This study was supported by grants from the National Research Foundation of Korea (NRF) funded by the Korean government (NRF-2017R1C1B2008406 and NRF-2021R1F1A1064350). Dr. Hee-Yeon Bae kindly provided the DF for primary culture.

This study was approved by the Institutional Review Board of Kyung Hee University Hospital at Gangdong (IRB approval no. KHNMC 2017-06-009).
1. Collect DF
NOTE: Patients gave informed consent before surgery for the removal of a mature or immature impacted third molar. Patients with the following disease were excluded: diabetes, hypertension, tuberculosis, hepatitis, acquired immunodeficiency syndrome. Pregnant women were also excluded.
<ol>
	<li>Harvest DF during the surgical extraction of impacted third molars (Figure 1A). 
	NOTE: Surgery was performed by an oral maxillofacial surgeon. Cooperation is required with a dentist for tissue collection.</li>
	<li>Store DF in Dulbecco&#39;s phosphate-buffered saline (DPBS) with 3% penicillin-streptomycin at 4 &#176;C before use. Perform isolation procedures on the day of DF harvest (Figure 1B).</li>
</ol>
2. Isolate single-cell populations from DF
<ol>
	<li>Prepare stock solutions of collagenase type I and protease in DPBS so that final concentrations of collagenase type I and protease are 1 mg/mL and 2.4 mg/mL, respectively.</li>
	<li>Prepare three 50 mL washing tubes with 20 mL of DPBS per tube. Label the tubes as 1, 2, and 3.</li>
	<li>Wash the DF in the washing tubes sequentially. Hold the DF with tweezers and place the DF in tube 1. Take the DF out of tube 1 and place it in tube 2. Take the DF out of tube 2 and place it in tube 3. Gently shake DF 10-15 times in each tube. After washing three times, place the DF in a 60 mm culture dish (Figure 2A).</li>
	<li>Mince the DF with tissue scissors (Figure 2B). Transfer only a small portion to the culture dish to minimize tissue loss. Repeat the cutting until the DF has a pulpy or squishy appearance (Figure 2C).</li>
	<li>Mix 1 mL of collagenase type I and 1 mL of protease solution in a 15 mL conical tube to obtain final concentrations of 1 mg/mL and 2.4 mg/mL, respectively.</li>
	<li>Transfer the minced DF into the 15 mL conical tube from step 2.5. Gently shake and incubate the tube for 1 h at 37 &#176;C.</li>
	<li>Add 5 mL of 0.05% trypsin-EDTA to the tube, shake, and incubate the tube for 15 min at 37 &#176;C.</li>
	<li>Prepare keratinocyte medium containing keratinocyte SFM 10% fetal bovine serum (FBS). Add 3 mL of keratinocyte medium into a new 50 mL conical tube. Place a 40 &#181;m strainer on top of this tube and use a 10 mL serological pipette to aspirate the supernatant from step 2.6 and pass it through the strainer. 
	NOTE: Minimize the incorporation of digested tissue remnants while taking the supernatant. Remove the tissue remnants with a 40 &#181;m strainer to minimize failure. Tissue remnants may pass through 70 &#181;m strainers and hinder colony formation. FBS in the keratinocyte medium will inactivate the enzymes.</li>
	<li>Repeat steps 2.7 and 2.8.</li>
	<li>Transfer the collected suspension to a 15 mL conical tube.</li>
	<li>Centrifuge the 15 mL conical tube at 288 &#215; g for 3 min at 4 &#176;C. Remove the supernatant. 
	NOTE: Be careful to avoid any accidental removal of pelleted cells, which are mostly invisible.</li>
	<li>Add 3 mL of keratinocyte SFM and wash the cells twice with a 1 mL pipette with centrifugation as in step 2.11.</li>
	<li>Plate the single-cell population into a 60 mm culture dish using keratinocyte SFM. Maintain the culture dish with a final volume of 5 mL in a humidified atmosphere of 5% CO2 at 37 &#176;C. Change the culture medium daily until no tissue or cell debris are observed. 
	NOTE: Remove floating debris in the culture medium by changing the medium. Delayed removal of tissue debris or dead cells has an unfavorable effect on the primary culture.</li>
	<li>Examine the plate from step 2.13 to check the growth of epithelial cells (Figure 3A). 
	NOTE: Epithelial cells grow within 7-10 days after plating single-cell populations.</li>
	<li>Expand the epithelial colonies and subculture the cells.
	<ol>
		<li>Aspirate the medium and wash the bottom of the culture plate once with 3 mL of keratinocyte SFM.</li>
		<li>Add 2 mL of cell dissociation protease and incubate in a humidified atmosphere of 5% CO2 at 37 &#176;C for 3 min. 
		NOTE: Repeat step 2.15.2 if cell detachment is not effective.</li>
		<li>Add 2 mL of keratinocyte medium to the culture plate and transfer the contents in a 15 mL conical tube. 
		NOTE: Adding more keratinocyte medium is not required if step 2.15.2 is repeated.</li>
		<li>Centrifuge the 15 mL conical tube at 288 &#215; g for 3 min at 4 &#176;C.</li>
		<li>Remove the supernatant and wash the cell pellet two times with 3 mL of keratinocyte SFM.</li>
		<li>Plate the cells in a 100 mm culture dish using keratinocyte SFM (final volume of 10 mL per 100 mm dish).</li>
	</ol>
	</li>
	<li>Prepare and store cell stocks in a liquid nitrogen tank.
	<ol>
		<li>Harvest cells as described in steps 2.15.1-2.15.5.</li>
		<li>Distribute the cells into cryovials in 1 mL of freezing medium (80% keratinocyte SFM, 10% dimethylsulfoxide, 10% FBS).</li>
		<li>Place the vials in a freezing container and store them at -80 &#176;C for 24 h.</li>
