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International Journal of Bioprinting 3D bioprinting for musculoskeletal system

complication following bone defect repair, and the risk of for producing functional grafts that more closely resemble
infection is heightened in the presence of open wounds or native tissue architectures and is therefore a promising
orthopedic implants. approach to cartilage tissue repair. Recent 3D bioprinting

When infectious bone defects occur, bacteria adhere to studies for cartilage regeneration are listed in Table 2.
aggregate and proliferate on the scaffold surface to form Numerous studies have attempted to evaluate the effects
biofilms that impair the function of osteoblasts, leading to of formulations or physical properties of bioinks (such
delayed union or nonunion. 75,76 It has been reported that as matrix stiffness) on the maintenance of chondrocyte
doxycycline can be released from a 3D-bioprinted scaffold, phenotype and subsequent influence on cartilage-specific
which is capable of inhibiting bacteria to reduce the risk ECM production. Conventional bioprinted hydrogels
of infection, to promote the expression of BMP-2 for usually have poor mechanical strength, so it is a challenge
stimulating new bone formation. to engineer mechanically robust cartilage constructs that
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can withstand high load-bearing environments. A feasible
3.2. Cartilage strategy for improving the mechanical strength of tissue
Cartilage is an important tissue responsible for a variety constructs is to incorporate stiffer polymer components
of critical functions, including cushioning stress, reducing into the bioink to strengthen its network. 106,107 Inspired
friction between adjacent bones, and composing organs. by this strategy, an alginate hydrogel reinforced with
Cartilage consists mainly of proteoglycans, water, type II short submicron polylactide was designed as a bioink
collagen, and a few chondrocytes. The articular cartilage has for the bioprinting of cartilaginous construct. Round
a specific zonal orientation (superficial, middle, deep, and chondrocytes with high cell viability were observed in the
calcified zones), and its structure and composition vary in bioprinted constructs which had an elastic modulus three
a depth-dependent manner. Trauma, aging, disease, and times higher than that of the pristine alginate constructs.
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other factors can increase the risk of damage to cartilage, A similar approach was used in another study to develop
especially articular cartilage, resulting in joint dysfunction. fiber-reinforced cartilage ECM-based bioinks for cartilage
According to the depth of the lesion, articular cartilage regeneration. The incorporation of ECM promoted the
defects can be divided into partial cartilage defects, full- growth and chondrogenic differentiation of stem cells
thickness cartilage defects, and osteochondral defects. Due in the bioink. Furthermore, the bioprinted constructs
to the inherent characteristics such as low cell density and augmented with polycaprolactone (PCL) fibers displayed a
absence of blood vessels and nerves, the self-healing ability compression modulus comparable to that of native articular
of articular cartilage is significantly limited. Without cartilage. In addition to the mechanical performance
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timely and potent intervention, chondral lesions often required by motion forces, the engineering of biomimetic
progress to secondary osteoarthritis, leading to severe pain cartilage tissues should focus on their chondrogenic
and even disability. Eventually, patients with end-stage function. To address this issue, de Melo et al. developed
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diseases have to undergo total joint replacement. Therefore, a new tissue design option for cartilage regeneration.
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the repair and regeneration of cartilage tissue has attracted Based on spatially organized bioprinting, this strategy
much attention. The common clinical treatment strategies enables human mesenchymal stem cell (hMSC) spheroids
for cartilage defects include debridement, bone marrow to maintain the chondrogenic behavior without detriment
stimulation, and osteochondral transplantation. 80,81 to the macro mechanical properties of engineered tissues.
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Among them, debridement and bone marrow stimulation Pei et al. used extrusion printing to construct a cartilage
are classified as palliative treatments, which cannot repair scaffold in which mesenchymal stem cells (MSCs)
achieve the curative effect. The application of transplant were transfected with microRNA-410. The up-regulation
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technology is constrained by several shortcomings, such of microRNA-410 enhanced the migration, proliferation,
as the need for reoperation, insufficient donor tissue, and chondrogenic differentiation of loaded cells.
and increased risk of immune rejection and disease Compared with the nontransfected group, the transfected
transmission. The current available treatments, which group showed better cartilage regeneration in the rabbit
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are not widely available, often result in the development of cartilage defect model (Figure 2). Another important issue
fibrotic tissue, which is unfavorable to the native articular with the bioprinted grafts is their integration with native
cartilage and increases the tendency to degeneration. host tissue, which is deemed vital for successful cartilage
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Thus, it is imperative to develop innovative techniques regeneration. In response to this concern, a visible-light-
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capable of effectively enhancing the regeneration of responsive bioink was designed for chondral repair. The
cartilage tissue. The emergence of bioprinting technology bioink material consists mainly of a dual-functionalized
represents a significant advancement in the field of tyramine and GelMA and tris (2,2′-bipyridyl) ruthenium
cartilage regeneration. Bioprinting is a potential method (II) chloride and sodium persulfate (Ru/SPS) that acts as

Volume 10 Issue 1 (2024) 82 https://doi.org/10.36922/ijb.1037