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Papers by Madhusudan Peshwa

The American Journal of Surgery, 1993

The pursuit of a bioartificial liver is well documented in the literature. Early techniques of ar... more The pursuit of a bioartificial liver is well documented in the literature. Early techniques of artificial liver support that have undergone clinical testing included simple exchange transfusions, extracorporeal xenogeneic or allogeneic liver perfusion, cross-circulation, hemodialysis, charcoal hemoperfusion, and plasmapheresis with plasma exchange. These techniques failed because they were unable to adequately support those hepatic functions essential for survival and because they lacked a back-up therapy, such as liver transplantation, for irreversible forms of liver disease. The concept evolved that hepatic functions essential for survival would be best performed by hepatocytes in an apparatus that allowed sustained or repetitive application. The best results have been achieved with bioartificial liver technologies that employ hepatocytes as implantable systems or extracorporeal devices. Implantable bioartificial liver systems include hepatocytes that have been on coated microcarrier beads, within microencapsulated gel droplets, within biodegradable polymeric substrates, or as spheroid hepatocyte aggregates. Extracorporeal systems include hepatocytes in suspension, on flat plates, and in hollow fiber bioreactors. Several extracorporeal systems have undergone extensive animal testing and are entering the early stages of human clinical trials. Randomized trials are needed to establish the value of bioartificial liver support in the treatment of patients with acute hepatic failure or as a bridge to liver transplantation.

Cytotechnology, 1997

Liver failure is a major cause of mortality. A bioartificial liver (BAL) employing isolated hepat... more Liver failure is a major cause of mortality. A bioartificial liver (BAL) employing isolated hepatocytes can potentially provide temporary support for liver failure patients. We have developed a bioartificial liver by entrapping hepatocytes in collagen loaded in the luminal side of a hollow fiber bioreactor. In the first phase of development, liver-specific metabolic activities of biosynthesis, biotransformation and conjugation were demonstrated. Subsequently anhepatic rabbits were used to show that rat hepatocytes continued to function after the BAL was linked to the test animal. For scale-up studies, a canine liver failure model was developed using D-galactosamine overdose. In order to secure a sufficient number of hepatocytes for large animal treatment, a collagenase perfusion protocol was established for harvesting porcine hepatocytes at high yield and viability. An instrumented bioreactor system, which included dissolved oxygen measurement, pH control, flow rate control, an oxyg...

Biotechnology and Bioengineering, 1993

We have developed a hepatocyte entrapment hollow fiber bioreactor for potential use as a bioartif... more We have developed a hepatocyte entrapment hollow fiber bioreactor for potential use as a bioartificial liver. Hepatocytes were entrapped in collagen gel inside the lumen of the hollow fibers. Medium was perfused through the intraluminal region after contraction of the hepatocyte-entrapment gel. Another medium stream, comparable to the patient's blood during clinical application, passed through the extracapillary space. Viability of hepatocytes remained high after 5 days as judged by the rate of oxygen uptake and viability staining. Urea and albumin synthetic activities were also sustained. Transmission electron microscopic examination demonstrated normal ultrastructural integrity of hepatocytes in such a bioreactor. With its potential for short-term, extracorporeal support of acute liver failure, the current bioreactor warrants further investigation. 0 1993 John Wiley & Sons, Inc.

Cytotechnology, 1997

Liver failure is a major cause of mortality. A bioartificial liver (BAL) employing isolated hepat... more Liver failure is a major cause of mortality. A bioartificial liver (BAL) employing isolated hepatocytes can potentially provide temporary support for liver failure patients. We have developed a bioartificial liver by entrapping hepatocytes in collagen loaded in the luminal side of a hollow fiber bioreactor. In the first phase of development, liver-specific metabolic activities of biosynthesis, biotransformation and conjugation were demonstrated. Subsequently anhepatic rabbits were used to show that rat hepatocytes continued to function after the BAL was linked to the test animal. For scale-up studies, a canine liver failure model was developed using D-galactosamine overdose. In order to secure a sufficient number of hepatocytes for large animal treatment, a collagenase perfusion protocol was established for harvesting porcine hepatocytes at high yield and viability. An instrumented bioreactor system, which included dissolved oxygen measurement, pH control, flow rate control, an oxyg...

