Resurfacing complex full thickness wounds requires free tissue transfer which creates donor site morbidity. We describe a method to fabricate a skin flap equivalent with a hierarchical microvascular ...network.
We fabricated a flap of skin-like tissue containing a hierarchical vascular network by sacrificing Pluronic
F127 macrofibers and interwoven microfibers within collagen encapsulating human pericytes and fibroblasts. Channels were seeded with smooth muscle and endothelial cells. Constructs were topically seeded with keratinocytes.
After 28 days in culture, multiphoton microscopy revealed a hierarchical interconnected network of macro- and micro-vessels; larger vessels (>100 μm) were lined with a monolayer endothelial neointima and a subendothelial smooth muscle neomedia. Neoangiogenic sprouts formed in the collagen protodermis and pericytes self-assembled around both fabricated vessels and neoangiogenic sprouts.
We fabricated a prevascularized scaffold containing a hierarchical 3D network of interconnected macro- and microchannels within a collagen protodermis subjacent to an overlying protoepidermis with the potential for recipient microvascular anastomosis.
Multiphoton microscopy (MPM) is an emerging, nonlinear, optical-biopsy technique, which can generate subcellular-resolution images from unprocessed and unstained tissue in real time.
To assess the ...potential of MPM for lung tumor diagnosis.
Fresh sections from tumor and adjacent nonneoplastic lung were imaged with MPM and then compared with corresponding hematoxylin-eosin slides.
Alveoli, bronchi, blood vessels, pleura, smokers' macrophages, and lymphocytes were readily identified with MPM in nonneoplastic tissue. Atypical adenomatous hyperplasia (a preinvasive lesion) was identified in tissue adjacent to the tumor in one case. Of the 25 tumor specimens used for blinded pathologic diagnosis, 23 were diagnosable with MPM. Of these 23 cases, all but one adenocarcinoma (15 of 16; 94%) was correctly diagnosed on MPM, along with their histologic patterns. For squamous cell carcinoma, 4 of 7 specimens (57%) were correctly diagnosed. For the remaining 3 squamous cell carcinoma specimens, the solid pattern was correctly diagnosed in 2 additional cases (29%), but it was not possible to distinguish the squamous cell carcinoma from adenocarcinoma. The other squamous cell carcinoma specimen (1 of 7; 14%) was misdiagnosed as adenocarcinoma because of pseudogland formation. Invasive adenocarcinomas with acinar and solid pattern showed statistically significant increases in collagen. Interobserver agreement for collagen quantification (among 3 observers) was 80%.
Our pilot study provides a proof of principle that MPM can differentiate neoplastic from nonneoplastic lung tissue and identify tumor subtypes. If confirmed in a future, larger study, we foresee real-time intraoperative applications of MPM, using miniaturized instruments for directing lung biopsies, assessing their adequacy for subsequent histopathologic analysis or banking, and evaluating surgical margins in limited lung resections.
Endocytosis Mukherjee, S; Ghosh, R N; Maxfield, F R
Physiological reviews,
07/1997, Volume:
77, Issue:
3
Journal Article
Peer reviewed
Mammalian cells take up extracellular material by a variety of different mechanisms that are collectively termed endocytosis. Endocytic mechanisms serve many important cellular functions including ...the uptake of extracellular nutrients, regulation of cell-surface receptor expression, maintenance of cell polarity, and antigen presentation. Endocytic pathways are also utilized by viruses, toxins, and symbiotic microorganisms to gain entry into cells. One of the best-characterized endocytic mechanisms is receptor-mediated endocytosis via clathrin-coated pits. This type of endocytosis constitutes the major emphasis of this review, with a brief discussion of other endocytic mechanisms and their comparison with the receptor-mediated pathway. This review describes and evaluates critically current understanding of the mechanisms of entry of plasma membrane components such as the receptor-ligand complexes and membrane lipids as well as the extracellular fluid into cells. The intracellular sorting and trafficking of these molecules upon internalization are also described. The roles of endocytosis in physiological and pathological processes are discussed. These include maintenance of cell polarization, antigen presentation, glucose transport, atherosclerosis, Alzheimer's disease, and the endocytosis of toxins and viruses.
