Maji Somnath, Aliabouzar Mitra, Quesada Carole, Chiravuri Anjali, Macpherson Aidan, Pinch Abigail, Kazyak Karsyn, Emara Ziyad, Abeid Bachir A, Kent Robert N, Midekssa Firaol S, Zhang Man, Baker Brendon M, Franceschi Renny T, Fabiilli Mario L
Department of Radiology, University of Michigan, Ann Arbor, MI, USA.
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.
Bioact Mater. 2024 Sep 20;43:82-97. doi: 10.1016/j.bioactmat.2024.09.018. eCollection 2025 Jan.
Hydrogels can improve the delivery of mesenchymal stromal cells (MSCs) by providing crucial biophysical cues that mimic the extracellular matrix. The differentiation of MSCs is dependent on biophysical cues like stiffness and viscoelasticity, yet conventional hydrogels cannot be dynamically altered after fabrication and implantation to actively direct differentiation. We developed a composite hydrogel, consisting of type I collagen and phase-shift emulsion, where osteogenic differentiation of MSCs can be non-invasively modulated using ultrasound. When exposed to ultrasound, the emulsion within the hydrogel was non-thermally vaporized into bubbles, which locally compacted and stiffened the collagen matrix surrounding each bubble. Bubble growth and matrix compaction were correlated, with collagen regions proximal (i.e., ≤ ∼60 μm) to the bubble displaying a 2.5-fold increase in Young's modulus compared to distal regions (i.e., > ∼60 μm). The viability and proliferation of MSCs, which were encapsulated within the composite hydrogel, were not impacted by bubble formation. In vitro and in vivo studies revealed encapsulated MSCs exhibited significantly elevated levels of RUNX2 and osteocalcin, markers of osteogenic differentiation, in collagen regions proximal to the bubble compared to distal regions. Additionally, alkaline phosphatase activity and calcium deposition were enhanced adjacent to the bubble. An opposite trend was observed for CD90, a marker of MSC stemness. Following subcutaneous implantation, bubbles persisted in the hydrogels for two weeks, which led to localized collagen alignment and increases in nuclear asymmetry. These results are a significant step toward controlling the 3D differentiation of MSCs in a non-invasive and on-demand manner.
水凝胶可以通过提供模仿细胞外基质的关键生物物理线索来改善间充质基质细胞（MSCs）的递送。MSCs的分化取决于诸如硬度和粘弹性等生物物理线索，然而传统水凝胶在制造和植入后不能动态改变以积极引导分化。我们开发了一种由I型胶原蛋白和相移乳液组成的复合水凝胶，其中MSCs的成骨分化可以通过超声进行非侵入性调节。当暴露于超声时，水凝胶内的乳液非热蒸发成气泡，这些气泡局部压实并使每个气泡周围的胶原基质变硬。气泡生长与基质压实相关，与气泡近端（即≤约60μm）的胶原区域相比，远端区域（即>约60μm）的杨氏模量增加了2.5倍。封装在复合水凝胶中的MSCs的活力和增殖不受气泡形成的影响。体外和体内研究表明，与远端区域相比，封装在复合水凝胶中的MSCs在气泡近端的胶原区域中，成骨分化标志物RUNX2和骨钙素的水平显著升高。此外，气泡附近的碱性磷酸酶活性和钙沉积增强。观察到MSCs干性标志物CD90呈现相反的趋势。皮下植入后，气泡在水凝胶中持续存在两周，这导致局部胶原排列和核不对称性增加。这些结果朝着以非侵入性和按需方式控制MSCs的三维分化迈出了重要一步。
