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International Journal of Bioprinting 3D-bioprinting of osteochondral plugs

facilitate the production and maintenance of the cartilage lesions, has generally good short to mid-term results,
ECM. 1,4,5 The subchondral bone, which sits directly below but as the fibrocartilage wears out, pain recurs. 22–25 More
the calcified cartilage zone, not only anchors the cartilage recently, cell-based therapies that expand a population
and distributes mechanical forces, but also provides of the patient’s cells ex vivo have been developed for the
much of the nutrient supply needed to maintain healthy treatment of focal lesions (e.g., matrix-assisted/induced
cartilage. autologous chondrocyte implantation [MACI]). 26,27
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Osteoarthritis, the most common form of arthritis, There is conflicting evidence on the long-term benefits
involves the gradual breakdown of hyaline cartilage on the of MACI when compared to microfracture. Moreover,
joint surfaces. More than half of people diagnosed with MACI and similar cellular grafts and membranes do
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osteoarthritis are under the age of 65. As there is no cure not address the subchondral bone, which can lead to
for osteoarthritis, symptomatic disease progression results cartilage treatment failure in the absence of a stable base
in chronic pain and substantially reduced quality of life. for cartilage repair. Successful treatment of OC injury
The development of osteoarthritis is linked to, among other requires the development of a treatment that adequately
things, aging, genetics, and injury. Cartilage injuries and simultaneously regenerates both the cartilage and
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typically result from acute trauma, repeated loading, joint bone. 28,29 The only current treatment that addresses both
misalignment, and/or the presence of foreign bodies in the cartilage and bone regeneration is an OC graft. Autologous
joint space. Posttraumatic osteoarthritis (PTOA) results and allogeneic OC grafts replace damaged OC tissue with
from an acute traumatic joint injury and is a leading cause donor tissue. Autologous grafts may result in donor site
of secondary osteoarthritis. 11,12 PTOA can develop from morbidity and poor healing in arthritis-stricken joints,
chondral and osteochondral (OC) injuries, as well as while allogeneic grafts suffer from difficulties in sourcing
injuries to the meniscus and ligaments that change joint relatively young and healthy cadaveric tissue and ensuring
biomechanics. PTOA is thought to account for more than viable cell populations. 26,30–33 Moreover, there are size
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10% of osteoarthritis cases and is an especially important and shape limitations for both autologous and allogenic
factor in early-onset osteoarthritis. 11 grafts. 30,34 For advanced osteoarthritis, joint arthroplasty
and arthrodesis are the most effective treatments but
Due to the strenuous physical demands and their
propensity for joint injury, athletes, military service preclude participation in many activities and result in
substantially reduced mobility and chronic pain. Therefore,
members, and members of professions that require
physical conditioning and activity suffer higher rates of an innovative approach that addresses both cartilage and
osteoarthritis than the general population. 14–18 Combat bone regeneration is required to effectively treat chondral
injuries involving traumatic injury to the knee or ankle and OC injuries with long-term efficacy, ensuring a high
result in the development of osteoarthritis in more than quality of life.
90% of cases. Hence, new treatments are needed to prevent 3D printing technologies offer promise for addressing
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the onset of osteoarthritis by addressing traumatic joint OC injuries with improved long-term outcomes. 3D
injuries effectively. OC injuries present distinct challenges printing, in which structures are fabricated based on digital
due to the poor regenerative capacity of cartilage, which models, offers distinct advantages for the fabrication of tissue
usually does not fully heal. Chondrocytes in mature and scaffolds that aim to recapitulate the complexity of native
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healthy cartilage do not proliferate or do so very slowly. OC tissue. 35,36 The field of tissue engineering (TE), which aims
injuries that extend to the subchondral bone can recruit to mimic the complexity of native tissue via a combination
cells from the vascularized subchondral bone to induce of cells, scaffolds, and biochemical or biomechanical
a healing response, but the damaged tissue is replaced by stimuli, reaps substantial benefits from the use of 3D
fibrocartilaginous tissue rather than hyaline cartilage. 20,21 printing. For example, 3D printing of TE constructs, or 3D
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The inferior wear properties of fibrocartilage compared to bioprinting, can be used to create structures with material,
hyaline cartilage result in cartilage erosion and, in many stiffness, porosity, and cell density gradients similar
cases, lead to the development of osteoarthritis. to native OC tissue. Unlike many traditional scaffold
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Surgical and non-surgical techniques have been fabrication techniques, bioprinting can readily incorporate
developed in an attempt to repair cartilage and abate multiple materials and embed live human cells and growth
osteoarthritis progression. As mentioned, there factors into scaffolds during printing. 35,37,39 Prior work has
unfortunately is no cure for osteoarthritis, and the demonstrated the bioprinting of relatively simple thin disks
articular surface continues to degenerate with age. Non- of a single material for chondral TE to complex biomimetic
surgical treatments focus on temporary symptomatic relief multiphasic structures of OC tissue. 40,41 A range of natural
but fail to halt disease progression. Minimally invasive and synthetic materials have been bioprinted for OC TE,
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microfracture, which is widely used to treat small chondral including alginate, agarose, collagen, gelatin, HA,
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Volume 10 Issue 4 (2024) 533 doi: 10.36922/ijb.4053