3.1 Cell source and culture conditions of HMC-1 cell line
The HMC-1 cell line is often sourced from cell banks (20 of 50), with
the most provided by Dr. Joseph H. Butterfield from Mayo Clinic (6 of
50) followed by American Type
Culture Collection (ATCC) (5 of 50), Sigma-Aldrich (2 of 50), and
Korean Cell Line Bank (KCLB) (2
of 50). Other cell banks include the Cellcook Biotechnology (CB),
National Platform of experimental cell resources (NPECC), National
Centre for Cell Science (NCCS), Wu-Han University Cell Collection Center
(WUCCC), and Chinese Academy of Sciences (CAS). In addition, HMC-1 cell
line from 11 out of 50 publications were gifted by other institutions,
with the most from Eiichi Morri Osaka University (4 of 50). Following
that, Prof. Jae-Young Um from KyungHee University and Prof. Jong-Sik Jin
from Jeonbuk University contributed 2 out of 50 publications each. Other
institutes include Hoseo Univeristy (Prof. Hyun-Ja Jeong), Second
Military Medical University (ZhiLiang Yu), and Sangji University.
However, the authors did not report the original source of their gifted
HMC-1 cell line. Finally, 19 of the shortlisted publications did not
specify the cell origin. The sources of HMC-1 are summarized in Figure
2.
The composition of the growth medium used for HMC-1 cell line
propagation varies among publications. Sigma-Aldrich and MERCK recommend
HMC-1 cell line to be maintained in IMDM supplemented with 10% Fetal
Bovine Serum (FBS), 1.2mM α-thioglycerol, and 1× penicillin/streptomycin
in a 37°C humidified environment with 5% CO2. In actual
protocols employed in the publications, most of the articles maintain
HMC-1 cell line in IMDM (43 of 50), followed by RPMI-1640 (5 of 50),
DMEM (1 of 50) and IMEM (1 of 50). In addition, the media was
supplemented with 10% FBS (45 of 50), penicillin/streptomycin (44 of
50), 2mM L-glutamine (4 of 50), monothioglycerol (3 of 50),
α-thioglycerol (2 of 50), 10% fetal calf serum (FCS) (2 of 50),
2-mercaptoethanol (1 of 50), amphotericin B (1 of 50), and sodium
bicarbonate (1 of 50). Table 1 summarizes the culture medium and
conditions to grow HMC-1 cells.
The choice of medium and composition are crucial to provide an optimal
environment for cell growth and survival. IMDM, a highly enriched
synthetic medium, is often recommended for rapidly proliferating and
high-density cell lines. While no studies have reported the correlation
between medium composition and the growth of HMC-1 cells, evidence shows
that DMEM and RPMI-1640 media can affect the growth and differentiation
of several cell lines 25,26. The medium’s excess or
lack of calcium ion
(Ca2+) and inorganic phosphate (Pi) may attenuate the
differentiation of several cell lines. The concentration of 1.8 mM and
0.09 mM of Ca2+ and Pi, respectively, are optimum for
cell proliferation 27. L-glutamine is supplemented to
the medium to serve as an energy source for rapidly dividing cell lines28. The degradation of L-glutamine to ammonia may be
toxic to the cells, where 2 to 3 mM is sufficient to reduce cell growth.
Yet, such occurrence is dependent on the cell line 29.
In addition, there are contradictory reports on supplementing media with
L-glutamine on cytokine release. Coëffier et al. (2001) demonstrated the
reduction in pro-inflammatory cytokines (IL-6 and IL-8) from human
intestinal mucosa by glutamine via a post-transcriptional pathway30. Glutamine has also decreased the expression of
leukotriene C4, monocyte chemoattractant protein (MCP),
macrophage inflammatory protein (MIP)-1β, tumor necrosis factor alpha
(TNF-α), interleukin (IL)-15, and IL-18 in human intestinal mast cells,
and lobectomy patients 31,32. In contrast, several
publications observed an increase in Th1 cytokines (IL-2 and IFN-γ) in
PMACI-treated intestinal intraepithelial lymphocytes by glutamine33. Similarly, IL-1 and IL-10 were upregulated in
glutamine-treated lobectomy patients 32. Other
supplements, such as sodium pyruvate in IMDM, have been shown to impair
cytokine production by inhibiting inflammatory signalling pathways34.