Cell transplantation

Metabolic activity of a gel-entrapment, hollow fiber, bioartificial liver was evaluated in vitro ... more Metabolic activity of a gel-entrapment, hollow fiber, bioartificial liver was evaluated in vitro and during extracorporeal hemoperfusion in an anhepatic rabbit model. The bioartificial liver contained either 100 million rat hepatocytes (n = 12), fibroblasts (n = 3), or no cells (n = 7) during hemoperfusion of anhepatic rabbits. Eight other anhepatic rabbits were studied without hemoperfusion as anhepatic controls, and three sham rabbits served as normal controls. Albumin production rates (mean +/- SEM) were similar during in vitro (17.0 +/- 2.8 micrograms/h) and extracorporeal (18.0 +/- 4.0 micrograms/h) application of the hepatocyte bioartificial liver. Exogenous glucose requirements were reduced (p < 0.01) and euglycemia was prolonged (p < 0.001) in anhepatic rabbits treated with the hepatocyte bioartificial liver. The maximum rate of glucose production by the hepatocyte bioartificial liver ranged from 50-80 micrograms/h. Plasma concentrations of aromatic amino acids, prolin...

Molecular Therapy, 2006

Viral vectors show promise as gene therapy treatments for a number of diseases. However, it has b... more Viral vectors show promise as gene therapy treatments for a number of diseases. However, it has been difficult to develop a robust system for generating large volumes of high-titer viral vectors based on lentivirus, alphavirus and adeno-associated virus (AAV) that are needed for clinical applications. Problems stem from the lack of stable producer cell lines and inherent inefficiencies associated with introducing multiple plasmids into adherent monolayer cells by conventional transient transfection techniques (i.e., calcium phosphate precipitation or cationic lipids). Other researchers have demonstrated that suspension cells of lymphoid origin, which can be grown at much higher density than adherent cells, can be converted into efficient retroviral vector producer cell lines (Chan et al., 2001. Gene Ther. 8: 697). However, commercially available transient transfection systems are not optimal for large volume co-transfection of suspension cells, especially hematopoietic cells. MaxCyte's proprietary high-throughput electroporation technology provides a closed, robust, scalable system for high efficiency transfection of both adherent and suspension cells. The MaxCyte system previously was used to produce high titer alphaviral vectors from >10 x10 9 Vero cells and lentiviral vectors from >1 x10 9 adherent HEK 293T cells. To improve the efficiency of lentiviral vector production at large scale and to demonstrate the feasibility of lentivector production in suspension cells, we used the MaxCyte system to transfect large volumes (38 x10 9 cells in 380 mL) of K562 human hematopoietic cells rapidly (within 20 minutes) with a plasmid encoding the green fluorescent protein (GFP) marker gene. The transfected cells were collected in fractions of 35-40 mL. Cells were cultured from each fraction or pooled samples to monitor consistency of the highthroughput electroporation. Greater than 90% of the cells expressed GFP when analyzed by flow cytometry at 48 hrs postelectroporation for all fractionated and pooled cell samples. Propidium iodide (PI) exclusion revealed the cell viability of all the fractionated and pooled cell samples to be greater than 90%. In addition, we were able to produce lentivirus in K562 cells by smallscale electroporation of 10 x10 6 cells with four plasmids encoding components of a lentiviral vector derived from HIV carrying the eGFP marker gene. In conclusion, these studies will demonstrate that use of suspension cells processed by MaxCyte's highthroughput electroporation-based transfection system is a feasible approach for generating large volumes of high-titer viral vectors suitable for clinical / commercial applications in human gene therapy.