		<li>Transfer the vials from the deep freezer to a liquid nitrogen tank.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Tucker, A., Sharpe, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+cutting-edge+of+mammalian+development;+How+the+embryo+makes+teeth.">The cutting-edge of mammalian development; How the embryo makes teeth.</a> Nature Reviews Genetics. 5 (7), 499-508 (2004).</li><li>Choung, H. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+CPNE7+on+periodontal+regeneration.">The effect of CPNE7 on periodontal regeneration.</a> Connective Tissue Research. 60 (5), 419-430 (2019).</li><li>Li, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+immortalized+Hertwig's+epithelial+root+sheath+cell+lines+for+cementum+and+dentin+regeneration.">Development of immortalized Hertwig's epithelial root sheath cell lines for cementum and dentin regeneration.</a> Stem Cell Research and Therapy. 10 (1), 3 (2019).</li><li>Huang, X. F., Bringas, P., Slavkin, H. C., Chai, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fate+of+HERS+during+tooth+root+development.">Fate of HERS during tooth root development.</a> Developmental Biology. 334 (1), 22-30 (2009).</li><li>Farea, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+enhancement+of+a+homogenous+in+vitro+human+Hertwig's+epithelial+root+sheath+cell+population.">Isolation and enhancement of a homogenous in vitro human Hertwig's epithelial root sheath cell population.</a> International Journal of Molecular Sciences. 14 (6), 11157-11170 (2013).</li><li>Jung, H. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directing+the+differentiation+of+human+dental+follicle+cells+into+cementoblasts+and/or+osteoblasts+by+a+combination+of+HERS+and+pulp+cells.">Directing the differentiation of human dental follicle cells into cementoblasts and/or osteoblasts by a combination of HERS and pulp cells.</a> Journal of Molecular Histology. 42 (3), 227-235 (2011).</li><li>Fang, J., Tang, L., Liu, X. H., Wen, L. Y., Jin, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+of+the+unique+odontogenic+properties+of+rat+apical+bud+cells+under+the+developing+apical+complex+microenvironment.">Changes of the unique odontogenic properties of rat apical bud cells under the developing apical complex microenvironment.</a> International Journal of Oral Science. 1 (1), 26-33 (2009).</li><li>Oh, J. E., Yi, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+dental+follicle-derived+Hertwig's+epithelial+root+sheath+cells.">Isolation and characterization of dental follicle-derived Hertwig's epithelial root sheath cells.</a> Clinical Oral Investigations. 25 (4), 1787-1796 (2021).</li><li>Oh, J. E., Kim, R. H., Shin, K. H., Park, N. H., Kang, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delta+Np63+alpha+protein+triggers+epithelial-mesenchymal+transition+and+confers+stem+cell+properties+in+normal+human+keratinocytes.">Delta Np63 alpha protein triggers epithelial-mesenchymal transition and confers stem cell properties in normal human keratinocytes.</a> Journal of Biological Chemistry. 286 (44), 38757-38767 (2011).</li><li>Morsczeck, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+precursor+cells+(PCs)+from+human+dental+follicle+of+wisdom+teeth.">Isolation of precursor cells (PCs) from human dental follicle of wisdom teeth.</a> Matrix Biology. 24 (2), 155-165 (2005).</li><li>Nam, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+profile+of+the+stem+cell+markers+in+human+Hertwig's+epithelial+root+sheath/Epithelial+rests+of+Malassez+cells.">Expression profile of the stem cell markers in human Hertwig's epithelial root sheath/Epithelial rests of Malassez cells.</a> Molecular and Cells. 31 (4), 355-360 (2011).</li><li>Lee, J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dental+follicle+cells+and+cementoblasts+induce+apoptosis+of+ameloblast-lineage+and+Hertwig's+epithelial+root+sheath/epithelial+rests+of+Malassez+cells+through+the+Fas-Fas+ligand+pathway.">Dental follicle cells and cementoblasts induce apoptosis of ameloblast-lineage and Hertwig's epithelial root sheath/epithelial rests of Malassez cells through the Fas-Fas ligand pathway.</a> European Journal of Oral Sciences. 120 (1), 29-37 (2012).</li><li>Wan, A. C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recapitulating+cell-cell+Interactions+for+organoid+construction+-+are+biomaterials+dispensable.">Recapitulating cell-cell Interactions for organoid construction - are biomaterials dispensable.</a> Trends in Biotechnology. 34 (9), 711-721 (2016).</li><li>Guo, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Are+Hertwig's+epithelial+root+sheath+cells+necessary+for+periodontal+formation+by+dental+follicle+cells.">Are Hertwig's epithelial root sheath cells necessary for periodontal formation by dental follicle cells.</a> Archives of Oral Biology. 94, 1-9 (2018).</li><li>Sugaya, T., Tomita, M., Motoki, Y., Miyaji, H., Kawamami, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+enamel+matrix+derivative+on+healing+of+root+surfaces+after+bonding+treatment+and+intentional+replantation+of+vertically+fractured+roots.">Influence of enamel matrix derivative on healing of root surfaces after bonding treatment and intentional replantation of vertically fractured roots.</a> Dental Traumatology. 32 (5), 397-401 (2016).</li><li>Fong, H. K., Foster, B. L., Popowics, T. E., Somerman, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+crowning+achievement:+getting+to+the+root+of+the+problem.">The crowning achievement: getting to the root of the problem.</a> Journal of Dental Education. 69 (5), 555-570 (2005).</li><li>Bonczek, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tooth+agenesis:+What+do+we+know+and+is+there+a+connection+to+cancer.">Tooth agenesis: What do we know and is there a connection to cancer.</a> Clinical Genetics. 99 (4), 493-502 (2021).</li></ol>

