Lab-grown bone marrow reveals how physical environment shields blood cells from damage
Researchers created an artificial bone marrow using silk that better mimics real human physiology than standard lab cultures. The finding suggests that conventional blood cell research has been dramatically overstating DNA damage and cell stress—with implications for developing safer blood treatments and understanding why some therapies fail.
Originaltitel: A bioprinted silk marrow niche reveals mechanical regulation of human megakaryopoiesis under genotoxic stress
**Biotuskriven siden omdefinierar testning av blodbildning under cellgift** Dagens laboratorietester av blodbildande stamceller underskattar margens beskyddande effekt, vilket förvrider bedömningen av läkemedelstoxicitet och genombeskadning. Italienska forskare från Pavia universitet har utvecklat SilkInk — en 3D-bioprintbar biomaterial baserad på silkefibroin — som återställer benmärgens viskoelastiska miljö i kontrollerad form. I SilkInk bevarade blodbildande stamceller sin klonala potential och genomstabilitet även under exponering för 5-fluorouracil, medan traditionella 2D-kulturer aktiverade stressresponser och försämrad mogning av trombocyter. Stamcellsekvensering visade att SilkInk stödde koordinerad endomitos och celldifferentiering motsvarande frisk märg. För läkemedelstillverkare och regionala inköpare betyder detta en mer tillförlitlig screeningmetod för benmärgstoxicitet före kliniska prövningar. Plattformen minskar risken för negativa överraskningar i fas II och kan accelerera utvecklingstider för cytostatika.
Hematopoietic stem and progenitor cells (HSPCs) reside in a mechanically distinct bone marrow niche, yet how niche biomechanics shape genome stability and stress responses has been difficult to test because conventional two-dimensional (2D) culture lacks marrow viscoelasticity and uses surfaces that activate platelets, confounding hematopoietic readouts. Here, we show that this methodological gap has masked a basic principle: the marrow niche actively constrains genotoxic stress signaling in HSPCs, and 2D culture systematically overstates DNA damage and impairs differentiation in vitro. We engineered silk fibroin, a biologically inert biomaterial that does not activate platelets and recapitulates marrow viscoelasticity, into SilkInk, a 3D-bioprintable bioink, and used it to reconstruct a biomimetic marrow microenvironment. HSPCs encapsulated in SilkInk preserved clonogenic potential and multilineage differentiation, whereas 2D-cultured HSPCs activated cytoskeletal-tension and genome-surveillance programs characteristic of chronic stress, including pathways related to replication stress, DNA damage response, and redox stress. Cell phenotyping and single-cell RNA sequencing during megakaryopoiesis revealed that SilkInk supported coordinated endomitotic progression and terminal maturation, with progression from CD34+CD61-CD41-CD42b- progenitors to CD34-CD61+CD41+CD42b+ megakaryocytes, including increased 8N and >16N populations, whereas 2D culture and conventional 3D hydrogels sustained DNA damage signaling and impaired thrombopoiesis. The same hierarchy held under cytotoxic challenge, as 5-fluorouracil amplified DNA damage and crippled platelet output in 2D, whereas SilkInk-encapsulated HSPCs maintained differentiation, mirroring native marrow resilience. These findings reposition niche mechanics as an active determinant of hematopoietic genome stability and establish SilkInk as a physiologically faithful platform for studying hematopoiesis and predicting marrow responses to chemotherapy.