Human corneal endothelial cells (HCEnCs) form a monolayer of hexagonal cells whose main function is to maintain corneal clarity by regulating corneal hydration. HCEnCs are derived from neural crest and are arrested in the post-mitotic state. Thus cell loss due to aging or corneal endothelial disorders leads to corneal edema and blindness-the leading indication for corneal transplantation. Here we show the existence of morphologically distinct subpopulations of HCEnCs that are interspersed among primary cells and exhibit enhanced self-renewal competence and lack of phenotypic signs of cellular senescence. Colonies of these uniform and hexagonal HCEnCs (HCEnC-21) were selectively isolated and demonstrated high proliferative potential that was dependent on endogenous upregulation of telomerase and cyclin D/CDK4. Further transduction of HCEnC-21 with telomerase yielded a highly proliferative corneal endothelial cell line (HCEnT-21T) that was devoid of oncogenic transformation and retained critical corneal endothelial cell characteristics and functionality. This study will significantly impact the fields of corneal cell biology and regenerative medicine.
PURPOSE: To analyze the morphology and density of corneal epithelial cells, keratocytes, and subbasal nerves, in patients with early stage Fuchs' endothelial corneal dystrophy (FECD) by in vivo confocal microscopy (IVCM).
METHODS: IVCM (Confoscan 4, Nidek, Inc.) of the central cornea was performed in 30 corneas of 30 patients with early stage FECD and 13 corneas of 13 normal controls. Images were analyzed for morphology and density of the superficial and basal epithelial cells, keratocyte density, endothelial cell density (ECD), as well as subbasal corneal nerve parameters. Central corneal thickness (CCT) was measured in all patients and normals by ultrasound pachymetry.
RESULTS: The ECD was significantly lower (-45.5%, P<0.001) in FECD patients as compared with controls. Total number of nerves and main nerve trunks were significantly reduced (-46.3%, P<0.001; -39.7%, P<0.001) in patients with FECD. Posterior keratocyte density was significantly higher in FECD patients (P<0.001). Significant inverse correlations were found between CCT and total number of nerves (r=-0.69, P<0.001), CCT and main nerve trunks (-0.47, P=0.016), as well as CCT and total nerve length (r=-0.62, P=0.006). Significant correlation was found between ECD and total number of nerves (r=0.44, P=0.012) as well as between ECD and main nerve trunks (r=0.65, P<0.001).
CONCLUSIONS: IVCM demonstrates alterations in corneal innervation in patients with early stage FECD, suggesting a potential role of corneal nerves in the pathogenesis of FECD. Additional studies are required to investigate whether subbasal nerve alterations are caused by nonspecific corneal edema, from FECD-induced decrease in ECD, or potentially leading to loss of endothelial cells.
There is currently considerable controversy about existence and classification of "lymphatic vessels" in the eye. Some of the confusion is certainly caused by inappropriate use (or nonuse) of the correct immunohistochemical markers. Many experts in the field expressed the need for a consensus statement, and, in this perspective, authors offer arguments and solutions to reliably continue with immunohistochemical ocular lymphatic research.
Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening conditions with high morbidity and mortality. Supportive care management of SJS/TEN is highly variable. A systematic review of the literature was performed by dermatologists, ophthalmologists, intensivists, and gynecologists with expertise in SJS/TEN to generate statements for supportive care guideline development. Members of the Society of Dermatology Hospitalists with expertise in SJS/TEN were invited to participate in a modified, online Delphi-consensus. Participants were administered 9-point Likert scale questionnaires regarding 135 statements. The RAND/UCLA Appropriateness Method was used to evaluate and select proposed statements for guideline inclusion; statements with median ratings of 6.5 to 9 and a disagreement index of ≤1 were included in the guideline. For the final round, the guidelines were appraised by all of the participants. Included are an evidence-based discussion and recommendations for hospital setting and care team, wound care, ocular care, oral care, urogenital care, pain management, infection surveillance, fluid and electrolyte management, nutrition and stress ulcer prophylaxis, airway management, and anticoagulation in adult patients with SJS/TEN.
