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4.3.1. Scaffolds as stiffness and adhesiveness, significantly influence key
cellular behavior, including adhesion, survival, migration,
Homeostatic collagen degradation is a crucial mechanism proliferation, and differentiation in vitro, so the scaffold
for maintaining the dynamic equilibrium of tendon tissue.
Under physiological conditions, controlled collagen should possess mechanical properties (e.g., stiffness,
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breakdown creates spatial microenvironments that elasticity, strength) appropriate for tendon development.
facilitate the migration and differentiation of stem cells. To translate these design principles into practice, the
However, abnormal collagen degradation disrupts the choice of scaffold material is crucial, as it must support
topological architecture of the ECM, initiating a vicious cellular functions while providing appropriate mechanical
cycle: Disorganized mechanical signaling impairs the and biochemical cues. Ideal scaffolds should support cell
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directional differentiation of tendon stem cells, driving migration, proliferation, and matrix deposition. They must
them to secrete pro-fibrotic factors that exacerbate also exhibit excellent biocompatibility, biodegradability, and
abnormal collagen cross-linking. 66,112 Our prior work mechanical performance. In organoid research, Matrigel—a
demonstrates that targeting critical nodes in this cycle can reconstituted basement membrane matrix rich in laminin,
halt degenerative progression. 112,113 Consequently, effective collagen IV, and growth factors—has been extensively used
scaffold design for tendon organoids must transcend mere as a default scaffold for diverse organoids due to its ability
structural support and actively address this biological to support 3D self-organization. 119-121 Its composition,
complexity. It must achieve dual objectives—mimicking rich in basement membrane proteins, enables it to mimic
the phased degradation of healthy collagen to support the ECM, while also containing biochemical factors that
dynamic cellular demands while simultaneously blocking enhance cell-matrix interactions and promote tissue
pathological degradation pathways that compromise ECM development. However, due to the complex composition
and cellular integrity. This necessitates a multifaceted of Matrigel, proteomic analyses have revealed considerable
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design approach. variability. In addition, batch-to-batch differences in
Scaffolds provide structural support for stem cells and mechanical properties, such as elastic modulus, can lead to
facilitate the formation of 3D structures that mimic the inconsistent local mechanical performance in 3D culture
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cellular niches found in native tendon tissue. As mentioned systems, significantly impacting organoid cultivation.
earlier, the ECM is a major component of tendons, These limitations underscore the need for more defined
with collagen proteins conferring unique mechanical and tunable scaffold systems specifically engineered for
properties and biocompatibility. Studies have shown tendon organoids.
that optimizing the material composition and structural Hydrogels, which are highly hydrated polymer
design of scaffolds can better replicate the physiological networks, have been widely used in the in vitro construction
environment of tendons, promoting the formation of of organoids. Their high-water content mimics the
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tendon organoids. Beyond material selection, the design native ECM environment, and their physicochemical
of scaffolds involves deliberate engineering of biomimetic properties can be extensively customized through design.
architecture, dynamic degradation profile, mechanical Hydrogel scaffold materials can be derived from natural,
properties, and bioactivity. Tendon regeneration is sensitive synthetic, or composite sources. Natural materials, such
to the topology of the substitute, so replicating the highly as collagen, gelatin, silk fibroin, hyaluronic acid,
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organized, aligned fibrous structure of native tendons is and decellularized tendon slices, are commonly used in
paramount for guiding cell orientation, force transmission, tendon tissue engineering due to their biocompatibility
and ultimately, functional tissue formation. Adequate and biodegradability. However, natural materials often
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porosity and interconnectivity are crucial for uniform lack sufficient mechanical strength and have degradation
cell distribution, efficient nutrient/waste exchange, and rates that are difficult to control precisely. To address
potential vascularization in larger constructs. The scaffold’s these limitations, they are frequently combined with
degradation kinetics also should be tuned to mirror other materials to modify their properties. Synthetic
physiological ECM turnover, creating space for new matrix materials, including polylactic acid, polyglycolic acid, and
deposition and cell activity without triggering instability or polyethylene glycol (PEG), can be chemically modified
pathological cascades. Critically, the concept of temporally to introduce functional groups and enhance bioactivity,
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matched biological constraints has been proposed, of which the biocompatibility is often inferior to that of
where scaffolds are engineered to provide spatially and natural hydrogels. Consequently, composite materials
temporally evolving mechanical cues that actively guide have gained popularity. 72,88,127 This composite approach
the sequential phases of tendon repair and maturation, as enables the independent tuning of mechanical properties,
exemplified by studies employing micro-nano hierarchical degradation rate, and bioactivity. For example, one study
designs to deliver stage-specific mechanical stimuli. The utilized rigid aramid nanofibers and flexible polyvinyl
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mechanical properties of stem cell culture substrates, such alcohol to create a highly aligned network that mimics the

Volume 1 Issue 3 (2025) 9 doi: 10.36922/OR025170016