D29-25 Positron Emission Tomography (PET) Tracking of Lung Progenitor Cell Engraftment in Bleomycin-Injured Mouse Lungs
A Serra Marques, A Ogasawara, J Yun, P Dragovich, M Nichane, H Gill, A Arlantico, E Shamir, Y Rao, K Barck, D Dunlap, C Jones, C Harvnar, J Eastham, J Marik, K Loh, T J Desai, H Jasper, J R Rock, S WilliamsAbstract
Rationale
Pulmonary fibrosis is characterized by chronic inflammation, fibroblast expansion, collagen deposition, and impaired tissue repair. Allogeneic epithelial cell transplantation for lung disease could help regenerate lung tissue and restore lung function, but the limited availability of cells from deceased donors and the lack of tools to assess engraftment and longterm benefit make this a difficult therapy to establish. A sensitive method to longitudinally track therapeutic cell engraftment and expansion in vivo would aid preclinical development and translation.
Methods
Mouse induced lung progenitor cells (iLPs) were generated and engineered to express RFP and human CD8 (hCD8) as a PET (Positron Emission Tomography) reporter. hCD8⁺ iLPs were expanded and sorted prior to intratracheal delivery (1 ×106 cells/mouse) into the lungs of mice 7 days post bleomycin treatment; control animals received bleomycin only. PET imaging was performed using an ¹⁸Flabeled antihCD8 VHH tracer (¹⁸FhCD8.VHH) on days 24, 37, 52, 60, and 99 postengraftment. Lungs were segmented and quantified from the images to determine normalized tracer concentration as percent injected dose per gram (%ID/g) and CD8⁺ tissue volume. Immunohistochemistry (IHC) for hCD8 was performed on lungs after imaging to evaluate iLP engraftment.
Results
¹⁸FhCD8.VHH PET showed focal tracer uptake in lung regions of bleomycintreated mice receiving hCD8⁺ iLPs, with minimal lung signal in bleomycinonly controls. Lung PET signal intensified in the hCD8⁺ iLP group progressively over 99 days, while control mice consistently showed minimal signal. Quantitative analysis indicated that the overall volume of CD8⁺ tissue was established early after engraftment, whereas PET signal intensity within these regions increased over time, consistent with local expansion of engrafted cells. hCD8 IHC confirmed iLP engraftment, correlated with the spatial distribution of PET signal, and co-localized with RFP and alveolar epithelial markers.
Conclusions
Intratracheally administered hCD8+ iLPs can engraft into the lungs of bleomycininjured mice. PET imaging with ¹⁸FhCD8.VHH enables longitudinal, noninvasive tracking of hCD8⁺ cells in this model of pulmonary fibrosis. Conspicuous PET signal over time in the injured lungs reflects persistence and potential expansion of engrafted iLPs. This proofofconcept study using a PET tracer highlights the potential of PET imaging to monitor biodistribution and cell kinetics of cellbased therapeutics.
This abstract is funded by: Genentech