The pathogenesis of immune-mediated lacrimal gland (LG) dysfunction in Sjögren's syndrome has been thoroughly studied. However, the majority of dry eye (DE) is not related to Sjögren type, and its pathophysiology remains unclear. The purpose of this study was to determine and investigate the protective mechanisms against DE stress in mice. DE induced prominent blood vessel loss without apoptosis or necrosis in the LG. Autophagic vacuoles, distressed mitochondria, and stressed endoplasmic reticulum were observed via electron microscopy. Immunoblotting confirmed the increase in autophagic markers. Glycolytic activities were enhanced with increasing levels of succinate and malate that, in turn, activated hypoxia-inducible factor (HIF)-1α. Interestingly, the areas of stable HIF-1α expression overlapped with COX-2 and MMP-9 upregulation in LGs of DE-induced mice. We generated HIF-1α conditional knockout (CKO) mice in which HIF-1α expression was lost in the LG. Surprisingly, normal LG polarities and morphologies were completely lost with DE induction, and tremendous acinar cell apoptosis was observed. Similar to Sjögren's syndrome, CD3(+) and CD11b(+) cells infiltrated HIF-1α CKO LGs. Our results show that DE induced the expression of HIF-1α that activated autophagy signals to prevent further acinar cell damage and to maintain normal LG function.
PURPOSE: To evaluate the changes in anterior corneal topography induced by short-time wear of scleral contact lenses (SLs) in keratoconic subjects with and without a history of corneal cross-linking (CXL). METHODS: Nine keratoconic patients (14 eyes) were fitted with 18.5 mm SLs for optical rehabilitation. Subjects were divided into 2 groups: 7 eyes without a history of CXL (Non-CXL group) and 7 with a history of CXL (CXL group). Corneal topography was performed at baseline and after 2 and 5 hours of lens wear. The differences for simulated flat (Kflat), steep (Ksteep) and maximal (Kmax) corneal curvatures, central corneal astigmatism (CCA), and central cornea thickness were evaluated. RESULTS: No statistically significant difference was detected between Non-CXL and CXL groups in any of these measures. Statistically significant flattening was detected in Ksteep Repeated measures analysis of variance ([RM-ANOVA), F (2,24) = 11.32, P < 0.0001], CCA [RM-ANOVA, F (2,24) = 15.34, P < 0.0001], and Kmax [RM-ANOVA, F (2,24) = 19.10, P < 0.0001). From baseline to 5 hours of SL wear, Ksteep decreased on average from 53.1 to 52.4 D, Kmax decreased from 56.7 to 55.8 D, and CCA decreased from 7.2 to 6.3 D. Kmax showed a trend toward more flattening in the Non-CXL group. Central cornea thickness showed significant thickening over time from baseline (451 μm) to 5 hours (458 μm) of SL wear [RM-ANOVA, F (1,12) = 319.3, P < 0.0001]. CONCLUSIONS: Short-term scleral lens wear in keratoconic patients may cause flattening of the anterior cornea. A history of CXL treatment does not guarantee corneal shape stability after scleral lens wear. Practitioners should be aware of these changes because scleral lens wear may mask the signs of keratoconus progression.
Corneal immune privilege is integral in maintaining the clear avascular window to the foreign world. The presence of distinct populations of corneal leukocytes (CLs) in the normal cornea has been firmly established. However, their precise function and kinetics remain, as of yet, unclear. Through intravital multiphoton microscopy (IV-MPM), allowing the means to accumulate critical spatial and temporal cellular information, we provide details for long-term investigation of CL morphology and kinetics under steady state and following inflammation. Significant alterations in size and morphology of corneal CD11c dendritic cells (DCs) were noted following acute sterile inflammation, including cell volume (4364.4 ± 489.6 vs. 1787.6 ± 111.0 μm, P < 0.001) and sphericity (0.82 ± 0.01 vs. 0.42 ± 0.02, P < 0.001) compared with steady state. Furthermore, IV-MPM analyses revealed alterations in both the CD11c DC and major histocompatibility complex class II (MHC)-II mature antigen-presenting cell population kinetics during inflammation, including track displacement length (CD11c: 16.57 ± 1.41 vs. 4.64 ± 0.56 μm, P < 0.001; MHC-II: 9.03 ± 0.37 vs. 4.09 ± 0.39, P < 0.001) and velocity (CD11c: 1.91 ± 0.07 μm/min vs. 1.73 ± 0.1302 μm/min; MHC-II: 2.97 ± 0.07 vs. 1.62 ± 0.08, P < 0.001) compared with steady state. Our results reveal in vivo evidence of sessile CL populations exhibiting dendritic morphology under steady state and increased velocity of spherical leukocytes following inflammation. IV-MPM represents a powerful tool to study leukocytes in corneal diseases in context.-Seyed-Razavi, Y., Lopez, M. J., Mantopoulos, D., Zheng, L., Massberg, S., Sendra, V. G., Harris, D. L., Hamrah, P. Kinetics of corneal leukocytes by intravital multiphoton microscopy.
