Biomimetic ECM Scaffolds Prepared from Cultured Cells - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 244

To demonstrate the biocompatibility of the aECM scaffolds, aECM-
mF scaffolds are implanted into a subcutaneous pocket of the respective
ICR mouse where the fi broblasts are isolated. The host tissue responses
to the aECM scaffolds are compared with those to allogeneic ECM scaf-
folds (ECM scaffolds prepared from allogeneic mouse cells), xenogeneic
bovine collagen sponge (BCS) and PLGA mesh. After implantation for one
week, the materials are harvested with the surrounding tissues for analy-
sis of infl ammatory and immune host responses. Hematoxylin and eosin
(HE) staining shows that the host cells have penetrated into the aECM-mF
and allogeneic ECM-mF scaffolds. No dense fi brous layers surrounding
the implanted materials are observed. However, the BCS and PLGA are
wrapped by dense fi brous layers without being remodeled.
Immunocytochemical staining of the 1-week implants shows some
neutrophils are observed only in the PLGA, BCS, and allogeneic groups.
Among the four implanted materials, the lowest number of macrophages
is in the aECM-mF scaffolds. Comparison of percentage of macrophages/
total cells in different groups indicates that the lowest proportion of mac-
rophages is found in the aECM group. The macrophage percentage of the
allogeneic group is signifi cantly higher than that of the aECM scaffolds.
The macrophage percentages elicited by the BCS and PLGA scaffolds
are signifi cantly higher than those elicited by the ECM scaffolds. When
biomaterials are implanted, neutrophils and macrophages have been
reported to be involved in the infl ammatory responses at the implanta-
tion site. Neutrophils serve to remove foreign materials and trigger other
host responses by secreting factors that summon other immunocytes [36].
And macrophages become activated and act as the main mediators of the
host tissue responses. The excretion of soluble mediators by macrophages
can infl uence the behavior of other leukocytes. The absence of neutro-
phils and lowest macrophage percentage indicate aECM-mF scaffold
induces the lowest infl ammatory responses. A few MHC class II antigen-
presenting cells are observed in the allogeneic ECM-mF and BCS implan-
tation groups. These immunogenic antigen-presenting cells are supposed
to exacerbate infl ammation and immunological reactions. No T cells are
detected in any of the groups after 1-week implantation.
Cytokine profi les, which are the key mediators in the host tissue
response, are also investigated. The expressions of genes encoding inter-
leukin-10 ( Il10 ), interleukin-2 ( Il2 ), interleukin-4 ( Il4 ), and tumor necrosis
factor- ( Tnf ) in the connective tissues under the 1-week implanted materi-
als are analyzed by real-time RT-PCR. The expression of Il10 is lower in
the aECM and control groups than that in the allogeneic ECM, BSC and
PLGA groups. Among the samples, there is no signifi cant difference in
the transcription level of Tnf although it is lower in the aECM group. No
Il2 and Il4 gene expressions are detected. These results indicate aECM-
mF induce minimal cytokine mediation to modulate the host responses.