Purpose Although microdissection testicular sperm extraction has become first line therapy for sperm retrieval in men with nonobstructive azoospermia, there are challenges to the procedure, including ...difficulty differentiating between seminiferous tubules with normal and abnormal spermatogenesis. Multiphoton microscopy illuminates tissue with a near infrared laser to elicit autofluorescence, which enables real-time imaging of unprocessed tissue without labels. We hypothesized that we could accurately characterize seminiferous tubular histology in humans using multiphoton microscopy. Materials and Methods Seven men with normal or abnormal spermatogenesis underwent testicular biopsies, which were imaged by multiphoton microscopy. We assessed these images in blinded fashion. The diagnosis rendered with multiphoton microscopy was then correlated with that of hematoxylin and eosin stained tissue. We evaluated the ability of multiphoton microscopy to differentiate normal from abnormal seminiferous tubules by examining autofluorescence characteristics and diameters, as imaged by multiphoton microscopy. Assessment was repeated with stained slides and results were compared. Results The overall concordance rate between multiphoton microscopy and stained slides was 86%. The seminiferous tubules of patients with nonobstructive azoospermia were smaller than those of controls when measured by multiphoton microscopy and staining (p <0.05). The proportion of normal tubules and the diameters obtained with multiphoton microscopy were not different from those obtained with hematoxylin and eosin (p >0.05). Conclusion Multiphoton microscopy can be used to differentiate normal from abnormal spermatogenesis. Its characterization of seminiferous tubular architecture is similar to that provided by hematoxylin and eosin staining. Further investigation of the clinical applications of multiphoton microscopy may improve surgical sperm retrieval outcomes for patients with nonobstructive azoospermia.
Purpose Microdissection testicular sperm extraction has replaced conventional testis biopsies for men with nonobstructive azoospermia and it has become first line treatment. The current problem is ...that the decision to retrieve tubules is based only on appearance and there is no guarantee that the tubules removed contain sperm. Multiphoton microscopy enables label-free immediate visualization of many biological processes in living tissue at subcellular resolution. Materials and Methods We used multiphoton microscopy to study the different developmental stages of spermatogenesis using neonatal, pubertal and adult rat testes. We used a testis hypothermia plus ischemia model to study different testicular histopathologies with multiphoton microscopy. To assess the risk of photo damage DNA fragmentation in testis biopsies imaged at different intensities was assessed by TUNEL assay. Results Multiphoton microscopy identified the stage of spermatogenesis in a seminiferous tubule in fresh tissue without using exogenous labels. We noted significant differences in fluorescence and spectroscopic characteristics between tubules with and without sperm. Sertoli's-cell only tubules had abundant autofluorescence in the 420 to 490 and 550 to 650 nm wavelength ranges while tubules containing sperm had autofluorescence only in the 420 to 490 nm range. On DNA fragmentation assay sperm from tubules imaged by multiphoton microscopy had minimal DNA fragmentation at the laser intensities needed to distinguish tubules with and without sperm. Conclusions Multiphoton microscopy has the potential to facilitate real-time visualization of spermatogenesis in humans and aid in clinical applications, such as testicular sperm extraction for men with infertility.