Molecular Therapy, 2006

The identification of the chemokine receptor CCR5 as the major co-receptor required for HIV entry... more The identification of the chemokine receptor CCR5 as the major co-receptor required for HIV entry into CD4 T-cells has made the targeted disruption of CCR5 an attractive potential therapeutic approach for treating HIV-infected patients. Yet, no current method permits the efficient therapeutic disruption of a chosen gene in the human genome. We have developed designed zinc-finger protein nucleases (ZFNs) that specifically target the coding sequence of the CCR5 gene. Using standard delivery methods, we have shown these ZFNs can efficiently stimulate the formation of a double strand break (DSB) in the CCR5 locus to allow the natural DNA repair pathways, including Non-Homologous End Joining (NHEJ), to subsequently repair the DSB. Importantly, however, NHEJ is error prone and thus can result in frameshift mutations, leading to permanent disruption in >10% of K562 cells.

Biotechnology Progress, 1994

Cultured hepatocytes have been explored for use in a bioartificial liver. Spheroids formed by cul... more Cultured hepatocytes have been explored for use in a bioartificial liver. Spheroids formed by cultured hepatocytes exhibit enhanced liver-specific functions. The kinetics of spheroid formation, using rat hepatocytes, was studied on positively charged surfaces that were either uncoated or coated with collagen or (hydroxyethy1)methacrylate (HEMA). Optimal spheroid formation was obtained on positively charged (Primaria) surfaces at inoculum densities in the range of (3-9) x lo4 cells/cm2. Cells initially attached and spread out on the surface. Subsequent retraction led to the emergence of small clumps of cells attached to the surface, from which spheroids formed and shed off into suspension. The process of spheroid formation took more than 72 h and was accompanied by a decrease in the surface area occupied by attached cells. Optical sectioning of fluorescently stained spheroids using confocal microscopy indicated that most of the cells in the spheroid were viable. Spheroids also maintained a constant albumin synthesis rate for over 7 days in culture. Spheroid formation was evaluated in terms of the changes in spheroid diameter, the surface area covered by attached cells, and the total protein content of the fraction of cells that formed spheroids. The quantitative methodologies developed were used to assess the effect of inoculum cell concentration on spheroid formation and to evaluate the kinetics of spheroid formation on different surfaces both favorable and nonfavorable to spheroid formation.

The American Journal of Surgery, 1993

The pursuit of a bioartificial liver is well documented in the literature. Early techniques of ar... more The pursuit of a bioartificial liver is well documented in the literature. Early techniques of artificial liver support that have undergone clinical testing included simple exchange transfusions, extracorporeal xenogeneic or allogeneic liver perfusion, cross-circulation, hemodialysis, charcoal hemoperfusion, and plasmapheresis with plasma exchange. These techniques failed because they were unable to adequately support those hepatic functions essential for survival and because they lacked a back-up therapy, such as liver transplantation, for irreversible forms of liver disease. The concept evolved that hepatic functions essential for survival would be best performed by hepatocytes in an apparatus that allowed sustained or repetitive application. The best results have been achieved with bioartificial liver technologies that employ hepatocytes as implantable systems or extracorporeal devices. Implantable bioartificial liver systems include hepatocytes that have been on coated microcarrier beads, within microencapsulated gel droplets, within biodegradable polymeric substrates, or as spheroid hepatocyte aggregates. Extracorporeal systems include hepatocytes in suspension, on flat plates, and in hollow fiber bioreactors. Several extracorporeal systems have undergone extensive animal testing and are entering the early stages of human clinical trials. Randomized trials are needed to establish the value of bioartificial liver support in the treatment of patients with acute hepatic failure or as a bridge to liver transplantation.

Cytotechnology, 1997

Liver failure is a major cause of mortality. A bioartificial liver (BAL) employing isolated hepat... more Liver failure is a major cause of mortality. A bioartificial liver (BAL) employing isolated hepatocytes can potentially provide temporary support for liver failure patients. We have developed a bioartificial liver by entrapping hepatocytes in collagen loaded in the luminal side of a hollow fiber bioreactor. In the first phase of development, liver-specific metabolic activities of biosynthesis, biotransformation and conjugation were demonstrated. Subsequently anhepatic rabbits were used to show that rat hepatocytes continued to function after the BAL was linked to the test animal. For scale-up studies, a canine liver failure model was developed using D-galactosamine overdose. In order to secure a sufficient number of hepatocytes for large animal treatment, a collagenase perfusion protocol was established for harvesting porcine hepatocytes at high yield and viability. An instrumented bioreactor system, which included dissolved oxygen measurement, pH control, flow rate control, an oxyg...