The authors declare that they have no conflicts of interest.

This protocol includes critical steps. Harvesting single-cell populations is essential for the successful isolation of epithelial cells from DF. We sought to isolate epithelial cells from the DF based on our hypothesis that there are more epithelial cells in the DF. The mincing procedure enhances the detachment and release of cells from the DF. The mincing procedure was improved, and mincing repeated until the DF appeared pulpy to facilitate the release of single cells. Obtaining the maximum number of single cells increa...

Tooth formation begins with the invagination of the oral epithelium1. According to the tooth developmental stage, the oral epithelium has different names, including inner and outer enamel epithelium, cervical loop, and Hertwig&#39;s epithelial root sheath (HERS). The epithelial compartments communicate with the surrounding mesenchymal cells. Epithelial-mesenchymal interactions regulate tooth formation and tissue regeneration. Procuring dental epithelial cells, such as oral keratinocytes and Hertwig&#39;s epithelial root sheath cells (HERSCs), is crucial for the study of dental epithelial-mesenchymal interactions2.
Rodent-derived dental epithelial cells are isolated from the epithelial structure, such as the HERS. Li and colleagues isolated and immortalized rat molar-derived HERSCs after harvesting the apical portion of the developing tooth germs from 8-day-old rats3. The HERS was separated from apical tissue under magnification. Considering the tooth developmental stage and age, harvesting the HERS from humans is nearly impossible because of ethical issues: a developing tooth germ needs to be removed from a young child to harvest the human HERS. Immature tooth germs are rarely extracted. Human dental epithelial cells can be isolated from the gingiva and periodontal ligament (PDL). Epithelial structure-derived cells participate in tooth formation together with mesenchymal components and might be more suitable for the study of dental epithelial-mesenchymal interactions than oral keratinocytes. Epithelial cell rests of Malassez (ERM) are HERS-derived epithelial remnants and reside in small numbers in the PDL4. Studies report the isolation of human HERSCs from PDL5. However, harvesting human HERSCs from PDL tissue is not always successful because of the scarcity of the epithelial population in this location5,6.
Although rodent-derived HERSCs are maintained in serum-containing media3,7, human DF-derived epithelial cells are cultured with serum-free media similar to other human epithelial cells, such as normal human epidermal keratinocytes and normal human oral keratinocytes8,9. This implies physiologic or functional differences between rodent dental epithelial cells and human dental epithelial cells. Understanding the mechanism regarding dental epithelial-mesenchymal interactions might contribute to the development of clinical applications, including periodontal reattachment during replantation, periodontal regeneration in periodontal disease, pulp-dentin complex regeneration, and bio-tooth generation. Considering the characteristics of translational research, human dental epithelial cells may be more appropriate than rodent dental epithelial cells for the study of epithelial-mesenchymal interactions.
The human DF is a loose connective tissue and often resides in an impacted tooth. The DF contains mesenchymal precursors10. However, to our knowledge, no study has reported the isolation of epithelial cells from dental follicles before 2021. Oh and Yi reported the isolation of epithelial cells from human DF in 20218. The epithelial phenotype was confirmed by western blotting and morphologic analysis. Analysis of the origin of DF-derived epithelial cells demonstrated similar results with other studies. DF-derived epithelial cells were neither endothelial nor hematopoietic5,11, and Oh and Yi suggested naming these cells as DF-HERSCs. The DF has a larger volume than the PDL, and more epithelial cells can be isolated from the DF. This enhances the emergence of epithelial colonies and results in a high success rate in harvesting epithelial cells from DF. This study suggests using the DF as a tissue source for the isolation of dental epithelial cells.
In the present study, single cells were isolated from the DF according to previously described procedures10,12. The DF contains heterogeneous cell populations, and several cell types could be present at the early stage of the procedure. Morsczek and colleagues isolated DF-derived mesenchymal stem cells10. We hypothesized that the DF contains epithelial cells and that only epithelial cells can survive under serum-free conditions. This study differs from that of Morsczek et al. in terms of the selection of the epithelial population and the inhibition of mesenchymal cells. The selection was performed using keratinocyte serum-free media (SFM), which allows epithelial cell proliferation and inhibits mesenchymal cell proliferation. This study originated from a report by Oh and Yi8. The aim of this study was to describe details of the method used in that report for the isolation of epithelial cells from human DF.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>EMSURE ACS,ISO,Reag. Ph Eur 2-Propanol</td>
