The extracellular matrix (ECM) presents a framework for various biological cues and regulates homeostasis during both developing and mature stages of tissues. During development of cartilage, the ECM plays a critical role in endowing both biophysical and biochemical cues to the progenitor cells. Hence, designing microenvironments that recapitulate these biological cues as provided by the ECM during development may facilitate the engineering of cartilage tissue. In the present study, we fabricated an injectable interpenetrating hydrogel (IPN) system which serves as an artificial ECM and provides chondro-inductive niches for the differentiation of stem cells to chondrocytes. The hydrogel was designed to replicate the gradual stiffening (as a biophysical cue) and the presentation of growth factors (as a biochemical cue) as provided by the natural ECM of the tissue, thus exemplifying a biomimetic approach. This dynamic stiffening was achieved by incorporating silk fibroin, while the growth factor presentation was accomplished using sulfated-carboxymethyl cellulose. Silk fibroin and sulfated-carboxymethyl cellulose (s-CMC) were combined with tyraminated-carboxymethyl cellulose (t-CMC) and crosslinked using HRP/H₂O₂ to fabricate s-CMC/t-CMC/silk IPN hydrogels. Initially, the fabricated hydrogel imparted a soft microenvironment to promote chondrogenic differentiation, and with time it gradually stiffened to offer mechanical support to the joint. Additionally, the presence of s-CMC conferred the hydrogel with the property of sequestering cationic growth factors such as TGF-β and allowing their prolonged presentation to the cells. More importantly, TGF-β loaded in the developed hydrogel system remained active and induced chondrogenic differentiation of stem cells, resulting in the deposition of cartilage ECM components which was comparable to the hydrogels that were treated with TGF-β provided through media. Overall, the developed hydrogel system acts as a reservoir of the necessary biological cues for cartilage regeneration and simultaneously provides mechanical support for load-bearing tissues such as cartilage.

中文翻译：

---

工程化基于硫酸化多糖和丝素蛋白的可注射 IPN 水凝胶，具有软骨组织工程的硬化和生长因子呈现能力

细胞外基质（ECM）为各种生物线索提供了一个框架，并在组织的发育和成熟阶段调节体内平衡。在软骨发育过程中，ECM 在向祖细胞赋予生物物理和生化信号方面发挥着关键作用。因此，设计重现 ECM 在发育过程中提供的这些生物线索的微环境可能有助于软骨组织的工程化。在本研究中，我们制造了一种可注射的互穿水凝胶（IPN）系统，该系统用作人工ECM，并为干细胞分化为软骨细胞提供软骨诱导生态位。水凝胶的设计目的是复制由组织的天然 ECM 提供的逐渐变硬（作为生物物理线索）和生长因子的呈现（作为生化线索），从而体现了仿生方法。这种动态硬化是通过掺入丝素蛋白来实现的，而生长因子的呈现是通过使用硫酸化羧甲基纤维素来实现的。将丝素蛋白和硫酸化羧甲基纤维素(s-CMC)与酪胺化羧甲基纤维素(t-CMC)组合并使用HRP/H ₂ O ₂交联以制备s-CMC/t-CMC/丝IPN水凝胶。最初，制造的水凝胶提供了一个柔软的微环境，以促进软骨分化，随着时间的推移，它逐渐变硬，为关节提供机械支撑。此外，s-CMC 的存在使水凝胶具有隔离阳离子生长因子（如 TGF-β）的特性，并允许其长时间呈现给细胞。更重要的是，加载在开发的水凝胶系统中的TGF-β保持活性并诱导干细胞的软骨分化，导致软骨ECM成分的沉积，这与通过培养基提供的TGF-β处理的水凝胶相当。总体而言，开发的水凝胶系统充当软骨再生所需生物信号的储存库，同时为软骨等承重组织提供机械支撑。