PURPOSE: To characterize diphtheroid corneal infections in eyes in the chronic phase of Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). METHODS: Observational case series. RESULTS: Four eyes of 3 patients were included in this review. Each eye presented with persistent corneal epithelial defect with corneal thinning in the chronic phase of SJS/TEN. None of the epithelial defects were associated with stromal infiltration. The corneas were cultured at the time of workup of persistent epithelial defect (3 eyes) or at time of tectonic penetrating keratoplasty after perforation (1 eye). Cultures yielded abundant growth of Corynebacterium spp., including Corynebacterium jeikeium (n = 2), Corynebacterium glucuronolyticum (n = 1), and a multidrug-resistant Corynebacterium striatum isolate (n = 1). The ocular surface was stabilized with surgical intervention (1 eye) or with introduction of fortified topical antibiotic based on laboratory identification and susceptibility testing of the isolated organisms (3 eyes). Numerous risk factors for microbial keratitis were present in all 4 eyes. CONCLUSIONS: In eyes with a persistent corneal epithelial defect in the chronic phase of SJS/TEN, even in the absence of an infiltrate, corneal culture should be undertaken. Recognition and treatment of Corynebacterium spp. as opportunistic pathogens may lead to favorable outcomes in cases of clinically sterile ulceration during the chronic phase of SJS/TEN.
PURPOSE: To describe the long-term effect of a treatment protocol for ocular involvement in acute Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN), including focused ocular examination and pathology-appropriate use of lubrication, topical corticosteroids, topical antibiotics, and amniotic membrane transplantation (AMT). DESIGN: Retrospective, comparative case series. METHODS: A total of 48 patients (96 eyes) were included in this study. Nine of 48 patients (18 eyes) had acute SJS/TEN from 2000 to 2007 and did not receive protocol care (Group I). Thirty-nine of 48 patients (78 eyes) had acute SJS/TEN from 2008 to 2017 and received protocol care (Group II). The main outcome measures were best-corrected visual acuity (BCVA) at final follow-up visit and incidence of complications in the chronic phase. RESULTS: No eyes in Group I received AMT for SJS/TEN, compared to 87% of qualifying eyes in Group II (P < .0001) There was a significant difference in the proportion of eyes with BCVA ≥20/40 at last follow-up between Group I and Group II (33% vs 92%, P < .001). The proportion of eyes with vision-threatening complications in the chronic phase was significantly higher in Group I versus Group II (67% vs 17%, P = .002), with most complications occurring in the first 2 years after disease onset in both groups. CONCLUSIONS: A specific protocol for acute ocular care in SJS/TEN, including aggressive use of AMT, was highly successful in reducing corneal blindness and severe vision-threatening complications of the disorder.
PURPOSE: To review the published literature on outcomes of keratolimbal allograft (KLAL) for the surgical treatment of limbal stem cell deficiency (LSCD) and corneal blindness after severe corneal chemical injury. METHODS: Literature searches were conducted in the following electronic databases: MEDLINE, EMBASE, Science Citation Index, CINAHL, LILACS and the Cochrane Library. Standard systematic review methodology was applied. The main outcome measure was the proportion of eyes with best-corrected visual acuity (BCVA) ≥20/200 at last follow-up. Other measures of allograft success were also collected. RESULTS: We identified six reports in which KLAL outcomes in the eyes after chemical injury could be distinguished. There were no randomised controlled studies. The outcomes of KLAL in 36 eyes of 33 patients were analysed. One study with seven eyes did not specify KLAL follow-up specific to chemical injury. Median postoperative follow-up for the other 29 eyes in 26 patients was 42 months (range 6.2-114 months). In the same 29 eyes, 69% (20/29) had BCVA ≥20/200 at the last follow-up examination. Eighty-nine per cent of all eyes (32/36) underwent penetrating keratoplasty simultaneous or subsequent to KLAL. CONCLUSIONS: The number of studies where outcomes of KLAL in eyes with severe corneal chemical injury could be discerned was limited, and variability was observed in outcome reporting. The quality of evidence to support the use of KLAL in LSCD in severe chemical corneal burns was low. Standardisation and longer follow-up are needed to better define evidence-based best practice when contemplating surgical intervention for blindness after corneal chemical injury. PROSPERO REGISTRATION NUMBER: CRD42017054733.