			<td>EMD millipore Co., MA, USA</td>
			<td>1096341011</td>
			<td>1 L</td>
		</tr>
		<tr>
			<td>0.05% trypsin-EDTA</td>
			<td>Gibco, Grand island, NY, USA</td>
			<td>25300054</td>
			<td>100 mL</td>
		</tr>
		<tr>
			<td>40 &#956;m cell strainer</td>
			<td>Falcon, NC, USA</td>
			<td>352340</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture dish (100 x 20 mm)</td>
			<td>Thermo Fisher Scientific Inc., Waltham, USA</td>
			<td>172958</td>
			<td>Discontinued</td>
		</tr>
		<tr>
			<td>Cell culture dish (60 x 15 mm)</td>
			<td>Thermo Fisher Scientific Inc., Waltham, USA</td>
			<td>150326</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase type 1</td>
			<td>Gibco, Grand island, NY, USA</td>
			<td>17100017</td>
			<td>1 g</td>
		</tr>
		<tr>
			<td>Combi-514R / Refrigerated large capacity centrifuge</td>
			<td>Hanil science industrial Co., LTD., Daejeon, South Korea</td>
			<td>CB-514R</td>
			<td></td>
		</tr>
		<tr>
			<td>Conical tube</td>
			<td>SPL Life Sciences Co., Ltd., Gyeonggi-do, South Korea</td>
			<td>50015 
			50050</td>
			<td>15 mL 
			50 mL</td>
		</tr>
		<tr>
			<td>Cryogenic vial</td>
			<td>Corning Inc., NY, US</td>
			<td>430488</td>
			<td>2 mL</td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide (DMSO)</td>
			<td>Sigma-Aldrich, Missouri, US</td>
			<td>D2650-100ml</td>
			<td>100 mL</td>
		</tr>
		<tr>
			<td>Dispase</td>
			<td>Gibco, Grand island, NY, USA</td>
			<td>17105041</td>
			<td>1 g</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Phosphate-Buffered Saline</td>
			<td>Welgene Inc., Gyengsangbuk-do, South Korea</td>
			<td>&#160;LB 001-02</td>
			<td>500 mL</td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Gibco, Grand island, NY, USA</td>
			<td>16000044</td>
			<td>500 mL</td>
		</tr>
		<tr>
			<td>Heraeus BB 15 / CO2 incubator</td>
			<td>Thermo Fisher Scientific Inc., Waltham, USA</td>
			<td>51023121</td>
			<td></td>
		</tr>
		<tr>
			<td>Keratinocyte serum-free medium</td>
			<td>Gibco, Grand island, NY, USA</td>
			<td>10724-011</td>
			<td>500 mL</td>
		</tr>
		<tr>
			<td>MVE CryoSystem 2000</td>
			<td>MVE Biological Solutions Co., GA, USA</td>
			<td>CryoSystem 2000</td>
			<td></td>
		</tr>
		<tr>
			<td>Nalgene Mr. Frosty Freezing Container</td>
			<td>Thermo Fisher Scientific Inc., Waltham, USA</td>
			<td>5100-0001</td>
			<td>for 1.2-2 mL CryoVials</td>
		</tr>
		<tr>
			<td>Olympus CKX41 / Inverted cell culture microscope</td>
			<td>Olympus Life Science, 
			Waltham, Massachusetts</td>
			<td>22-00723-01</td>
			<td>Discontinued</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin Strep</td>
			<td>Gibco, Grand island, NY, USA</td>
			<td>15140122</td>
			<td>100 mL (10,000 U/mL)</td>
		</tr>
		<tr>
			<td>Pipet aid XP</td>
			<td>Drummond scientific Co., PA, USA</td>
			<td>HDR-4-000-201</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman Classic P1000</td>
			<td>Gilson, Villiers le Bel, France</td>
			<td>F123602</td>
			<td>100-1000 &#181;L</td>
		</tr>
		<tr>
			<td>Refrigerant</td>
			<td>Nihon freezer Co. Ltd., Tokyo, Japan</td>
			<td>CLN 540U</td>
			<td>~-80 &#176;C / Discontinued</td>
		</tr>
		<tr>
			<td>Serological pipet</td>
			<td>SPL Life Sciences Co., Ltd., Gyeonggi-do, South Korea</td>
			<td>91010</td>
			<td>10ml</td>
		</tr>
		<tr>
			<td>TrypLE Express Enzyme (1x), phenol red</td>
			<td>Thermo Fisher Scientific Inc., Waltham, USA</td>
			<td>12605010</td>
			<td>cell dissociation protease</td>
		</tr>
	</tbody>
</table>

isolation of epithelial cells from human dental follicle

The dental follicle (DF) was harvested during the removal of an impacted third molar by an oral maxillofacial surgeon. Epithelial cell isolation was performed on the day of DF harvest. The DF was washed three times with DPBS and then dissected with tissue scissors until the tissue had a pulpy or squishy consistency. Single-cell populations were pelleted by centrifugation and washed with keratinocyte serum-free medium. Heterogeneous cell populations were distributed in a culture dish. Keratinocyte serum-free medium was used to select the epithelial cells. The culture medium was changed daily until no floating debris or dead cells were observed. Epithelial cells appeared within 7-10 days after cell population distribution. Epithelial cells survived in serum-free medium, while &#945;-modification minimal essential medium supplemented with 10% fetal bovine serum allowed the proliferation of mesenchymal-type cells. The DF is a tissue source for the isolation of dental epithelial cells.
The purpose of this study was to establish a method for the isolation of epithelial cells from human DF. Periodontal ligament (PDL) was used for the isolation of human dental epithelial cells. Procuring epithelial cells from human PDL is not always successful due to the small tissue volume, leading to low numbers of epithelial cells. DF has a larger volume than PDL and contains more cells. DF can be a tissue source for the primary culture of human dental epithelial cells. This protocol is easier and more efficient than the isolation method using PDL. Procuring human dental epithelial cells may facilitate further studies of dental epithelial-mesenchymal interactions.

