Page 138 - IJB-10-3

International Journal of Bioprinting New challenges in liver tissue engineering

of liver disease. For example, Vishwakarma et al. used rat pullulan were recently used for encapsulating HepaRG
dECM scaffolds seeded with human EpCAM+ cells to treat cells and led to improved survival in mice with ALF.
117
rats with ALF and achieved an improved survival rate and Regarding the use of hydrogels as a tissue engineering
the maintenance of specific hepatic functions for up to 1 method to treat liver disease, different types of polymers,
155
month, while the decellularization of whole human liver including chitosan, Alg, or natural-derived ECM molecules,
lobes was first demonstrated in 2015. The same authors have been used as hydrogels for regenerative medicine. For
148
seeded human liver cubic scaffolds with three distinct instance, rat hepatocytes encapsulated in Alg microbeads
cell types (stellate cells, hepatocellular carcinoma, and confer metabolic support in an animal liver failure model
150
hepatoblastoma) and demonstrated their biocompatibility and have been suggested as a promising therapy for children
by xenotransplantation into immunocompetent mice, with ALF. The authors used cryopreserved PHHs
160
although not their therapeutic effect. To establish encapsulated into Alg microbeads, obtaining encouraging
148
scalability to human-sized techniques, engineered liver results, since four of the eight children tested avoided organ
grafts of pig dECM repopulated with endothelial cells and transplants. Despite the promising results, the safety of
160
primary hepatocytes were used in pigs subjected to a 60% the procedure continues to be uncertain since Alg is non-
liver hepatectomy. The study showed that dysfunction biodegradable in mammals and its lasting effects have not
156
markers such as transaminases levels, bilirubin, or been thoroughly analyzed. For this reason, other authors
161
inflammation markers were lower in the transplanted have used other approaches like Col-based hydrogels. 162-164
animals, indicating that these bioengineered grafts Zhao et al. used Col hydrogels seeded with neonatal and
functioned at clinical level. Although using dECM is a adult hepatocytes for the treatment of liver fibrosis in a
156
potential tissue engineering approach for the treatment of multi-site injection strategy that enabled transplanting a
end-stage liver disease, important issues related to possible huge number of liver cells into liver parenchyma in a single
risk of xenogeneic/allogeneic tissues, recellularization (cell intervention, and they observed a reduction in fibrosis
sources, flow rate, migration and repopulation, etc.), or afterward. Interestingly, Chiang et al. used an HGF-
163
the enduring stability of the decellularized/recellularized releasing hydrogels for the transplantation of iPSC-derived
tissues should be solved before its clinical translation. 154 HLCs, which manifested increased antioxidant and anti-
Other authors have explored using synthetic scaffolds apoptotic potential after the procedure and improved the
152
seeded with different types of hepatic cells, since they results in treating ALF.
not only provide a 3D microenvironment, but their The use of cell-sheet engineering for treating liver
5
interconnected pore structure also provides a suitable disease has also been studied. Nagamoto et al. showed that
nutrient supply. Some studies have used the scaffolds transplanting human iPSC-HLC sheets into animals with
5
to improve the differentiation potential of multipotent CCl -induced liver failure reduced lethality, and the siRNA
4
stem cells before transplanting, while others employed experiments showed that the HGF produced from the
157
165
the scaffolds as a delivery method and studied the HLC sheets played a key role in the HGF/c-met pathway.
differentiation potential in vivo. 158,159 Alg scaffolds seeded Fibroblasts used as a feeder in combination with primary
with bone marrow MSC were shown to promote liver hepatocytes have been shown to be effective for treating
166
regeneration in rats after partial hepatectomy, and the radiation-induced liver failure in rats.
158
transplanted cells were endowed with specific hepatic
functions such as glycogen production or albumin secretion 8. Conclusions and future perspectives
and able to differentiate in vivo when transplanted within Despite the key advances in the liver tissue engineering
scaffolds. While many studies used mesenchymal stem field, some major challenges must be overcome before
158
cells to recapitulate fully functional hepatic activity, certain they can be widely applied in both preclinical and clinical
authors utilized hepatocyte-laden scaffolds to treat liver settings. One of the major limitations lies in the cell
disease, e.g., Alg scaffolds seeded with fetal liver cells were sources used, since, although PHHs are the gold standard,
used to treat a Wilson’s disease animal model, showing a the shortage of liver tissue for isolating hepatocytes, their
significant therapeutic effect on the copper metabolism variability and instability, and the short length when
deficiency. Biodegradable materials offer an advantage in culture restrict their application. Of the different
153
for clinical application over other strategies such as using alternatives proposed, HLCs obtained from iPSCs present
Alg. We recently showed that Gel-HA scaffolds containing an unlimited self-renewal and proliferation capacity and
PHH improved hepatic functions in an acetaminophen- reflect the patient’s phenotype, although they have shown
ALF animal model compared to intrasplenic injection of an immature phenotype after differentiation. The use of
single cells. Other natural polymers such as dextran and iPSCs could also help to expand the applications of the
90

Volume 10 Issue 3 (2024) 130 doi: 10.36922/ijb.2706