Amniotic membrane (AM) transplantation, when performed in the acute phase in Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) for patients with ocular complications, is known to reduce the morbidity of ocular complications in the chronic phase. In conditions such as SJS/TEN, AM needs to be secured to the ocular surface as well as the eyelids. Previously, techniques of securing a large sheet of AM with fibrin glue to the ocular surface and with sutures and bolsters to the eyelids have been described in the acute phase of SJS/TEN. These techniques often necessitate the use of an operating room in acutely ill patients. We describe a bedside technique that uses cyanoacrylate glue to secure the AM to the eyelids, as well as long-term outcomes in 4 patients with acute SJS/TEN. The combination of a custom symblepharon ring to secure AM over the entire ocular surface and cyanoacrylate glue to secure AM to the eyelid margins is quick, painless, does not require local or general anesthesia, and might prove useful in other conditions previously shown to benefit from AMT, such as ocular chemical injuries.
PURPOSE: To report the long-term outcomes of amniotic membrane (AM) use in the form of transplantation (AMT) and self-retained amniotic membrane (ProKera® device, PD) in acute Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). METHODS: Electronic records of all patients with a diagnosis of SJS/TEN at Massachusetts Eye and Ear between January 2008 and January 2018 were reviewed. Patients who received AM in acute SJS/TEN were selected. Only patients with follow-up ≥ 3 months after discharge were included. RESULTS: Data of 55 eyes of 29 patients were analyzed. All 55 eyes received the first AM at a median interval of 5 days (inter-quartile range (IQR): 3-7 days) after onset of skin rash. Fifty-six percent of eyes (31/55) received AMT while 44% (24/55) received PD. Forty percent of eyes (22/55) required a repeat AMT or PD. Median follow-up after initial AM was 2.5 years (IQR: 1.2-3.6 years). At last follow-up, the best-corrected visual acuity was ≥20/40 in 87% of eyes (48/55). The most common complications in the chronic phase were meibomian gland disease and dry eye, seen in 78% of eyes (43/55) and 58% of eyes (32/55) respectively. CONCLUSIONS: Long-term results show that early use of AM in the acute phase of SJS/TEN may be effective in mitigating severe vision loss after SJS/TEN. However, eyelid-related complications and dry eye remain a common problem even with the use of AM.
BACKGROUND: Regulatory T (Treg) cell-based immunotherapies have been studied as potential cell-based modalities for promoting transplant survival. However, the efficacy of local delivery of Treg cells in corneal transplantation has not been fully elucidated. Herein, we investigated the kinetics of migration of subconjunctivally injected Treg cells and their role in promoting corneal allograft survival. METHODS: GFPCD4CD25Foxp3 Treg cells were isolated from draining lymph nodes (DLNs) of GFP transgenic mice and were subconjunctivally injected to corneal allograft recipients. Next, Treg cells, conventional T cells (Tconv) or a combination of both was locally injected to graft recipients, and graft survival was determined by evaluating opacity scores for 10 weeks. Transplanted mice without treatment served as controls. The frequencies of major histocompatibility complex-IICD11b antigen-presenting cells, IFNγCD4 Th1 cells, and CD45 cells in the DLNs and cornea were evaluated at week 2 posttransplantation using flow cytometry. Expressions of IFNγ, IL-10 and TGF-β in the grafts were assessed using reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. RESULTS: GFP Treg cells were detected in the ipsilateral cornea and DLNs of recipients 6 hours after injection. Subconjunctival injection of Treg cells significantly decreased the frequencies of mature antigen-presenting cells in the graft and DLNs, suppressed Th1 frequencies in DLNs, and inhibited CD45 cell infiltration to the graft. Finally, locally delivered Treg cells significantly reduced the expression of IFN-γ, enhanced the levels of IL-10 and TGF-β in the graft, and promoted long-term allograft survival. CONCLUSIONS: Our study elucidates the kinetics of migration of locally delivered Treg cells and shows their role in suppressing host immune response against the allograft.
