Early Committed Clockwise Cell Chirality Upregulates Adipogenic Differentiation of Mesenchymal Stem Cells

Abstract

determine the LR asymmetry in morphogenesis. [2] For example, chirality has been found in Xenopus egg cortex before fertilization, [1] and can be passed down to more differentiated cells that establish LR body axis of animal body plan, [7] organ distribution, [8-10] and epithelial movement that leads to axial torsion and overall handedness of hindgut. [11,12] For specialized adult cells derived from somatic tissue, footprints of cell chirality can still be seen by their ability of generating cellular torque, [6,13] migration with LR bias, [14-16] or forming specific alignment in the multicellular level. [15,17,18] Through cell-cell communication, the chiral behavior causes LR-biased cell assembly of multicellular structure [15] and regulates permeability of intercellular junctions. [19] Clearly, cell chirality can be manifested in diverse forms and coordinate different morphogenic dynamics, resulting in distinct forms of tissue and organ architecture. Actin cytoskeleton plays an important role in cell chirality. When cultured on micropatterned substrate, the accumulation of actomyosin stress fibers at micropattern boundary is essential to activate the LR bias in cell migration and orientation. [15,17] Molecular studies suggest helical motion of actin filament as the underlying mechanism for the chirality at cellular level. [20,21] Functioning as a built-in machinery, actomyosin cytoskeleton allows chiral nucleus rotation of single cell [21] and generation of cellular torque with rotational bias. [13] Through a series of amplification process, the actin chirality ultimately determines the symmetry breaking in early embryonic development, [1,7,22] cardiac looping, [4,8,23] and organ laterality [9] in vivo. To give rise to such diverse forms of cell chirality, cell differentiation should play a role. [13,15,17] Cell differentiation is a process coupling with chemical [24] and physical factors. [25-27] Based on variation of key proteins in cytoskeleton, [28] cytoskeleton can be changed at early stage of cell differentiation, as shown by upregulation of cytoskeletal contractility [29] and cell morphological features, which can even forecast the cell lineage fate. [28] It suggests that cytoskeletal components, particularly actin, may early respond to the induction of cell differentiation and then actively participate the signal cascades to engage cell fate. Evidences can be found by regulation of cell differentiation via changed cell shape and cell spreading by physical cues [30-38]

Cell chirality reversal through tilted balance between polymerization of radial fibers and clockwise-swirling of transverse arc

“…3a). Using automated image processing to analyze the tilting angle of actin lament with respect to the radial axis of each cell 23 , a ACW bias was found (Fig. 3b), which is consistent with previous ndings 22 and the nucleus rotation mentioned above.…”

“…We next explored the potential regulation of cell differentiation by adjusting the cell chirality. Previously we have shown that hMSCs would early committed to a CW chirality with adipogenic induction, which may possibly serve as the mechanical precursor to engage the cell phenotype toward the adipogenic lineage 23 . To explore whether the expression of mDia2 can guide the lineage speci cation, we applied mDia2 silencing to hMSCs (24 hours of transfection and 12 hours of recovery in growth media) before adipogenic and osteogenic dual induction and count the lineage speci cation by Oil Red O staining (for adipocytes) and Fast Blue staining (for osteoblasts) (Fig.…”

“…The percentages of ACW or CW transient rotation of each cell was determined within the entire duration and averaged among many cells Analysis of Fiber Orientation on Circular Pattern. The quantitative analysis of actin ber orientation was carried out in Matlab as described previously 23 . In brief, adaptive threshold and Gaussian lter was applied on cropped actin image to generate a binarized image of actin.…”

“…Speci cally, when cultured on micropatterned circles, radial actin bers that point from cell periphery to nucleus are unidirectionally tilted, forming a chiral swirling pattern of actin lament. With such chiral patterns, the intracellular actin lament serves as the main driver of this chiral torque and rotation 12,23,24 .…”

The osteogenic response to chirality-patterned surface potential distribution of CFO/P(VDF-TrFE) membranes

“…13 Geometric chirality modulates the enhancement or cancellation of the intrinsic chirality of the cytoskeleton, thereby altering cytoskeleton contractility to mediate asymmetric cell fates and significantly affect the osteogenic differentiation behavior of cells. 20 That is, the intracellular actin organization mechanism is the physical mechanism in which the cells are modulated by material chirality bias. 21…”