Brief Reports: Lysosomal Cross-Correction by Hematopoietic Stem Cell-Derived Macrophages Via Tunneling Nanotubes

Abstract

Despite controversies on the potential of hematopoietic stem cells (HSCs) to promote tissue repair, we previously showed that HSC transplantation could correct cystinosis, a multi-systemic lysosomal storage disease, caused by a defective lysosomal membrane cystine transporter, cystinosin (CTNS). Addressing the cellular mechanisms, we here report vesicular cross-correction after HSC differentiation into macrophages. Upon co-culture with cystinotic fibroblasts, macrophages produced tunneling nanotubes (TNTs) allowing transfer of cystinosin-bearing lysosomes into Ctns-deficient cells, which exploited the same route to retrogradely transfer cystine-loaded lysosomes to macrophages, providing a bidirectional correction mechanism. TNT formation was enhanced by contact with diseased cells. In vivo, HSCs grafted to cystinotic kidneys also generated nanotubular extensions resembling invadopodia that crossed the dense basement membranes and delivered cystinosin into diseased proximal tubular cells. This is the first report of correction of a genetic lysosomal defect by bidirectional vesicular exchange via TNTs and suggests broader potential for HSC transplantation for other disorders due to defective vesicular proteins.

Treatment of Inherited Eye Defects by Systemic Hematopoietic Stem Cell Transplantation

“…[42][43][44] kely to provide lysosomal cross-correction by delivering cystinosin-bearing lysosomes to the adjacent diseased corneal cells, thereby providing functional cystine clearance mechanisms for Ctns À/À cells, similar to the TNT-mediated crossing of the tubular membrane that halts kidney degeneration. 29 Therefore, TNTs generated by MHC class II þ bone marrowderived cells, which penetrate corneal layers, are likely leading to the our presented findings of structural and functional preservation in corneas. Cystinosin-containing microvesicle transfer from the bone marrow-derived macrophages to the host cells is an alternative route for cystinosin cross-correction.…”

“…Interestingly, we observed that these macrophages generated TNTs as observed previously within the kidney. 29 These membrane extensions are heterogeneous cell-connecting tubules that have been involved in pathogen spreading and intercellular communication. 40,41 In vivo existence of TNT was reported initially in MHC II-positive cells present in mouse corneal stroma.…”

“…29 Here, we asked whether the same mechanism is observed in eyes. Confocal microscopy showed that most HSPC progeny in the cornea differentiated into mature macrophages, as confirmed by the colocalization of all bone marrow-derived DsRed-positive cells with F4/80 (Fig.…”

“…ScaIþ HSCs were isolated as described previously. 29 One million GFP cells were directly transplanted in lethally irradiated (8 Gy) DsRed Ctns À/À mice by tail vein injection while DsRed Ctns À/À cells were first transduced with SIN lentivirus expressing the fused protein CTNS-GFP before transplantation in lethally irradiated (8 Gy) Ctns À/À mice as described previously. 29 To analyze bone marrow engraftment of the transplanted cells, fresh blood was treated with red blood cell lysis buffer (eBioscience, San Diego, CA, USA) and subsequently analyzed by flow cytometry to the GFP-expressing cells.…”

Senescent cells communicate via intercellular protein transfer

“…Nevertheless, cells can also transfer proteins from different cellular compartments and even entire organelles to other cells without secretion (Davis and Sowinski 2008;Abounit and Zurzolo 2012;Naphade et al 2015). Cytoplasmic bridges (CBs), which are membrane protrusions connecting two cells over a long distance, are such a way of cellular communication that allows direct protein transfer between cells.…”