Modular flow chamber for engineering bone marrow architecture and function

Abstract

The bone marrow is a soft, spongy, gelatinous tissue found in the hollow cavities of flat and long bones that support hematopoiesis in order to maintain the physiologic turnover of all blood cells. Silk fibroin, derived from Bombyx mori silkworm cocoons, is a promising biomaterial for bone marrow engineering, because of its tunable architecture and mechanical properties, the capacity of incorporating labile compounds without loss of bioactivity and demonstrated ability to support blood cell formation. In this study, we developed a bone marrow scaffold consisting of a modular flow chamber made of polydimethylsiloxane, holding a silk sponge, prepared with salt leaching methods and functionalized with extracellular matrix components. The silk sponge was able to support efficient platelet formation when megakaryocytes were seeded in the system. Perfusion of the chamber allowed the recovery of functional platelets based on multiple activation tests. Further, inhibition of AKT signaling molecule, which has been shown to be crucial in regulating physiologic platelet formation, significantly reduced the number of collected platelets, suggesting the applicability of this tissue model for evaluation of the effects of bone marrow exposure to compounds that may affect platelet formation. In conclusion, we have bioengineered a novel modular system that, along with multi-porous silk sponges, can provide a useful technology for reproducing a simplified bone marrow scaffold for blood cell production ex vivo.

In vitro culture of murine megakaryocytes from fetal liver-derived hematopoietic stem cells

“…The adoption of these differentiation and culture systems has permitted further study of the events leading to megakaryopoiesis and subsequent proplatelet formation. (5–7) In addition, ex vivo MK culture opened the door to the possibility of creating donor-independent platelets for transfusion.…”

“…(8–11) Such groups exploiting CD34 + cells have concentrated on studying and sustaining MK differentiation and platelet production using various methods, including bioreactors, co-culturing systems, and elegantly bioengineered scaffolding materials to recreate the complex bone marrow microenvironment. (7, 12–17) Stemming from these initial studies, promising techniques such as UCB-derived platelet perfusion systems were established shortly after, detailing production of up to 3.0 −6.0 × 10 11 platelets (up to 20 platelets per starting HSC); a clinically acceptable amount for transfusion. (16) Both UCB & mPB MKs have been found to have similar levels of CD34 + expression, indicating comparable rates of MK production.…”

Multiscale engineering of immune cells and lymphoid organs

“…Fluid flow plays an integral role in tissue homeostasis 47 and can be implemented in bone marrow models using bioreactors. Materials-based systems with fluid flow have advanced our understanding of platelet generation by megakaryocytes [48][49][50][51][52] and of the progression of different disease states, such as multiple myeloma [53][54][55] . For example, using a template made of polyethylene oxide (PEO), silk-based films can be fabricated with a porous architecture 50 .…”

Tissue engineered models of healthy and malignant human bone marrow

“…Excessive bleeding, sepsis, cancer-related thrombocytopenia, among other medical indications, can all necessitate administration of platelet transfusions [99]. In an effort to address this need for ex vivo produced platelets, a modular flow chamber was established featuring a silk fibroin scaffold and enabling efficient formation of platelets and release of megakaryocytes and recoverable platelets [100]. This model was later expanded into a perfusion bioreactor system with tight control of scaffold architecture and flow behavior [101].…”