DF harvesting 
Surgery was performed by an oral maxillofacial surgeon. Human-derived materials, including the tooth fragment, gingival tissue, and DF, were collected by a surgeon (Figure 1A). The DF might be attached to the tooth fragment. An oral maxillofacial surgeon will be able to identify the DF. Cooperation and communication with the surgeon are required for tissue collection. The DF is an irregularly shaped membrane-like tissue. Gingival tissue has a keratinized ...

Watch this Scientific Journal Video about Isolation of Epithelial Cells from Human Dental Follicle at JoVE.com

Isolation of Epithelial Cells from Human Dental Follicle

The dental follicle contains an epithelial population and mesenchymal cells. The epithelial population was selected from the heterogeneous dental follicle cell population by providing a distinct culture medium. Epithelial cells survived and formed colonies in a serum-free medium.

The dental follicle (DF) was harvested during the removal of an impacted third molar by an oral maxillofacial surgeon. Epithelial cell isolation was ...

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2.7K Views.  Kyung Hee University Dental Hospital at Gangdong. The dental follicle contains an epithelial population and mesenchymal cells. The epithelial population was selected from the heterogeneous dental follicle cell population by providing a distinct culture medium. Epithelial cells survived and formed colonies in a serum-free medium. 

Video: Isolation of Epithelial Cells from Human Dental Follicle

Primary Human Bronchial Epithelial Cells Grown from Explants

Human bronchial epithelial cells are needed for cell models of disease and to investigate the effect of excipients and pharmacologic agents on the function and structure of human epithelial cells. Here we describe in detail the method of growing bronchial epithelial cells from bronchial airway tissue that is harvested by the surgeon at the times of lung surgery (e.g. lung cancer or lung volume reduction surgery). With ethics approval and informed consent, the surgeon takes what is needed for pathology and provides us with a bronchial portion that is remote from the diseased areas. The tissue is then used as a source of explants that can be used for growing primary bronchial epithelial cells in culture. Bronchial segments about 0.5-1cm long and &le;1cm in diameter are rinsed with cold EBSS and excess parenchymal tissue is removed. Segments are cut open and minced into 2-3mm3 pieces of tissue. The pieces are used as a source of primary cells. After coating 100mm culture plates for 1-2 hr with a combination of collagen (30 &mu;g/ml), fibronectin (10 &mu;g/ml), and BSA (10 &mu;g/ml), the plates are scratched in 4-5 areas and tissue pieces are placed in the scratched areas, then culture medium (DMEM/Ham F-12 with additives) suitable for epithelial cell growth is added and plates are placed in an incubator at 37&deg;C in 5% CO2 humidified air. The culture medium is changed every 3-4 days. The epithelial cells grow from the pieces forming about 1.5 cm diameter rings in 3-4 weeks. Explants can be re-used up to 6 times by moving them into new pre-coated plates. Cells are lifted using trypsin/EDTA, pooled, counted, and re-plated in T75 Cell Bind flasks to increase their numbers. T75 flasks seeded with 2-3 million cells grow to 80% confluence in 4 weeks. Expanded primary human epithelial cells can be cultured and allowed to differentiate on air-liquid interface. Methods described here provide an abundant source of human bronchial epithelial cells from freshly isolated tissues and allow for studying these cells as models of disease and for pharmacology and toxicology screening.

Here we describe a detailed method for growing primary human bronchial epithelial cells from explants of human bronchial airway tissue including differentiated growth on an air-liquid interface. This method provides an abundant source of primary cells for investigating the role of the airway epithelium in human lung health and disease.

Human bronchial epithelial cells are needed for cell models of disease and to investigate the effect of excipients and pharmacologic agents on the ...

Isolation of Stem Cells from Human Pancreatic Cancer Xenografts

Cancer stem cells (CSCs) have been identified in a growing number of malignancies and are functionally defined by their ability to undergo self-renewal and produce differentiated progeny1. These properties allow CSCs to recapitulate the original tumor when injected into immunocompromised mice. CSCs within an epithelial malignancy were first described in breast cancer and found to display specific cell surface antigen expression (CD44+CD24low/-)2. Since then, CSCs have been identified in an increasing number of other human malignancies using CD44 and CD24 as well as a number of other surface antigens. Physiologic properties, including aldehyde dehydrogenase (ALDH) activity, have also been used to isolate CSCs from malignant tissues3-5.
Recently, we and others identified CSCs from pancreatic adenocarcinoma based on
ALDH activity and the expression of the cell surface antigens CD44 and CD24, and CD1336-8. These highly tumorigenic populations may or may not be overlapping and display other functions. We found that ALDH+ and CD44+CD24+ pancreatic CSCs are similarly tumorigenic, but ALDH+ cells are relatively more invasive8. In this protocol we describe a method to isolate viable pancreatic CSCs from low-passage human
xenografts9. Xenografted tumors are harvested from mice and made into a single-cell suspension. Tissue debris and dead cells are separated from live cells and then stained using antibodies against CD44 and CD24 and using the ALDEFLUOR reagent,
a fluorescent substrate of ALDH10. CSCs are then isolated by fluorescence activated cell sorting. Isolated CSCs can then be used for analytical or functional assays requiring viable cells.

