Noah Thompson
ENGL 105
Sarah George
7 February 2016
Decellularization
Nervousness begins to set in as you slowly make your way down the seemingly
endless hospital corridors. How could someone design a place so drab and lifeless when
life is exactly what a hospital is meant to restore? Sanitary paper crinkles as you sit on the
pre-op table and it becomes real that in a few hours you’ll wake up with a new liver and a
scar. However, being cut open and having an organ removed isn’t even the scariest
element of a transplant procedure; the thought of your body rejecting and attacking your
new organ is truly terrifying. For many patients undergoing a transplant means
complications and life-long medication dependence. Luckily for transplant patients, this
reality is becoming a fear of the past. Organ and tissue engineering by decellularization
reduces any chances of rejection by the organ recipient’s body.
Decellularization is a biomedical engineering process that produces organs that
will not be rejected after being transplanted. Scientists take a donor organ, remove the
cells, and are left with an extracellular matrix. This extracellular matrix is called a
scaffold because it maintains the shape of the donor organ without any living cells
present. Scientists can then introduce the donor recipient’s cells to the scaffold and organ
tissues will begin to grow. This creates a viable transplant organ that the recipient will not
reject since their body will not attack its own cells.
Methods and Materials
A recent study, conducted by researchers at Tehran University of Medical
Sciences and Children’s Hospital Medical Center in Tehran, Iran, analyzes the
effectiveness of two different methods of decellularization and recellularization of sheep
and rat livers. Researchers tested the effectiveness of decellularization via a sodium
dodecyl sulfate (SDS) versus a combination of SDS and Triton X-100 (SDS+TX). The
decellularization process begins by perfusing distilled water through the livers. Next, in
the SDS+TX test, a diluted 0.2L solution of Triton X-100 is added to the organ to break
down cell membranes. In the SDS only test this step is bypassed. Researchers again wash
the livers with distilled water, and then introduce a 0.05% solution of SDS in both tests.
After this step all cell membranes, proteins, and nuclear remnants are gone. To remove
all SDS residue the livers are washed with distilled water again. This process creates the
extracellular matrix scaffold (ECM), which is stored in a saline solution until the
recellularization process begins.
Figure 1. A. shows the liver at beginning of the decellularization process and B.
shows the remaining liver scaffold after the decellularization period. Note the
white and translucent nature of the scaffold.
The scientists tested in vivo, “in body”, recellularization by “implanting small
pieces of rat and sheep DLMs(decellularized liver matrices) to the subhepatic area of four
rats to evaluate the biocompatibility of the scaffolds with analogous and dissimilar
origins (Sabetkish, et al.)” Researchers maintain observation of the rats for eight weeks
post-operative, and then sacrifice the rats to examine in vivo immunoreactions, and the
effectiveness of in vivo implantation as a cell seeding process. To test in vitro, “in glass”,
recellularization four rat DLMs were added to 100 mL glass bottles. Over a two day
period a researcher adds a 70 mL medium containing around 18 million cells to the glass
bottles. Cell seeding and recellularization continues for 15 days and the medium is
changed every three days. After this time period the researcher removes the recellularized
matrices from the glass bottles to analyze histological samples of each liver.
Findings
An observation of the physical properties of each decellularized liver reveals that
the SDS+TX method produces an ECM that is white and translucent while the SDS only
method produced liver ECMs that are less translucent. Both methods the scaffolds
maintain shape and size. Researchers conduct histological examinations by staining the
ECMs with hematoxylin and eosin (H&E). H&E staining reveals that method two,
decellularization with SDS only, distorts the architecture and structure of the organ
scaffold. Method one, SDS+TX, does not compromise the structure of the scaffold and
important liver structures like Glisson’s capsule and central veins are observable.
Researchers conclude that “H&E staining of normal and decellularized scaffolds with
method 1 and 2 demonstrated a vast difference in ECM composition of the two scaffolds,
which shows the superiority of method 1 in ECM preservation” (Sabetkish, et al.). After
tensile testing the researchers were also able to conclude that scaffolds decellularized
with SDS+TX have a maximal load parameter most similar to natural liver tissues.
Researchers then analyzed the differences between the in vivo and in vitro
recellularization processes. The researchers found that the in vitro recellularized livers
contained more organized hepatocytes, liver cells, and were more structurally similar
than the livers recellularized in vivo. Within the in vivo testing researchers were able to
conclude that “homograft was more successful as compared with the xenograft”
(Sabetkish, et al.)
Figure 2. A-C show H&E staining of normal and decellularized scaffolds.
D-F shows DAPI staining of normal and decellularized scaffolds. G-I shows
results from a tensile test of normal and decellularized livers.
Conclusion:
Although the future of decellularization looks promising, transplantation is the
only effective treatment for organ failure. Since there is a shortage of organ donors and
survival rate remains low the demand for effective decellularization methods increases.
As decellularization technology advances and evolves researchers should be able to better
preserve organ architecture and structure during decellularization. Such a development
could result in viable recellularized organs to be used in transplants. Currently, the most
effective method of engineering an organ involves decellularization with Triton-X100
and SDS combined with recellularization in vitro. Researchers hope that this study will
lay the groundwork for in situ recellularization by implanting a DLM into a diseased host
liver.
Citation:
Sabetkish S, Kajbafzadeh et al. 2015. “Whole-organ tissue engineering: Decellularization
and recellularization of three-dimensional matrix liver scaffolds.” Journal of
Biomedical Materials Research 103.4 (2015): 1498-1508. Web.
Figures 1 and 2 came directly from the report released by researchers Sabetkish, et al..