Facultative heterochromatin is cell-type specific, well documented by electron microscopy and found lining the lamina at the inside of the nucleus.
In contrast to PDGFR α+ cells, CD56+ cells were not observed around ectopic fat and in fibrotic areas where many PDGFR α+ cells were localized, but they were located on the inside of the basal lamina.
For example, in intestine, migrasome-like structures are inside blood capillaries or lymph capillaries, in the lamina propria of ileum crypts, or in connective tissue.
CD56+ cells contributed predominantly to nuclei inside the basal lamina of muscle fibres, i.e. within either muscle fibres and/or satellite cells.
Interestingly, when we compared the percentage of donor nuclei located inside the basal lamina (which must be either myonuclei or satellite cells) between the three groups, the highest percentage was found in the muscles grafted with CD56+ cells (82.15±5.94%, mean ± SEM at 4 weeks and 86.86±3.60%, mean ± SEM at 8 weeks after grafting).
We could exclude the presence of Pax7− and Dlk1+ cells inside the basal lamina of myofibres labelled by anti-laminin (Fig. 7f i).
However, Figure 5 i shows only tangentially running fibers inside the superficial lamina, and Figure 5 iv,v shows very high anisotropy in that region.
Muscle progenitor cells Pax7+ and NCAM+, Pax7− and NCAM+, MyoD+ or myogenin+ inside the basal lamina of some dystrophin negative myofibres or regenerating NCAM+ myofibres were not labelled by anti-Dlk1.
Furthermore in regions where the surface voxels of 2 cortical areas touch due to cortical folding, the fODF peaks inside the superficial lamina may be subject to partial voluming with adjacent tissue.
The mean number of SCs per fibre (total SCs/fibre), previously calculated for each subject (Lindstrom and Thornell 2009) (i.e. all cells identified by their staining for Pax7 and/or NCAM inside the basal lamina of the myofibres divided by the total number of analysed myofibres) was used to estimate the proportion of SCs labelled by anti-MyoD and anti-myogenin.