Cancer stem cells (CSCs) have been identified in a number of malignancies. In this protocol we describe a flow cytometric method utilizing aldehyde dehydrogenase activity and CD44 and CD24 expression to isolate CSCs from human pancreatic adenocarcinoma xenografts. These viable cells can then be used in functional and analytical studies.

Cancer stem cells (CSCs) have been identified in a growing number of malignancies and are functionally defined by their ability to undergo self-renewal ...

Isolation and Culture of Adult Epithelial Stem Cells from Human Skin

The homeostasis of all self-renewing tissues is dependent on adult stem cells. As undifferentiated stem cells undergo asymmetric divisions, they generate daughter cells that retain the stem cell phenotype and transit-amplifying cells (TA cells) that migrate from the stem cell niche, undergo rapid proliferation and terminally differentiate to repopulate the tissue.
Epithelial stem cells have been identified in the epidermis, hair follicle, and intestine as cells with a high in vitro proliferative potential and as slow-cycling label-retaining cells in vivo 1-3. Adult, tissue-specific stem cells are responsible for the regeneration of the tissues in which they reside during normal physiologic turnover as well as during times of stress 4-5. Moreover, stem cells are generally considered to be multi-potent, possessing the capacity to give rise to multiple cell types within the tissue 6. For example, rodent hair follicle stem cells can generate epidermis, sebaceous glands, and hair follicles 7-9. We have shown that stem cells from the human hair follicle bulge region exhibit multi-potentiality 10.
Stem cells have become a valuable tool in biomedical research, due to their utility as an in vitro system for studying developmental biology, differentiation, tumorigenesis and for their possible therapeutic utility. It is likely that adult epithelial stem cells will be useful in the treatment of diseases such as ectodermal dysplasias, monilethrix, Netherton syndrome, Menkes disease, hereditary epidermolysis bullosa and alopecias 11-13. Additionally, other skin problems such as burn wounds, chronic wounds and ulcers will benefit from stem cell related therapies 14,15. Given the potential for reprogramming of adult cells into a pluripotent state (iPS cells)16,17, the readily accessible and expandable adult stem cells in human skin may provide a valuable source of cells for induction and downstream therapy for a wide range of disease including diabetes and Parkinson's disease.

A rapid, robust way of isolating viable adult epithelial stem cells from human skin is described. The method utilizes enzymatic digestion of skin collagen matrix , followed by plucking of hair follicles and isolation of single cell suspensions or tissue fragments for cell culture.

The homeostasis of all self-renewing tissues is dependent on adult stem cells. As undifferentiated stem cells undergo asymmetric divisions, they generate ...

Isolation of Mammary Epithelial Cells from Three-dimensional Mixed-cell Spheroid Co-culture

While enormous efforts have gone into identifying signaling pathways and molecules involved in normal and malignant cell behaviors1-2, much of this work has been done using classical two-dimensional cell culture models, which allow for easy cell manipulation. It has become clear that intracellular signaling pathways are affected by extracellular forces, including dimensionality and cell surface tension3-4. Multiple approaches have been taken to develop three-dimensional models that more accurately represent biologic tissue architecture3. While these models incorporate multi-dimensionality and architectural stresses, study of the consequent effects on cells is less facile than in two-dimensional tissue culture due to the limitations of the models and the difficulty in extracting cells for subsequent analysis.
The important role of the microenvironment around tumors in tumorigenesis and tumor behavior is becoming increasingly recognized4. Tumor stroma is composed of multiple cell types and extracellular molecules. During tumor development there are bidirectional signals between tumor cells and stromal cells5. Although some factors participating in tumor-stroma co-evolution have been identified, there is still a need to develop simple techniques to systematically identify and study the full array of these signals6. Fibroblasts are the most abundant cell type in normal or tumor-associated stromal tissues, and contribute to deposition and maintenance of basement membrane and paracrine growth factors7.
Many groups have used three dimensional culture systems to study the role of fibroblasts on various cellular functions, including tumor response to therapies, recruitment of immune cells, signaling molecules, proliferation, apoptosis, angiogenesis, and invasion8-15. We have optimized a simple method for assessing the effects of mammary fibroblasts on mammary epithelial cells using a commercially available extracellular matrix model to create three-dimensional cultures of mixed cell populations (co-cultures)16-22. With continued co-culture the cells form spheroids with the fibroblasts clustering in the interior and the epithelial cells largely on the exterior of the spheroids and forming multi-cellular projections into the matrix. Manipulation of the fibroblasts that leads to altered epithelial cell invasiveness can be readily quantified by changes in numbers and length of epithelial projections23. Furthermore, we have devised a method for isolating epithelial cells out of three-dimensional co-culture that facilitates analysis of the effects of fibroblast exposure on epithelial behavior. We have found that the effects of co-culture persist for weeks after epithelial cell isolation, permitting ample time to perform multiple assays. This method is adaptable to cells of varying malignant potential and requires no specialized equipment. This technique allows for rapid evaluation of in vitro cell models under multiple conditions, and the corresponding results can be compared to in vivo animal tissue models as well as human tissue samples.

