Zhou Bin's group used cell proliferation tracking technology to draw mammalian postnatal cardiomyocyte proliferation map

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Cardiovascular disease is an important cause of human mortality, and the incidence continues to increase
.

Cardiac regeneration research has always been a frontier scientific issue and research hotspot in the field

The above studies on cardiomyocyte proliferation mainly used measurement methods, EdU or BrdU incorporation methods and molecular markers of cell proliferation (Aurora B, Ki67, etc.
) staining
.

These methods can only study cell proliferation at a certain time point (or a very short period of time), and are not suitable for studying cell proliferation within a certain period of time (such as weeks to months)

ProTracer (R26-DreER; Ki67-CrexER; R26-GFP ) technology can be used to capture in vivo cell proliferation events uninterruptedly over a long period of time
.

In R26-DreER;Ki67-CrexER;R26-GFP mice, DreER is widely expressed in most cells, and the Dre-rox recombination reaction occurs under the induction of tamoxifen to excise the ER element and convert the Ki67-Crex ER for Ki67-Cre mice

In order to avoid non-cardiomyocyte proliferation signals from interfering with the objective detection of cardiomyocyte proliferation ability, researchers constructed cardiomyocyte-specific cell proliferation tracking technology using Tnnt2-mTnG tool mice ( R26-DreER; Ki67-CrexER ;Tnnt2-mTn G)
.

After tamoxifen induction, if the cells proliferate, they will express Ki67 and initiate the expression of Cre homologous recombinase, the Cre-loxP homologous recombination reaction occurs, and the cardiomyocytes are labeled as mTnG, while the proliferating non-cardiomyocytes do not will be marked

The first two methods mainly rely on Ki67 to mark proliferating cells.
In order to mark proliferating cells from different angles, researchers use another cell proliferation marker, Ccna2, to carry out research
.

The researchers constructed a cell proliferation tracking technology based on the Ccna2-CrexER tool mouse ( R26-DreER; Ccna2-CrexER; R26-GFP )

This work uses the cell proliferation tracking technology ProTracer to continuously record the proliferation activity of cells in different stages of the mouse postnatal period, and draws a detailed map of cell proliferation in the process of mouse postnatal to puberty
.

The researchers observed a rapid decline in cardiomyocyte proliferative capacity from postnatal to puberty, and no peak in cardiomyocyte proliferation on postnatal days 14 to 15

　　Associate researcher Pu Wenjuan and PhD student Zhang Mingjun of the Center of Excellence for Molecular Cells are the co-first authors of the paper
.

Researcher Zhou Bin from the Center of Excellence for Molecular Cells and Professor He Ben from Shanghai Chest Hospital are the co-corresponding authors of the paper

　　Article link: https://

Figure: Cell proliferation tracing technology reveals a rapid decline in the proliferative viability of mammalian cardiomyocytes from postnatal to puberty

　　A, Construction strategy map of cell proliferation tracking technology based on Ki67-CrexER
tool mice .

B, Experimental strategy diagram
.
C, Flow cytometry was used to detect the proportion of GFP ⁺ cardiomyocytes at different time points to analyze the proliferation of cardiomyocytes.
The right side is the statistical result
.
D.
Heart tissues were collected at different time points for frozen section and immunofluorescence staining for GFP and TNNI3
.
^{And count the number of GFP +} cardiomyocytes in heart samples at different time points
.
E, Diagram of the construction strategy of Tnn2-mTnG mice, and immunostaining results of tdTmato, GFP and TNNI3 in ACTB-Cre;Tnn2-mTnG
mouse hearts .
F, Diagram of the construction strategy of cardiomyocyte-specific cell proliferation tracking technology based on Tnnt2-mTn
G tool mice .
G, Cardiomyocyte-specific cell proliferation tracking technology mouse heart tissue at different time points was collected for frozen section and tdTmato, GFP and TNNI3 immunofluorescence staining
.
^{And count the number of mTnG +} cardiomyocytes in heart samples at different time points
.
H, Construction strategy map of cell proliferation tracing technology based on Ccna2-CrexER
tool mice .
I, Heart tissues were collected at different time points for frozen section and immunofluorescence staining for GFP and TNNI3
.
^{And count the number of GFP +} cardiomyocytes in heart samples at different time points
.