Keratoconus (KC) is a multi-factorial corneal ectasia with unknown etiology affecting approximately 1:2000 people worldwide. Dysregulated gene expression, using RNA-Seq technology, have been reported in KC corneal tissue. However, the differential expression of genes, in KC corneal stromal cells have been widely ignored. We utilized mRNA-Seq to analyze gene expression in primary human corneal stromal cells derived from five non-Keratoconus healthy (HCF) and four Keratoconus (HKC) donors. Selected genes were further validated using real time PCR (RT-PCR). We have identified 423 differentially expressed genes with 187 down- and 236 up-regulated in KC-affected corneal stromal cells. Gene ontology analysis using WebGestalt indicates the enrichment of genes involved in cell migration, extracellular matrix, adherens junction, and MAPK signaling. Our protein-protein interaction network analysis identified several network seeds, such as EGFR, NEDD4, SNTA1, LGALS3BP, HSPB1, SDC2, MME, and HIF1A. Our work provides an otherwise unknown information on the transcriptional changes in HKCs, and reveals critical mechanisms of the cellular compartment. It also highlights the importance of human-based in vitro studies on a disease that currently lacks strong biomarkers and animal models.
PURPOSE: To evaluate the effects of electron-beam (E-beam) irradiation on the human cornea and the potential for E-beam sterilization of Boston keratoprosthesis (BK) devices when pre-assembled with a donor cornea prior to sterilization. METHODS: Human donor corneas and corneas pre-assembled in BK devices were immersed in recombinant human serum albumin (rHSA) media and E-beam irradiated at 25 kGy. Mechanical (tensile strength and modulus, and compression modulus), chemical, optical, structural, and degradation properties of the corneal tissue after irradiation and after 6 months of preservation were evaluated. RESULTS: The mechanical evaluation showed that E-beam irradiation enhanced the tensile and compression moduli of human donor corneas, with no impact on their tensile strength. By chemical and mechanical analysis, E-beam irradiation caused a minor degree of crosslinking between collagen fibrils. No ultrastructural changes due to E-beam irradiation were observed. E-beam irradiation slightly increased the stability of the cornea against collagenase-induced degradation and had no impact on glucose diffusion. The optical evaluation showed transparency of the cornea was maintained. E-beam irradiated corneal tissues and BK-cornea pre-assembled devices were stable for 6 months after room-temperature preservation. CONCLUSIONS: E-beam irradiation generated no detrimental effects on the corneal tissues or BK-cornea pre-assembled devices and improved native properties of the corneal tissue, enabling prolonged preservation at room temperature. The pre-assembly of BK in a donor cornea, followed by E-beam irradiation, offers the potential for an off-the-shelf, ready to implant keratoprosthesis device.
Electron beam (E-beam) irradiation is an attractive and efficient method for sterilizing clinically implantable medical devices made of natural and/or synthetic materials such as poly(methyl methacrylate) (PMMA). As ionizing irradiation can affect the physicochemical properties of PMMA, understanding the consequences of E-beam sterilization on the intrinsic properties of PMMA is vital for clinical implementation. A detailed assessment of the chemical, optical, mechanical, morphological, and biological properties of medical-grade PMMA after E-beam sterilization at 25 and 50 kiloGray (kGy) is reported. Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry studies indicate that E-beam irradiation has minimal effect on the chemical properties of the PMMA at these doses. While 25 kGy irradiation does not alter the mechanical and optical properties of the PMMA, 50 kGy reduces the flexural strength and transparency by 10% and 2%, respectively. Atomic force microscopy demonstrates that E-beam irradiation reduces the surface roughness of PMMA in a dose dependent manner. Live-Dead, AlamarBlue, immunocytochemistry, and complement activation studies show that E-beam irradiation up to 50 kGy has no adverse effect on the biocompatibility of the PMMA. These findings suggest that E-beam irradiation at 25 kGy may be a safe and efficient alternative for PMMA sterilization.