A simple method is described for analyzing effects of tissue fibroblasts on associated epithelial cells. The combination of this method and three-dimensional tissue culture can facilitate analysis of cells after isolation from 3D. The technique is applicable to cells of varying malignant potential, allowing systematic study of effects of tumor-associated stroma on tumor cells.

While enormous efforts have gone into identifying signaling pathways and molecules involved in normal and malignant cell behaviors1-2, much of this work ...

Chromatin Isolation by RNA Purification (ChIRP)

Long noncoding RNAs are key regulators of chromatin states for important biological processes such as dosage compensation, imprinting, and developmental gene expression 1,2,3,4,5,6,7. The recent discovery of thousands of lncRNAs in association with specific chromatin modification complexes, such as Polycomb Repressive Complex 2 (PRC2) that mediates histone H3 lysine 27 trimethylation (H3K27me3), suggests broad roles for numerous lncRNAs in managing chromatin states in a gene-specific fashion 8,9. While some lncRNAs are thought to work in cis on neighboring genes, other lncRNAs work in trans to regulate distantly located genes. For instance, Drosophila lncRNAs roX1 and roX2 bind numerous regions on the X chromosome of male cells, and are critical for dosage compensation 10,11. However, the exact locations of their binding sites are not known at high resolution. Similarly, human lncRNA HOTAIR can affect PRC2 occupancy on hundreds of genes genome-wide 3,12,13, but how specificity is achieved is unclear. LncRNAs can also serve as modular scaffolds to recruit the assembly of multiple protein complexes. The classic trans-acting RNA scaffold is the TERC RNA that serves as the template and scaffold for the telomerase complex 14; HOTAIR can also serve as a scaffold for PRC2 and a H3K4 demethylase complex 13.
Prior studies mapping RNA occupancy at chromatin have revealed substantial insights 15,16, but only at a single gene locus at a time. The occupancy sites of most lncRNAs are not known, and the roles of lncRNAs in chromatin regulation have been mostly inferred from the indirect effects of lncRNA perturbation. Just as chromatin immunoprecipitation followed by microarray or deep sequencing (ChIP-chip or ChIP-seq, respectively) has greatly improved our understanding of protein-DNA interactions on a genomic scale, here we illustrate a recently published strategy to map long RNA occupancy genome-wide at high resolution 17. This method, Chromatin Isolation by RNA Purification (ChIRP) (Figure 1), is based on affinity capture of target lncRNA:chromatin complex by tiling antisense-oligos, which then generates a map of genomic binding sites at a resolution of several hundred bases with high sensitivity and low background. ChIRP is applicable to many lncRNAs because the design of affinity-probes is straightforward given the RNA sequence and requires no knowledge of the RNA's structure or functional domains.

Chromatin Isolation by RNA Purification ChIRP

ChIRP is a novel and rapid technique to map genomic binding sites of long noncoding RNAs (lncRNAs). The method takes advantage of the specificity of anti-sense tiling oligonucleotides to allow the enumeration of lncRNA-bound genomic sites.

Long noncoding RNAs are key regulators of chromatin states for important biological processes such as dosage compensation, imprinting, and developmental ...

Induction and Analysis of Epithelial to Mesenchymal Transition

Epithelial to mesenchymal transition (EMT) is essential for proper morphogenesis during development. Misregulation of this process has been implicated as a key event in fibrosis and the progression of carcinomas to a metastatic state. Understanding the processes that underlie EMT is imperative for the early diagnosis and clinical control of these disease states. Reliable induction of EMT in vitro is a useful tool for drug discovery as well as to identify common gene expression signatures for diagnostic purposes. Here we demonstrate a straightforward method for the induction of EMT in a variety of cell types. Methods for the analysis of cells pre- and post-EMT induction by immunocytochemistry are also included. Additionally, we demonstrate the effectiveness of this method through antibody-based array analysis and migration/invasion assays.

A straightforward method is described for the induction of epithelial to mesenchymal transition (EMT) in a variety of cell types. Methods for the analysis of cells in EMT states by immunocytochemistry are included.

Epithelial  to mesenchymal transition (EMT) is essential for proper morphogenesis during  development. Misregulation of this  process has been implicated ...

Manual Isolation of Adipose-derived Stem Cells from Human Lipoaspirates

In 2001, researchers at the University of California, Los Angeles, described the isolation of a new population of adult stem cells from liposuctioned adipose tissue that they initially termed Processed Lipoaspirate Cells or PLA cells. Since then, these stem cells have been renamed as Adipose-derived Stem Cells or ASCs and have gone on to become one of the most popular adult stem cells populations in the fields of stem cell research and regenerative medicine. Thousands of articles now describe the use of ASCs in a variety of regenerative animal models, including bone regeneration, peripheral nerve repair and cardiovascular engineering. Recent articles have begun to describe the myriad of uses for ASCs in the clinic. The protocol shown in this article outlines the basic procedure for manually and enzymatically isolating ASCs from large amounts of lipoaspirates obtained from cosmetic procedures. This protocol can easily be scaled up or down to accommodate the volume of lipoaspirate and can be adapted to isolate ASCs from fat tissue obtained through abdominoplasties and other similar procedures.