Biotechnology and Bioengineering, 1993

We have developed a hepatocyte entrapment hollow fiber bioreactor for potential use as a bioartif... more We have developed a hepatocyte entrapment hollow fiber bioreactor for potential use as a bioartificial liver. Hepatocytes were entrapped in collagen gel inside the lumen of the hollow fibers. Medium was perfused through the intraluminal region after contraction of the hepatocyte-entrapment gel. Another medium stream, comparable to the patient's blood during clinical application, passed through the extracapillary space. Viability of hepatocytes remained high after 5 days as judged by the rate of oxygen uptake and viability staining. Urea and albumin synthetic activities were also sustained. Transmission electron microscopic examination demonstrated normal ultrastructural integrity of hepatocytes in such a bioreactor. With its potential for short-term, extracorporeal support of acute liver failure, the current bioreactor warrants further investigation. 0 1993 John Wiley & Sons, Inc.

Cytotechnology, 1997

Liver failure is a major cause of mortality. A bioartificial liver (BAL) employing isolated hepat... more Liver failure is a major cause of mortality. A bioartificial liver (BAL) employing isolated hepatocytes can potentially provide temporary support for liver failure patients. We have developed a bioartificial liver by entrapping hepatocytes in collagen loaded in the luminal side of a hollow fiber bioreactor. In the first phase of development, liver-specific metabolic activities of biosynthesis, biotransformation and conjugation were demonstrated. Subsequently anhepatic rabbits were used to show that rat hepatocytes continued to function after the BAL was linked to the test animal. For scale-up studies, a canine liver failure model was developed using D-galactosamine overdose. In order to secure a sufficient number of hepatocytes for large animal treatment, a collagenase perfusion protocol was established for harvesting porcine hepatocytes at high yield and viability. An instrumented bioreactor system, which included dissolved oxygen measurement, pH control, flow rate control, an oxyg...

Cell transplantation

Metabolic activity of a gel-entrapment, hollow fiber, bioartificial liver was evaluated in vitro ... more Metabolic activity of a gel-entrapment, hollow fiber, bioartificial liver was evaluated in vitro and during extracorporeal hemoperfusion in an anhepatic rabbit model. The bioartificial liver contained either 100 million rat hepatocytes (n = 12), fibroblasts (n = 3), or no cells (n = 7) during hemoperfusion of anhepatic rabbits. Eight other anhepatic rabbits were studied without hemoperfusion as anhepatic controls, and three sham rabbits served as normal controls. Albumin production rates (mean +/- SEM) were similar during in vitro (17.0 +/- 2.8 micrograms/h) and extracorporeal (18.0 +/- 4.0 micrograms/h) application of the hepatocyte bioartificial liver. Exogenous glucose requirements were reduced (p < 0.01) and euglycemia was prolonged (p < 0.001) in anhepatic rabbits treated with the hepatocyte bioartificial liver. The maximum rate of glucose production by the hepatocyte bioartificial liver ranged from 50-80 micrograms/h. Plasma concentrations of aromatic amino acids, prolin...