Numerous animal species have been proposed as sources of corneal tissue for obtaining decellularized xenografts. The selection of an appropriate animal model must take into consideration the differences in the composition and structure of corneal proteins between humans and other animal species in order to minimize immune response and improve outcome of the xenotransplant. Here, we compared the amino-acid sequences of 16 proteins present in the corneal stromal matrix of 14 different animal species using Basic Local Alignment Search Tool, and calculated a similarity score compared to the respective human sequence. Primary amino acid structures, isoelectric point and grand average of hydropathy (GRAVY) values of the 7 most abundant proteins (i.e. collagen α-1 (I), α-1 (VI), α-2 (I) and α-3 (VI), as well as decorin, lumican, and keratocan) were also extracted and compared to those of human. The pig had the highest similarity score (91.8%). All species showed a lower proline content compared to human. Isoelectric point of pig (7.1) was the closest to the human. Most species have higher GRAVY values compared to human except horse. Our results suggest that porcine cornea has a higher relative suitability for corneal transplantation into humans compared to other studied species.
PURPOSE: The purpose of this study was to investigate the presence of progenitor cells in the uninjured, adult rat lacrimal gland (LG). METHODS: The presence of progenitor cells was examined in LG sections from male rats using antibodies against selected stem cell markers and α-smooth muscle actin (SMA), which marks myoepithelial cells (MECs), by immunofluorescence microscopy (IF). Small, immature cells were isolated after digestion of LG with collagenase and culture in RPMI 1640 for 2 weeks. Immature cells were examined for expression of stem cell markers by IF. Immature cell were grown in neuronal, epithelial, and myoepithelial cell media, and examined by light morphology and IF using antibodies to markers of different cell lineages. RESULTS: In the intact LGs, MECs expressed the stem cell markers nestin, Musashi 1, ABCG2, Pax6, Chx 10, ΔN p63, and Sox 2. All markers colocalized with SMA. Isolated immature cells contained Ki-67, nestin, Musashi 1, Pax 6, and CHX 10. In neuronal media, immature cells differentiated and assumed a neuronal cell morphology expressing neurofilament 200. In media for human corneal endothelial cells, immature cells differentiated, assumed cobblestone morphology, and labeled with the epithelial marker AE1/AE3. In RPMI media immature cells differentiated into cells with MEC-like morphology, and expressed the MEC markers SMA, α-actinin, adenylate cyclase II, and vimentin. CONCLUSIONS: We conclude that uninjured, adult LG contains progenitor cells that may be MECs, which can be isolated and differentiated into multiple lineages.
The purpose of this study was to investigate the changes that occur in the lacrimal glands (LGs) in female thrombospondin 1 knockout (TSP1(-/-)) mice, a mouse model of the autoimmune disease Sjogren's syndrome. The LGs of 4, 12, and 24 week-old female TSP1(-/-) and C57BL/6J (wild type, WT) mice were used. qPCR was performed to measure cytokine expression. To study the architecture, LG sections were stained with hematoxylin and eosin. Cell proliferation was measured using bromo-deoxyuridine and immunohistochemistry. Amount of CD47 and stem cell markers was analyzed by western blot analysis and location by immunofluorescence microscopy. Expression of stem cell transcription factors was performed using Mouse Stem Cell Transcription Factors RT(2) Profiler PCR Array. Cytokine levels significantly increased in LGs of 24 week-old TSP1(-/-) mice while morphological changes were detected at 12 weeks. Proliferation was decreased in 12 week-old TSP1(-/-) mice. Three transcription factors were overexpressed and eleven underexpressed in TSP1(-/-) compared to WT LGs. The amount of CD47, Musashi1, and Sox2 was decreased while the amount of ABCG2 was increased in 12 week-old TSP1(-/-) mice. We conclude that TSP1 is necessary for maintaining normal LG homeostasis. Absence of TSP1 alters cytokine levels and stem cell transcription factors, LG cellular architecture, decreases cell proliferation, and alters amount of stem cell markers.