget twin

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

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

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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,

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.