Molecular Therapy, 2006

Viral vectors show promise as gene therapy treatments for a number of diseases. However, it has b... more Viral vectors show promise as gene therapy treatments for a number of diseases. However, it has been difficult to develop a robust system for generating large volumes of high-titer viral vectors based on lentivirus, alphavirus and adeno-associated virus (AAV) that are needed for clinical applications. Problems stem from the lack of stable producer cell lines and inherent inefficiencies associated with introducing multiple plasmids into adherent monolayer cells by conventional transient transfection techniques (i.e., calcium phosphate precipitation or cationic lipids). Other researchers have demonstrated that suspension cells of lymphoid origin, which can be grown at much higher density than adherent cells, can be converted into efficient retroviral vector producer cell lines (Chan et al., 2001. Gene Ther. 8: 697). However, commercially available transient transfection systems are not optimal for large volume co-transfection of suspension cells, especially hematopoietic cells. MaxCyte's proprietary high-throughput electroporation technology provides a closed, robust, scalable system for high efficiency transfection of both adherent and suspension cells. The MaxCyte system previously was used to produce high titer alphaviral vectors from >10 x10 9 Vero cells and lentiviral vectors from >1 x10 9 adherent HEK 293T cells. To improve the efficiency of lentiviral vector production at large scale and to demonstrate the feasibility of lentivector production in suspension cells, we used the MaxCyte system to transfect large volumes (38 x10 9 cells in 380 mL) of K562 human hematopoietic cells rapidly (within 20 minutes) with a plasmid encoding the green fluorescent protein (GFP) marker gene. The transfected cells were collected in fractions of 35-40 mL. Cells were cultured from each fraction or pooled samples to monitor consistency of the highthroughput electroporation. Greater than 90% of the cells expressed GFP when analyzed by flow cytometry at 48 hrs postelectroporation for all fractionated and pooled cell samples. Propidium iodide (PI) exclusion revealed the cell viability of all the fractionated and pooled cell samples to be greater than 90%. In addition, we were able to produce lentivirus in K562 cells by smallscale electroporation of 10 x10 6 cells with four plasmids encoding components of a lentiviral vector derived from HIV carrying the eGFP marker gene. In conclusion, these studies will demonstrate that use of suspension cells processed by MaxCyte's highthroughput electroporation-based transfection system is a feasible approach for generating large volumes of high-titer viral vectors suitable for clinical / commercial applications in human gene therapy.

Molecular Therapy, 2006

The identification of the chemokine receptor CCR5 as the major co-receptor required for HIV entry... more The identification of the chemokine receptor CCR5 as the major co-receptor required for HIV entry into CD4 T-cells has made the targeted disruption of CCR5 an attractive potential therapeutic approach for treating HIV-infected patients. Yet, no current method permits the efficient therapeutic disruption of a chosen gene in the human genome. We have developed designed zinc-finger protein nucleases (ZFNs) that specifically target the coding sequence of the CCR5 gene. Using standard delivery methods, we have shown these ZFNs can efficiently stimulate the formation of a double strand break (DSB) in the CCR5 locus to allow the natural DNA repair pathways, including Non-Homologous End Joining (NHEJ), to subsequently repair the DSB. Importantly, however, NHEJ is error prone and thus can result in frameshift mutations, leading to permanent disruption in >10% of K562 cells.

Biotechnology Progress, 1994

Cultured hepatocytes have been explored for use in a bioartificial liver. Spheroids formed by cul... more Cultured hepatocytes have been explored for use in a bioartificial liver. Spheroids formed by cultured hepatocytes exhibit enhanced liver-specific functions. The kinetics of spheroid formation, using rat hepatocytes, was studied on positively charged surfaces that were either uncoated or coated with collagen or (hydroxyethy1)methacrylate (HEMA). Optimal spheroid formation was obtained on positively charged (Primaria) surfaces at inoculum densities in the range of (3-9) x lo4 cells/cm2. Cells initially attached and spread out on the surface. Subsequent retraction led to the emergence of small clumps of cells attached to the surface, from which spheroids formed and shed off into suspension. The process of spheroid formation took more than 72 h and was accompanied by a decrease in the surface area occupied by attached cells. Optical sectioning of fluorescently stained spheroids using confocal microscopy indicated that most of the cells in the spheroid were viable. Spheroids also maintained a constant albumin synthesis rate for over 7 days in culture. Spheroid formation was evaluated in terms of the changes in spheroid diameter, the surface area covered by attached cells, and the total protein content of the fraction of cells that formed spheroids. The quantitative methodologies developed were used to assess the effect of inoculum cell concentration on spheroid formation and to evaluate the kinetics of spheroid formation on different surfaces both favorable and nonfavorable to spheroid formation.