Figure 3.

Analysis of Human Mononucleated Muscle Cells after fiber Transplantation

(A) Immediately after fiber injection. PAX7 cells survive and localize outside of the human fiber basement membrane. Top: immunostaining for PAX7, LAMININ, and CD29. Human cells are marked by anti-CD29 antibody (BioLegend TS2/16) (hCD29) that detects human, but not mouse, CD29 by immunostaining (see Figure S2 for antibody controls). Bottom: PAX7, MYF5, and CD29. Human PAX7 cells express MYF5 after transplantation. Arrows indicate PAX7-positive nuclei.

(B) 1 week after fiber injection. Human fibers have degenerated. Immunostaining for MYF5, hCD29, and PAX7. Surviving human cells (marked by hCD29 cy5, red pseudocolor, arrows) express MYF5. PAX7 (cy3, red pseudocolor) is not detected in these cells (right panel).

(C) 5 weeks after fiber injection. Human PAX7 cells occupy the satellite cell niche on new human fibers. Top row: immunostaining for PAX7, CD56, and LAMININ. Sublaminar PAX7 cell expresses apical hCD56. Middle row: PAX7, hCD29, and LAMININ. Note sublaminar PAX7 cell and marking of the satellite cell and the fiber membrane by hCD29. Bottom row: PAX7, CD56, and CD29. Human satellite cell expressing high PAX7, apical CD56, and circumferential CD29.

Sections were co-stained with DAPI. Scale bars, 20 μm. See also Figure S2.