Biomedical subjects

Maja Matic

Publications and source records attributed to Maja Matic.

5 recordsLinked to original sources

PubMed2005

A subpopulation of human basal keratinocytes has a low/negative MHC class I expression.

By means of flow cytometry, we demonstrate that a subpopulation of cells in the basal layer of the human epidermis has undetectable levels of major histocompatibility complex (MHC) class I molecule. The percentage of MHC class I-negative cells in the basal layer ranged 0.5%-2%. MHC class I-negative cells were characterized by small size (low forward scatter) and low granularity (low side scatter). Upon culturing of MHC class I-negative cells, increase of MHC class I expression was observed. This expression was lower than the expression of MHC class I molecule both in cultured MHC class I-positive cells and in ex vivo keratinocytes. Furthermore, stimulation of MHC class I-negative keratinocytes with interferon gamma (IFN-gamma) did not bring about further increase in MHC class I expression. MHC class I-negative cells were identified as keratinocytes as they expressed keratin 14 and formed keratinocyte colonies in vitro.

Epidermal Cells↗

PubMed2005

Analysis of connexin 43 expression on keratinocytes using flow cytometry.

Single-cell suspensions of primary keratinocytes comprise a heterogeneous cell population that consists of basal cells (stem cells, transient amplifying cells, and post-mitotic basal cells) and suprabasal cells at different stages of differentiation. Quantitative data for the differential expression of epitopes on single cells can be obtained using a flow cytometer. Simultaneous analysis of two intracellular epitopes, keratin 14 and connexin 43, using flow cytometry after keratinocyte isolation, fixation, permeabilization, and fluorescent immunolabeling is described. Three subsets of cells could be distinguished: stem cells (basal cells [keratin 14 positive] that lack connexin 43 expression); suprabasal cells (connexin 43-positive, keratin 14-negative cells); and basal cells (keratin 14 positive) that express connexin 43. The last population of keratinocytes includes both transient amplifying cells and postmitotic basal cells. The scatter characteristics of each cell population are also described.

Animals↗

PubMed2003

Nestin expression in hair follicle sheath progenitor cells.

The intermediate filament protein, nestin, marks progenitor cells of the CNS. Such CNS stem cells are selectively labeled by placing GFP under the control of the nestin regulatory sequences. During early anagen or growth phase of the hair follicle, nestin-expressing cells, marked by GFP fluorescence in nestin-GFP transgenic mice, appear in the permanent upper hair follicle immediately below the sebaceous glands in the follicle bulge. This is where stem cells for the hair follicle outer-root sheath are thought to be located. The relatively small, oval-shaped, nestin-expressing cells in the bulge area surround the hair shaft and are interconnected by short dendrites. The precise locations of the nestin-expressing cells in the hair follicle vary with the hair cycle. During telogen or resting phase and in early anagen, the GFP-positive cells are mainly in the bulge area. However, in mid- and late anagen, the GFP-expressing cells are located in the upper outer-root sheath as well as in the bulge area but not in the hair matrix bulb. These observations show that the nestin-expressing cells form the outer-root sheath. Results of the immunohistochemical staining showed that nestin, GFP, keratin 5/8, and keratin 15 colocalize in the hair follicle bulge cells, outer-root sheath cells, and basal cells of the sebaceous glands. These data indicate that nestin-expressing cells, marked by GFP, in the hair follicle bulge are indeed progenitors of the follicle outer-root sheath. The expression of the unique protein, nestin, in both neural stem cells and hair follicle stem cells suggests their possible relation.

Animals↗

PubMed2003

Label-retaining cells (presumptive stem cells) of mice vibrissae do not express gap junction protein connexin 43.

We investigated whether connexin 43, a gap junction protein present in human epidermis and mouse hair follicle, can serve as a negative marker for keratinocyte stem cells. Experiments carried out in mouse pelage and vibrissae hair follicles demonstrated that most of the slowly cycling cells, detected as label-retaining cells, do not express connexin 43. In humans, cells with immunohistochemically undetectable levels of connexin 43 are found in the epidermal basal layer of neonatal foreskin, and in the follicular bulge region. About 10% of the basal keratinocytes are connexin 43 negative, as determined by flow cytometry. These cells are uniformly small and low in granularity suggesting that presumptive keratinocyte stem cells can be identified and separated based on connexin 43 expression.

Animals↗

PubMed2002

Epidermal stem cells do not communicate through gap junctions.

Although enrichment of putative epidermal stem cells has been achieved, a need for additional markers that can enable isolation of live keratinocytes is crucial for characterization of these cells. Earlier work has shown that connexin proteins are absent from basal cells in the limbal epithelium, a region of the corneal epithelium enriched in corneal stem cells. Accordingly, we investigated whether connexin 43, a gap junction protein present in the basal layer of normal human epidermis, can serve as a negative marker for keratinocyte stem cells. In humans, cells with immunohistochemically undetectable levels of connexin 43 are found in the epidermal basal layer of neonatal foreskin and in the follicular bulge region. About 10% of the basal keratinocytes are connexin 43 negative, as determined by flow cytometry. These cells are uniformly small and low in granularity. Restricted gap junction communication was confirmed by the failure of low molecular weight dyes to transfer between cells. Experiments carried out in mouse epidermis demonstrated that most of the slowly cycling cells, detected as label-retaining cells, do not express connexin 43. Thus, presumptive keratinocyte stem cells can be identified and separated based on connexin 43 expression.

Adult↗