Page 50 - IJB-9-4

International Journal of Bioprinting 3D-Bioprinted human lipoaspirate-derived cell-laden skin constructs

re-epithelialization through contact with keratinocytes or III in each group (Figure 9A). The ratio of collagen III to
by affecting granulation tissue . collagen I in the ADSC-laden adECM–GelMA–HAMA
[52]
group (0.5 ± 0.04) was remarkably higher than those in the
3.8. Histopathological analysis of repaired skin ADSC-laden GelMA–HAMA, adECM–GelMA–HAMA,
At day 14, the ADSC-laden adECM–GelMA–HAMA GelMA–HAMA, and blank control groups (0.44 ± 0.05,
group was superior to the other groups for promoting the 0.19 ± 0.05, 0.16 ± 0.03, and 0.08 ± 0.03, respectively)
collagen III/I ratio, the deposition of collagen, and the (Figure 9B).These results indicate that adECM and ADSCs,
expression of CD31. In vivo wound healing after treatment in combination or individually, can increase the content of
with different scaffolds was further evaluated histologically collagen type III and promote scarless wound healing. The
through H&E staining. On day 14 after implantation, collagen ratio reflects a dynamically evolving process, and
the harvested tissues from the two ADSC-laden groups during the maturation phase, the collagen fibers reorganize
showed a well-organized epidermal structure and a well- from type III collagen to type I collagen to complete the
distributed dermal structure with clear vascular and tissue remodeling [56,57] .
fibrous tissues and minimal inflammatory cell infiltration. Angiogenesis and neovascularization are critical
We speculate that the limited inflammatory infiltration determinants during the wound-healing process . Blood
[58]
may be related to modulation of neutrophil, macrophage, vessels provide oxygen and nutrients to maintain cell
and lymphocyte responses by MSC-secreted growth proliferation and structural remodeling . The expression
[59]
factors and cytokines . In comparison, the epidermis of endothelial cell biomarker CD31 was detected by
[53]
was fractured in samples from the two groups treated immunohistochemical staining, and then wound
with acellular scaffolds, and fibrous tissue hyperplasia was neovascularization also was evaluated. Positive expression
found in the dermis, especially in the GelMA–HAMA of CD31 was seen in all groups on day 14 after implantation
group. In the blank control group, no covered squamous (Figure 9C). The number of blood vessels in tissue samples
epithelium was observed, and the dermis was dominated from the ADSC-laden adECM–GelMA–HAMA group
by inflammatory granulation tissue (Figure 8D). Porous (60.5 ± 6.14/field) was remarkably higher than those
scaffold structures have recently been shown to facilitate from the ADSC-laden GelMA–HAMA, adECM–GelMA–
healthy fibroblast activity and inhibit myofibroblast HAMA, GelMA–HAMA, and blank control groups
activation . The adipogenesis reported in previous studies (50.38 ± 4.32, 35.75 ± 5.45, 29.38 ± 3.77, and 15.75 ± 3.96/
[54]
was not observed here after implantation of ADSC-laden field). Significant differences in the numbers of blood
adECM–GelMA–HAMA scaffolds . vessels were observed among all the groups (Figure 9D).
[55]
Collagen synthesis and remodeling were evaluated These results indicate that adECM and ADSCs could
using Masson’s trichrome staining with quantitative analysis promote angiogenesis during wound healing, whether
at 14 days after implantation. Collagen fibers in tissue acting together or alone.
samples from the ADSC-laden adECM–GelMA–HAMA These differences in wound neovascularization suggest
and ADSC-laden GelMA–HAMA groups were denser and that adECM and ADSCs alone or in combination can
arranged in a more orderly fashion (Figure 8E) compared promote the formation of key physiological structures
with those in the other groups. The collagen contents of in wounds after implantation. ECM contributes to
samples from the ADSC-laden adECM–GelMA–HAMA cell adhesion, tissue anchoring, cell signaling, and cell
and ADSC-laden GelMA–HAMA (52.62% ± 3.4% and recruitment . To date, the vast majority of natural
[60]
44.41% ± 2.57%, respectively) were remarkably higher or synthetic materials do not fully replicate all the
than those of samples from the adECM–GelMA–HAMA, natural features of ECM . The adECM was chosen
[37]
GelMA–HAMA, and blank control groups (34.05% ± as the bioink component herein to provide a natural
4.85%, 26.79% ± 3.61%, and 15.77% ± 3.55%, respectively), microenvironment similar to that of native adipose
with significant differences observed among the groups tissue for ADSCs, which may facilitate cell survival and
(Figure 8F).
retention of characteristics [61,62] . Upon placement in the
The histological morphology of collagen I and III in wound microenvironment in vivo, ADSCs can continue
each group was observed using Picrosirius red staining to adapt to the wound microenvironment to function in
14 days after implantation. Under polarized light promoting wound healing. Xu et al. injected adECM into
microscopy, collagen I showed red or yellow birefringence, the skin of mice and found that adECM increased dermal
and collagen III showed green birefringence. Thus, the thickness, proliferating cell abundance, capillary density,
collagen content differed among the groups, which was and collagen types I and III expression . This suggests
[63]
consistent with Masson’s trichrome staining, and the that the microenvironment may play a determining
proportion of collagen I was higher than that of collagen role in the direction of tissue generation, independent

Volume 9 Issue 4 (2023) 42 https://doi.org/10.18063/ijb.718