Molecular Anatomy of the Developing Human Retina

Clinical and genetic heterogeneity associated with retinal diseases makes stem-cell-based therapies an attractive strategy for personalized medicine. However, we have limited understanding of the timing of key events in the developing human retina, and in particular the factors critical for generating the unique architecture of the fovea and surrounding macula. Here we define three key epochs in the transcriptome dynamics of human retina from fetal day (D) 52 to 136. Coincident histological analyses confirmed the cellular basis of transcriptional changes and highlighted the dramatic acceleration of development in the fovea compared with peripheral retina. Human and mouse retinal transcriptomes show remarkable similarity in developmental stages, although morphogenesis was greatly expanded in humans. Integration of DNA accessibility data allowed us to reconstruct transcriptional networks controlling photoreceptor differentiation. Our studies provide insights into human retinal development and serve as a resource for molecular staging of human stem-cell-derived retinal organoids.

Abstract 283: p27 kip1 Dose Affects Collateralization Through Arterial Wall Cells

Objectives: p27 deficiency (p27 -/- ) improves blood flow after hindlimb ischemia through enlargement of a bridge collateral pathway. p27 -/- VSMC both migrate and proliferate more than wt VSMC. We hypothesized that p27’s effect on ischemic collateralization is from arterial wall cells and not from bone marrow derived cells.

Methods: p27 -/- and wt (C57BL/6) after reciprocal bone marrow transplantation (BMT) and p27 +/- female mice underwent left femoral artery ligation. Footpad laser Doppler perfusion imaging was performed weekly. MicroCT scans were performed on both hindlimbs after sacrifice (days 14 and 28 for BMT and p27 +/- mice respectively). VSMC were isolated from all groups and used in cell proliferation, migration, and gel contraction assays.

Results: p27 -/- mice transplanted with wt bone marrow recovered significantly more blood flow and enlarged bridge collaterals than wt mice transplanted with p27 -/- bone marrow (117±15 vs. 55±7 μm, p<0.001). p27 +/- mice had intermediate blood flow recovery and had intermediate bridge collateral size (wt 82 ± 22, p27 +/- 122±15, and p27 -/- 158±18 μm, p < 0.05, Figure 1). In vitro studies showed that p27 +/- VSMC proliferated more but did not migrate more than wt VSMC.

Conclusions: p27 deficiency enhances ischemic collateralization via effects on local arterial wall cells rather than on bone marrow derived cells. This may be secondary to increased VSMC proliferation.

Figure 1. MicroCT scans of the ischemic hindlimb of p27 -/- , p27 +/- and wt mice showing enlargement of bridge collaterals in p27 -/- more than p27 +/- mice, and absence of this pathway in wt mice. Digital pseudocoloring has been added (magenta-femoral, saphenous, popliteal arteries, blue-collateral arteries, red-unnamed muscular arteries). L-ligation site, 1-bridge collaterals, 2-gracilis collaterals.

Haemodynamics of stable renal transplant recipients

1. Haemodynamics, blood volume, plasma renin concentration and creatinine clearance were evaluated in 24 stable renal transplant recipients. 2. The mean cardiac index of the transplant recipients was not different from that of the normal subjects. 3. The transplant recipients comprised eight hypertensive and 16 normotensive patients. The mean cardiac index was the same in eight hypertensive and 16 normotensive patients. Thus the hypertension of stable renal transplant recipients is sustained by a high total peripheral resistance. 4. The mean blood volume, plasma renin concentration and creatinine clearance were similar in eight hypertensive and 16 normotensive patients. Therefore the hypertension of stable renal transplant recipients is not related to blood volume expansion, elevated peripheral renin or low creatinine clearance. The cause of the elevated total peripheral resistance in hypertension in stable renal transplant recipients remains to be elucidated.

Immune complex glomerulonephritis in a case of retroperitoneal fibrosis

The nephropathology associated with retroperitoneal fibrosis has been commonly related to compression of the ureters and hydronephrosis. This assumption has been made without the use of immunofluorescent microscopy and electron microscopy. The authors studied renal tissue from a patient with retroperitoneal fibrosis by light microscopy, immunofluorescent microscopy and electron microscopy. In addition to the gross and microscopic changes of obstructive nephropathy, histologic findings of glomerular immune-complex deposition were also present. It is postulated that in some cases of retroperitoneal fibrosis, destruction may be mediated by both obstructive and immunologic processes.