A dynamic cell adhesion surface regulates tissue architecture in growth plate cartilage

Abstract

The architecture and morphogenetic properties of tissues are founded in the tissue-specific regulation of cell behaviors. In endochondral bones, the growth plate cartilage promotes bone elongation via regulated chondrocyte maturation within an ordered, three-dimensional cell array. A key event in the process that generates this cell array is the transformation of disordered resting chondrocytes into clonal columns of discoid proliferative cells aligned with the primary growth vector. Previous analysis showed that column-forming chondrocytes display planar cell divisions, and the resulting daughter cells rearrange by ∼90°t o align with the lengthening column. However, these previous studies provided limited information about the mechanisms underlying this dynamic process. Here we present new mechanistic insights generated by application of a novel time-lapse confocal microscopy method along with immunofluorescence and electron microscopy. We show that, during cell division, daughter chondrocytes establish a cell-cell adhesion surface enriched in cadherins and β-catenin. Rearrangement into columns occurs concomitant with expansion of this adhesion surface in a process more similar to cell spreading than to migration. Column formation requires cell-cell adhesion, as reducing cadherin binding via chelation of extracellular calcium inhibits chondrocyte rearrangement. Importantly, physical indicators of cell polarity, such as cell body alignment, are not prerequisites for oriented cell behavior. Our results support a model in which regulation of adhesive surface dynamics and cortical tension by extrinsic signaling modifies the thermodynamic landscape to promote organization of daughter cells in the context of the three-dimensional growth plate tissue.

A Tunable, Three-DimensionalIn VitroCulture Model of Growth Plate Cartilage Using Alginate Hydrogel Scaffolds

“…3A, B) demonstrate that PTHrP pathway functions are maintained in chondrocytes within our alginate cultures. 3,6 Like wise, our data show that functions of the IHH signaling pathway Fig. 7.…”

“…2 These resting zone chondrocytes are progres sively recruited into the proliferative zone, where cell cycle ac tivation and changes in cell morphology and cell organization result in expansion of isogenic columns of chondrocytes along the axis of growth. 3 As columns lengthen, chondrocytes at the proximal (meta physeal) end of the column withdraw from the cell cycle and increase in volume (hypertrophy) in two steps that are char acteristic of the prehypertrophic and the hypertrophic chon drocytes. 4,5 Growth is generated from chondrocyte hypertrophy through increased cell mass and deposition of specialized ma trix.…”

Long bone human anlage longitudinal and circumferential growth in the fetal period and comparison with the growth plate cartilage of the postnatal age

“…Dodds () has highlighted the relationship between the oriented chondrocyte duplication and the flattened shape of the lacunae, thus distinguishing different modes of division of discoid cells in rows. Li and Dudley (), Romereim and Dudley (), and Romereim, Conoan, Chen, and Dudley () have advanced the hypothesis that the alignment of the chondrocytes was the result of a revolvement of the duplicated cells prior to the formation of the matrix septum. The internal adhesion of the chondrocyte membrane to the surrounding matrix was the force hypothesized to induce rotation as a result of a cell volume increase.…”

Growth and shaping of metacarpal and carpal cartilage anlagen: application of morphometry to the development of short and long bone. A study of human hand anlagen in the fetal period

“…However, the chondrocytes paired into a single lacuna or the structuring bipartite lacunae could be correlated to the intralacunar mitoses. We have no evidences that the paired chondrocytes axis corresponded to that of the original mitotic spindle, because the dividing chondrocytes could have revolved in the passage from Zone 3 to subzone 2e before formation of the matrix septum (Li & Dudley, ; Romereim, Canoan, Chen, & Dudley, ; Romereim & Dudley, ). However, once the paired chondrocytes position had been fixed by this diaphragm, any further change of orientation is unlikely.…”