Hematopoiesis after anti-CD117 monoclonal antibody treatment in the settings of wild-type and Fanconi anemia mice.

Anti-CD117 monoclonal antibody (mAb) agents have emerged as exciting alternative conditioning strategies to traditional genotoxic irradiation or chemotherapy for both allogeneic and autologous gene-modified hematopoietic stem cell transplantation. Furthermore, these agents are concurrently being explored in the treatment of mast cell disorders. Despite promising results in animal models and more recently in patients, the short- and long-term effects of these treatments have not been fully explored. We conducted rigorous assessments to evaluate the effects of an antagonistic anti-mCD117 mAb, ACK2, on hematopoiesis in wild-type and Fanconi anemia (FA) mice. Importantly, we found no evidence of short-term DNA damage in either setting following this treatment, suggesting that ACK2 does not induce immediate genotoxicity, providing crucial insights into its safety profile. Surprisingly, FA mice exhibited an increase in colony formation after ACK2 treatment, indicating a potential targeting of hematopoietic stem cells and expansion of hematopoietic progenitor cells. Moreover, the long-term phenotypic and functional changes in hematopoietic stem and progenitor cells did not differ significantly between the ACK2-treated and control groups, in either setting, suggesting that ACK2 does not adversely affect hematopoietic capacity. These findings underscore the safety of these agents when utilized as a short-course treatment in the context of conditioning, as they did not induce significant DNA damage in hematopoietic stem or progenitor cells. However, single-cell RNA sequencing, used to compare gene expression between untreated and treated mice, revealed that the ACK2 mAb, via c-Kit downregulation, effectively modulated the MAPK pathway with Fos downregulation in wild-type and FA mice. Importantly, this modulation was achieved without causing prolonged disruptions. These findings validate the safety of anti-CD117 mAb treatment and also enhance our understanding of its intricate mode of action at the molecular level.

The MarrowMiner: A Novel Minimally Invasive and Effective Device for the Harvest of Bone Marrow.

Bone marrow (BM) is a rich source of hematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs), and other important stem/progenitor cells. It is the traditional source of cells used in hematopoietic cell transplantation, which is a proven curative treatment for many blood and immune diseases. BM-derived cells have also been shown to have other diverse clinical uses and are increasingly being used in orthopedic medicine, regenerative medicine, and gene therapy applications. Traditional methods for harvesting BM are crude, tedious, time-consuming, and expensive, requiring multiple bone punctures under general anesthesia with serial small-volume aspirates often diluted with peripheral blood. The MarrowMiner (MM) is a novel device designed for rapid and minimally invasive BM harvest. Here we show the safety and efficacy of the MM in both preclinical and clinical settings. In a large-animal porcine model, the MM enabled effective BM collection with similar total nucleated cell collection and increased colony formation compared with standard methods. The MM was subsequently evaluated in a clinical study showing effective and complication-free anterior and posterior BM collection of 20 patients under only local anesthesia or light sedation. Increased total nucleated and mononucleated cell collection was achieved with the MM compared with standard methods in the same patients. Importantly, stem cell content was high with trends toward increased HSC, MSC, and endothelial progenitor cells with similar T cell content. Given the MM is a novel device approved by the US Food and Drug Administration, enabling safe, effective, and minimally invasive harvest of BM, we anticipate rapid adoption for various applications.