November 2018 — Vol 138 No 11

(a) Immunofluorescence staining of human C7 in noninjected healthy SEs (6 months after grafting); vehicle-injected RDEB SEs (1 month after injection); and RDEB SEs at 1, 2, 4, and 6 months after hBM-MSCs ID injection. hBM-MSC–injected RDEB SE showed re-expression of C7 at the dermal-epidermal junction compared with vehicle-injected RDEB SE. Staining of the stratum corneum with the C7 antibody is nonspecific. Nuclei are stained blue by DAPI. Scale bar = 20 µm. (b) Ultrastructural analysis of grafted SE by TEM. Pictures display the presence of AF showing typical loop-shaped structures inserted into lamina densa in hBM-MSC–injected RDEB SE up to 6 months. From 2 to 6 months, the lamina densa is continuous, and AFs are structurally similar to healthy SE. AFs are indicated by red arrowheads. Scale bar = 200 nm. (c) Mean average of fluorescence intensity of human C7 protein production over 3 × 5-µm areas in each sample ± standard error of the mean. (d) Mean average of number of AFs = 4 in areas of 10 µm of the basement membrane in each sample ± standard error of the mean. Nonparametric Mann-Whitney test. *P < 0.05, **P < 0.01. n = 3 mice for each time point. AF, anchoring fibril; C7, collagen type VII; hBM-MSC, human bone marrow mesenchymal stromal cell; ID, intradermal; ns, not significant; RDEB, recessive dystrophic epidermolysis bullosa; SE, skin equivalent; TEM, transmission electron microscopy.

In a Letter to the Editor, Ganier and coworkers report extended persistence of type VII collagen and anchoring fibrils in a model of Recessive Dystrophic Epidermolysis Bullosa (RDEB) after local injection of human bone marrow mesenchymal stromal cells (hBM-MSC) into RDEB skin equivalents that had been grafted onto immune-compromised nude mice. They attribute correction that is prolonged relative to that previously reported to the extended survival of hBM-MSC in an immune tolerant environment. See pages 2483-86 for details.