To understand the mechanisms for endocytic sorting of lipids, we investigated the trafficking of three lipid-mimetic dialkylindocarbocyanine (DiI) derivatives, DiIC16(3) ...(1,1′-dihexadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate), DiIC12(3) (1,1′-didodecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate), and FAST DiI (1,1′-dilinoleyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate), in CHO cells by quantitative fluorescence microscopy. All three DiIs have the same head group, but differ in their alkyl tail length or unsaturation; these differences are expected to affect their distribution in membrane domains of varying fluidity or curvature. All three DiIs initially enter sorting endosomes containing endocytosed transferrin. DiIC16(3), with two long 16-carbon saturated tails is then delivered to late endosomes, whereas FAST DiI, with two cis double bonds in each tail, and DiIC12(3), with saturated but shorter (12-carbon) tails, are mainly found in the endocytic recycling compartment. We also find that DiOC16(3) (3,3′-dihexadecyloxacarbocyanine perchlorate) and FAST DiO (3,3′-dilinoleyloxacarbocyanine perchlorate) behave similarly to their DiI counterparts. Furthermore, whereas a phosphatidylcholine analogue with a BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) fluorophore attached at the end of a 5-carbon acyl chain is delivered efficiently to the endocytic recycling compartment, a significant fraction of another derivative with BODIPY attached to a 12-carbon acyl chain entered late endosomes. Our results thus suggest that endocytic organelles can sort membrane components efficiently based on their preference for association with domains of varying characteristics.
We studied the trafficking of sterols, lipids and proteins in Niemann‐Pick type C (NPC) cells. The NPC is an inherited disorder involving the accumulation of sterol and lipids in modified ...late‐endosome/lysosome‐like storage organelles. Most sterol accumulation studies in NPC cells have been carried out using low‐density lipoprotein (LDL) as the sterol source, and it has been shown that sterol efflux from late endosomes is impaired in NPC cells. In this study, we used a fluorescent sterol analog, dehydroergosterol, which can be quickly and efficiently delivered to the plasma membrane. Thus, we were able to study the trafficking kinetics of the non‐LDL‐derived sterol pool, and we found that dehydroergosterol accumulates in the storage organelles over the course of several hours in NPC cells. We also found that dialkylindocarbocyanine lipid‐mimetic analogs that recycle efficiently from early endosomes in wild‐type cells are targeted to late endosomal organelles in NPC cells, and transferrin receptors recycle slowly and inefficiently in NPC cells. These data are consistent with multiple trafficking defects in both early and late endosomes in NPC cells.
The biological membrane is a highly organized anisotropic molecular assembly. While the center of the bilayer is nearly isotropic, the upper portion, only a few angstroms away toward the membrane ...surface, is highly ordered. How this organization correlates with the degree of water penetration into the bilayer interior is not clear. In general, it is believed that there is not much water in the deeper hydrocarbon regions of the bilayer. In this study, we have utilized the phenomenon of wavelength-selective fluorescence to address this question. We show here that when the same fluorescent group (i.e., 7-nitrobenz-2-oxa-1,3-diazol-4-yl or NBD) is localized at different depths within the bilayer (viz., near the membrane interface in case of the headgroup-labeled NBD-phosphatidylethanolamine (NBD-PE) and near the center of the bilayer in NBD-cholesterol), the degrees to which their fluorescence properties exhibit solvent-induced effects are markedly different. For example, the headgroup-labeled NBD-PE exhibits a much stronger red edge excitation shift (REES) relative to that of NBD-cholesterol. This indicates lesser restriction to mobility in this region as compared to the polar/hydrocarbon interface. In the gel phase, however, REES of NBD-PE did not show any significant change while NBD-cholesterol exhibited no REES. In addition, NBD-cholesterol exhibits a stronger dependence of fluorescence polarization on excitation wavelength in fluid membranes. We attribute these results to the more compact arrangement of the lipid acyl chains in the gel phase which results in lesser water penetration. Since the hydrophobic core of the lipid bilayer is made up of methyl and methylene groups, the only solvent dipoles capable of any interaction with the dipole of the fluorophore giving rise to the REES effect in the fluid phase have to be water molecules that have penetrated deep into the bilayer close to the NBD moiety of NBD-cholesterol. Our results indicate that at least in the fluid phase of the membrane, penetration of water in the deep hydrocarbon region of the bilayer does indeed occur.
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