Page 39 - OR-1-2

cranial and facial bones, form through intramembranous technology supports rapid and large-scale production
ossification, bypassing a cartilage model by allowing models. The biocompatible materials used, such as GelMA/
osteoblasts to produce bone matrix and trabeculae AlgMA/hydroxyapatite, are derived from natural sources;
directly. After skeletal development is complete, the exhibiting excellent biocompatibility and can reduce
137
bone undergoes remodeling in response to internal and immune responses within the body, fostering cell growth
external mechanical loads, establishing a robust bone and differentiation. By adjusting the ratios of GelMA and
structure. Within the bone, a dynamic equilibrium exists AlgMA, and the amount of hydroxyapatite, the material’s
among osteoblasts, osteocytes, bone lining cells, and pre- mechanical properties and biodegradation rates can be
osteoblasts. Present experiments focusing on 2D cell controlled, meeting the diverse needs of various tissue
138
cultures and single-cell interaction models have limited engineering applications. Furthermore, incorporating
value in demonstrating bone repair. In contrast, the additional bioactive molecules, such as growth factors, can
construction of bone organoids offers greater reference further enhance the growth-promoting and regenerative
and application value for studying bone development and capabilities of these composite materials.
remodeling compared to traditional 2D cell culture models.
4.6.2. Cartilage
4.6.1. Bone Articular cartilage, which covers the ends of the bones
In large bone defects, insufficient callus tissue formation can at joint surfaces, is a smooth cartilage matrix that, along
lead to prolonged healing times or the failure of the defect with calcified cartilage and subchondral bone, forms the
139
to heal, leading to non-union. Using MSC aggregates basic structural unit of the joint. It consists of numerous
can enhance bone regeneration. However, differences in chondrocytes and is enveloped by collagen fibers and GAGs.
physiological callus tissue may limit further endogenous Cartilage lacks blood vessels, nerves, and lymphatic supply,
osteogenesis. Xie et al. employed digital light limiting its self-repair capacity and rendering conventional
141
140
processing-based 3D bioprinting technology with gelatin treatment often ineffective.
methacrylate (GelMA) hydrogels loaded with bone marrow- Shen et al. developed hydrogel microspheres with
143
derived stem cells (BMSCs). By sequentially inducing these uniform size, porous surfaces, and excellent swelling and
microspheres to aggregate into callus-like organoids, they degradation properties using a microfluidic system combined
effectively addressed issues of nutrient deprivation and with photopolymerization and self-assembly techniques
cell necrosis that are often encountered when preparing in (Figure 7C). These microspheres, composed of Arginine-
vitro large-scale cell aggregates. This technique enables the Glycine-Aspartic acid (RGD), a short peptide sequence
rapid, large-scale production of cell-laden microspheres mimicking the natural cartilage microenvironment, SF, and
with precise control over organoid size and structure, DNA hydrogel, are referred to as RGD-SF-DNA hydrogel
supporting efficient bone regeneration. Wang et al. microspheres (RSD-MS). By simulating the cartilage
141
142
developed a novel method for fabricating self-mineralizing microenvironment, RSD-MS promoted the proliferation,
bone organoids to address large bone defects (Figure 7A). adhesion, and chondrogenic differentiation of BMSCs. The
This approach utilizes a bioink inspired by natural bone study demonstrated that RSD-MS primarily drives cartilage
matrix, constructed using 3D bioprinting technology to formation through integrin-mediated adhesion pathways
create complex bone matrix analogs. Composed of GelMA/ and GAG biosynthesis. In vivo studies revealed that
alginate methacrylate (AlgMA)/hydroxyapatite, this bioink cartilage organoid pre-cursors formed by seeding BMSCs
provides excellent mechanical support. With bioprinted onto RSD-MS significantly enhanced cartilage regeneration
scaffolds, large-scale bone organoids can be cultured and (Figure 7D). Therefore, RSD-MS is an ideal material for
matured over extended periods. The self-mineralizing constructing and long-term culturing cartilage organoids,
properties of this bioink enhance mechanical performance providing an innovative strategy for cartilage regeneration
and allow for extensive in vitro and in vivo cultivation and tissue engineering. In addition, regenerating the
143
and multicellular differentiation (Figure 7B). These complex hierarchical structure of cartilage and subchondral
self-mineralizing constructs can replicate the structure bone presents significant challenges. Yang et al. developed
144
and function of natural bone tissue, offering necessary customized gelatin-based microcryogels for cartilage and
mechanical support and mimicking the ECM, thereby bone regeneration that self-assembled into osteochondral-
overcoming the limitations of traditional bone regeneration like structures in vivo. These tailored microcryogels exhibited
methods. 142 excellent cell compatibility and effectively induced MSCs to
The utilization of MSC aggregates in conjunction differentiate into cartilage and bone while facilitating self-
with DLP 3D bioprinting technology offers a rational assembly within the biphasic cartilage-bone structure. Gene
approach and strategy for effective internal nutrient supply expression analysis indicated that cartilage-type cryogels
to cells, significantly promoting bone regeneration. This promoted chondrocyte differentiation and suppressed

Volume 1 Issue 2 (2025) 18 doi: 10.36922/or.8262