In 2001, researchers at UCLA described the isolation of a population of adult stem cells, termed Adipose-derived Stem Cells or ASCs, from adipose tissue. This article outlines the isolation of ASCs from lipoaspirates using a manual, enzymatic digestion protocol using collagenase.

In 2001, researchers at the University of  California, Los Angeles, described the isolation of a new population of adult  stem cells from liposuctioned ...

Isolation and Culture of Dental Epithelial Stem Cells from the Adult Mouse Incisor

Understanding the cellular and molecular mechanisms that underlie tooth regeneration and renewal has become a topic of great interest1-4, and the mouse incisor provides a model for these processes. This remarkable organ grows continuously throughout the animal&#39;s life and generates all the necessary cell types from active pools of adult stem cells housed in the labial (toward the lip) and lingual (toward the tongue) cervical loop (CL) regions. Only the dental stem cells from the labial CL give rise to ameloblasts that generate enamel, the outer covering of teeth, on the labial surface. This asymmetric enamel formation allows abrasion at the incisor tip, and progenitors and stem cells in the proximal incisor ensure that the dental tissues are constantly replenished. The ability to isolate and grow these progenitor or stem cells in vitro allows their expansion and opens doors to numerous experiments not achievable in vivo, such as high throughput testing of potential stem cell regulatory factors. Here, we describe and demonstrate a reliable and consistent method to culture cells from the labial CL of the mouse incisor.

The continuously growing mouse incisor provides a model for studying renewal of dental tissues from dental epithelial stem cells (DESCs). A robust system for consistently and reliably obtaining these cells from the incisor and expanding them in vitro is reported here.

Understanding the cellular and molecular mechanisms that underlie tooth regeneration and renewal has become a topic of great interest1-4, and the mouse ...

Isolation and Enrichment of Human Lung Epithelial Progenitor Cells for Organoid Culture

Epithelial organoid models serve as valuable tools to study the basic biology of an organ system and for disease modeling. When grown as organoids, epithelial progenitor cells can self-renew and generate differentiating progeny that exhibit cellular functions similar to those of their in vivo counterparts. Herein we describe a step-by-step protocol to isolate region-specific progenitors from human lung and generate 3D organoid cultures as an experimental and validation tool. We define proximal and distal regions of the lung with the goal of isolating region-specific progenitor cells. We utilized a combination of enzymatic and mechanical dissociation to isolate total cells from the lung and trachea. Specific progenitor cells were then fractionated from the proximal or distal origin cells using fluorescence associated cell sorting (FACS) based on cell type-specific surface markers, such as NGFR&#160;for sorting basal cells and HTII-280 for sorting alveolar type II cells. Isolated basal or alveolar type II progenitors were used to generate 3D organoid cultures. Both distal and proximal progenitors formed organoids with a colony forming efficiency of 9-13% in distal region and 7-10% in proximal region when plated 5000 cell/well on day 30. Distal organoids maintained HTII-280+ alveolar type II cells in culture whereas proximal organoids differentiated into ciliated and secretory cells by day 30. These 3D organoid cultures can be used as an experimental tool for studying the cell biology of lung epithelium and epithelial mesenchymal interactions, as well as for the development and validation of therapeutic strategies targeting epithelial dysfunction in a disease.

This article provides a detailed methodology for tissue dissociation and cellular fractionation approaches allowing enrichment of viable epithelial cells from proximal and distal regions of the human lung. Herein these approaches are applied for the functional analysis of lung epithelial progenitor cells through the use of 3D organoids culture models.

Epithelial organoid models serve as valuable tools to study the basic biology of an organ system and for disease modeling. When grown as organoids, ...

Isolation and Culture of Primary Oral Keratinocytes from the Adult Mouse Palate

For years, most studies involving keratinocytes have been conducted using human and mouse skin epidermal keratinocytes. Recently, oral keratinocytes have attracted attention because of their unique function and characteristics. They maintain the homeostasis of the oral epithelium and serve as resources for applications in regenerative therapies. However, in vitro studies that use oral primary keratinocytes from adult mice have been limited due to the lack of an efficient and well-established culture protocol. Here, oral primary keratinocytes were isolated from the palate tissues of adult mice and cultured in a commercial low-calcium medium supplemented with a chelexed-serum. Under these conditions, keratinocytes were maintained in a proliferative or stem cell-like state, and their differentiation was inhibited even after increased passages. Marker expression analysis showed that the cultured oral keratinocytes expressed the basal cell markers p63, K14, and &#945;6-integrin and were negative for the differentiation marker K13 and the fibroblast marker PDGFR&#945;. This method produced viable and culturable cells suitable for downstream applications in the study of oral epithelial stem cell functions in vitro.

The present protocol describes the isolation and culture of oral keratinocytes derived from the adult mouse palate. An evaluation method using immunostaining is also reported.

For years, most studies involving keratinocytes have been conducted using human and mouse skin epidermal keratinocytes. Recently, oral keratinocytes have ...